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Environmental significance of 13C 12C and 18O 16O ratios of modern
land-snail shells from the southern great plains of North America
Meena Balakrishnana Crayton J Yappa James L Theler bBrian J Carter c Don G Wyckoff d
a Department of Geological Sciences Southern Methodist University Dallas TX 75275-0395 USAbDepartment of Sociology and Archaeology University of Wisconsin-La Crosse La Crosse WI 54601 USA
cDepartment of Plant and Soil Sciences Oklahoma State University Stillwater OK 74078 USAdOklahoma Museum of Natural History University of Oklahoma Norman OK 73019 USA
Received 11 March 2004
Available online 26 November 2004
Abstract
13C 12C and 18O 16O ratios of aragonite shells of modern land snails from the southern Great Plains of North America were measured for
samples from twelve localities in a narrow eastndashwest corridor that extended from the Flint Hills in North Central Oklahoma to the foothills of
the Sangre de Cristo Mountains in Northern New Mexico USA Across the study area shell y18O values (PDB scale) ranged from Agrave41x to
12x while y13C values ranged from Agrave132x to 00x y
18O values of the shell aragonite were predicted with a published steady state
evaporative flux balance model The predicted values differed (with one exception) by less than 1x from locality averages of measured y18O
values This similarity suggests that relative humidity at the time of snail activity is an important control on the y18O values of the aragonite
and emphasizes the seasonal nature of the climatic information preserved in the shells Correlated y13C values of coexisting Vallonia and
Gastrocopta suggest similar feeding habits and imply that these genera can provide information on variations in southern Great Plains plant
ecology Although there is considerable scatter multispecies transect average y13C values of the modern aragonite shells are related to
variations in the type of photosynthesis (ie C3 C4) in the local plant communities The results of this study emphasize the desirability of
obtaining isotope ratios representing averages of many shells in a locale to reduce possible biases associated with local variations among
individuals species etc and thus better represent the bneighborhoodQ scale temporal andor spatial environmental variations of interest in
studies of modern and ancient systems
D 2004 University of Washington All rights reserved
Keywords Land snails Oxygen isotopes Carbon isotopes Climate Relative humidity C3 plants C4 plants
Introduction
Studies of the isotopic compositions of the aragoniticshells of land snails from different parts of the world attest
to their value as environmental indicators (Goodfriend and
Ellis 2002 Goodfriend and Magaritz 1987 Goodfriend et
al 1989 Lecolle 1985 Magaritz and Heller 1980 1983
Magaritz et al 1981 Yapp 1979) y18O values of these
shells have been related to local climatic parameters and the
y18O of ambient meteoric water (eg Balakrishnan and
Yapp 2004 Goodfriend et al 1989 Lecolle 1985
Magaritz and Heller 1980 Magaritz et al 1981 Yapp1979) y13C values of shell aragonite may be correlated with
the y13C of local vegetation (eg Balakrishnan and Yapp
2004 Goodfriend and Magaritz 1987 Metref et al 2003
Stott 2002)
Goodfriend and Ellis (2002) conducted a study of the
y13C and y
18O variations of shell aragonite and shell organic
matrix in two species of land snails of the genus Rabdotus
along a transect from Northeast to Southwest Texas USA
They examined evidence for relationships between ambient
environmental parameters and the y13C or y18O values of
0033-5894$ - see front matter D 2004 University of Washington All rights reserved
doi101016jyqres200409009
Corresponding author Fax +1 214 768 2701
E-mail address cjyappmailsmuedu (CJ Yapp)
Quaternary Research 63 (2005) 15ndash30
wwwelseviercomlocateyqres
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shell aragonite y13C values of shell aragonite were
correlated with y13C values of organic matrix in the shell
which suggests that the shell y13C reflects diet with an offset
associated with the snail physiology and equilibrium and
kinetic fractionation processes Relationships of y18O
variations of Rabdotus to the environmental variables
discussed by Goodfriend and Ellis (2002) appeared to bemore problematic than for carbon
In the current paper we present measurements of
variations in the carbon and oxygen isotope compositions
of shells of other species of modern land snails from a
different portion of the southern Great Plains of North
America Samples in t his study are described in the work of
Theler et al (2004) and are from a narrow eastndashwest
corridor extending across much of Oklahoma and into
Northeastern New Mexico USA The data are discussed in
terms of their relationship to modern environmental
variables to examine the likelihood that isotopic data from
ancient land snails in the region might have paleoenvir-onmental significance
Samples and study area
Samples
The modern snail population procured for this study
f ormed part of an extensive terrestrial gastropod survey
(Theler et al 2004 Wyckoff et al 1997) in the southern
Great Plains of North America Samples were collected at
12 localities along an eastndashwest corridor extending from
North Central Oklahoma to Northeastern New Mexico
between 36826VN t o 3 6858VN latitude and 96849VW to
104857VW longitude (Theler et al 2004 Wyckoff et al
1997) The site names and locations are depicted in Figure
1 The study corridor is 640 km long east to west and about
100 km wide and extends from the Flint Hills of North
Central Oklahoma to the foothills of the Sangre de Cristo
Mountains near Cimarron New Mexico (Fig 1) Elevation
in the study area slowly increases from 330 m above sea
level at the eastern end of the corridor to about 2290 m
above sea level at the western end
Vegetation
There are four distinct biotic districts in the sampled area
(Fig 1) Mixed-grass plains occupy the eastern section
(Blair and Hubbell 1938 Carpenter 1940 Ostlie et al
1997 Shelford 1963) This district marks the transition
from tall grass prairie in the east to short grass prairie in the
west and is characterized by several species of Ascoparius
(Ascoparius saccharoides Ascoparius furcatus Ascoparius
smithii) grama grasses (Bouteloua gracilis Bouteloua
racemosa Bouteloua hirsuta and Bouteloua curtipendula)
and buffalo grass (Buchloe dactyloides) (Blair and Hubbell
1938 Bruner 1931 Carpenter 1940 Kuchler 1964 Ostlie
et al 1997 Risser 1985 1990 Shelford 1963 Weaver and
Albertson 1956)
The second biotic region short grass prairie (immedi-
ately to the west of the mixed-grass prairie Fig 1) contains
vegetation that includes buffalo grass hairy grama (B
hirsuta) blue grama (B gracilis) and western wheatgrass
(Pascopyrum smithii) (Blair and Hubbell 1938 Bruner1931 Carpenter 1940 Kuchler 1964 Ostlie et al 1997
Risser 1990 Shelford 1963)
A third biotic district the pinyonndashjuniper shrub grass-
land Raton subsection (Blair and Hubbell 1938) extends
from the northwest corner of the panhandle into the
northeastern corner of New Mexico (Fig 1) Vegetation in
this region includes junipers (Juniperus monosperma
Juniperus osteosperma) oak (Quercus mohriana) and pine
(Pinus edulis Pinus monophylla) along with plants such as
silverbeard grass (A saccharoides) blue grama and some
species of prickly pear cactus (Opuntia sp) (Blair and
Hubbell 1938 Ostlie et al 1997)The dry pine forest at the western end of the study area
(Fig 1) is not strictly a Plains ecosystem (Shelford 1963)
Vegetation includes oak and pine along with hairy and blue
grama grasses (Shelford 1963 Theler et al 2004 Wyckoff
et al 1997)
Climate and isotopes in precipitation
Average annual precipitation on the southern plains
generally decreases from over 1020 mmyr in the east to
255 mmyr in the west (Ostlie et al 1997) The mean
annual temperatures in the mixed-grass prairie range from
158 t o 178C while the corresponding mean annual
precipitation ranges from 670 to 790 mm (Blair and
Hubbell 1938) Annual temperatures in the short grass
prairie range from 128 to 138C and mean annual precip-
itation from 450 to 560 mm (Blair and Hubbell 1938)
Average annual temperatures in the dry pine forest of the
foothills of the Sangre de Cristo mountains are about 118C
and average rainfall is about 400 mm (Climate Data Center
New Mexico State University at wwwweathernmsuedu)
Precipitation in these regions derives principally from three
locations (Elliot 1949 Nativ and Riggio 1990)
From late March into July moisture is derived primarily
from the Gulf of Mexico (curveb
aQ
Fig 2) From October to early March the Northern Pacific Ocean is the primary
moisture source (Nativ and Riggio 1990) (curve bcQ Fig
2) In the western end of the study area (Northeastern New
Mexico) both the Gulf of Mexico and the central Pacific
Ocean contribute moisture during the middle to late summer
and early fall (curves baQ and bbQ Fig 2) although
contributions from the Gulf of Mexico are predominant
The central Pacific component of this moisture is brought in
by the Mexican monsoons (Douglas et al 1993 Nativ and
Riggio 1990)
The temperature and relative humidity at which ocean
water evaporates the air mass history and the local
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temperature of condensation are among the controls onthe isotopic composition of precipitation (Dansgaard
1964 Rozanski et al 1993) The different air masses
that contribute precipitation to the southern Plains impart
seasonally distinct y18O values to the rain andor snow
y18O values of summer rains originating from Gulf of
Mexico moisture are more positive than those of winter
precipitation originating from the North Pacific Ocean
(Nativ and Riggio 1990) This is primarily a consequence
of the higher elevations (lower temperatures) and longer
transport distances experienced by air masses from the
North Pacific (Nativ and Riggio 1990 Rozanski et al
1993)
Experimental
Sampling systematics
Results of an initial survey collection and documentation
of the modern gastropods in this region are found in Wyckoff
et al (1997) and Theler et al (2004) These include
description of the dominant vegetation types at each locality
Collections of the snails analyzed for the current work were
made at 12 localities along the 640-km sample corridor at
sites for which living snails could be expected (for sample
collection rationale see Theler et al 2004) Each sample
locality was restricted to a circle with a diameter of ~400 m
Figure 1 Map of the study area in the southern Great Plains of North America indicating the collection localities and the major ecological regions Localities 1
Kubic 2 Bluff Creek 3 Salt Fork 4 McDaniel 5 Burnham 6 Big Salt Plain 7 Skull Springs 8 Hitch 9 Black Mesa 10 Owensby 11 C S Ranch 12 Chase
(data sources Blair and Hubbell 1938 Carpenter 1940 Shelford 1963 Wyckoff et al 1997 Theler et al 2004)
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(Theler et al 2004 Wyckoff et al 1997) Each circle
contained several niches Niches (recognized by differences
in vegetation slope and aspect) favorable for snail habitation
were sampled along a linear btransect Q (Theler et al 2004
Wyckoff et al 1997) that was usually not more than 100 m in
length Along each transect there were three sample
collection sites (usually 10ndash20 m apart) called breplicationsQ
A B and C (Wyckoff et al 1997) The term bsampleQ was
substituted for breplicationQ by Theler et al (2004) However
in the current work we will retain breplicationQ (sensu
Wyckoff et al 1997) to avoid confusion with our more
generic use of the term bsampleQ which refers herein to any
collected material of interest Thus as an example the
sample locality bHitchQ has three transects (Hitch 21 Hitch
22 and Hitch 23) with each transect in Hitch in turn
comprised of three replications (eg Hitch 21A Hitch 21Band Hitch 21C) There is a total of 38 transects among the 12
localities and a total of 114 breplicationsQ summed over all of
the 38 transects (ie 3 Acirc 38) At each breplicationQ lower
parts of growing vegetation decaying vegetation and 2 cm
of topsoil from a 50 Acirc 50 cm area were collected (Wyckoff et
al 1997 Theler et al 2004) Wyckoff et al (1997) and
Theler et al (2004) sieved and sorted these samples in the
laboratory to extract the snail shells followed by identifica-
tion and population analyses
Because of the destructive nature of the isotopic analyses
and because it was necessary to retain snail shells for
archival purposes only those from sample sites represented
by large numbers of collected shells were analyzed Hence
of the total of 114 breplicationsQ among the 38 transects
only 71 replications from 34 transects are represented in this
study Most of the samples were collected in 1995
(collection from the Owensby site was made in 1996) and
were alive at the time or within 1 yr of collection (Theler et
al 2004 Wyckoff et al 1997)
Selection of species for isotopic analyses
Vallonia and Gastrocopta were the principal genera
employed for isotopic analyses of snail shells because they
are present throughout most or all of the study area (Theler
et al 2004 Wyckoff et al 1997) For some localities
snails representing a few other genera were also isotopically
analyzed but these other genera did not have the widedistribution exhibited by Vallonia or Gastrocopta The
genus Vallonia is represented by the species Vallonia
parvula at the lower elevations and Vallonia gracilicosta
at the higher elevations The latter is often associated with
deposits of Pleistocene age in the southern Great Plains
(Rossignol et al 2004 Theler et al 2004 Wyckoff et al
1997) Vallonia juveniles were also analyzed but could not
be identified at the species level (Theler et al 2004
Wyckoff et al 1997) The genus Gastrocopta was
represented by Gastrocopta contracta Gastrocopta holzin-
geri Gastrocopta pentodon Gastrocopta armifera Gastro-
copta cristata Gastrocopta pilsbryana Gastrocopta
Figure 2 Source regions and generalized trajectories of major moisture-bearing air masses that bring precipitation to the southern Great Plains of North
America Trajectory (a) March into July or August (b) middle to late summer and early fall (c) October to early March (see text) mP = maritime polar air
mass and mT = maritime tropical air mass (after Elliot 1949 Nativ and Riggio 1990) The shaded rectangle encompasses the land snail sites of Figure 1
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procera and Gastrocopta pellucida The two latter species
exhibit relatively large distribution ranges However G
procera was notably absent at the higher altitudes in the
survey (Theler et al 2004 Wyckoff et al 1997)
Laboratory preparations and analyses
Each isotopically analyzed sample consisted of multiple
entire shells of adults of a particular species (or genus for
juveniles of Vallonia) from a breplicationQ The shells were
initially rinsed with deionized water then treated ultrasoni-
cally in deionized water to remove any adhering particles of
organic matter or other debris The shells were gently crushed
and treated with 5 reagent-grade sodium hypochlorite at
room temperature for about 7ndash8 h to remove organic matter
They were then rinsed thoroughly with deionized water and
dried in air at about 40ndash508C The shell fragments were
subsequently reacted overnight in vacuum with 100 H3PO4
at 258
C following the method of McCrea (1950) The CO2
prepared from the shell aragonite was analyzed for y13C and
y18O on a Finnigan MAT 252 mass spectrometer Analytical
uncertainty is about F01x The y values are defined as
y13C or y18O frac14 R sample=R standard
Agrave AacuteAgrave 1
Acirc AtildeAcirc 1000 x
where R = 13C 12C or 18O 16O y13C and y18O are reported
relative to the PDB standard (Craig 1957)
Results and discussions
Ranges of d18O and d13C of aragonite in land-snail shells
y18O and y
13C values were measured for 162 samples
from the 12 localities of Figure 1 (see Appendix A) y18O
values of the aragonite shells of these modern snails ranged
from Agrave41x to 12x (Fig 3) Published y18O values of
shells from globally distributed modern land snails that are
wholly subaerial (as opposed to semiaquatic) range from
Agrave117x to 45x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Goodfriend et al 1989 Lecolle 1985
Magaritz and Heller 1980 Magaritz et al 1981 Sharpe et
al 1994 Yapp 1979) In North America reported y18O
values of land-snail shells range from Agrave117x to 02x(Goodfriend and Ellis 2002 Sharpe et al 1994 Yapp
1979) If the results for a carnivorous cold-tolerant snail of
the genus Vitrina (Sharpe et al 1994) from Deer Creek
Nevada are excluded y18O values analyzed to date for
North America range from Agrave58x to 02x The current
work extends the upper range of North American values by
10x (Fig 3)
Previous studies of y13C values of shell aragonite from
snails in their natural settings reported values ranging from
Agrave135x to 05x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Lecolle 1983 1984 Magaritz and
Heller 1980 1983 Magaritz et al 1981 Yapp 1979) For
North America published y13C values range from Agrave125x
to Agrave25x (Goodfriend and Ellis 2002 Yapp 1979) The
y13C values of snail shell aragonite studied for the current
work range from Agrave132x to 00x (Fig 3) By contrast
y13C values of shell aragonite of experimentally cultured
Helix aspersa that were fed a controlled diet ranged from
Agrave243x to 25x (Stott 2002) Controlled experiments also
indicate differences in y13C values among adults hatched
and 1-month-old individuals of H aspersa fed diets with
identical y13C values (Metref et al 2003)
Snail shell isotopic variation among populations
Variations in the isotopic composition of snail shells exist
among replications within a transect and also among species
in a replication (Appendix A) Within a sample locality
small-scale variations in topography vegetation local
moisture availability snail ages physiology etc are
expected Such variations might contribute to the observed
scatter in isotopic ratios among genera species or
individual samples
Isotopic analyses of Vallonia and Gastrocopta total 143
and represent the majority of the analyzed shell samples but
Figure 3 Ranges of Southern Great Plains land snails and snail shell y18O
and y13C values measured for breplicationsQ in the current study compared
with various published ranges (see text) Open portion of the range of North
Americany18
O values encompasses the values reported for shells from acarnivorous cold-tolerant snail (see text for reference)
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there were also analyses (numbers in parentheses) of
bunderrepresentedQ genera as follows (see Appendix A)
Pupoides (9) Succineidae (3) Pupilla (2) Cionella (1)
Zonitoides (1) Helicodiscus (1) Glyphyalinia (1) and
Hawaiia (1) The ranges of y18O values for Vallonia and
Gastrocopta are about 28x and 20x respectively (Fig
4a) Corresponding y18O values of Vallonia and Gastrocopta
indicate no correlation among the various sites (Fig 4a) A
similar lack of correlation was evident when y18O values of
underrepresented genera were compared wit h values for
coexisting Vallonia (Fig 5a) or Gastrocopta (Fig 5b) The
particular origins of these differences are unknown Without
studies under controlled age and environmental conditions
(eg Metref et al 2003 Stott 2002) distinguishing micro-environmental effects from the effects of age andor species-
related physiological differences is not possible at present
The respective ranges of y13C values for Vallonia and
Gastrocopta shell aragonite are each about 8ndash9x and
samples from the same breplicationsQ show a significant
correlation (Fig 4b) This correlation could indicate similar
feeding habits in both genera making them potential sources
of isotopic information on the paleoecology of a locale
Because of this correlation of Vallonia and Gastrocopta y13C
values y13C values of eight other genera that coexisted with
one or both of these genera in the various breplicationsQ are
plotted against y13
C of either Vallonia or Gastrocopta in asingle figure (Fig 5c) There are insufficient data to establish
whether the y13C values of any of the bunderrepresentedQ
genera might be correlated with Vallonia or Gastrocopta but
overall there is considerable scatter among the species
Additional comparative analyses of and controlled experi-
ments on these genera are needed
An exploratory evaluation of the effect of life histories
and ages on the isotopic composition of snails was
attempted using the data for adult and juvenile Vallonia
(see Appendix A) y18O values of shells of coexisting adult
and juvenile Vall onia from the breplicationsQ are not
correlated (Fig 6a) The y18O values of the adult snails
represent averages over longer periods of time than those of
the juveniles Short time scale environmental conditions that
affect the y18O values of the body fluid in juveniles should
determine the y18O values of the shell aragonite and these
conditions might contrast with the longer term-averages of
the adults
The absence of a correlation in the y18O data of Figure 6a
contrasts with the good correlation of the y13C values of the
adults and juveniles in Figure 6b The y13C correlation
could indicate that in these locales the carbon isotope
Figure 4 Southern Great Plains land snails Comparison of average
isotopic compositions of the aragonitic shells of Gastrocopta and Vallonia
from the same breplicationsQ (see text) (a) comparison of y18O values and
(b) comparison of y13
C values Dashed line in panel a is the reference liney = x Solid line in panel b is the linear regression of the data with the
corresponding equation r 2 and P
