Saskatchewan Geological Survey 1 Summary of Investigations 2009, Volume 1
Facies Characterization of the Lower Cretaceous Sparky, Waseca, and McLaren Formations (Mannville Group) of West-central
Saskatchewan
Alireza Morshedian 1
Morshedian, Alireza, MacEachern, James A., and Dashtgard, Shahin E. (2009): Facies characterization of the Lower Cretaceous Sparky, Waseca, and McLaren formations (Mannville Group) of west-central Saskatchewan; in Summary of Investigations 2009, Volume 1, Saskatchewan Geological Survey, Sask. Ministry of Energy and Resources, Misc. Rep. 2009-4.1, Paper A-9, 14p.
, James A. MacEachern 1, and Shahin E. Dashtgard 1
Abstract Preliminary results from ichnological and sedimentological facies analysis of 69 cored wells of the Lower Cretaceous (Lower to Middle Albian) Sparky, Waseca, and McLaren formations (Mannville Group) in the Lloydminster area of west-central Saskatchewan yield ten recurring facies that reflect conditions of reduced and fluctuating salinity, typical of brackish-water settings. The successions display physical sedimentological features dominated by abundant organic-rich mudstone drapes of probable fluid-mud origin, syneresis cracks, soft-sediment deformation, carbonaceous detritus, normally graded mudstones, low-angle undulatory parallel laminations, and wave, current and combined-flow ripples. Facies are generally heterolithic, attesting to autogenic fluctuations in depositional processes.
Ichnologically, bioturbation intensities (BI) range widely (BI 0 to BI 5), and facies are characterized by abundant diminutive ichnogenera comprising low-diversity (locally monogeneric) trace-fossil suites. Common ichnogenera include Gyrolithes, Teichichnus, Planolites, Palaeophycus, Cylindrichnus, Skolithos, Thalassinoides, Chondrites, and Lingulichnus. Rare but important secondary elements include Asterosoma, Lockeia, Phycosiphon, Rosselia, and Rhizocorallium. Most suites consist of mixtures of elements characteristic of both the Skolithos Ichnofacies and the Cruziana Ichnofacies. Persistent ichnogenera constitute facies-crossing elements that record permanent to semi-permanent dwellings of deposit-feeding infauna. Additional behaviour indicators include navichnia (sediment-swimming structures) and fugichnia (escape structures), consistent with rapid and episodic deposition of sand as well as mud (e.g., via flocculation). Variations in bioturbation intensity primarily attest to marked changes in sedimentation rates.
The integration of ichnological and sedimentological datasets indicates that deposition occurred within brackish-water embayments, bay-head deltas, tidal flats, and coastal-plain environments. Variations in trace-fossil diversities and the introduction of less markedly facies-crossing ichnogenera (e.g., Asterosoma, Phycosiphon, and Rhizocorallium) may suggest that elevated salinities occurred periodically within the study area.
Keywords: Mannville Group, brackish water, ichnology.
1. Introduction The Lower Cretaceous Mannville Group has been studied since the early 1940s and was first drilled in 1942. It unconformably overlies Paleozoic to Jura-Cretaceous strata, is disconformably overlain by the transgressive Joli Fou marine shale of the Colorado Group (Figure 1), and is composed of: 1) well cemented to weakly consolidated sandstone, 2) siltstone, 3) mudstone, 4) mixed sandstone and mudstone that form heterolithic stratification, and 5) minor coals.
The “Mannville Formation” was originally proposed by Nauss (1945), based on his work on cores from oil and gas wells in the Vermillion area of east-central Alberta. The type section was recognized from the Northwest Mannville No.1 well (01-18-50-8W4). Nauss subdivided the Mannville Formation (from top to bottom) into the O’Sullivan, Borradaile, Tovell, Islay, Cummings, and Dina members. Wickenden (1948) suggested that the Mannville can be divided into basal, middle, and upper units. The most commonly used stratigraphic nomenclature for the Mannville Group in the Lloydminster area of Saskatchewan and Alberta is based on unofficial driller’s terminology and electric log characteristics (Edmunds, 1948). These include (from top to bottom): Colony, McLaren, Waseca, Sparky, General Petroleums, Rex, Lloydminster, Cummings, and Dina, although no formal type section has been
1 ARISE, Department of Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6.
Saskatchewan Geological Survey 2 Summary of Investigations 2009, Volume 1
established to formalize this nomenclature. The Mannville was elevated to Group status by Badgley (1952). Vigrass (1977) and Orr et al. (1977) used the nine informal stratigraphic subdivisions of Edmunds (1948) except that Vigrass (1977) referred to them as members, whereas Orr et al. (1977) considered them as formations. For the purpose of this study, the units are assigned formation status, a hierarchal level commonly assigned to these units.
2. Study Area and Methodology
The study area is located between Townships 50 and 60, and between Range 19 west of the 3rd Meridian and Range 3 west of the 4th Meridian, for a total area of 12,400 km2 (Figure 2). The cored intervals were evaluated for trace fossils, sedimentary structures, lithological features, and stratigraphic discontinuities. Recurring successions have been assigned interpretations regarding facies relationships, facies associations, and depositional environments. Ichnological appraisal includes ichnogenera identification, trace-fossil