Figure 5 Southern Great Plains land snails Comparison of y18O of the aragonitic shells of other species used in this study with that of coexisting (a) Vallonia
and (b) Gastrocopta in the breplicationsQ (c) Comparison of y13C values of the shell aragonite of other species with those of coexisting Vallonia andor
Gastrocopta in the same breplicationsQ (see text) Dashed lines are the reference lines y = x
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composition of vegetation (as well as snail feeding patterns)
is not as variable on small scales as the oxygen isotope
composition of ambient moisture However the apparent
contrast in the respective oxygen and carbon isotope
relationships (adults or juveniles Figs 4 and 6) might also
be in part a consequence of the smaller ranges for the y18O
values Thus if the magnitude of the normal scatter in the
breplicationsQ data were comparable to the smaller total
range of the y18O values it would mask any evidence for a
broader y18
O correlation among genera or age groups
Snail shell isotope compositions and environmental
parameters
Carbon isotopes
As noted vegetation in the study area is dominantly
grasslands at lower elevations and trees at higher
elevations (Fig 1) Based on the nature of the photo-
synthetic pathway plants are classified as C3 C4 or CAM
(eg Jacobs et al 1999) y13C values of C3 plants range
from Agrave33x to Agrave21 x while y13C values of C4 plants
typically range from Agrave17x to Agrave9x (eg Cerling and
Quade 1993) CAM plants have y13C values that range
between the values for C3 and C4 plants (eg Cerling and
Quade 1993) Most of the grasses in the southern Great
Plains are C4 plants (Tieszen et al 1997) and the trees
and most of the forbs are C3 plants (Watson and Dallwitz
httpbiodiversityunoedudelta )
If snail shell y13C values are influenced by the y13C of their diets (eg Balakrishnan and Yapp 2004 Francey
1983 Goodfriend and Ellis 2002 Goodfriend and Magar-
itz 1987 Metref et al 2003 Stott 2002) the spatial
transitions in the ecology of the study corridor suggest that
the y13C values of the shells should be more negative at the
higher elevations toward the west y13C values of the shell
aragonite from all breplicationsQ (Appendix A) and their
averages for each transect (Table 1) are plotted against
elevation in Figures 7a and 7b respectively There is
considerable scatter but some suggestion of the expected
general shift to lower y13C values as altitude increases (Fig
7) However the regional vegetation trend does not explainthe very large range of snail shell y13C values at the lowest
elevations on the eastern end of the sample corridor (Figs
7a and 7b) Such a large range may be explained in part by
local variations in proportions of C3 and C4 plants
Wyckoff et al (1997) and Theler et al (2004)
identified plant species at each sample site in the study
corridor For the current work their identifications (no
quantitative estimates of type) were used to classify the
vegetation in each transect as C3-dominant C4-dominant
or mixed including CAM (Ehleringer et al 1997
Owensby et al 1997 Sage et al 1999 Appalachian
Farming Systems Research Center httpwwwarserrcgov
beckleyC3C4LISThtm ) The classifications are presented
in Table 1
The average y13C values of the land-snail shells from
each transect are listed in Table 1 and plotted in Figure 8
against the corresponding classification of local vegetation
which is arranged in a sequence from C4-dominant to C3-
dominant It is not known if the snails in the region ingest
CAM plants However examined in the manner of Figure
8 it is evident that the y13C values of snail shells of the
southern Great Plains are generally indicative of the type of
vegetation in their immediate environment although there
is still considerable scatter in the relationship In the
regions where C4 plants were identified as the dominant plant type the transect-average y
13C values of the snail
shell aragonite ranged from Agrave43x to Agrave19x with an
overall average of Agrave28x In localities where C3 plants
were documented to be the dominant type these transect-
average values ranged from Agrave101x to Agrave88x with an
overall average of Agrave90x (Fig 8) In the areas with mixed
vegetation types the shell y13C values are within the
extremes defined by the y13C values of the shells in areas
dominated by C3 or C4 plants These observations are in
agreement with earlier observations (Francey 1983 Good-
friend and Ellis 2002 Goodfriend and Magaritz 1987
Metref et al 2003 Stott 2002)
Figure 6 Comparison of coexisting adults and juveniles of southern Great
Plains Vallonia inb
replicationsQ
(see text) (a) y
18
O values of aragoniteshells and (b) y
13C values Solid line in panel b is the linear regression of
the data with the corresponding equation r 2 and P
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For the transects representing the Owensby and Bluff
Creek localities the plant species were not documented but
the relatively negative land-snail shelly13C values suggestthe
possible local dominance of C3 vegetation(hence the question
mark by the C3 symbol on the far right of the abscissa of Fig
8) Some of the scatter in Figure 8 may be a result of the
complicating effects of incorporation of relatively13
C-richdietary carbonate from limestone (eg Goodfriendand Hood
1983 Metref et al 2003 Yates et al 2002)
Oxygen isotopes
Average annual y18O of meteoric water is about Agrave56x at
Norman Oklahoma (USGS unpublished data Martha
Scholl personal communication) in the east and Agrave98 x
at the higher elevations of Clovis New Mexico (Nativ and
Riggio 1990) in the west As suggested by Figure 2 some of
this difference may be a consequence of differing proportions
of precipitation from different moisture sources and air
masses with different histories Irrespective of the particular
mechanisms producing lower y18O values of average annual
precipitation at the higher western elevations if the dominant
control on the y18O value of the snail shell aragonite was the
y18O value of annual precipitation the shell y18O should be
lower at higher altitude Figure 9a depicts snail shell y18O
values plotted against altitude for all of the analyzed
breplications
Q (Appendix A) There is no correlation of shell
y18O with elevation evident in Figure 9a
Average y18O values of samples in each transect are listed
in Table 1 and plotted against elevation in Figure 9b For the
transect-average values in Figure 9b there may be a weak
relationship of shell y18O with altitude indicating some
tendency for a decrease of shell y18O with increasing
elevation For an increase in elevation of ~2000 m the slope
of the linear regression indicates a decrease in shell y18O of
only ~1x However even if this weak correlation in Figure
9b was significant a decrease of ~1x is much less than the
decrease of ~4x expected if the y18O of annual precipitation
were the principal control on shell y18O values
Table 1
Transect averages (all species) of measured shell y13C and y
18O
Locality Transect Elevationa (m) Plant type Transect average Average y18O Model calculations
y13C y
18O Calculated locality y18Ocalc D
18O
Kubic 6 329 C3 Agrave85 Agrave21 Agrave20 Agrave22 Agrave02
Kubic 5 351 C4 Agrave35 Agrave19
Kubic 2 360 C4 C3 Agrave48 Agrave21Kubic 4 360 C4 Agrave23 Agrave17
Kubic 3 366 C4 Agrave19 Agrave01
Bluff Creek 36 348 C3 Agrave84 Agrave12 Agrave12 Agrave15 Agrave03
Salt Fork 9 320 C3 Agrave101 Agrave19 Agrave19 Agrave15 04
McDaniel 11 375 C4 C3 Agrave76 Agrave22 Agrave22 Agrave14 08
Burnham 17 519 C4 C3 Agrave83 Agrave08 Agrave10 Agrave09 01
Burnham 16 567 C4 CAM C3 Agrave54 Agrave18
Burnham 12 607 C4 C3 Agrave58 Agrave23
Burnham 14 607 C4 CAM C3 Agrave41 Agrave13
Burnham 13 610 C4 Agrave43 Agrave01
Big Salt Plain 15 482 C3 Agrave89 Agrave04 Agrave04 Agrave09 Agrave05
Skull Springs 18 671 C4 CAM C3 Agrave60 Agrave16 Agrave16 Agrave03 13
Skull Springs 19 665 C4 C3 Agrave40 Agrave17
Hitch 22 915 C4 CAM Agrave51 Agrave15 Agrave18 Agrave25 Agrave07
Hitch 21 933 C4 CAM C3 Agrave50 Agrave06Hitch 23 881 C3 Agrave85 Agrave23
Black Mesa 27 1312 C4 C3 Agrave61 Agrave27 Agrave22 Agrave21 01
Black Mesa 26 1324 C4 CAM C3 Agrave66 Agrave15
Black Mesa 24 1488 C4 CAM Agrave26 Agrave17
Black Mesa 25 1464 C4 CAM C3 Agrave72 Agrave25
Black Mesa 35 1464 C4 CAM C3 Agrave75 Agrave18
Owensby 61 2193 C3 Agrave105 Agrave19 Agrave20 Agrave25 Agrave05
Owensby 60 2242 C3 Agrave96 Agrave30
Owensby 59 2288 C3 Agrave109 Agrave19
CS Ranch 30 1922 C4 CAM C3 Agrave43 Agrave19 Agrave20 Agrave25 Agrave05
CS Ranch 29 1940 C4 CAM C3 Agrave49 Agrave25
Chase 34 1952 C4 C3 Agrave92 Agrave38 Agrave25 Agrave25 00
Chase 33 2184 C4 C3 Agrave86 Agrave22
Chase 31 2220 C4 C3 Agrave90 Agrave25
Chase 32 2233 C4 C3 Agrave89 Agrave23
Locality averages of measured y18O Also y
18O of shell at a locality as predicted from model calculations for diffusive evaporation (y18Ocalc) D18O =
y18Ocalc Agrave y
18Omeasa Sea level datum
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The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
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sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
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shell aragonite y13C values of shell aragonite were
correlated with y13C values of organic matrix in the shell
which suggests that the shell y13C reflects diet with an offset
associated with the snail physiology and equilibrium and
kinetic fractionation processes Relationships of y18O
variations of Rabdotus to the environmental variables
discussed by Goodfriend and Ellis (2002) appeared to bemore problematic than for carbon
In the current paper we present measurements of
variations in the carbon and oxygen isotope compositions
of shells of other species of modern land snails from a
different portion of the southern Great Plains of North
America Samples in t his study are described in the work of
Theler et al (2004) and are from a narrow eastndashwest
corridor extending across much of Oklahoma and into
Northeastern New Mexico USA The data are discussed in
terms of their relationship to modern environmental
variables to examine the likelihood that isotopic data from
ancient land snails in the region might have paleoenvir-onmental significance
Samples and study area
Samples
The modern snail population procured for this study
f ormed part of an extensive terrestrial gastropod survey
(Theler et al 2004 Wyckoff et al 1997) in the southern
Great Plains of North America Samples were collected at
12 localities along an eastndashwest corridor extending from
North Central Oklahoma to Northeastern New Mexico
between 36826VN t o 3 6858VN latitude and 96849VW to
104857VW longitude (Theler et al 2004 Wyckoff et al
1997) The site names and locations are depicted in Figure
1 The study corridor is 640 km long east to west and about
100 km wide and extends from the Flint Hills of North
Central Oklahoma to the foothills of the Sangre de Cristo
Mountains near Cimarron New Mexico (Fig 1) Elevation
in the study area slowly increases from 330 m above sea
level at the eastern end of the corridor to about 2290 m
above sea level at the western end
Vegetation
There are four distinct biotic districts in the sampled area
(Fig 1) Mixed-grass plains occupy the eastern section
(Blair and Hubbell 1938 Carpenter 1940 Ostlie et al
1997 Shelford 1963) This district marks the transition
from tall grass prairie in the east to short grass prairie in the
west and is characterized by several species of Ascoparius
(Ascoparius saccharoides Ascoparius furcatus Ascoparius
smithii) grama grasses (Bouteloua gracilis Bouteloua
racemosa Bouteloua hirsuta and Bouteloua curtipendula)
and buffalo grass (Buchloe dactyloides) (Blair and Hubbell
1938 Bruner 1931 Carpenter 1940 Kuchler 1964 Ostlie
et al 1997 Risser 1985 1990 Shelford 1963 Weaver and
Albertson 1956)
The second biotic region short grass prairie (immedi-
ately to the west of the mixed-grass prairie Fig 1) contains
vegetation that includes buffalo grass hairy grama (B
hirsuta) blue grama (B gracilis) and western wheatgrass
(Pascopyrum smithii) (Blair and Hubbell 1938 Bruner1931 Carpenter 1940 Kuchler 1964 Ostlie et al 1997
Risser 1990 Shelford 1963)
A third biotic district the pinyonndashjuniper shrub grass-
land Raton subsection (Blair and Hubbell 1938) extends
from the northwest corner of the panhandle into the
northeastern corner of New Mexico (Fig 1) Vegetation in
this region includes junipers (Juniperus monosperma
Juniperus osteosperma) oak (Quercus mohriana) and pine
(Pinus edulis Pinus monophylla) along with plants such as
silverbeard grass (A saccharoides) blue grama and some
species of prickly pear cactus (Opuntia sp) (Blair and
Hubbell 1938 Ostlie et al 1997)The dry pine forest at the western end of the study area
(Fig 1) is not strictly a Plains ecosystem (Shelford 1963)
Vegetation includes oak and pine along with hairy and blue
grama grasses (Shelford 1963 Theler et al 2004 Wyckoff
et al 1997)
Climate and isotopes in precipitation
Average annual precipitation on the southern plains
generally decreases from over 1020 mmyr in the east to
255 mmyr in the west (Ostlie et al 1997) The mean
annual temperatures in the mixed-grass prairie range from
158 t o 178C while the corresponding mean annual
precipitation ranges from 670 to 790 mm (Blair and
Hubbell 1938) Annual temperatures in the short grass
prairie range from 128 to 138C and mean annual precip-
itation from 450 to 560 mm (Blair and Hubbell 1938)
Average annual temperatures in the dry pine forest of the
foothills of the Sangre de Cristo mountains are about 118C
and average rainfall is about 400 mm (Climate Data Center
New Mexico State University at wwwweathernmsuedu)
Precipitation in these regions derives principally from three
locations (Elliot 1949 Nativ and Riggio 1990)
From late March into July moisture is derived primarily
from the Gulf of Mexico (curveb
aQ
Fig 2) From October to early March the Northern Pacific Ocean is the primary
moisture source (Nativ and Riggio 1990) (curve bcQ Fig
2) In the western end of the study area (Northeastern New
Mexico) both the Gulf of Mexico and the central Pacific
Ocean contribute moisture during the middle to late summer
and early fall (curves baQ and bbQ Fig 2) although
contributions from the Gulf of Mexico are predominant
The central Pacific component of this moisture is brought in
by the Mexican monsoons (Douglas et al 1993 Nativ and
Riggio 1990)
The temperature and relative humidity at which ocean
water evaporates the air mass history and the local
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temperature of condensation are among the controls onthe isotopic composition of precipitation (Dansgaard
1964 Rozanski et al 1993) The different air masses
that contribute precipitation to the southern Plains impart
seasonally distinct y18O values to the rain andor snow
y18O values of summer rains originating from Gulf of
Mexico moisture are more positive than those of winter
precipitation originating from the North Pacific Ocean
(Nativ and Riggio 1990) This is primarily a consequence
of the higher elevations (lower temperatures) and longer
transport distances experienced by air masses from the
North Pacific (Nativ and Riggio 1990 Rozanski et al
1993)
Experimental
Sampling systematics
Results of an initial survey collection and documentation
of the modern gastropods in this region are found in Wyckoff
et al (1997) and Theler et al (2004) These include
description of the dominant vegetation types at each locality
Collections of the snails analyzed for the current work were
made at 12 localities along the 640-km sample corridor at
sites for which living snails could be expected (for sample
collection rationale see Theler et al 2004) Each sample
locality was restricted to a circle with a diameter of ~400 m
Figure 1 Map of the study area in the southern Great Plains of North America indicating the collection localities and the major ecological regions Localities 1
Kubic 2 Bluff Creek 3 Salt Fork 4 McDaniel 5 Burnham 6 Big Salt Plain 7 Skull Springs 8 Hitch 9 Black Mesa 10 Owensby 11 C S Ranch 12 Chase
(data sources Blair and Hubbell 1938 Carpenter 1940 Shelford 1963 Wyckoff et al 1997 Theler et al 2004)
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(Theler et al 2004 Wyckoff et al 1997) Each circle
contained several niches Niches (recognized by differences
in vegetation slope and aspect) favorable for snail habitation
were sampled along a linear btransect Q (Theler et al 2004
Wyckoff et al 1997) that was usually not more than 100 m in
length Along each transect there were three sample
collection sites (usually 10ndash20 m apart) called breplicationsQ
A B and C (Wyckoff et al 1997) The term bsampleQ was
substituted for breplicationQ by Theler et al (2004) However
in the current work we will retain breplicationQ (sensu
Wyckoff et al 1997) to avoid confusion with our more
generic use of the term bsampleQ which refers herein to any
collected material of interest Thus as an example the
sample locality bHitchQ has three transects (Hitch 21 Hitch
22 and Hitch 23) with each transect in Hitch in turn
comprised of three replications (eg Hitch 21A Hitch 21Band Hitch 21C) There is a total of 38 transects among the 12
localities and a total of 114 breplicationsQ summed over all of
the 38 transects (ie 3 Acirc 38) At each breplicationQ lower
parts of growing vegetation decaying vegetation and 2 cm
of topsoil from a 50 Acirc 50 cm area were collected (Wyckoff et
al 1997 Theler et al 2004) Wyckoff et al (1997) and
Theler et al (2004) sieved and sorted these samples in the
laboratory to extract the snail shells followed by identifica-
tion and population analyses
Because of the destructive nature of the isotopic analyses
and because it was necessary to retain snail shells for
archival purposes only those from sample sites represented
by large numbers of collected shells were analyzed Hence
of the total of 114 breplicationsQ among the 38 transects
only 71 replications from 34 transects are represented in this
study Most of the samples were collected in 1995
(collection from the Owensby site was made in 1996) and
were alive at the time or within 1 yr of collection (Theler et
al 2004 Wyckoff et al 1997)
Selection of species for isotopic analyses
Vallonia and Gastrocopta were the principal genera
employed for isotopic analyses of snail shells because they
are present throughout most or all of the study area (Theler
et al 2004 Wyckoff et al 1997) For some localities
snails representing a few other genera were also isotopically
analyzed but these other genera did not have the widedistribution exhibited by Vallonia or Gastrocopta The
genus Vallonia is represented by the species Vallonia
parvula at the lower elevations and Vallonia gracilicosta
at the higher elevations The latter is often associated with
deposits of Pleistocene age in the southern Great Plains
(Rossignol et al 2004 Theler et al 2004 Wyckoff et al
1997) Vallonia juveniles were also analyzed but could not
be identified at the species level (Theler et al 2004
Wyckoff et al 1997) The genus Gastrocopta was
represented by Gastrocopta contracta Gastrocopta holzin-
geri Gastrocopta pentodon Gastrocopta armifera Gastro-
copta cristata Gastrocopta pilsbryana Gastrocopta
Figure 2 Source regions and generalized trajectories of major moisture-bearing air masses that bring precipitation to the southern Great Plains of North
America Trajectory (a) March into July or August (b) middle to late summer and early fall (c) October to early March (see text) mP = maritime polar air
mass and mT = maritime tropical air mass (after Elliot 1949 Nativ and Riggio 1990) The shaded rectangle encompasses the land snail sites of Figure 1
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procera and Gastrocopta pellucida The two latter species
exhibit relatively large distribution ranges However G
procera was notably absent at the higher altitudes in the
survey (Theler et al 2004 Wyckoff et al 1997)
Laboratory preparations and analyses
Each isotopically analyzed sample consisted of multiple
entire shells of adults of a particular species (or genus for
juveniles of Vallonia) from a breplicationQ The shells were
initially rinsed with deionized water then treated ultrasoni-
cally in deionized water to remove any adhering particles of
organic matter or other debris The shells were gently crushed
and treated with 5 reagent-grade sodium hypochlorite at
room temperature for about 7ndash8 h to remove organic matter
They were then rinsed thoroughly with deionized water and
dried in air at about 40ndash508C The shell fragments were
subsequently reacted overnight in vacuum with 100 H3PO4
at 258
C following the method of McCrea (1950) The CO2
prepared from the shell aragonite was analyzed for y13C and
y18O on a Finnigan MAT 252 mass spectrometer Analytical
uncertainty is about F01x The y values are defined as
y13C or y18O frac14 R sample=R standard
Agrave AacuteAgrave 1
Acirc AtildeAcirc 1000 x
where R = 13C 12C or 18O 16O y13C and y18O are reported
relative to the PDB standard (Craig 1957)
Results and discussions
Ranges of d18O and d13C of aragonite in land-snail shells
y18O and y
13C values were measured for 162 samples
from the 12 localities of Figure 1 (see Appendix A) y18O
values of the aragonite shells of these modern snails ranged
from Agrave41x to 12x (Fig 3) Published y18O values of
shells from globally distributed modern land snails that are
wholly subaerial (as opposed to semiaquatic) range from
Agrave117x to 45x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Goodfriend et al 1989 Lecolle 1985
Magaritz and Heller 1980 Magaritz et al 1981 Sharpe et
al 1994 Yapp 1979) In North America reported y18O
values of land-snail shells range from Agrave117x to 02x(Goodfriend and Ellis 2002 Sharpe et al 1994 Yapp
1979) If the results for a carnivorous cold-tolerant snail of
the genus Vitrina (Sharpe et al 1994) from Deer Creek
Nevada are excluded y18O values analyzed to date for
North America range from Agrave58x to 02x The current
work extends the upper range of North American values by
10x (Fig 3)
Previous studies of y13C values of shell aragonite from
snails in their natural settings reported values ranging from
Agrave135x to 05x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Lecolle 1983 1984 Magaritz and
Heller 1980 1983 Magaritz et al 1981 Yapp 1979) For
North America published y13C values range from Agrave125x
to Agrave25x (Goodfriend and Ellis 2002 Yapp 1979) The
y13C values of snail shell aragonite studied for the current
work range from Agrave132x to 00x (Fig 3) By contrast
y13C values of shell aragonite of experimentally cultured
Helix aspersa that were fed a controlled diet ranged from
Agrave243x to 25x (Stott 2002) Controlled experiments also
indicate differences in y13C values among adults hatched
and 1-month-old individuals of H aspersa fed diets with
identical y13C values (Metref et al 2003)
Snail shell isotopic variation among populations
Variations in the isotopic composition of snail shells exist
among replications within a transect and also among species
in a replication (Appendix A) Within a sample locality
small-scale variations in topography vegetation local
moisture availability snail ages physiology etc are
expected Such variations might contribute to the observed
scatter in isotopic ratios among genera species or
individual samples
Isotopic analyses of Vallonia and Gastrocopta total 143
and represent the majority of the analyzed shell samples but
Figure 3 Ranges of Southern Great Plains land snails and snail shell y18O
and y13C values measured for breplicationsQ in the current study compared
with various published ranges (see text) Open portion of the range of North
Americany18
O values encompasses the values reported for shells from acarnivorous cold-tolerant snail (see text for reference)
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there were also analyses (numbers in parentheses) of
bunderrepresentedQ genera as follows (see Appendix A)
Pupoides (9) Succineidae (3) Pupilla (2) Cionella (1)
Zonitoides (1) Helicodiscus (1) Glyphyalinia (1) and
Hawaiia (1) The ranges of y18O values for Vallonia and
Gastrocopta are about 28x and 20x respectively (Fig
4a) Corresponding y18O values of Vallonia and Gastrocopta
indicate no correlation among the various sites (Fig 4a) A
similar lack of correlation was evident when y18O values of
underrepresented genera were compared wit h values for
coexisting Vallonia (Fig 5a) or Gastrocopta (Fig 5b) The
particular origins of these differences are unknown Without
studies under controlled age and environmental conditions
(eg Metref et al 2003 Stott 2002) distinguishing micro-environmental effects from the effects of age andor species-
related physiological differences is not possible at present
The respective ranges of y13C values for Vallonia and
Gastrocopta shell aragonite are each about 8ndash9x and
samples from the same breplicationsQ show a significant
correlation (Fig 4b) This correlation could indicate similar
feeding habits in both genera making them potential sources
of isotopic information on the paleoecology of a locale
Because of this correlation of Vallonia and Gastrocopta y13C
values y13C values of eight other genera that coexisted with
one or both of these genera in the various breplicationsQ are
plotted against y13
C of either Vallonia or Gastrocopta in asingle figure (Fig 5c) There are insufficient data to establish
whether the y13C values of any of the bunderrepresentedQ
genera might be correlated with Vallonia or Gastrocopta but
overall there is considerable scatter among the species
Additional comparative analyses of and controlled experi-
ments on these genera are needed
An exploratory evaluation of the effect of life histories
and ages on the isotopic composition of snails was
attempted using the data for adult and juvenile Vallonia
(see Appendix A) y18O values of shells of coexisting adult
and juvenile Vall onia from the breplicationsQ are not
correlated (Fig 6a) The y18O values of the adult snails
represent averages over longer periods of time than those of
the juveniles Short time scale environmental conditions that
affect the y18O values of the body fluid in juveniles should
determine the y18O values of the shell aragonite and these
conditions might contrast with the longer term-averages of
the adults
The absence of a correlation in the y18O data of Figure 6a
contrasts with the good correlation of the y13C values of the
adults and juveniles in Figure 6b The y13C correlation
could indicate that in these locales the carbon isotope
Figure 4 Southern Great Plains land snails Comparison of average
isotopic compositions of the aragonitic shells of Gastrocopta and Vallonia
from the same breplicationsQ (see text) (a) comparison of y18O values and
(b) comparison of y13
C values Dashed line in panel a is the reference liney = x Solid line in panel b is the linear regression of the data with the
corresponding equation r 2 and P
Figure 5 Southern Great Plains land snails Comparison of y18O of the aragonitic shells of other species used in this study with that of coexisting (a) Vallonia
and (b) Gastrocopta in the breplicationsQ (c) Comparison of y13C values of the shell aragonite of other species with those of coexisting Vallonia andor
Gastrocopta in the same breplicationsQ (see text) Dashed lines are the reference lines y = x
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3020
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composition of vegetation (as well as snail feeding patterns)
is not as variable on small scales as the oxygen isotope
composition of ambient moisture However the apparent
contrast in the respective oxygen and carbon isotope
relationships (adults or juveniles Figs 4 and 6) might also
be in part a consequence of the smaller ranges for the y18O
values Thus if the magnitude of the normal scatter in the
breplicationsQ data were comparable to the smaller total
range of the y18O values it would mask any evidence for a
broader y18
O correlation among genera or age groups
Snail shell isotope compositions and environmental
parameters
Carbon isotopes
As noted vegetation in the study area is dominantly
grasslands at lower elevations and trees at higher
elevations (Fig 1) Based on the nature of the photo-
synthetic pathway plants are classified as C3 C4 or CAM
(eg Jacobs et al 1999) y13C values of C3 plants range
from Agrave33x to Agrave21 x while y13C values of C4 plants
typically range from Agrave17x to Agrave9x (eg Cerling and
Quade 1993) CAM plants have y13C values that range
between the values for C3 and C4 plants (eg Cerling and
Quade 1993) Most of the grasses in the southern Great
Plains are C4 plants (Tieszen et al 1997) and the trees
and most of the forbs are C3 plants (Watson and Dallwitz
httpbiodiversityunoedudelta )
If snail shell y13C values are influenced by the y13C of their diets (eg Balakrishnan and Yapp 2004 Francey
1983 Goodfriend and Ellis 2002 Goodfriend and Magar-
itz 1987 Metref et al 2003 Stott 2002) the spatial
transitions in the ecology of the study corridor suggest that
the y13C values of the shells should be more negative at the
higher elevations toward the west y13C values of the shell
aragonite from all breplicationsQ (Appendix A) and their
averages for each transect (Table 1) are plotted against
elevation in Figures 7a and 7b respectively There is
considerable scatter but some suggestion of the expected
general shift to lower y13C values as altitude increases (Fig
7) However the regional vegetation trend does not explainthe very large range of snail shell y13C values at the lowest
elevations on the eastern end of the sample corridor (Figs
7a and 7b) Such a large range may be explained in part by
local variations in proportions of C3 and C4 plants
Wyckoff et al (1997) and Theler et al (2004)
identified plant species at each sample site in the study
corridor For the current work their identifications (no
quantitative estimates of type) were used to classify the
vegetation in each transect as C3-dominant C4-dominant
or mixed including CAM (Ehleringer et al 1997
Owensby et al 1997 Sage et al 1999 Appalachian
Farming Systems Research Center httpwwwarserrcgov
beckleyC3C4LISThtm ) The classifications are presented
in Table 1
The average y13C values of the land-snail shells from
each transect are listed in Table 1 and plotted in Figure 8
against the corresponding classification of local vegetation
which is arranged in a sequence from C4-dominant to C3-
dominant It is not known if the snails in the region ingest
CAM plants However examined in the manner of Figure
8 it is evident that the y13C values of snail shells of the
southern Great Plains are generally indicative of the type of
vegetation in their immediate environment although there
is still considerable scatter in the relationship In the
regions where C4 plants were identified as the dominant plant type the transect-average y
13C values of the snail
shell aragonite ranged from Agrave43x to Agrave19x with an
overall average of Agrave28x In localities where C3 plants
were documented to be the dominant type these transect-
average values ranged from Agrave101x to Agrave88x with an
overall average of Agrave90x (Fig 8) In the areas with mixed
vegetation types the shell y13C values are within the
extremes defined by the y13C values of the shells in areas
dominated by C3 or C4 plants These observations are in
agreement with earlier observations (Francey 1983 Good-
friend and Ellis 2002 Goodfriend and Magaritz 1987
Metref et al 2003 Stott 2002)
Figure 6 Comparison of coexisting adults and juveniles of southern Great
Plains Vallonia inb
replicationsQ
(see text) (a) y
18
O values of aragoniteshells and (b) y
13C values Solid line in panel b is the linear regression of
the data with the corresponding equation r 2 and P
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For the transects representing the Owensby and Bluff
Creek localities the plant species were not documented but
the relatively negative land-snail shelly13C values suggestthe
possible local dominance of C3 vegetation(hence the question
mark by the C3 symbol on the far right of the abscissa of Fig
8) Some of the scatter in Figure 8 may be a result of the
complicating effects of incorporation of relatively13
C-richdietary carbonate from limestone (eg Goodfriendand Hood
1983 Metref et al 2003 Yates et al 2002)
Oxygen isotopes
Average annual y18O of meteoric water is about Agrave56x at
Norman Oklahoma (USGS unpublished data Martha
Scholl personal communication) in the east and Agrave98 x
at the higher elevations of Clovis New Mexico (Nativ and
Riggio 1990) in the west As suggested by Figure 2 some of
this difference may be a consequence of differing proportions
of precipitation from different moisture sources and air
masses with different histories Irrespective of the particular
mechanisms producing lower y18O values of average annual
precipitation at the higher western elevations if the dominant
control on the y18O value of the snail shell aragonite was the
y18O value of annual precipitation the shell y18O should be
lower at higher altitude Figure 9a depicts snail shell y18O
values plotted against altitude for all of the analyzed
breplications
Q (Appendix A) There is no correlation of shell
y18O with elevation evident in Figure 9a
Average y18O values of samples in each transect are listed
in Table 1 and plotted against elevation in Figure 9b For the
transect-average values in Figure 9b there may be a weak
relationship of shell y18O with altitude indicating some
tendency for a decrease of shell y18O with increasing
elevation For an increase in elevation of ~2000 m the slope
of the linear regression indicates a decrease in shell y18O of
only ~1x However even if this weak correlation in Figure
9b was significant a decrease of ~1x is much less than the
decrease of ~4x expected if the y18O of annual precipitation
were the principal control on shell y18O values
Table 1
Transect averages (all species) of measured shell y13C and y
18O
Locality Transect Elevationa (m) Plant type Transect average Average y18O Model calculations
y13C y
18O Calculated locality y18Ocalc D
18O
Kubic 6 329 C3 Agrave85 Agrave21 Agrave20 Agrave22 Agrave02
Kubic 5 351 C4 Agrave35 Agrave19
Kubic 2 360 C4 C3 Agrave48 Agrave21Kubic 4 360 C4 Agrave23 Agrave17
Kubic 3 366 C4 Agrave19 Agrave01
Bluff Creek 36 348 C3 Agrave84 Agrave12 Agrave12 Agrave15 Agrave03
Salt Fork 9 320 C3 Agrave101 Agrave19 Agrave19 Agrave15 04
McDaniel 11 375 C4 C3 Agrave76 Agrave22 Agrave22 Agrave14 08
Burnham 17 519 C4 C3 Agrave83 Agrave08 Agrave10 Agrave09 01
Burnham 16 567 C4 CAM C3 Agrave54 Agrave18
Burnham 12 607 C4 C3 Agrave58 Agrave23
Burnham 14 607 C4 CAM C3 Agrave41 Agrave13
Burnham 13 610 C4 Agrave43 Agrave01
Big Salt Plain 15 482 C3 Agrave89 Agrave04 Agrave04 Agrave09 Agrave05
Skull Springs 18 671 C4 CAM C3 Agrave60 Agrave16 Agrave16 Agrave03 13
Skull Springs 19 665 C4 C3 Agrave40 Agrave17
Hitch 22 915 C4 CAM Agrave51 Agrave15 Agrave18 Agrave25 Agrave07
Hitch 21 933 C4 CAM C3 Agrave50 Agrave06Hitch 23 881 C3 Agrave85 Agrave23
Black Mesa 27 1312 C4 C3 Agrave61 Agrave27 Agrave22 Agrave21 01
Black Mesa 26 1324 C4 CAM C3 Agrave66 Agrave15
Black Mesa 24 1488 C4 CAM Agrave26 Agrave17
Black Mesa 25 1464 C4 CAM C3 Agrave72 Agrave25
Black Mesa 35 1464 C4 CAM C3 Agrave75 Agrave18
Owensby 61 2193 C3 Agrave105 Agrave19 Agrave20 Agrave25 Agrave05
Owensby 60 2242 C3 Agrave96 Agrave30
Owensby 59 2288 C3 Agrave109 Agrave19
CS Ranch 30 1922 C4 CAM C3 Agrave43 Agrave19 Agrave20 Agrave25 Agrave05
CS Ranch 29 1940 C4 CAM C3 Agrave49 Agrave25
Chase 34 1952 C4 C3 Agrave92 Agrave38 Agrave25 Agrave25 00
Chase 33 2184 C4 C3 Agrave86 Agrave22
Chase 31 2220 C4 C3 Agrave90 Agrave25
Chase 32 2233 C4 C3 Agrave89 Agrave23
Locality averages of measured y18O Also y
18O of shell at a locality as predicted from model calculations for diffusive evaporation (y18Ocalc) D18O =
y18Ocalc Agrave y
18Omeasa Sea level datum
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The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
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sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
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temperature of condensation are among the controls onthe isotopic composition of precipitation (Dansgaard
1964 Rozanski et al 1993) The different air masses
that contribute precipitation to the southern Plains impart
seasonally distinct y18O values to the rain andor snow
y18O values of summer rains originating from Gulf of
Mexico moisture are more positive than those of winter
precipitation originating from the North Pacific Ocean
(Nativ and Riggio 1990) This is primarily a consequence
of the higher elevations (lower temperatures) and longer
transport distances experienced by air masses from the
North Pacific (Nativ and Riggio 1990 Rozanski et al
1993)
Experimental
Sampling systematics
Results of an initial survey collection and documentation
of the modern gastropods in this region are found in Wyckoff
et al (1997) and Theler et al (2004) These include
description of the dominant vegetation types at each locality
Collections of the snails analyzed for the current work were
made at 12 localities along the 640-km sample corridor at
sites for which living snails could be expected (for sample
collection rationale see Theler et al 2004) Each sample
locality was restricted to a circle with a diameter of ~400 m
Figure 1 Map of the study area in the southern Great Plains of North America indicating the collection localities and the major ecological regions Localities 1
Kubic 2 Bluff Creek 3 Salt Fork 4 McDaniel 5 Burnham 6 Big Salt Plain 7 Skull Springs 8 Hitch 9 Black Mesa 10 Owensby 11 C S Ranch 12 Chase
(data sources Blair and Hubbell 1938 Carpenter 1940 Shelford 1963 Wyckoff et al 1997 Theler et al 2004)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 17
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(Theler et al 2004 Wyckoff et al 1997) Each circle
contained several niches Niches (recognized by differences
in vegetation slope and aspect) favorable for snail habitation
were sampled along a linear btransect Q (Theler et al 2004
Wyckoff et al 1997) that was usually not more than 100 m in
length Along each transect there were three sample
collection sites (usually 10ndash20 m apart) called breplicationsQ
A B and C (Wyckoff et al 1997) The term bsampleQ was
substituted for breplicationQ by Theler et al (2004) However
in the current work we will retain breplicationQ (sensu
Wyckoff et al 1997) to avoid confusion with our more
generic use of the term bsampleQ which refers herein to any
collected material of interest Thus as an example the
sample locality bHitchQ has three transects (Hitch 21 Hitch
22 and Hitch 23) with each transect in Hitch in turn
comprised of three replications (eg Hitch 21A Hitch 21Band Hitch 21C) There is a total of 38 transects among the 12
localities and a total of 114 breplicationsQ summed over all of
the 38 transects (ie 3 Acirc 38) At each breplicationQ lower
parts of growing vegetation decaying vegetation and 2 cm
of topsoil from a 50 Acirc 50 cm area were collected (Wyckoff et
al 1997 Theler et al 2004) Wyckoff et al (1997) and
Theler et al (2004) sieved and sorted these samples in the
laboratory to extract the snail shells followed by identifica-
tion and population analyses
Because of the destructive nature of the isotopic analyses
and because it was necessary to retain snail shells for
archival purposes only those from sample sites represented
by large numbers of collected shells were analyzed Hence
of the total of 114 breplicationsQ among the 38 transects
only 71 replications from 34 transects are represented in this
study Most of the samples were collected in 1995
(collection from the Owensby site was made in 1996) and
were alive at the time or within 1 yr of collection (Theler et
al 2004 Wyckoff et al 1997)
Selection of species for isotopic analyses
Vallonia and Gastrocopta were the principal genera
employed for isotopic analyses of snail shells because they
are present throughout most or all of the study area (Theler
et al 2004 Wyckoff et al 1997) For some localities
snails representing a few other genera were also isotopically
analyzed but these other genera did not have the widedistribution exhibited by Vallonia or Gastrocopta The
genus Vallonia is represented by the species Vallonia
parvula at the lower elevations and Vallonia gracilicosta
at the higher elevations The latter is often associated with
deposits of Pleistocene age in the southern Great Plains
(Rossignol et al 2004 Theler et al 2004 Wyckoff et al
1997) Vallonia juveniles were also analyzed but could not
be identified at the species level (Theler et al 2004
Wyckoff et al 1997) The genus Gastrocopta was
represented by Gastrocopta contracta Gastrocopta holzin-
geri Gastrocopta pentodon Gastrocopta armifera Gastro-
copta cristata Gastrocopta pilsbryana Gastrocopta
Figure 2 Source regions and generalized trajectories of major moisture-bearing air masses that bring precipitation to the southern Great Plains of North
America Trajectory (a) March into July or August (b) middle to late summer and early fall (c) October to early March (see text) mP = maritime polar air
mass and mT = maritime tropical air mass (after Elliot 1949 Nativ and Riggio 1990) The shaded rectangle encompasses the land snail sites of Figure 1
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procera and Gastrocopta pellucida The two latter species
exhibit relatively large distribution ranges However G
procera was notably absent at the higher altitudes in the
survey (Theler et al 2004 Wyckoff et al 1997)
Laboratory preparations and analyses
Each isotopically analyzed sample consisted of multiple
entire shells of adults of a particular species (or genus for
juveniles of Vallonia) from a breplicationQ The shells were
initially rinsed with deionized water then treated ultrasoni-
cally in deionized water to remove any adhering particles of
organic matter or other debris The shells were gently crushed
and treated with 5 reagent-grade sodium hypochlorite at
room temperature for about 7ndash8 h to remove organic matter
They were then rinsed thoroughly with deionized water and
dried in air at about 40ndash508C The shell fragments were
subsequently reacted overnight in vacuum with 100 H3PO4
at 258
C following the method of McCrea (1950) The CO2
prepared from the shell aragonite was analyzed for y13C and
y18O on a Finnigan MAT 252 mass spectrometer Analytical
uncertainty is about F01x The y values are defined as
y13C or y18O frac14 R sample=R standard
Agrave AacuteAgrave 1
Acirc AtildeAcirc 1000 x
where R = 13C 12C or 18O 16O y13C and y18O are reported
relative to the PDB standard (Craig 1957)
Results and discussions
Ranges of d18O and d13C of aragonite in land-snail shells
y18O and y
13C values were measured for 162 samples
from the 12 localities of Figure 1 (see Appendix A) y18O
values of the aragonite shells of these modern snails ranged
from Agrave41x to 12x (Fig 3) Published y18O values of
shells from globally distributed modern land snails that are
wholly subaerial (as opposed to semiaquatic) range from
Agrave117x to 45x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Goodfriend et al 1989 Lecolle 1985
Magaritz and Heller 1980 Magaritz et al 1981 Sharpe et
al 1994 Yapp 1979) In North America reported y18O
values of land-snail shells range from Agrave117x to 02x(Goodfriend and Ellis 2002 Sharpe et al 1994 Yapp
1979) If the results for a carnivorous cold-tolerant snail of
the genus Vitrina (Sharpe et al 1994) from Deer Creek
Nevada are excluded y18O values analyzed to date for
North America range from Agrave58x to 02x The current
work extends the upper range of North American values by
10x (Fig 3)
Previous studies of y13C values of shell aragonite from
snails in their natural settings reported values ranging from
Agrave135x to 05x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Lecolle 1983 1984 Magaritz and
Heller 1980 1983 Magaritz et al 1981 Yapp 1979) For
North America published y13C values range from Agrave125x
to Agrave25x (Goodfriend and Ellis 2002 Yapp 1979) The
y13C values of snail shell aragonite studied for the current
work range from Agrave132x to 00x (Fig 3) By contrast
y13C values of shell aragonite of experimentally cultured
Helix aspersa that were fed a controlled diet ranged from
Agrave243x to 25x (Stott 2002) Controlled experiments also
indicate differences in y13C values among adults hatched
and 1-month-old individuals of H aspersa fed diets with
identical y13C values (Metref et al 2003)
Snail shell isotopic variation among populations
Variations in the isotopic composition of snail shells exist
among replications within a transect and also among species
in a replication (Appendix A) Within a sample locality
small-scale variations in topography vegetation local
moisture availability snail ages physiology etc are
expected Such variations might contribute to the observed
scatter in isotopic ratios among genera species or
individual samples
Isotopic analyses of Vallonia and Gastrocopta total 143
and represent the majority of the analyzed shell samples but
Figure 3 Ranges of Southern Great Plains land snails and snail shell y18O
and y13C values measured for breplicationsQ in the current study compared
with various published ranges (see text) Open portion of the range of North
Americany18
O values encompasses the values reported for shells from acarnivorous cold-tolerant snail (see text for reference)
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there were also analyses (numbers in parentheses) of
bunderrepresentedQ genera as follows (see Appendix A)
Pupoides (9) Succineidae (3) Pupilla (2) Cionella (1)
Zonitoides (1) Helicodiscus (1) Glyphyalinia (1) and
Hawaiia (1) The ranges of y18O values for Vallonia and
Gastrocopta are about 28x and 20x respectively (Fig
4a) Corresponding y18O values of Vallonia and Gastrocopta
indicate no correlation among the various sites (Fig 4a) A
similar lack of correlation was evident when y18O values of
underrepresented genera were compared wit h values for
coexisting Vallonia (Fig 5a) or Gastrocopta (Fig 5b) The
particular origins of these differences are unknown Without
studies under controlled age and environmental conditions
(eg Metref et al 2003 Stott 2002) distinguishing micro-environmental effects from the effects of age andor species-
related physiological differences is not possible at present
The respective ranges of y13C values for Vallonia and
Gastrocopta shell aragonite are each about 8ndash9x and
samples from the same breplicationsQ show a significant
correlation (Fig 4b) This correlation could indicate similar
feeding habits in both genera making them potential sources
of isotopic information on the paleoecology of a locale
Because of this correlation of Vallonia and Gastrocopta y13C
values y13C values of eight other genera that coexisted with
one or both of these genera in the various breplicationsQ are
plotted against y13
C of either Vallonia or Gastrocopta in asingle figure (Fig 5c) There are insufficient data to establish
whether the y13C values of any of the bunderrepresentedQ
genera might be correlated with Vallonia or Gastrocopta but
overall there is considerable scatter among the species
Additional comparative analyses of and controlled experi-
ments on these genera are needed
An exploratory evaluation of the effect of life histories
and ages on the isotopic composition of snails was
attempted using the data for adult and juvenile Vallonia
(see Appendix A) y18O values of shells of coexisting adult
and juvenile Vall onia from the breplicationsQ are not
correlated (Fig 6a) The y18O values of the adult snails
represent averages over longer periods of time than those of
the juveniles Short time scale environmental conditions that
affect the y18O values of the body fluid in juveniles should
determine the y18O values of the shell aragonite and these
conditions might contrast with the longer term-averages of
the adults
The absence of a correlation in the y18O data of Figure 6a
contrasts with the good correlation of the y13C values of the
adults and juveniles in Figure 6b The y13C correlation
could indicate that in these locales the carbon isotope
Figure 4 Southern Great Plains land snails Comparison of average
isotopic compositions of the aragonitic shells of Gastrocopta and Vallonia
from the same breplicationsQ (see text) (a) comparison of y18O values and
(b) comparison of y13
C values Dashed line in panel a is the reference liney = x Solid line in panel b is the linear regression of the data with the
corresponding equation r 2 and P
Figure 5 Southern Great Plains land snails Comparison of y18O of the aragonitic shells of other species used in this study with that of coexisting (a) Vallonia
and (b) Gastrocopta in the breplicationsQ (c) Comparison of y13C values of the shell aragonite of other species with those of coexisting Vallonia andor
Gastrocopta in the same breplicationsQ (see text) Dashed lines are the reference lines y = x
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composition of vegetation (as well as snail feeding patterns)
is not as variable on small scales as the oxygen isotope
composition of ambient moisture However the apparent
contrast in the respective oxygen and carbon isotope
relationships (adults or juveniles Figs 4 and 6) might also
be in part a consequence of the smaller ranges for the y18O
values Thus if the magnitude of the normal scatter in the
breplicationsQ data were comparable to the smaller total
range of the y18O values it would mask any evidence for a
broader y18
O correlation among genera or age groups
Snail shell isotope compositions and environmental
parameters
Carbon isotopes
As noted vegetation in the study area is dominantly
grasslands at lower elevations and trees at higher
elevations (Fig 1) Based on the nature of the photo-
synthetic pathway plants are classified as C3 C4 or CAM
(eg Jacobs et al 1999) y13C values of C3 plants range
from Agrave33x to Agrave21 x while y13C values of C4 plants
typically range from Agrave17x to Agrave9x (eg Cerling and
Quade 1993) CAM plants have y13C values that range
between the values for C3 and C4 plants (eg Cerling and
Quade 1993) Most of the grasses in the southern Great
Plains are C4 plants (Tieszen et al 1997) and the trees
and most of the forbs are C3 plants (Watson and Dallwitz
httpbiodiversityunoedudelta )
If snail shell y13C values are influenced by the y13C of their diets (eg Balakrishnan and Yapp 2004 Francey
1983 Goodfriend and Ellis 2002 Goodfriend and Magar-
itz 1987 Metref et al 2003 Stott 2002) the spatial
transitions in the ecology of the study corridor suggest that
the y13C values of the shells should be more negative at the
higher elevations toward the west y13C values of the shell
aragonite from all breplicationsQ (Appendix A) and their
averages for each transect (Table 1) are plotted against
elevation in Figures 7a and 7b respectively There is
considerable scatter but some suggestion of the expected
general shift to lower y13C values as altitude increases (Fig
7) However the regional vegetation trend does not explainthe very large range of snail shell y13C values at the lowest
elevations on the eastern end of the sample corridor (Figs
7a and 7b) Such a large range may be explained in part by
local variations in proportions of C3 and C4 plants
Wyckoff et al (1997) and Theler et al (2004)
identified plant species at each sample site in the study
corridor For the current work their identifications (no
quantitative estimates of type) were used to classify the
vegetation in each transect as C3-dominant C4-dominant
or mixed including CAM (Ehleringer et al 1997
Owensby et al 1997 Sage et al 1999 Appalachian
Farming Systems Research Center httpwwwarserrcgov
beckleyC3C4LISThtm ) The classifications are presented
in Table 1
The average y13C values of the land-snail shells from
each transect are listed in Table 1 and plotted in Figure 8
against the corresponding classification of local vegetation
which is arranged in a sequence from C4-dominant to C3-
dominant It is not known if the snails in the region ingest
CAM plants However examined in the manner of Figure
8 it is evident that the y13C values of snail shells of the
southern Great Plains are generally indicative of the type of
vegetation in their immediate environment although there
is still considerable scatter in the relationship In the
regions where C4 plants were identified as the dominant plant type the transect-average y
13C values of the snail
shell aragonite ranged from Agrave43x to Agrave19x with an
overall average of Agrave28x In localities where C3 plants
were documented to be the dominant type these transect-
average values ranged from Agrave101x to Agrave88x with an
overall average of Agrave90x (Fig 8) In the areas with mixed
vegetation types the shell y13C values are within the
extremes defined by the y13C values of the shells in areas
dominated by C3 or C4 plants These observations are in
agreement with earlier observations (Francey 1983 Good-
friend and Ellis 2002 Goodfriend and Magaritz 1987
Metref et al 2003 Stott 2002)
Figure 6 Comparison of coexisting adults and juveniles of southern Great
Plains Vallonia inb
replicationsQ
(see text) (a) y
18
O values of aragoniteshells and (b) y
13C values Solid line in panel b is the linear regression of
the data with the corresponding equation r 2 and P
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For the transects representing the Owensby and Bluff
Creek localities the plant species were not documented but
the relatively negative land-snail shelly13C values suggestthe
possible local dominance of C3 vegetation(hence the question
mark by the C3 symbol on the far right of the abscissa of Fig
8) Some of the scatter in Figure 8 may be a result of the
complicating effects of incorporation of relatively13
C-richdietary carbonate from limestone (eg Goodfriendand Hood
1983 Metref et al 2003 Yates et al 2002)
Oxygen isotopes
Average annual y18O of meteoric water is about Agrave56x at
Norman Oklahoma (USGS unpublished data Martha
Scholl personal communication) in the east and Agrave98 x
at the higher elevations of Clovis New Mexico (Nativ and
Riggio 1990) in the west As suggested by Figure 2 some of
this difference may be a consequence of differing proportions
of precipitation from different moisture sources and air
masses with different histories Irrespective of the particular
mechanisms producing lower y18O values of average annual
precipitation at the higher western elevations if the dominant
control on the y18O value of the snail shell aragonite was the
y18O value of annual precipitation the shell y18O should be
lower at higher altitude Figure 9a depicts snail shell y18O
values plotted against altitude for all of the analyzed
breplications
Q (Appendix A) There is no correlation of shell
y18O with elevation evident in Figure 9a
Average y18O values of samples in each transect are listed
in Table 1 and plotted against elevation in Figure 9b For the
transect-average values in Figure 9b there may be a weak
relationship of shell y18O with altitude indicating some
tendency for a decrease of shell y18O with increasing
elevation For an increase in elevation of ~2000 m the slope
of the linear regression indicates a decrease in shell y18O of
only ~1x However even if this weak correlation in Figure
9b was significant a decrease of ~1x is much less than the
decrease of ~4x expected if the y18O of annual precipitation
were the principal control on shell y18O values
Table 1
Transect averages (all species) of measured shell y13C and y
18O
Locality Transect Elevationa (m) Plant type Transect average Average y18O Model calculations
y13C y
18O Calculated locality y18Ocalc D
18O
Kubic 6 329 C3 Agrave85 Agrave21 Agrave20 Agrave22 Agrave02
Kubic 5 351 C4 Agrave35 Agrave19
Kubic 2 360 C4 C3 Agrave48 Agrave21Kubic 4 360 C4 Agrave23 Agrave17
Kubic 3 366 C4 Agrave19 Agrave01
Bluff Creek 36 348 C3 Agrave84 Agrave12 Agrave12 Agrave15 Agrave03
Salt Fork 9 320 C3 Agrave101 Agrave19 Agrave19 Agrave15 04
McDaniel 11 375 C4 C3 Agrave76 Agrave22 Agrave22 Agrave14 08
Burnham 17 519 C4 C3 Agrave83 Agrave08 Agrave10 Agrave09 01
Burnham 16 567 C4 CAM C3 Agrave54 Agrave18
Burnham 12 607 C4 C3 Agrave58 Agrave23
Burnham 14 607 C4 CAM C3 Agrave41 Agrave13
Burnham 13 610 C4 Agrave43 Agrave01
Big Salt Plain 15 482 C3 Agrave89 Agrave04 Agrave04 Agrave09 Agrave05
Skull Springs 18 671 C4 CAM C3 Agrave60 Agrave16 Agrave16 Agrave03 13
Skull Springs 19 665 C4 C3 Agrave40 Agrave17
Hitch 22 915 C4 CAM Agrave51 Agrave15 Agrave18 Agrave25 Agrave07
Hitch 21 933 C4 CAM C3 Agrave50 Agrave06Hitch 23 881 C3 Agrave85 Agrave23
Black Mesa 27 1312 C4 C3 Agrave61 Agrave27 Agrave22 Agrave21 01
Black Mesa 26 1324 C4 CAM C3 Agrave66 Agrave15
Black Mesa 24 1488 C4 CAM Agrave26 Agrave17
Black Mesa 25 1464 C4 CAM C3 Agrave72 Agrave25
Black Mesa 35 1464 C4 CAM C3 Agrave75 Agrave18
Owensby 61 2193 C3 Agrave105 Agrave19 Agrave20 Agrave25 Agrave05
Owensby 60 2242 C3 Agrave96 Agrave30
Owensby 59 2288 C3 Agrave109 Agrave19
CS Ranch 30 1922 C4 CAM C3 Agrave43 Agrave19 Agrave20 Agrave25 Agrave05
CS Ranch 29 1940 C4 CAM C3 Agrave49 Agrave25
Chase 34 1952 C4 C3 Agrave92 Agrave38 Agrave25 Agrave25 00
Chase 33 2184 C4 C3 Agrave86 Agrave22
Chase 31 2220 C4 C3 Agrave90 Agrave25
Chase 32 2233 C4 C3 Agrave89 Agrave23
Locality averages of measured y18O Also y
18O of shell at a locality as predicted from model calculations for diffusive evaporation (y18Ocalc) D18O =
y18Ocalc Agrave y
18Omeasa Sea level datum
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The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
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sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
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determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
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(Theler et al 2004 Wyckoff et al 1997) Each circle
contained several niches Niches (recognized by differences
in vegetation slope and aspect) favorable for snail habitation
were sampled along a linear btransect Q (Theler et al 2004
Wyckoff et al 1997) that was usually not more than 100 m in
length Along each transect there were three sample
collection sites (usually 10ndash20 m apart) called breplicationsQ
A B and C (Wyckoff et al 1997) The term bsampleQ was
substituted for breplicationQ by Theler et al (2004) However
in the current work we will retain breplicationQ (sensu
Wyckoff et al 1997) to avoid confusion with our more
generic use of the term bsampleQ which refers herein to any
collected material of interest Thus as an example the
sample locality bHitchQ has three transects (Hitch 21 Hitch
22 and Hitch 23) with each transect in Hitch in turn
comprised of three replications (eg Hitch 21A Hitch 21Band Hitch 21C) There is a total of 38 transects among the 12
localities and a total of 114 breplicationsQ summed over all of
the 38 transects (ie 3 Acirc 38) At each breplicationQ lower
parts of growing vegetation decaying vegetation and 2 cm
of topsoil from a 50 Acirc 50 cm area were collected (Wyckoff et
al 1997 Theler et al 2004) Wyckoff et al (1997) and
Theler et al (2004) sieved and sorted these samples in the
laboratory to extract the snail shells followed by identifica-
tion and population analyses
Because of the destructive nature of the isotopic analyses
and because it was necessary to retain snail shells for
archival purposes only those from sample sites represented
by large numbers of collected shells were analyzed Hence
of the total of 114 breplicationsQ among the 38 transects
only 71 replications from 34 transects are represented in this
study Most of the samples were collected in 1995
(collection from the Owensby site was made in 1996) and
were alive at the time or within 1 yr of collection (Theler et
al 2004 Wyckoff et al 1997)
Selection of species for isotopic analyses
Vallonia and Gastrocopta were the principal genera
employed for isotopic analyses of snail shells because they
are present throughout most or all of the study area (Theler
et al 2004 Wyckoff et al 1997) For some localities
snails representing a few other genera were also isotopically
analyzed but these other genera did not have the widedistribution exhibited by Vallonia or Gastrocopta The
genus Vallonia is represented by the species Vallonia
parvula at the lower elevations and Vallonia gracilicosta
at the higher elevations The latter is often associated with
deposits of Pleistocene age in the southern Great Plains
(Rossignol et al 2004 Theler et al 2004 Wyckoff et al
1997) Vallonia juveniles were also analyzed but could not
be identified at the species level (Theler et al 2004
Wyckoff et al 1997) The genus Gastrocopta was
represented by Gastrocopta contracta Gastrocopta holzin-
geri Gastrocopta pentodon Gastrocopta armifera Gastro-
copta cristata Gastrocopta pilsbryana Gastrocopta
Figure 2 Source regions and generalized trajectories of major moisture-bearing air masses that bring precipitation to the southern Great Plains of North
America Trajectory (a) March into July or August (b) middle to late summer and early fall (c) October to early March (see text) mP = maritime polar air
mass and mT = maritime tropical air mass (after Elliot 1949 Nativ and Riggio 1990) The shaded rectangle encompasses the land snail sites of Figure 1
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3018
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procera and Gastrocopta pellucida The two latter species
exhibit relatively large distribution ranges However G
procera was notably absent at the higher altitudes in the
survey (Theler et al 2004 Wyckoff et al 1997)
Laboratory preparations and analyses
Each isotopically analyzed sample consisted of multiple
entire shells of adults of a particular species (or genus for
juveniles of Vallonia) from a breplicationQ The shells were
initially rinsed with deionized water then treated ultrasoni-
cally in deionized water to remove any adhering particles of
organic matter or other debris The shells were gently crushed
and treated with 5 reagent-grade sodium hypochlorite at
room temperature for about 7ndash8 h to remove organic matter
They were then rinsed thoroughly with deionized water and
dried in air at about 40ndash508C The shell fragments were
subsequently reacted overnight in vacuum with 100 H3PO4
at 258
C following the method of McCrea (1950) The CO2
prepared from the shell aragonite was analyzed for y13C and
y18O on a Finnigan MAT 252 mass spectrometer Analytical
uncertainty is about F01x The y values are defined as
y13C or y18O frac14 R sample=R standard
Agrave AacuteAgrave 1
Acirc AtildeAcirc 1000 x
where R = 13C 12C or 18O 16O y13C and y18O are reported
relative to the PDB standard (Craig 1957)
Results and discussions
Ranges of d18O and d13C of aragonite in land-snail shells
y18O and y
13C values were measured for 162 samples
from the 12 localities of Figure 1 (see Appendix A) y18O
values of the aragonite shells of these modern snails ranged
from Agrave41x to 12x (Fig 3) Published y18O values of
shells from globally distributed modern land snails that are
wholly subaerial (as opposed to semiaquatic) range from
Agrave117x to 45x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Goodfriend et al 1989 Lecolle 1985
Magaritz and Heller 1980 Magaritz et al 1981 Sharpe et
al 1994 Yapp 1979) In North America reported y18O
values of land-snail shells range from Agrave117x to 02x(Goodfriend and Ellis 2002 Sharpe et al 1994 Yapp
1979) If the results for a carnivorous cold-tolerant snail of
the genus Vitrina (Sharpe et al 1994) from Deer Creek
Nevada are excluded y18O values analyzed to date for
North America range from Agrave58x to 02x The current
work extends the upper range of North American values by
10x (Fig 3)
Previous studies of y13C values of shell aragonite from
snails in their natural settings reported values ranging from
Agrave135x to 05x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Lecolle 1983 1984 Magaritz and
Heller 1980 1983 Magaritz et al 1981 Yapp 1979) For
North America published y13C values range from Agrave125x
to Agrave25x (Goodfriend and Ellis 2002 Yapp 1979) The
y13C values of snail shell aragonite studied for the current
work range from Agrave132x to 00x (Fig 3) By contrast
y13C values of shell aragonite of experimentally cultured
Helix aspersa that were fed a controlled diet ranged from
Agrave243x to 25x (Stott 2002) Controlled experiments also
indicate differences in y13C values among adults hatched
and 1-month-old individuals of H aspersa fed diets with
identical y13C values (Metref et al 2003)
Snail shell isotopic variation among populations
Variations in the isotopic composition of snail shells exist
among replications within a transect and also among species
in a replication (Appendix A) Within a sample locality
small-scale variations in topography vegetation local
moisture availability snail ages physiology etc are
expected Such variations might contribute to the observed
scatter in isotopic ratios among genera species or
individual samples
Isotopic analyses of Vallonia and Gastrocopta total 143
and represent the majority of the analyzed shell samples but
Figure 3 Ranges of Southern Great Plains land snails and snail shell y18O
and y13C values measured for breplicationsQ in the current study compared
with various published ranges (see text) Open portion of the range of North
Americany18
O values encompasses the values reported for shells from acarnivorous cold-tolerant snail (see text for reference)
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there were also analyses (numbers in parentheses) of
bunderrepresentedQ genera as follows (see Appendix A)
Pupoides (9) Succineidae (3) Pupilla (2) Cionella (1)
Zonitoides (1) Helicodiscus (1) Glyphyalinia (1) and
Hawaiia (1) The ranges of y18O values for Vallonia and
Gastrocopta are about 28x and 20x respectively (Fig
4a) Corresponding y18O values of Vallonia and Gastrocopta
indicate no correlation among the various sites (Fig 4a) A
similar lack of correlation was evident when y18O values of
underrepresented genera were compared wit h values for
coexisting Vallonia (Fig 5a) or Gastrocopta (Fig 5b) The
particular origins of these differences are unknown Without
studies under controlled age and environmental conditions
(eg Metref et al 2003 Stott 2002) distinguishing micro-environmental effects from the effects of age andor species-
related physiological differences is not possible at present
The respective ranges of y13C values for Vallonia and
Gastrocopta shell aragonite are each about 8ndash9x and
samples from the same breplicationsQ show a significant
correlation (Fig 4b) This correlation could indicate similar
feeding habits in both genera making them potential sources
of isotopic information on the paleoecology of a locale
Because of this correlation of Vallonia and Gastrocopta y13C
values y13C values of eight other genera that coexisted with
one or both of these genera in the various breplicationsQ are
plotted against y13
C of either Vallonia or Gastrocopta in asingle figure (Fig 5c) There are insufficient data to establish
whether the y13C values of any of the bunderrepresentedQ
genera might be correlated with Vallonia or Gastrocopta but
overall there is considerable scatter among the species
Additional comparative analyses of and controlled experi-
ments on these genera are needed
An exploratory evaluation of the effect of life histories
and ages on the isotopic composition of snails was
attempted using the data for adult and juvenile Vallonia
(see Appendix A) y18O values of shells of coexisting adult
and juvenile Vall onia from the breplicationsQ are not
correlated (Fig 6a) The y18O values of the adult snails
represent averages over longer periods of time than those of
the juveniles Short time scale environmental conditions that
affect the y18O values of the body fluid in juveniles should
determine the y18O values of the shell aragonite and these
conditions might contrast with the longer term-averages of
the adults
The absence of a correlation in the y18O data of Figure 6a
contrasts with the good correlation of the y13C values of the
adults and juveniles in Figure 6b The y13C correlation
could indicate that in these locales the carbon isotope
Figure 4 Southern Great Plains land snails Comparison of average
isotopic compositions of the aragonitic shells of Gastrocopta and Vallonia
from the same breplicationsQ (see text) (a) comparison of y18O values and
(b) comparison of y13
C values Dashed line in panel a is the reference liney = x Solid line in panel b is the linear regression of the data with the
corresponding equation r 2 and P
Figure 5 Southern Great Plains land snails Comparison of y18O of the aragonitic shells of other species used in this study with that of coexisting (a) Vallonia
and (b) Gastrocopta in the breplicationsQ (c) Comparison of y13C values of the shell aragonite of other species with those of coexisting Vallonia andor
Gastrocopta in the same breplicationsQ (see text) Dashed lines are the reference lines y = x
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composition of vegetation (as well as snail feeding patterns)
is not as variable on small scales as the oxygen isotope
composition of ambient moisture However the apparent
contrast in the respective oxygen and carbon isotope
relationships (adults or juveniles Figs 4 and 6) might also
be in part a consequence of the smaller ranges for the y18O
values Thus if the magnitude of the normal scatter in the
breplicationsQ data were comparable to the smaller total
range of the y18O values it would mask any evidence for a
broader y18
O correlation among genera or age groups
Snail shell isotope compositions and environmental
parameters
Carbon isotopes
As noted vegetation in the study area is dominantly
grasslands at lower elevations and trees at higher
elevations (Fig 1) Based on the nature of the photo-
synthetic pathway plants are classified as C3 C4 or CAM
(eg Jacobs et al 1999) y13C values of C3 plants range
from Agrave33x to Agrave21 x while y13C values of C4 plants
typically range from Agrave17x to Agrave9x (eg Cerling and
Quade 1993) CAM plants have y13C values that range
between the values for C3 and C4 plants (eg Cerling and
Quade 1993) Most of the grasses in the southern Great
Plains are C4 plants (Tieszen et al 1997) and the trees
and most of the forbs are C3 plants (Watson and Dallwitz
httpbiodiversityunoedudelta )
If snail shell y13C values are influenced by the y13C of their diets (eg Balakrishnan and Yapp 2004 Francey
1983 Goodfriend and Ellis 2002 Goodfriend and Magar-
itz 1987 Metref et al 2003 Stott 2002) the spatial
transitions in the ecology of the study corridor suggest that
the y13C values of the shells should be more negative at the
higher elevations toward the west y13C values of the shell
aragonite from all breplicationsQ (Appendix A) and their
averages for each transect (Table 1) are plotted against
elevation in Figures 7a and 7b respectively There is
considerable scatter but some suggestion of the expected
general shift to lower y13C values as altitude increases (Fig
7) However the regional vegetation trend does not explainthe very large range of snail shell y13C values at the lowest
elevations on the eastern end of the sample corridor (Figs
7a and 7b) Such a large range may be explained in part by
local variations in proportions of C3 and C4 plants
Wyckoff et al (1997) and Theler et al (2004)
identified plant species at each sample site in the study
corridor For the current work their identifications (no
quantitative estimates of type) were used to classify the
vegetation in each transect as C3-dominant C4-dominant
or mixed including CAM (Ehleringer et al 1997
Owensby et al 1997 Sage et al 1999 Appalachian
Farming Systems Research Center httpwwwarserrcgov
beckleyC3C4LISThtm ) The classifications are presented
in Table 1
The average y13C values of the land-snail shells from
each transect are listed in Table 1 and plotted in Figure 8
against the corresponding classification of local vegetation
which is arranged in a sequence from C4-dominant to C3-
dominant It is not known if the snails in the region ingest
CAM plants However examined in the manner of Figure
8 it is evident that the y13C values of snail shells of the
southern Great Plains are generally indicative of the type of
vegetation in their immediate environment although there
is still considerable scatter in the relationship In the
regions where C4 plants were identified as the dominant plant type the transect-average y
13C values of the snail
shell aragonite ranged from Agrave43x to Agrave19x with an
overall average of Agrave28x In localities where C3 plants
were documented to be the dominant type these transect-
average values ranged from Agrave101x to Agrave88x with an
overall average of Agrave90x (Fig 8) In the areas with mixed
vegetation types the shell y13C values are within the
extremes defined by the y13C values of the shells in areas
dominated by C3 or C4 plants These observations are in
agreement with earlier observations (Francey 1983 Good-
friend and Ellis 2002 Goodfriend and Magaritz 1987
Metref et al 2003 Stott 2002)
Figure 6 Comparison of coexisting adults and juveniles of southern Great
Plains Vallonia inb
replicationsQ
(see text) (a) y
18
O values of aragoniteshells and (b) y
13C values Solid line in panel b is the linear regression of
the data with the corresponding equation r 2 and P
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For the transects representing the Owensby and Bluff
Creek localities the plant species were not documented but
the relatively negative land-snail shelly13C values suggestthe
possible local dominance of C3 vegetation(hence the question
mark by the C3 symbol on the far right of the abscissa of Fig
8) Some of the scatter in Figure 8 may be a result of the
complicating effects of incorporation of relatively13
C-richdietary carbonate from limestone (eg Goodfriendand Hood
1983 Metref et al 2003 Yates et al 2002)
Oxygen isotopes
Average annual y18O of meteoric water is about Agrave56x at
Norman Oklahoma (USGS unpublished data Martha
Scholl personal communication) in the east and Agrave98 x
at the higher elevations of Clovis New Mexico (Nativ and
Riggio 1990) in the west As suggested by Figure 2 some of
this difference may be a consequence of differing proportions
of precipitation from different moisture sources and air
masses with different histories Irrespective of the particular
mechanisms producing lower y18O values of average annual
precipitation at the higher western elevations if the dominant
control on the y18O value of the snail shell aragonite was the
y18O value of annual precipitation the shell y18O should be
lower at higher altitude Figure 9a depicts snail shell y18O
values plotted against altitude for all of the analyzed
breplications
Q (Appendix A) There is no correlation of shell
y18O with elevation evident in Figure 9a
Average y18O values of samples in each transect are listed
in Table 1 and plotted against elevation in Figure 9b For the
transect-average values in Figure 9b there may be a weak
relationship of shell y18O with altitude indicating some
tendency for a decrease of shell y18O with increasing
elevation For an increase in elevation of ~2000 m the slope
of the linear regression indicates a decrease in shell y18O of
only ~1x However even if this weak correlation in Figure
9b was significant a decrease of ~1x is much less than the
decrease of ~4x expected if the y18O of annual precipitation
were the principal control on shell y18O values
Table 1
Transect averages (all species) of measured shell y13C and y
18O
Locality Transect Elevationa (m) Plant type Transect average Average y18O Model calculations
y13C y
18O Calculated locality y18Ocalc D
18O
Kubic 6 329 C3 Agrave85 Agrave21 Agrave20 Agrave22 Agrave02
Kubic 5 351 C4 Agrave35 Agrave19
Kubic 2 360 C4 C3 Agrave48 Agrave21Kubic 4 360 C4 Agrave23 Agrave17
Kubic 3 366 C4 Agrave19 Agrave01
Bluff Creek 36 348 C3 Agrave84 Agrave12 Agrave12 Agrave15 Agrave03
Salt Fork 9 320 C3 Agrave101 Agrave19 Agrave19 Agrave15 04
McDaniel 11 375 C4 C3 Agrave76 Agrave22 Agrave22 Agrave14 08
Burnham 17 519 C4 C3 Agrave83 Agrave08 Agrave10 Agrave09 01
Burnham 16 567 C4 CAM C3 Agrave54 Agrave18
Burnham 12 607 C4 C3 Agrave58 Agrave23
Burnham 14 607 C4 CAM C3 Agrave41 Agrave13
Burnham 13 610 C4 Agrave43 Agrave01
Big Salt Plain 15 482 C3 Agrave89 Agrave04 Agrave04 Agrave09 Agrave05
Skull Springs 18 671 C4 CAM C3 Agrave60 Agrave16 Agrave16 Agrave03 13
Skull Springs 19 665 C4 C3 Agrave40 Agrave17
Hitch 22 915 C4 CAM Agrave51 Agrave15 Agrave18 Agrave25 Agrave07
Hitch 21 933 C4 CAM C3 Agrave50 Agrave06Hitch 23 881 C3 Agrave85 Agrave23
Black Mesa 27 1312 C4 C3 Agrave61 Agrave27 Agrave22 Agrave21 01
Black Mesa 26 1324 C4 CAM C3 Agrave66 Agrave15
Black Mesa 24 1488 C4 CAM Agrave26 Agrave17
Black Mesa 25 1464 C4 CAM C3 Agrave72 Agrave25
Black Mesa 35 1464 C4 CAM C3 Agrave75 Agrave18
Owensby 61 2193 C3 Agrave105 Agrave19 Agrave20 Agrave25 Agrave05
Owensby 60 2242 C3 Agrave96 Agrave30
Owensby 59 2288 C3 Agrave109 Agrave19
CS Ranch 30 1922 C4 CAM C3 Agrave43 Agrave19 Agrave20 Agrave25 Agrave05
CS Ranch 29 1940 C4 CAM C3 Agrave49 Agrave25
Chase 34 1952 C4 C3 Agrave92 Agrave38 Agrave25 Agrave25 00
Chase 33 2184 C4 C3 Agrave86 Agrave22
Chase 31 2220 C4 C3 Agrave90 Agrave25
Chase 32 2233 C4 C3 Agrave89 Agrave23
Locality averages of measured y18O Also y
18O of shell at a locality as predicted from model calculations for diffusive evaporation (y18Ocalc) D18O =
y18Ocalc Agrave y
18Omeasa Sea level datum
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The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
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sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
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determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
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procera and Gastrocopta pellucida The two latter species
exhibit relatively large distribution ranges However G
procera was notably absent at the higher altitudes in the
survey (Theler et al 2004 Wyckoff et al 1997)
Laboratory preparations and analyses
Each isotopically analyzed sample consisted of multiple
entire shells of adults of a particular species (or genus for
juveniles of Vallonia) from a breplicationQ The shells were
initially rinsed with deionized water then treated ultrasoni-
cally in deionized water to remove any adhering particles of
organic matter or other debris The shells were gently crushed
and treated with 5 reagent-grade sodium hypochlorite at
room temperature for about 7ndash8 h to remove organic matter
They were then rinsed thoroughly with deionized water and
dried in air at about 40ndash508C The shell fragments were
subsequently reacted overnight in vacuum with 100 H3PO4
at 258
C following the method of McCrea (1950) The CO2
prepared from the shell aragonite was analyzed for y13C and
y18O on a Finnigan MAT 252 mass spectrometer Analytical
uncertainty is about F01x The y values are defined as
y13C or y18O frac14 R sample=R standard
Agrave AacuteAgrave 1
Acirc AtildeAcirc 1000 x
where R = 13C 12C or 18O 16O y13C and y18O are reported
relative to the PDB standard (Craig 1957)
Results and discussions
Ranges of d18O and d13C of aragonite in land-snail shells
y18O and y
13C values were measured for 162 samples
from the 12 localities of Figure 1 (see Appendix A) y18O
values of the aragonite shells of these modern snails ranged
from Agrave41x to 12x (Fig 3) Published y18O values of
shells from globally distributed modern land snails that are
wholly subaerial (as opposed to semiaquatic) range from
Agrave117x to 45x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Goodfriend et al 1989 Lecolle 1985
Magaritz and Heller 1980 Magaritz et al 1981 Sharpe et
al 1994 Yapp 1979) In North America reported y18O
values of land-snail shells range from Agrave117x to 02x(Goodfriend and Ellis 2002 Sharpe et al 1994 Yapp
1979) If the results for a carnivorous cold-tolerant snail of
the genus Vitrina (Sharpe et al 1994) from Deer Creek
Nevada are excluded y18O values analyzed to date for
North America range from Agrave58x to 02x The current
work extends the upper range of North American values by
10x (Fig 3)
Previous studies of y13C values of shell aragonite from
snails in their natural settings reported values ranging from
Agrave135x to 05x (Goodfriend and Ellis 2002 Goodfriend
and Magaritz 1987 Lecolle 1983 1984 Magaritz and
Heller 1980 1983 Magaritz et al 1981 Yapp 1979) For
North America published y13C values range from Agrave125x
to Agrave25x (Goodfriend and Ellis 2002 Yapp 1979) The
y13C values of snail shell aragonite studied for the current
work range from Agrave132x to 00x (Fig 3) By contrast
y13C values of shell aragonite of experimentally cultured
Helix aspersa that were fed a controlled diet ranged from
Agrave243x to 25x (Stott 2002) Controlled experiments also
indicate differences in y13C values among adults hatched
and 1-month-old individuals of H aspersa fed diets with
identical y13C values (Metref et al 2003)
Snail shell isotopic variation among populations
Variations in the isotopic composition of snail shells exist
among replications within a transect and also among species
in a replication (Appendix A) Within a sample locality
small-scale variations in topography vegetation local
moisture availability snail ages physiology etc are
expected Such variations might contribute to the observed
scatter in isotopic ratios among genera species or
individual samples
Isotopic analyses of Vallonia and Gastrocopta total 143
and represent the majority of the analyzed shell samples but
Figure 3 Ranges of Southern Great Plains land snails and snail shell y18O
and y13C values measured for breplicationsQ in the current study compared
with various published ranges (see text) Open portion of the range of North
Americany18
O values encompasses the values reported for shells from acarnivorous cold-tolerant snail (see text for reference)
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there were also analyses (numbers in parentheses) of
bunderrepresentedQ genera as follows (see Appendix A)
Pupoides (9) Succineidae (3) Pupilla (2) Cionella (1)
Zonitoides (1) Helicodiscus (1) Glyphyalinia (1) and
Hawaiia (1) The ranges of y18O values for Vallonia and
Gastrocopta are about 28x and 20x respectively (Fig
4a) Corresponding y18O values of Vallonia and Gastrocopta
indicate no correlation among the various sites (Fig 4a) A
similar lack of correlation was evident when y18O values of
underrepresented genera were compared wit h values for
coexisting Vallonia (Fig 5a) or Gastrocopta (Fig 5b) The
particular origins of these differences are unknown Without
studies under controlled age and environmental conditions
(eg Metref et al 2003 Stott 2002) distinguishing micro-environmental effects from the effects of age andor species-
related physiological differences is not possible at present
The respective ranges of y13C values for Vallonia and
Gastrocopta shell aragonite are each about 8ndash9x and
samples from the same breplicationsQ show a significant
correlation (Fig 4b) This correlation could indicate similar
feeding habits in both genera making them potential sources
of isotopic information on the paleoecology of a locale
Because of this correlation of Vallonia and Gastrocopta y13C
values y13C values of eight other genera that coexisted with
one or both of these genera in the various breplicationsQ are
plotted against y13
C of either Vallonia or Gastrocopta in asingle figure (Fig 5c) There are insufficient data to establish
whether the y13C values of any of the bunderrepresentedQ
genera might be correlated with Vallonia or Gastrocopta but
overall there is considerable scatter among the species
Additional comparative analyses of and controlled experi-
ments on these genera are needed
An exploratory evaluation of the effect of life histories
and ages on the isotopic composition of snails was
attempted using the data for adult and juvenile Vallonia
(see Appendix A) y18O values of shells of coexisting adult
and juvenile Vall onia from the breplicationsQ are not
correlated (Fig 6a) The y18O values of the adult snails
represent averages over longer periods of time than those of
the juveniles Short time scale environmental conditions that
affect the y18O values of the body fluid in juveniles should
determine the y18O values of the shell aragonite and these
conditions might contrast with the longer term-averages of
the adults
The absence of a correlation in the y18O data of Figure 6a
contrasts with the good correlation of the y13C values of the
adults and juveniles in Figure 6b The y13C correlation
could indicate that in these locales the carbon isotope
Figure 4 Southern Great Plains land snails Comparison of average
isotopic compositions of the aragonitic shells of Gastrocopta and Vallonia
from the same breplicationsQ (see text) (a) comparison of y18O values and
(b) comparison of y13
C values Dashed line in panel a is the reference liney = x Solid line in panel b is the linear regression of the data with the
corresponding equation r 2 and P
Figure 5 Southern Great Plains land snails Comparison of y18O of the aragonitic shells of other species used in this study with that of coexisting (a) Vallonia
and (b) Gastrocopta in the breplicationsQ (c) Comparison of y13C values of the shell aragonite of other species with those of coexisting Vallonia andor
Gastrocopta in the same breplicationsQ (see text) Dashed lines are the reference lines y = x
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3020
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composition of vegetation (as well as snail feeding patterns)
is not as variable on small scales as the oxygen isotope
composition of ambient moisture However the apparent
contrast in the respective oxygen and carbon isotope
relationships (adults or juveniles Figs 4 and 6) might also
be in part a consequence of the smaller ranges for the y18O
values Thus if the magnitude of the normal scatter in the
breplicationsQ data were comparable to the smaller total
range of the y18O values it would mask any evidence for a
broader y18
O correlation among genera or age groups
Snail shell isotope compositions and environmental
parameters
Carbon isotopes
As noted vegetation in the study area is dominantly
grasslands at lower elevations and trees at higher
elevations (Fig 1) Based on the nature of the photo-
synthetic pathway plants are classified as C3 C4 or CAM
(eg Jacobs et al 1999) y13C values of C3 plants range
from Agrave33x to Agrave21 x while y13C values of C4 plants
typically range from Agrave17x to Agrave9x (eg Cerling and
Quade 1993) CAM plants have y13C values that range
between the values for C3 and C4 plants (eg Cerling and
Quade 1993) Most of the grasses in the southern Great
Plains are C4 plants (Tieszen et al 1997) and the trees
and most of the forbs are C3 plants (Watson and Dallwitz
httpbiodiversityunoedudelta )
If snail shell y13C values are influenced by the y13C of their diets (eg Balakrishnan and Yapp 2004 Francey
1983 Goodfriend and Ellis 2002 Goodfriend and Magar-
itz 1987 Metref et al 2003 Stott 2002) the spatial
transitions in the ecology of the study corridor suggest that
the y13C values of the shells should be more negative at the
higher elevations toward the west y13C values of the shell
aragonite from all breplicationsQ (Appendix A) and their
averages for each transect (Table 1) are plotted against
elevation in Figures 7a and 7b respectively There is
considerable scatter but some suggestion of the expected
general shift to lower y13C values as altitude increases (Fig
7) However the regional vegetation trend does not explainthe very large range of snail shell y13C values at the lowest
elevations on the eastern end of the sample corridor (Figs
7a and 7b) Such a large range may be explained in part by
local variations in proportions of C3 and C4 plants
Wyckoff et al (1997) and Theler et al (2004)
identified plant species at each sample site in the study
corridor For the current work their identifications (no
quantitative estimates of type) were used to classify the
vegetation in each transect as C3-dominant C4-dominant
or mixed including CAM (Ehleringer et al 1997
Owensby et al 1997 Sage et al 1999 Appalachian
Farming Systems Research Center httpwwwarserrcgov
beckleyC3C4LISThtm ) The classifications are presented
in Table 1
The average y13C values of the land-snail shells from
each transect are listed in Table 1 and plotted in Figure 8
against the corresponding classification of local vegetation
which is arranged in a sequence from C4-dominant to C3-
dominant It is not known if the snails in the region ingest
CAM plants However examined in the manner of Figure
8 it is evident that the y13C values of snail shells of the
southern Great Plains are generally indicative of the type of
vegetation in their immediate environment although there
is still considerable scatter in the relationship In the
regions where C4 plants were identified as the dominant plant type the transect-average y
13C values of the snail
shell aragonite ranged from Agrave43x to Agrave19x with an
overall average of Agrave28x In localities where C3 plants
were documented to be the dominant type these transect-
average values ranged from Agrave101x to Agrave88x with an
overall average of Agrave90x (Fig 8) In the areas with mixed
vegetation types the shell y13C values are within the
extremes defined by the y13C values of the shells in areas
dominated by C3 or C4 plants These observations are in
agreement with earlier observations (Francey 1983 Good-
friend and Ellis 2002 Goodfriend and Magaritz 1987
Metref et al 2003 Stott 2002)
Figure 6 Comparison of coexisting adults and juveniles of southern Great
Plains Vallonia inb
replicationsQ
(see text) (a) y
18
O values of aragoniteshells and (b) y
13C values Solid line in panel b is the linear regression of
the data with the corresponding equation r 2 and P
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For the transects representing the Owensby and Bluff
Creek localities the plant species were not documented but
the relatively negative land-snail shelly13C values suggestthe
possible local dominance of C3 vegetation(hence the question
mark by the C3 symbol on the far right of the abscissa of Fig
8) Some of the scatter in Figure 8 may be a result of the
complicating effects of incorporation of relatively13
C-richdietary carbonate from limestone (eg Goodfriendand Hood
1983 Metref et al 2003 Yates et al 2002)
Oxygen isotopes
Average annual y18O of meteoric water is about Agrave56x at
Norman Oklahoma (USGS unpublished data Martha
Scholl personal communication) in the east and Agrave98 x
at the higher elevations of Clovis New Mexico (Nativ and
Riggio 1990) in the west As suggested by Figure 2 some of
this difference may be a consequence of differing proportions
of precipitation from different moisture sources and air
masses with different histories Irrespective of the particular
mechanisms producing lower y18O values of average annual
precipitation at the higher western elevations if the dominant
control on the y18O value of the snail shell aragonite was the
y18O value of annual precipitation the shell y18O should be
lower at higher altitude Figure 9a depicts snail shell y18O
values plotted against altitude for all of the analyzed
breplications
Q (Appendix A) There is no correlation of shell
y18O with elevation evident in Figure 9a
Average y18O values of samples in each transect are listed
in Table 1 and plotted against elevation in Figure 9b For the
transect-average values in Figure 9b there may be a weak
relationship of shell y18O with altitude indicating some
tendency for a decrease of shell y18O with increasing
elevation For an increase in elevation of ~2000 m the slope
of the linear regression indicates a decrease in shell y18O of
only ~1x However even if this weak correlation in Figure
9b was significant a decrease of ~1x is much less than the
decrease of ~4x expected if the y18O of annual precipitation
were the principal control on shell y18O values
Table 1
Transect averages (all species) of measured shell y13C and y
18O
Locality Transect Elevationa (m) Plant type Transect average Average y18O Model calculations
y13C y
18O Calculated locality y18Ocalc D
18O
Kubic 6 329 C3 Agrave85 Agrave21 Agrave20 Agrave22 Agrave02
Kubic 5 351 C4 Agrave35 Agrave19
Kubic 2 360 C4 C3 Agrave48 Agrave21Kubic 4 360 C4 Agrave23 Agrave17
Kubic 3 366 C4 Agrave19 Agrave01
Bluff Creek 36 348 C3 Agrave84 Agrave12 Agrave12 Agrave15 Agrave03
Salt Fork 9 320 C3 Agrave101 Agrave19 Agrave19 Agrave15 04
McDaniel 11 375 C4 C3 Agrave76 Agrave22 Agrave22 Agrave14 08
Burnham 17 519 C4 C3 Agrave83 Agrave08 Agrave10 Agrave09 01
Burnham 16 567 C4 CAM C3 Agrave54 Agrave18
Burnham 12 607 C4 C3 Agrave58 Agrave23
Burnham 14 607 C4 CAM C3 Agrave41 Agrave13
Burnham 13 610 C4 Agrave43 Agrave01
Big Salt Plain 15 482 C3 Agrave89 Agrave04 Agrave04 Agrave09 Agrave05
Skull Springs 18 671 C4 CAM C3 Agrave60 Agrave16 Agrave16 Agrave03 13
Skull Springs 19 665 C4 C3 Agrave40 Agrave17
Hitch 22 915 C4 CAM Agrave51 Agrave15 Agrave18 Agrave25 Agrave07
Hitch 21 933 C4 CAM C3 Agrave50 Agrave06Hitch 23 881 C3 Agrave85 Agrave23
Black Mesa 27 1312 C4 C3 Agrave61 Agrave27 Agrave22 Agrave21 01
Black Mesa 26 1324 C4 CAM C3 Agrave66 Agrave15
Black Mesa 24 1488 C4 CAM Agrave26 Agrave17
Black Mesa 25 1464 C4 CAM C3 Agrave72 Agrave25
Black Mesa 35 1464 C4 CAM C3 Agrave75 Agrave18
Owensby 61 2193 C3 Agrave105 Agrave19 Agrave20 Agrave25 Agrave05
Owensby 60 2242 C3 Agrave96 Agrave30
Owensby 59 2288 C3 Agrave109 Agrave19
CS Ranch 30 1922 C4 CAM C3 Agrave43 Agrave19 Agrave20 Agrave25 Agrave05
CS Ranch 29 1940 C4 CAM C3 Agrave49 Agrave25
Chase 34 1952 C4 C3 Agrave92 Agrave38 Agrave25 Agrave25 00
Chase 33 2184 C4 C3 Agrave86 Agrave22
Chase 31 2220 C4 C3 Agrave90 Agrave25
Chase 32 2233 C4 C3 Agrave89 Agrave23
Locality averages of measured y18O Also y
18O of shell at a locality as predicted from model calculations for diffusive evaporation (y18Ocalc) D18O =
y18Ocalc Agrave y
18Omeasa Sea level datum
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The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
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determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
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there were also analyses (numbers in parentheses) of
bunderrepresentedQ genera as follows (see Appendix A)
Pupoides (9) Succineidae (3) Pupilla (2) Cionella (1)
Zonitoides (1) Helicodiscus (1) Glyphyalinia (1) and
Hawaiia (1) The ranges of y18O values for Vallonia and
Gastrocopta are about 28x and 20x respectively (Fig
4a) Corresponding y18O values of Vallonia and Gastrocopta
indicate no correlation among the various sites (Fig 4a) A
similar lack of correlation was evident when y18O values of
underrepresented genera were compared wit h values for
coexisting Vallonia (Fig 5a) or Gastrocopta (Fig 5b) The
particular origins of these differences are unknown Without
studies under controlled age and environmental conditions
(eg Metref et al 2003 Stott 2002) distinguishing micro-environmental effects from the effects of age andor species-
related physiological differences is not possible at present
The respective ranges of y13C values for Vallonia and
Gastrocopta shell aragonite are each about 8ndash9x and
samples from the same breplicationsQ show a significant
correlation (Fig 4b) This correlation could indicate similar
feeding habits in both genera making them potential sources
of isotopic information on the paleoecology of a locale
Because of this correlation of Vallonia and Gastrocopta y13C
values y13C values of eight other genera that coexisted with
one or both of these genera in the various breplicationsQ are
plotted against y13
C of either Vallonia or Gastrocopta in asingle figure (Fig 5c) There are insufficient data to establish
whether the y13C values of any of the bunderrepresentedQ
genera might be correlated with Vallonia or Gastrocopta but
overall there is considerable scatter among the species
Additional comparative analyses of and controlled experi-
ments on these genera are needed
An exploratory evaluation of the effect of life histories
and ages on the isotopic composition of snails was
attempted using the data for adult and juvenile Vallonia
(see Appendix A) y18O values of shells of coexisting adult
and juvenile Vall onia from the breplicationsQ are not
correlated (Fig 6a) The y18O values of the adult snails
represent averages over longer periods of time than those of
the juveniles Short time scale environmental conditions that
affect the y18O values of the body fluid in juveniles should
determine the y18O values of the shell aragonite and these
conditions might contrast with the longer term-averages of
the adults
The absence of a correlation in the y18O data of Figure 6a
contrasts with the good correlation of the y13C values of the
adults and juveniles in Figure 6b The y13C correlation
could indicate that in these locales the carbon isotope
Figure 4 Southern Great Plains land snails Comparison of average
isotopic compositions of the aragonitic shells of Gastrocopta and Vallonia
from the same breplicationsQ (see text) (a) comparison of y18O values and
(b) comparison of y13
C values Dashed line in panel a is the reference liney = x Solid line in panel b is the linear regression of the data with the
corresponding equation r 2 and P
Figure 5 Southern Great Plains land snails Comparison of y18O of the aragonitic shells of other species used in this study with that of coexisting (a) Vallonia
and (b) Gastrocopta in the breplicationsQ (c) Comparison of y13C values of the shell aragonite of other species with those of coexisting Vallonia andor
Gastrocopta in the same breplicationsQ (see text) Dashed lines are the reference lines y = x
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3020
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composition of vegetation (as well as snail feeding patterns)
is not as variable on small scales as the oxygen isotope
composition of ambient moisture However the apparent
contrast in the respective oxygen and carbon isotope
relationships (adults or juveniles Figs 4 and 6) might also
be in part a consequence of the smaller ranges for the y18O
values Thus if the magnitude of the normal scatter in the
breplicationsQ data were comparable to the smaller total
range of the y18O values it would mask any evidence for a
broader y18
O correlation among genera or age groups
Snail shell isotope compositions and environmental
parameters
Carbon isotopes
As noted vegetation in the study area is dominantly
grasslands at lower elevations and trees at higher
elevations (Fig 1) Based on the nature of the photo-
synthetic pathway plants are classified as C3 C4 or CAM
(eg Jacobs et al 1999) y13C values of C3 plants range
from Agrave33x to Agrave21 x while y13C values of C4 plants
typically range from Agrave17x to Agrave9x (eg Cerling and
Quade 1993) CAM plants have y13C values that range
between the values for C3 and C4 plants (eg Cerling and
Quade 1993) Most of the grasses in the southern Great
Plains are C4 plants (Tieszen et al 1997) and the trees
and most of the forbs are C3 plants (Watson and Dallwitz
httpbiodiversityunoedudelta )
If snail shell y13C values are influenced by the y13C of their diets (eg Balakrishnan and Yapp 2004 Francey
1983 Goodfriend and Ellis 2002 Goodfriend and Magar-
itz 1987 Metref et al 2003 Stott 2002) the spatial
transitions in the ecology of the study corridor suggest that
the y13C values of the shells should be more negative at the
higher elevations toward the west y13C values of the shell
aragonite from all breplicationsQ (Appendix A) and their
averages for each transect (Table 1) are plotted against
elevation in Figures 7a and 7b respectively There is
considerable scatter but some suggestion of the expected
general shift to lower y13C values as altitude increases (Fig
7) However the regional vegetation trend does not explainthe very large range of snail shell y13C values at the lowest
elevations on the eastern end of the sample corridor (Figs
7a and 7b) Such a large range may be explained in part by
local variations in proportions of C3 and C4 plants
Wyckoff et al (1997) and Theler et al (2004)
identified plant species at each sample site in the study
corridor For the current work their identifications (no
quantitative estimates of type) were used to classify the
vegetation in each transect as C3-dominant C4-dominant
or mixed including CAM (Ehleringer et al 1997
Owensby et al 1997 Sage et al 1999 Appalachian
Farming Systems Research Center httpwwwarserrcgov
beckleyC3C4LISThtm ) The classifications are presented
in Table 1
The average y13C values of the land-snail shells from
each transect are listed in Table 1 and plotted in Figure 8
against the corresponding classification of local vegetation
which is arranged in a sequence from C4-dominant to C3-
dominant It is not known if the snails in the region ingest
CAM plants However examined in the manner of Figure
8 it is evident that the y13C values of snail shells of the
southern Great Plains are generally indicative of the type of
vegetation in their immediate environment although there
is still considerable scatter in the relationship In the
regions where C4 plants were identified as the dominant plant type the transect-average y
13C values of the snail
shell aragonite ranged from Agrave43x to Agrave19x with an
overall average of Agrave28x In localities where C3 plants
were documented to be the dominant type these transect-
average values ranged from Agrave101x to Agrave88x with an
overall average of Agrave90x (Fig 8) In the areas with mixed
vegetation types the shell y13C values are within the
extremes defined by the y13C values of the shells in areas
dominated by C3 or C4 plants These observations are in
agreement with earlier observations (Francey 1983 Good-
friend and Ellis 2002 Goodfriend and Magaritz 1987
Metref et al 2003 Stott 2002)
Figure 6 Comparison of coexisting adults and juveniles of southern Great
Plains Vallonia inb
replicationsQ
(see text) (a) y
18
O values of aragoniteshells and (b) y
13C values Solid line in panel b is the linear regression of
the data with the corresponding equation r 2 and P
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For the transects representing the Owensby and Bluff
Creek localities the plant species were not documented but
the relatively negative land-snail shelly13C values suggestthe
possible local dominance of C3 vegetation(hence the question
mark by the C3 symbol on the far right of the abscissa of Fig
8) Some of the scatter in Figure 8 may be a result of the
complicating effects of incorporation of relatively13
C-richdietary carbonate from limestone (eg Goodfriendand Hood
1983 Metref et al 2003 Yates et al 2002)
Oxygen isotopes
Average annual y18O of meteoric water is about Agrave56x at
Norman Oklahoma (USGS unpublished data Martha
Scholl personal communication) in the east and Agrave98 x
at the higher elevations of Clovis New Mexico (Nativ and
Riggio 1990) in the west As suggested by Figure 2 some of
this difference may be a consequence of differing proportions
of precipitation from different moisture sources and air
masses with different histories Irrespective of the particular
mechanisms producing lower y18O values of average annual
precipitation at the higher western elevations if the dominant
control on the y18O value of the snail shell aragonite was the
y18O value of annual precipitation the shell y18O should be
lower at higher altitude Figure 9a depicts snail shell y18O
values plotted against altitude for all of the analyzed
breplications
Q (Appendix A) There is no correlation of shell
y18O with elevation evident in Figure 9a
Average y18O values of samples in each transect are listed
in Table 1 and plotted against elevation in Figure 9b For the
transect-average values in Figure 9b there may be a weak
relationship of shell y18O with altitude indicating some
tendency for a decrease of shell y18O with increasing
elevation For an increase in elevation of ~2000 m the slope
of the linear regression indicates a decrease in shell y18O of
only ~1x However even if this weak correlation in Figure
9b was significant a decrease of ~1x is much less than the
decrease of ~4x expected if the y18O of annual precipitation
were the principal control on shell y18O values
Table 1
Transect averages (all species) of measured shell y13C and y
18O
Locality Transect Elevationa (m) Plant type Transect average Average y18O Model calculations
y13C y
18O Calculated locality y18Ocalc D
18O
Kubic 6 329 C3 Agrave85 Agrave21 Agrave20 Agrave22 Agrave02
Kubic 5 351 C4 Agrave35 Agrave19
Kubic 2 360 C4 C3 Agrave48 Agrave21Kubic 4 360 C4 Agrave23 Agrave17
Kubic 3 366 C4 Agrave19 Agrave01
Bluff Creek 36 348 C3 Agrave84 Agrave12 Agrave12 Agrave15 Agrave03
Salt Fork 9 320 C3 Agrave101 Agrave19 Agrave19 Agrave15 04
McDaniel 11 375 C4 C3 Agrave76 Agrave22 Agrave22 Agrave14 08
Burnham 17 519 C4 C3 Agrave83 Agrave08 Agrave10 Agrave09 01
Burnham 16 567 C4 CAM C3 Agrave54 Agrave18
Burnham 12 607 C4 C3 Agrave58 Agrave23
Burnham 14 607 C4 CAM C3 Agrave41 Agrave13
Burnham 13 610 C4 Agrave43 Agrave01
Big Salt Plain 15 482 C3 Agrave89 Agrave04 Agrave04 Agrave09 Agrave05
Skull Springs 18 671 C4 CAM C3 Agrave60 Agrave16 Agrave16 Agrave03 13
Skull Springs 19 665 C4 C3 Agrave40 Agrave17
Hitch 22 915 C4 CAM Agrave51 Agrave15 Agrave18 Agrave25 Agrave07
Hitch 21 933 C4 CAM C3 Agrave50 Agrave06Hitch 23 881 C3 Agrave85 Agrave23
Black Mesa 27 1312 C4 C3 Agrave61 Agrave27 Agrave22 Agrave21 01
Black Mesa 26 1324 C4 CAM C3 Agrave66 Agrave15
Black Mesa 24 1488 C4 CAM Agrave26 Agrave17
Black Mesa 25 1464 C4 CAM C3 Agrave72 Agrave25
Black Mesa 35 1464 C4 CAM C3 Agrave75 Agrave18
Owensby 61 2193 C3 Agrave105 Agrave19 Agrave20 Agrave25 Agrave05
Owensby 60 2242 C3 Agrave96 Agrave30
Owensby 59 2288 C3 Agrave109 Agrave19
CS Ranch 30 1922 C4 CAM C3 Agrave43 Agrave19 Agrave20 Agrave25 Agrave05
CS Ranch 29 1940 C4 CAM C3 Agrave49 Agrave25
Chase 34 1952 C4 C3 Agrave92 Agrave38 Agrave25 Agrave25 00
Chase 33 2184 C4 C3 Agrave86 Agrave22
Chase 31 2220 C4 C3 Agrave90 Agrave25
Chase 32 2233 C4 C3 Agrave89 Agrave23
Locality averages of measured y18O Also y
18O of shell at a locality as predicted from model calculations for diffusive evaporation (y18Ocalc) D18O =
y18Ocalc Agrave y
18Omeasa Sea level datum
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The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 23
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 25
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3026
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 27
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 716
composition of vegetation (as well as snail feeding patterns)
is not as variable on small scales as the oxygen isotope
composition of ambient moisture However the apparent
contrast in the respective oxygen and carbon isotope
relationships (adults or juveniles Figs 4 and 6) might also
be in part a consequence of the smaller ranges for the y18O
values Thus if the magnitude of the normal scatter in the
breplicationsQ data were comparable to the smaller total
range of the y18O values it would mask any evidence for a
broader y18
O correlation among genera or age groups
Snail shell isotope compositions and environmental
parameters
Carbon isotopes
As noted vegetation in the study area is dominantly
grasslands at lower elevations and trees at higher
elevations (Fig 1) Based on the nature of the photo-
synthetic pathway plants are classified as C3 C4 or CAM
(eg Jacobs et al 1999) y13C values of C3 plants range
from Agrave33x to Agrave21 x while y13C values of C4 plants
typically range from Agrave17x to Agrave9x (eg Cerling and
Quade 1993) CAM plants have y13C values that range
between the values for C3 and C4 plants (eg Cerling and
Quade 1993) Most of the grasses in the southern Great
Plains are C4 plants (Tieszen et al 1997) and the trees
and most of the forbs are C3 plants (Watson and Dallwitz
httpbiodiversityunoedudelta )
If snail shell y13C values are influenced by the y13C of their diets (eg Balakrishnan and Yapp 2004 Francey
1983 Goodfriend and Ellis 2002 Goodfriend and Magar-
itz 1987 Metref et al 2003 Stott 2002) the spatial
transitions in the ecology of the study corridor suggest that
the y13C values of the shells should be more negative at the
higher elevations toward the west y13C values of the shell
aragonite from all breplicationsQ (Appendix A) and their
averages for each transect (Table 1) are plotted against
elevation in Figures 7a and 7b respectively There is
considerable scatter but some suggestion of the expected
general shift to lower y13C values as altitude increases (Fig
7) However the regional vegetation trend does not explainthe very large range of snail shell y13C values at the lowest
elevations on the eastern end of the sample corridor (Figs
7a and 7b) Such a large range may be explained in part by
local variations in proportions of C3 and C4 plants
Wyckoff et al (1997) and Theler et al (2004)
identified plant species at each sample site in the study
corridor For the current work their identifications (no
quantitative estimates of type) were used to classify the
vegetation in each transect as C3-dominant C4-dominant
or mixed including CAM (Ehleringer et al 1997
Owensby et al 1997 Sage et al 1999 Appalachian
Farming Systems Research Center httpwwwarserrcgov
beckleyC3C4LISThtm ) The classifications are presented
in Table 1
The average y13C values of the land-snail shells from
each transect are listed in Table 1 and plotted in Figure 8
against the corresponding classification of local vegetation
which is arranged in a sequence from C4-dominant to C3-
dominant It is not known if the snails in the region ingest
CAM plants However examined in the manner of Figure
8 it is evident that the y13C values of snail shells of the
southern Great Plains are generally indicative of the type of
vegetation in their immediate environment although there
is still considerable scatter in the relationship In the
regions where C4 plants were identified as the dominant plant type the transect-average y
13C values of the snail
shell aragonite ranged from Agrave43x to Agrave19x with an
overall average of Agrave28x In localities where C3 plants
were documented to be the dominant type these transect-
average values ranged from Agrave101x to Agrave88x with an
overall average of Agrave90x (Fig 8) In the areas with mixed
vegetation types the shell y13C values are within the
extremes defined by the y13C values of the shells in areas
dominated by C3 or C4 plants These observations are in
agreement with earlier observations (Francey 1983 Good-
friend and Ellis 2002 Goodfriend and Magaritz 1987
Metref et al 2003 Stott 2002)
Figure 6 Comparison of coexisting adults and juveniles of southern Great
Plains Vallonia inb
replicationsQ
(see text) (a) y
18
O values of aragoniteshells and (b) y
13C values Solid line in panel b is the linear regression of
the data with the corresponding equation r 2 and P
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For the transects representing the Owensby and Bluff
Creek localities the plant species were not documented but
the relatively negative land-snail shelly13C values suggestthe
possible local dominance of C3 vegetation(hence the question
mark by the C3 symbol on the far right of the abscissa of Fig
8) Some of the scatter in Figure 8 may be a result of the
complicating effects of incorporation of relatively13
C-richdietary carbonate from limestone (eg Goodfriendand Hood
1983 Metref et al 2003 Yates et al 2002)
Oxygen isotopes
Average annual y18O of meteoric water is about Agrave56x at
Norman Oklahoma (USGS unpublished data Martha
Scholl personal communication) in the east and Agrave98 x
at the higher elevations of Clovis New Mexico (Nativ and
Riggio 1990) in the west As suggested by Figure 2 some of
this difference may be a consequence of differing proportions
of precipitation from different moisture sources and air
masses with different histories Irrespective of the particular
mechanisms producing lower y18O values of average annual
precipitation at the higher western elevations if the dominant
control on the y18O value of the snail shell aragonite was the
y18O value of annual precipitation the shell y18O should be
lower at higher altitude Figure 9a depicts snail shell y18O
values plotted against altitude for all of the analyzed
breplications
Q (Appendix A) There is no correlation of shell
y18O with elevation evident in Figure 9a
Average y18O values of samples in each transect are listed
in Table 1 and plotted against elevation in Figure 9b For the
transect-average values in Figure 9b there may be a weak
relationship of shell y18O with altitude indicating some
tendency for a decrease of shell y18O with increasing
elevation For an increase in elevation of ~2000 m the slope
of the linear regression indicates a decrease in shell y18O of
only ~1x However even if this weak correlation in Figure
9b was significant a decrease of ~1x is much less than the
decrease of ~4x expected if the y18O of annual precipitation
were the principal control on shell y18O values
Table 1
Transect averages (all species) of measured shell y13C and y
18O
Locality Transect Elevationa (m) Plant type Transect average Average y18O Model calculations
y13C y
18O Calculated locality y18Ocalc D
18O
Kubic 6 329 C3 Agrave85 Agrave21 Agrave20 Agrave22 Agrave02
Kubic 5 351 C4 Agrave35 Agrave19
Kubic 2 360 C4 C3 Agrave48 Agrave21Kubic 4 360 C4 Agrave23 Agrave17
Kubic 3 366 C4 Agrave19 Agrave01
Bluff Creek 36 348 C3 Agrave84 Agrave12 Agrave12 Agrave15 Agrave03
Salt Fork 9 320 C3 Agrave101 Agrave19 Agrave19 Agrave15 04
McDaniel 11 375 C4 C3 Agrave76 Agrave22 Agrave22 Agrave14 08
Burnham 17 519 C4 C3 Agrave83 Agrave08 Agrave10 Agrave09 01
Burnham 16 567 C4 CAM C3 Agrave54 Agrave18
Burnham 12 607 C4 C3 Agrave58 Agrave23
Burnham 14 607 C4 CAM C3 Agrave41 Agrave13
Burnham 13 610 C4 Agrave43 Agrave01
Big Salt Plain 15 482 C3 Agrave89 Agrave04 Agrave04 Agrave09 Agrave05
Skull Springs 18 671 C4 CAM C3 Agrave60 Agrave16 Agrave16 Agrave03 13
Skull Springs 19 665 C4 C3 Agrave40 Agrave17
Hitch 22 915 C4 CAM Agrave51 Agrave15 Agrave18 Agrave25 Agrave07
Hitch 21 933 C4 CAM C3 Agrave50 Agrave06Hitch 23 881 C3 Agrave85 Agrave23
Black Mesa 27 1312 C4 C3 Agrave61 Agrave27 Agrave22 Agrave21 01
Black Mesa 26 1324 C4 CAM C3 Agrave66 Agrave15
Black Mesa 24 1488 C4 CAM Agrave26 Agrave17
Black Mesa 25 1464 C4 CAM C3 Agrave72 Agrave25
Black Mesa 35 1464 C4 CAM C3 Agrave75 Agrave18
Owensby 61 2193 C3 Agrave105 Agrave19 Agrave20 Agrave25 Agrave05
Owensby 60 2242 C3 Agrave96 Agrave30
Owensby 59 2288 C3 Agrave109 Agrave19
CS Ranch 30 1922 C4 CAM C3 Agrave43 Agrave19 Agrave20 Agrave25 Agrave05
CS Ranch 29 1940 C4 CAM C3 Agrave49 Agrave25
Chase 34 1952 C4 C3 Agrave92 Agrave38 Agrave25 Agrave25 00
Chase 33 2184 C4 C3 Agrave86 Agrave22
Chase 31 2220 C4 C3 Agrave90 Agrave25
Chase 32 2233 C4 C3 Agrave89 Agrave23
Locality averages of measured y18O Also y
18O of shell at a locality as predicted from model calculations for diffusive evaporation (y18Ocalc) D18O =
y18Ocalc Agrave y
18Omeasa Sea level datum
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The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
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sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
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determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
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For the transects representing the Owensby and Bluff
Creek localities the plant species were not documented but
the relatively negative land-snail shelly13C values suggestthe
possible local dominance of C3 vegetation(hence the question
mark by the C3 symbol on the far right of the abscissa of Fig
8) Some of the scatter in Figure 8 may be a result of the
complicating effects of incorporation of relatively13
C-richdietary carbonate from limestone (eg Goodfriendand Hood
1983 Metref et al 2003 Yates et al 2002)
Oxygen isotopes
Average annual y18O of meteoric water is about Agrave56x at
Norman Oklahoma (USGS unpublished data Martha
Scholl personal communication) in the east and Agrave98 x
at the higher elevations of Clovis New Mexico (Nativ and
Riggio 1990) in the west As suggested by Figure 2 some of
this difference may be a consequence of differing proportions
of precipitation from different moisture sources and air
masses with different histories Irrespective of the particular
mechanisms producing lower y18O values of average annual
precipitation at the higher western elevations if the dominant
control on the y18O value of the snail shell aragonite was the
y18O value of annual precipitation the shell y18O should be
lower at higher altitude Figure 9a depicts snail shell y18O
values plotted against altitude for all of the analyzed
breplications
Q (Appendix A) There is no correlation of shell
y18O with elevation evident in Figure 9a
Average y18O values of samples in each transect are listed
in Table 1 and plotted against elevation in Figure 9b For the
transect-average values in Figure 9b there may be a weak
relationship of shell y18O with altitude indicating some
tendency for a decrease of shell y18O with increasing
elevation For an increase in elevation of ~2000 m the slope
of the linear regression indicates a decrease in shell y18O of
only ~1x However even if this weak correlation in Figure
9b was significant a decrease of ~1x is much less than the
decrease of ~4x expected if the y18O of annual precipitation
were the principal control on shell y18O values
Table 1
Transect averages (all species) of measured shell y13C and y
18O
Locality Transect Elevationa (m) Plant type Transect average Average y18O Model calculations
y13C y
18O Calculated locality y18Ocalc D
18O
Kubic 6 329 C3 Agrave85 Agrave21 Agrave20 Agrave22 Agrave02
Kubic 5 351 C4 Agrave35 Agrave19
Kubic 2 360 C4 C3 Agrave48 Agrave21Kubic 4 360 C4 Agrave23 Agrave17
Kubic 3 366 C4 Agrave19 Agrave01
Bluff Creek 36 348 C3 Agrave84 Agrave12 Agrave12 Agrave15 Agrave03
Salt Fork 9 320 C3 Agrave101 Agrave19 Agrave19 Agrave15 04
McDaniel 11 375 C4 C3 Agrave76 Agrave22 Agrave22 Agrave14 08
Burnham 17 519 C4 C3 Agrave83 Agrave08 Agrave10 Agrave09 01
Burnham 16 567 C4 CAM C3 Agrave54 Agrave18
Burnham 12 607 C4 C3 Agrave58 Agrave23
Burnham 14 607 C4 CAM C3 Agrave41 Agrave13
Burnham 13 610 C4 Agrave43 Agrave01
Big Salt Plain 15 482 C3 Agrave89 Agrave04 Agrave04 Agrave09 Agrave05
Skull Springs 18 671 C4 CAM C3 Agrave60 Agrave16 Agrave16 Agrave03 13
Skull Springs 19 665 C4 C3 Agrave40 Agrave17
Hitch 22 915 C4 CAM Agrave51 Agrave15 Agrave18 Agrave25 Agrave07
Hitch 21 933 C4 CAM C3 Agrave50 Agrave06Hitch 23 881 C3 Agrave85 Agrave23
Black Mesa 27 1312 C4 C3 Agrave61 Agrave27 Agrave22 Agrave21 01
Black Mesa 26 1324 C4 CAM C3 Agrave66 Agrave15
Black Mesa 24 1488 C4 CAM Agrave26 Agrave17
Black Mesa 25 1464 C4 CAM C3 Agrave72 Agrave25
Black Mesa 35 1464 C4 CAM C3 Agrave75 Agrave18
Owensby 61 2193 C3 Agrave105 Agrave19 Agrave20 Agrave25 Agrave05
Owensby 60 2242 C3 Agrave96 Agrave30
Owensby 59 2288 C3 Agrave109 Agrave19
CS Ranch 30 1922 C4 CAM C3 Agrave43 Agrave19 Agrave20 Agrave25 Agrave05
CS Ranch 29 1940 C4 CAM C3 Agrave49 Agrave25
Chase 34 1952 C4 C3 Agrave92 Agrave38 Agrave25 Agrave25 00
Chase 33 2184 C4 C3 Agrave86 Agrave22
Chase 31 2220 C4 C3 Agrave90 Agrave25
Chase 32 2233 C4 C3 Agrave89 Agrave23
Locality averages of measured y18O Also y
18O of shell at a locality as predicted from model calculations for diffusive evaporation (y18Ocalc) D18O =
y18Ocalc Agrave y
18Omeasa Sea level datum
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The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3026
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 27
872019 Balakrishnan et al 2004
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 916
The data of Figures 9a and 9b imply that factors other
than the y18O of annual precipitation are involved in
regulating the y18O values of the shells of land snails from
the southern Plains In general land snails are not active at
temperatures below 108C and above 278C (Cowie 1984
Thompson and Cheny 1996) nor are they active at values of
relative humidity (RH) of less than about 070mdashexpressing
RH as a decimal fraction (Van der Schalie and Getz 1961
1963) Thus land snails are active only at night or following
rains (Cook 1979 Edelstam and Palmer 1950 Gelperin
1974 Heatwole and Heatwole 1978 Newell 1966 Wardand Slotow 1992 Wells 1944) Moreover snail shells are
only precipitated when snails are active (Cowie 1984)
Therefore y18O values of snail shell aragonite should reflect
conditions within comparatively narrow ranges of high
relative humidities and moderate temperatures
The steady-state flux balance model of Balakrishnan and
Yapp (2004) may provide some insight into the oxygen
isotope systematics of the snail shells of this study The
relevant model inputs for calculations of expected shell
y18O values are temperatures relative humidities (RH) and
y18O values of precipitation estimated to be representative
of the local environments at the times of snail activity As
mentioned these periods of activity are primarily evenings
andor immediately after rainfall From the archives of the
Climate Data Center of New Mexico State University
(wwwweathernmsuedu) meteorological data for 1994
were available for one relevant station in New Mexico
(Clayton see Appendix A) For the year 1994 hourly
meteorological parameters for seven stations in Oklahoma(Appendix A) were available from Mesonet data (courtesy
of Oklahoma State University and University of Oklahoma)
Average temperatures characteristic of the aforementioned
conditions of land-snail activity appear to reasonably
represent the temperatures of the snail environment (Balak-
rishnan and Yapp 2004) and these temperatures were
employed in our calculations (excluding days when temper-
atures were below 108C or above 278C) We also used
averages of nighttime RH for RH N 070 and 108C b T b
278Cmdashie the range conditions for snail activity These
temperature and RH data are in Table 2 For th e
calculations it was assumed that essentially all of the water imbibed by the snail was lost via evaporation (ie h = 0)
and that the ambient vapor was in isotopic equilibrium with
the input rain (for an explanation of model assumptions and
definition of terms see Balakrishnan and Yapp 2004)
Isotopic compositions of active season precipitation
were only available from three sites in the vicinity of the
study area (1) Norman Oklahoma (USGS unpublished
data Martha Scholl personal communication) (2) Ama-
rillo Texas and (3) Paducah Texas (Nativ and Riggio
1990) The average for Norman represents the years 1996ndash Figure 7 y13C of southern Great Plains snail shell aragonite as a function of
elevation (a) y13C values for all breplicationsQ (b) average y13C values for
each transect (see text) Error bars in panel b represent one standard
deviation of the mean for the indicated transect
Figure 8 Southern Great Plains land-snail shells Open diamonds are
transect-averagey13C values of shells compared to the vegetation types at a
site (see text) Filled squares are average values of the respective transect
averages for each vegetation classification Error bars are one standard
deviation of the various means
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 23
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3024
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3026
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 27
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
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determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
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2001 whereas the Amarillo data are for t he years 1984
1985 The average values are in Table 2 Model calcu-
lations for each snail locality used the geographically
nearest active season meteorological data and isotopic
compositions of rain (Table 2) Because the measured
environmental parameters are not precisely coincidenteither spatially or temporally with the respective snail
localities some unknown error is introduced into the
comparisons of calculated and measured shell y18O values
Nevertheless the comparisons are instructive
In the flux balance model of Balakrishnan and Yapp
(2004) it is assumed that the shell aragonite crystallized in
oxygen isotope equilibrium with snail body fluid that was
undergoing isotopic steady-state diffusive evaporation The
aragonitendashwater oxygen isotope fractionation equation of
Grossman and Ku (1986) is assumed to be applicable in
these model calculations Let D18O = y18Ocalc Agrave y
18Omeas
where y18Ocalc = the model-predicted y
18O of the aragonite
and y18Omeas = the measured y18O of the aragonite shell
Note that D18O values of zero represent exact agreement
between predicted and measured y18O For this compar-
ison averages (Table 1) of measured y18O values of all
analyzed species at each locality were employed with the
idea that variations associated with differences among
individuals species times of shell formation microenvir-
onments etc would be bsmoothed out Q and therefore
possibly better represent the average conditions reflected in
the meteorological data These locality-average D18O
values calculated with diffusive evaporation scatter
around zero and with one exception differ from zero by
1x or less (solid diamonds in Fig 10)In contrast for an assumption of oxygen isotopic
equilibrium between aragonite and land-snail body fluid
(local rain) that had experienced no evaporation prior to or
during snail activity predicted shell y18O values are
significantly different from measured values For this case
the calculated D18O values differ from zero by more than
30x (solid triangles Fig 10) and all of these D18O values
for no evaporation are negative (Agrave57 to Agrave34x)
The fact that locality averageD18O values for the diffusive
evaporation model scatter around and near zero suggests that
this evaporation model may approximate the processes
operating in these land snails of the southern Great Plains
and implies that the ambient relative humidity has an
important influence on the y18O values observed in the shells
(Balakrishnan and Yapp 2004 Yapp 1979) All other things
being equal the evaporation model predicts that a decimal
fraction decrease in RH of only 001 produces a predicted
increase in shell y
18
O of about 04x This apparent sensitivity to RH and the westward decrease of 003ndash006
in the average active season nighttime RH (Table 2) may
partially compensate for the somewhat lower y18O values of
Table 2
Active season temperature relative humidity and rainfall y18O
Weather station Summer T8C RHa y18O of summer rainb Rain isotope data station Proximal snail sample localities
Blackwell OK 220 091 Agrave51 Norman OK Kubic
Medford OK 224 089 Agrave51 Norman Bluff Creek Salt Fork
Cherokee OK 220 089 Agrave51 Norman McDaniel
Alva OK 212 088Agrave
51 Norman Burnham Big Salt PlainBeaver OK 223 086 Agrave50 Paducah TX Skull Springs
Goodwell OK 228 087 Agrave67 Amarillo TX Hitch
Boiser OK 228 086 Agrave67 Amarillo Black Mesa
Clayton NM 214 088 Agrave67 Amarillo Owensby CS Ranch Chase
a RH as a decimal fractionb See text for source of data
Figure 9 Southern Great Plains land-snail shells Measured y18O values of
snail shell aragonite as a function of elevation (a) y18O values of all
breplicationsQ and (b) average y18O values for each transect (see text) The
solid lines and associated equations in each figure represent the respective
linear regressions of the data
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3024
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precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1116
precipitation expected at the higher elevations and could
explain whyt heshell y18O values are not well correlated with
elevation (Fig 9)
Land snails of the genus Vallonia are commonly
associated with ancient sediments of the southern Great
Plains (Theler et al 2004 Wyckoff et al 1997) and the
diffusive evaporation model could provide a basis for
interpretation of many paleoenvironments in which this
genus was present Therefore y18O values of snail shell
aragonite predicted by the diffusive evaporation model
were compared only with the average measured y18O
values of adult Vallonia at each of the 12 modern
localities With one exception y18O values predicted by
the diffusive evaporation model (Balakrishnan and Yapp
2004) differed from the measured y18O values of Vallonia
by no more than 08x (shaded diamonds Fig 10) At
present we have no explanation for the single exception
In contrast for the case of no evaporation all predicted
y
18
O values of Vallonia were significantly different frommeasured y
18O values (28ndash54x more negative shaded
triangles Fig 10)
The approximate agreement between averages of meas-
ured shell y18O values of southern Great Plains land snails
and values predicted by the diffusive evaporation model is
in accord with the result obtained by Balakrishnan and Yapp
(2004) with reference to y18O data for western European
land snails measured by Lecolle (1985) Therefore the
steady-state isotopic effects of evaporation (thus relative
humidity) appear to be manifested in the y18O values of
land-snail shells of different species from two widely
separated regions with distinctly different climates
Conclusion
At various southern Great Plains sample sites transect-
average y13C values of land-snail shell aragonite are related
to the type of photosynthesis (ie C3 C4 or mixed) extant in
the local plant communities There is considerable scatter in
the relationship which suggests that caution should be
exercised in the interpretation of variations of shell y13C
values (eg Goodfriend and Hood 1983 Metref et al 2003
Yates et al 2002) However measured y13C values of
coexisting Vallonia and Gastrocopta are well-correlated
which appears to indicate similar feeding habits and suggests
that ancient samples of shells from these genera may be
useful sources of information on variations in southern Great
Plains plant ecology
Measured y18O values of land-snail shells averaged over
these sample localities appear to be controlled primarily by
the local temperature relative humidity and y18O value of
rain at the times of snail activity (ie nighttime or after rainfall in warmer months) This conclusion is supported by
the relatively good agreement between measured shell y18O
values and shell y18O values predicted with the evaporation
model of Balakrishnan and Yapp (2004)
Scatter of measured shell y18O values among and within
species at a site and among snails of different ages within a
genus (eg coexisting adults and juveniles of Vallonia)
indicates that the environmental information recorded by any
single small sample of land snails from the southern Great
Plains may depart significantly from the climatic bnormQ in a
locale For paleoclimatic studies such scatter emphasizes the
desirability of measuring if possible large numbers of
Figure 10 D18O vs average y18Omeas for each locality of southern Great Plains land snails D18O = (y18Ocalc Agrave y
18Omeas) Diamonds represent the comparison
of calculated and measured shell y18O for shell y18O values calculated with diffusive evaporation of snail body fluid (solid diamonds averages of all analyzed
specimens in a locality shaded diamonds averages of adult Vallonia only) Triangles represent D18O determined with the assumption that the snail shell was in
isotopic equilibrium with active season rain that experienced no evaporation either prior to or after being imbibed by the snails (solid triangles averages of all
analyzed species in a locality shaded triangles averages of adult Vallonia only)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 25
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individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3026
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Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 27
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References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1216
individual snail shells from each defined sample to obtain
average values that might better represent the larger
(bneighborhoodQ ) scale temporal andor spatial variations of
ancient climate that are of interest The results presented here
for modern land-snail shells from the southern Great Plains of
North America suggest that meaningful climatic interpreta-
tions can be obtained from such averages but it must be kept in mind that the climatic information refers to the times of
snail activity and that more than one climatically relevant
parameter influences the shell y18O values
Acknowledgments
We thank Martha Scholl of the United States Geological
Survey for data on the isotopic composition of precipitation
in Norman Oklahoma and Mesonet of the University of
Oklahoma and Oklahoma State University for meteorolog-
ical data The paper benefited from the helpful comments of DD Rousseau and an anonymous reviewer This research
was supported in part by the Office of Graduate Studies at
SMU and NSF grant EAR-9614265 to CJY
Appendix A
Measured d13C and d18O values of Great Plains snails in this work
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Kubic 6B 329 C3 G contractaAgrave
78Agrave
06Kubic 6C 329 C3 G contracta Agrave91 Agrave22
Kubic 6C 329 C3 G holzingeri Agrave94 Agrave17
Kubic 6C 329 C3 G pentodon Agrave91 Agrave21
Kubic 6C 329 C3 V parvula Agrave89 Agrave31
Kubic 6C 329 C3 Vallonia sp (juveniles) Agrave88 Agrave31
Kubic 6C 329 C3 Glyphyalinia indentata Agrave91 Agrave16
Kubic 6C 329 C3 Hawaiia minuscula Agrave61 Agrave26
Kubic 5B 351 C4 G procera Agrave34 Agrave14
Kubic 5B 351 C4 V parvula Agrave29 Agrave23
Kubic 5B 351 C4 Vallonia sp (juveniles) Agrave37 Agrave27
Kubic 5C 351 C4 G procera Agrave34 Agrave12
Kubic 5C 351 C4 Vallonia sp (juveniles) Agrave43 Agrave19
Kubic 1B 351 C4 G contracta Agrave25 Agrave26
Kubic 1B 351 C4 G procera Agrave19 Agrave12
Kubic 1C 351 C4 G procera Agrave22 Agrave19Kubic 2A 360 C4 C3 G pellucida Agrave43 Agrave25
Kubic 2A 360 C4 C3 G procera Agrave41 Agrave24
Kubic 2A 360 C4 C3 V parvula Agrave42 Agrave30
Kubic 2A 360 C4 C3 G contracta Agrave52 Agrave26
Kubic 2A 360 C4 C3 Vallonia sp (juveniles) Agrave54 Agrave09
Kubic 2A 360 C4 C3 Helicodiscus parallelus Agrave57 Agrave34
Kubic 2B 360 C4 C3 G armifera Agrave61 Agrave23
Kubic 2B 360 C4 C3 G holzingeri Agrave71 Agrave21
Kubic 2B 360 C4 C3 G pellucida Agrave65 Agrave15
Kubic 2B 360 C4 C3 G procera Agrave64 Agrave18
Kubic 2B 360 C4 C3 Pupoides albilabris Agrave21 Agrave17
Kubic 2B 360 C4 C3 V parvula Agrave49 Agrave25
Kubic 2B 360 C4 C3 Vallonia sp (juveniles) Agrave39 Agrave17
Kubic 2C 360 C4 C3 G pellucida Agrave39 Agrave17
Kubic 2C 360 C4 C3 G procera Agrave34 Agrave20Kubic 2C 360 C4 C3 Vallonia sp (juveniles) Agrave28 Agrave29
Kubic 4A 360 C4 G armifera Agrave24 Agrave12
Kubic 4A 360 C4 G contracta Agrave07 Agrave28
Kubic 4A 360 C4 G pellucida Agrave24 Agrave22
Kubic 4A 360 C4 G procera Agrave31 Agrave25
Kubic 4B 360 C4 G procera Agrave27 Agrave21
Kubic 4C 360 C4 G armifera Agrave18 Agrave16
Kubic 4C 360 C4 G contracta 00 Agrave16
Kubic 4C 360 C4 G pellucida Agrave16 Agrave17
Kubic 4C 360 C4 G procera Agrave31 Agrave04
Kubic 4C 360 C4 V parvula Agrave44 Agrave20
Kubic 4C 360 C4 Vallonia sp (juveniles) Agrave27 Agrave11
Kubic 3C 366 C4 G procera Agrave19 Agrave01
Bluff Creek 36A 348 C3 G procera Agrave68 Agrave11
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3026
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1316
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 27
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1416
References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1316
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Bluff Creek 36B 348 C3 G procera Agrave100 Agrave13
Salt Fork 9A 320 C3 G pellucida Agrave103 Agrave12
Salt Fork 9A 320 C3 V parvula Agrave99 Agrave20
Salt Fork 9A 320 C3 Vallonia sp (juveniles) Agrave101 Agrave21
Salt Fork 9B 320 C3 G pellucidaAgrave
106Agrave
20Salt Fork 9B 320 C3 V parvula Agrave100 Agrave21
Salt Fork 9B 320 C3 Vallonia sp (juveniles) Agrave100 Agrave18
Salt Fork 9C 320 C3 G pellucida Agrave100 Agrave17
Salt Fork 9C 320 C3 V parvula Agrave104 Agrave21
Salt Fork 9C 320 C3 Vallonia sp (juveniles) Agrave98 Agrave19
McDaniel 11C 375 C4 C3 G procera Agrave61 Agrave28
McDaniel 11A 375 C4 C3 G procera Agrave91 Agrave16
Burnham 17B 519 C4 C3 G pellucida Agrave94 Agrave08
Burnham 17B 519 C4 C3 G procera Agrave71 Agrave09
Burnham 16A 567 C4 CAM C3 G procera Agrave48 Agrave19
Burnham 16B 567 C4 CAM C3 G procera Agrave59 Agrave17
Burnham 12A 607 C4 C3 G pellucida Agrave54 Agrave23
Burnham 12A 607 C4 C3 G procera Agrave56 Agrave19
Burnham 12A 607 C4 C3 V parvula Agrave65 Agrave26
Burnham 14A 607 C4 CAM C3 G pellucida Agrave28 Agrave20Burnham 14A 607 C4 CAM C3 G procera Agrave31 Agrave02
Burnham 14B 607 C4 CAM C3 G pellucida Agrave59 Agrave07
Burnham 14B 607 C4 CAM C3 G procera Agrave40 Agrave21
Burnham 14C 607 C4 CAM C3 G pellucida Agrave49 Agrave09
Burnham 14C 607 C4 CAM C3 G procera Agrave41 Agrave16
Burnham 13A 610 C4 G pellucida Agrave30 11
Burnham 13A 610 C4 G procera Agrave38 04
Burnham 13B 610 C4 G pellucida Agrave38 12
Burnham 13B 610 C4 G procera Agrave55 Agrave18
Burnham 13C 610 C4 G procera Agrave49 Agrave14
Big Salt Plain 15A 482 C3 G pellucida Agrave81 Agrave10
Big Salt Plain 15A 482 C3 G procera Agrave93 Agrave06
Big Salt Plain 15B 482 C3 G procera Agrave94 05
Skull Springs 18A 671 C4 CAM C3 G procera Agrave51 Agrave22
Skull Springs 18A 671 C4 CAM C3 P albilabris Agrave47 Agrave16Skull Springs 18B 671 C4 CAM C3 G procera Agrave68 Agrave10
Skull Springs 18C 671 C4 CAM C3 G procera Agrave72 Agrave14
Skull Springs 19A 665 C4 C3 G cristata Agrave28 Agrave07
Skull Springs 19C 665 C4 C3 G cristata Agrave52 Agrave26
Hitch 22A 915 C4 CAM G procera Agrave42 Agrave15
Hitch 22A 915 C4 CAM P albilabris Agrave57 Agrave18
Hitch 22A 915 C4 CAM Succineidae Agrave65 Agrave03
Hitch 22B 915 C4 CAM Succineidae Agrave46 Agrave15
Hitch 22B 915 C4 CAM G procera Agrave44 Agrave22
Hitch 21A 933 C4 CAM C3 G procera Agrave34 Agrave01
Hitch 21A 933 C4 CAM C3 P albilabris Agrave56 00
Hitch 21C 933 C4 CAM C3 Succineidae Agrave59 Agrave16
Hitch 23A 881 C3 G cristata Agrave90 Agrave26
Hitch 23A 881 C3 G procera Agrave89 Agrave14
Hitch 23A 881 C3 P albilabris Agrave93 Agrave25Hitch 23A 881 C3 V parvula Agrave99 Agrave27
Hitch 23A 881 C3 Vallonia sp (juveniles) Agrave94 Agrave32
Hitch 23B 881 C3 G cristata Agrave82 Agrave16
Hitch 23B 881 C3 V parvula Agrave88 Agrave22
Hitch 23B 881 C3 Vallonia sp (juveniles) Agrave89 Agrave28
Hitch 23C 881 C3 G cristata Agrave37 Agrave18
Black Mesa 27A 1312 C4 C3 V gracilicosta Agrave86 Agrave27
Black Mesa 27A 1312 C4 C3 Vallonia sp (juveniles) Agrave93 Agrave16
Black Mesa 27B 1312 C4 C3 G procera Agrave51 Agrave23
Black Mesa 27B 1312 C4 C3 V gracilicosta Agrave45 Agrave26
Black Mesa 27B 1312 C4 C3 Vallonia sp (juveniles) Agrave53 Agrave29
Black Mesa 27C 1312 C4 C3 Vallonia sp (juveniles) Agrave58 Agrave30
Black Mesa 27C 1312 C4 C3 G pellucida Agrave57 Agrave25
(continued on next page)
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 27
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1416
References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1416
References
Balakrishnan M Yapp CJ 2004 Flux balance models for the oxygen
and carbon isotope compositions of land snail shells Geochimica et
Cosmochimica Acta 68 2007ndash2024
Blair WF Hubbell TH 1938 The biotic districts of Oklahoma
American Midland Naturalist 20 425ndash455
Bruner WE 1931 The vegetation of Oklahoma Ecological Mono-
graphs 2 100ndash188
Carpenter JR 1940 The grassland biome Ecological Monographs 10
617ndash684
Cerling TE Quade J 1993 Stable carbon and oxygen isotopes in soil
carbonates In Swart PK Lohman KC McKenzie J Savin S
(Eds) Climate change in continental isotopic records Geophy-
Appendix A (continued )
Locality Transect and replication Elevation (m) Plant type Land-snail species y13C y
18O
Black Mesa 27C 1312 C4 C3 G procera Agrave62 Agrave25
Black Mesa 27C 1312 C4 C3 P albilabris Agrave36 Agrave24
Black Mesa 27C 1312 C4 C3 V gracilicosta Agrave63 Agrave31
Black Mesa 27C 1312 C4 C3 V parvula Agrave68 Agrave41
Black Mesa 26A 1324 C4 CAM C3 V gracilicostaAgrave
77Agrave
10Black Mesa 26A 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave59 Agrave19
Black Mesa 26B 1324 C4 CAM C3 G pellucida Agrave38 Agrave14
Black Mesa 26B 1324 C4 CAM C3 G procera Agrave71 Agrave30
Black Mesa 26B 1324 C4 CAM C3 V gracilicosta Agrave83 Agrave07
Black Mesa 26B 1324 C4 CAM C3 Vallonia sp (juveniles) Agrave67 Agrave25
Black Mesa 24B 1488 C4 CAM P albilabris Agrave26 Agrave17
Black Mesa 25A 1464 C4 CAM C3 G pellucida Agrave57 Agrave14
Black Mesa 25A 1464 C4 CAM C3 G procera Agrave68 Agrave05
Black Mesa 25A 1464 C4 CAM C3 V gracilicosta Agrave68 Agrave34
Black Mesa 25A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave79 Agrave25
Black Mesa 25B 1464 C4 CAM C3 G pellucida Agrave79 Agrave30
Black Mesa 25B 1464 C4 CAM C3 V gracilicosta Agrave82 Agrave33
Black Mesa 25B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave87 Agrave21
Black Mesa 25C 1464 C4 CAM C3 G pellucida Agrave65 Agrave19
Black Mesa 25C 1464 C4 CAM C3 V gracilicosta Agrave73 Agrave38Black Mesa 25C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave65 Agrave26
Black Mesa 35A 1464 C4 CAM C3 G pellucida Agrave48 Agrave11
Black Mesa 35A 1464 C4 CAM C3 V gracilicosta Agrave67 Agrave22
Black Mesa 35A 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave71 Agrave24
Black Mesa 35B 1464 C4 CAM C3 G pellucida Agrave73 Agrave20
Black Mesa 35B 1464 C4 CAM C3 V gracilicosta Agrave78 Agrave28
Black Mesa 35B 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave82 Agrave26
Black Mesa 35C 1464 C4 CAM C3 G pellucida Agrave82 Agrave21
Black Mesa 35C 1464 C4 CAM C3 Pupilla muscorum Agrave87 Agrave17
Black Mesa 35C 1464 C4 CAM C3 V gracilicosta Agrave84 Agrave08
Black Mesa 35C 1464 C4 CAM C3 Vallonia sp (juveniles) Agrave81 Agrave05
Owensby 61A 2193 C3 P muscorum Agrave132 Agrave18
Owensby 61A 2193 C3 V gracilicosta Agrave111 Agrave17
Owensby 61A 2193 C3 Vallonia sp (juveniles) Agrave93 Agrave23
Owensby 61C 2193 C3 V gracilicosta Agrave84 Agrave16Owensby 60B 2242 C3 Vallonia sp (juveniles) Agrave96 Agrave30
Owensby 59A 2288 C3 V gracilicosta Agrave104 Agrave31
Owensby 59A 2288 C3 Vallonia sp (juveniles) Agrave100 Agrave07
Owensby 59B 2288 C3 V gracilicosta Agrave109 Agrave13
Owensby 59B 2288 C3 Vallonia sp (juveniles) Agrave115 Agrave37
Owensby 59C 2288 C3 V gracilicosta Agrave117 Agrave10
CS Ranch 30A 1922 C4 CAM C3 P albilabris Agrave43 Agrave19
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave47 Agrave24
CS Ranch 29B 1940 C4 CAM C3 G pellucida Agrave50 Agrave26
CS Ranch 29C 1940 C4 CAM C3 P albilabris Agrave50 Agrave10
Chase 34A 1952 C4 C3 V gracilicosta Agrave92 Agrave38
Chase 33A 2184 C4 C3 G pilsbryana Agrave69 Agrave33
Chase 33B 2184 C4 C3 Cionella lubrica Agrave88 Agrave15
Chase 33B 2184 C4 C3 G pilsbryana Agrave93 Agrave25
Chase 33B 2184 C4 C3 G pellucida Agrave92 Agrave16Chase 31C 2220 C4 C3 G pilsbryana Agrave85 Agrave13
Chase 31C 2220 C4 C3 Zonitoides arboreus Agrave94 Agrave37
Chase 32C 2233 C4 C3 V gracilicosta Agrave93 Agrave18
Chase 32C 2233 C4 C3 Vallonia sp (juveniles) Agrave86 Agrave27
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3028
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1516
sical Monograph vol 78 American Geophysical Union Washington
pp 217ndash231
Cook A 1979 Homing in the gastropoda Malacologia 18 315ndash318
Cowie RH 1984 The life-cycle and productivity of the land snail
Theba pisana (Mollusca Helicidae) Journal of Animal Ecology 53
311ndash325
Craig H 1957 Isotopic standard for carbon and oxygen and correction
factors for mass spectrometric analysis of carbon dioxide Geochimicaet Cosmochimica Acta 12 133ndash149
Douglas MW Maddox RA Howard K 1993 The Mexican monsoon
Journal of Climate 6 1665ndash1677
Dansgaard W 1964 Stable isotopes in precipitation Tellus 16
436ndash469
Edelstam C Palmer C 1950 Homing behaviour in gastropods Okios 2
259ndash270
Ehleringer JR Cerling TE Helliker BR 1997 C4 photosynthesis
atmospheric CO2 and climate Oecologia 112 285ndash299
Elliot RD 1949 Forecasting the weathermdashThe weather types of North
America Weatherwise 2 15ndash 18
Francey RJ 1983 A comment on 13C 12C in land snail shells Earth and
Planetary Science Letters 63 142 ndash 143
Gelperin A 1974 Olfactory basis of homing in the giant garden slug
Limax maximus Proceedings of the National Academy of ScienceUnited States of America 71 966ndash970
Goodfriend GA Ellis GL 2002 Stable carbon and oxygen isotopic
variations in modern Rabdotus land snail shell in the southern Great
Plains USA and their relation to environment Geochimica et
Cosmochimica Acta 66 1987ndash2002
Goodfriend GA Hood DJ 1983 Carbon isotope analysis of land snail
shells implications for carbon sources and radiocarbon dating Radio-
carbon 25 810ndash830
Goodfriend GA Magaritz M 1987 Carbon and oxygen isotope
composition of shell carbonate of desert land snails Earth and Planetary
Science Letters 86 377ndash388
Goodfriend GA Magaritz M Gat JR 1989 Stable isotope
composition of land snail body water and its relation to environmental
waters and shell carbonate Geochimica et Cosmochimica Acta 53
3215ndash3221Grossman EL Ku T-L 1986 Oxygen and carbon isotope fractiona-
tion in biogenic aragonite temperature effects Chemical Geology 59
59ndash74
Heatwole H Heatwole A 1978 Ecology of the Puerto Rican Camaenid
tree-snails Malacologia 17 241ndash315
Kuchler AW 1964 Potential vegetation of the conterminous United
States American Geographic Society Special Publication 36
Jacobs BF Kingston JD Jacobs LL 1999 The origin of grass-
dominated ecosystems Annals of the Missouri Botanical Gardens 86
590ndash643
Lecolle P 1983 Relation entre les teneurs en 18O et 13C des tests de
Gasteropodes terrestres et le climat oceanique et alpin Comptes
Rendus de lrsquoAcademie des Sciences Serie II 297 863 ndash 866
Lecolle P 1984 Influence de lrsquoaltitude en climat mediterraneen sur les
teneurs en oxygene-18 et carbone-13 des coquilles de Gasteropodesterrestres Comptes Rendus de lrsquoAcademie des Sciences Serie II 298
211ndash214
Lecolle P 1985 The oxygen isotope composition of land snail shells as a
climatic indicator applications to hydrogeology and paleoclimatology
Chemical Geology 58 157ndash 181
Magaritz M Heller J 1980 A desert migration indicator-oxygen isotopic
composition of land snail shells Palaeogeography Palaeoclimatology
Palaeoecology 32 153ndash162
Magaritz M Heller J 1983 A comment of 13C 12C in land snail shells-
reply Earth and Planetary Science Letters 63 144ndash145
Magaritz M Heller J Volokita M 1981 Land-air boundary
environment as recorded by the 18O 16O and 13C 12C isotope ration
in the shells of land snails Earth and Planetary Science Letters 52
101ndash106
McCrea JM 1950 On the isotopic chemistry of carbonates and a
paleotemperature scale Journal of Chemical Physics 18 849ndash857
Metref S Rousseau D-D Bentaleb I Labonne M Vianey-Liaud M
2003 Study of the diet effect on y13C of shell carbonate of the land
snail Helix aspersa in experimental conditions Earth and Planetary
Science Letters 211 381 ndash 393
Nativ R Riggio R 1990 Precipitation in the Southern High Plains
meteorologic and isotopic features Journal of Geophysical Research95 22559ndash 22564
Newell PF 1966 The nocturnal behaviour of slugs Medical Biology
Illustrated 16 146 ndash 159
Ostlie WR Schneider RE Aldrich JM Faust TM McKim RLB
Chaplin SJ 1997 The Status of Biodiversity in the Great Plains The
Nature Conservancy Arlington VA USA
Owensby CE Ham JM Knapp AK Bremer D Auen LM 1997
Water vapour fluxes and their impact under elevated CO2 in a C4-
tallgrass prairie Global Change Biology 3 189ndash195
Risser PG 1985 Grasslands In Chabot BF Mooney HA (Eds)
Physiological Ecology of North American Plant Communities Chap-
man and Hall New York pp 232ndash256
Risser PG 1990 Landscape processes and the vegetation of the North
American grassland In Collins SL Wallace LL (Eds) Fire in
North American Tallgrass Prairies University of Oklahoma PressNorman pp 133ndash146
Rossignol J Moine O Rousseau D-D 2004 The Buzzardrsquos Roost and
Eustis mollusc sequences comparison between the paleoenvironments
of two sites in the Wisconsinan loess of Nebraska USA Boreas 33
145ndash154
Rozanski K Araguas-Araguas L Gonfiantini R 1993 Isotopic patterns
in modern global precipitation In Swart PK Lohman KC
McKenzie J Savin S (Eds) Climate Change in Continental Isotopic
Records Geophysical Monograph vol 78 American Geophysical
Union Washington pp 1 ndash 36
Sage RF Li M Monson RK 1999 The taxonomic distribution of C4
photosynthesis In Sage RF Monson RK (Eds) C4 Plant Biology
Academic Press pp 551ndash 584
Sharpe SE Forester RM Whelan JF McConnaughey T 1994
Molluscs as climate indicators preliminary stable isotope and com-munity analyses Proceedings of the 5th International High-level
Radioactive Waste Management Conference and Exposition Las Vegas
Nevada pp 2538ndash 2544
Shelford VE 1963 The Ecology of North America University of Illinois
Press Urbana
Stott LD 2002 The influence of diet on the y13C of shell carbon in the
pulmonate snail Helix aspersa Earth and Planetary Science Letter 195
249ndash259
Theler JL Wyckoff DG Carter BJ 2004 The Southern Plains
gastropod survey the distribution of land snail populations in an
American grassland environment American Malacological Bulletin 18
(12) 1ndash16
Thompson R Cheny S 1996 Raising snails National Agriculture
Library Special Reference Briefs NAL SRB 96-05
Tieszen L Reed BC Bliss NB Wylie BK DeJong DD 1997NDVI C3 and C4 production and distribution in great plains grassland
land cover classes Ecological Applications 7 59ndash78
Van der Schalie A Getz LL 1961 Comparison of adult and young
Pomatiopsis cincinnatiensis (lea) in respect to moisture requirements
Transactions of the American Microscopical Society 80 211 ndash 220
Van der Schalie A Getz LL 1963 Comparison of temperature and
moisture responses of the snail genera Pomatiopsis and Oncomelania
Ecology 44 73ndash83
Ward D Slotow R 1992 The effects of water availability on the life
history of the desert snail Trochoidea seetzeni An experimental field
manipulation Oecologia 90 572ndash580
Weaver JE Albertson FW 1956 Grasslands of the Great Plains Their
Nature and Use Johnsen Publishing Co Lincoln NE
Wells GP 1944 The water relations of snails and slugs III Factors
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash30 29
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030
872019 Balakrishnan et al 2004
httpslidepdfcomreaderfullbalakrishnan-et-al-2004 1616
determining the activity of Helix pomatia L Journal of Experimental
Biology 44 73ndash83
Wyckoff DG Theler JL Carter BJ 1997 Southern Plains gastropods
modern occurrences prehistoric implications Final Report to the
National Geographic Society 46 pp
Yapp CJ 1979 Oxygen and carbon isotope measurements of land snail
shell carbonate Geochimica et Cosmochimica Acta 43 629ndash635
Yates TJS Spiro BF Vita-Finzi C 2002 Stable isotope variability and
the selection of terrestrial mollusk shell samples for 14C dating
Quaternary International 87 87ndash100
M Balakrishnan et al Quaternary Research 63 (2005) 15ndash3030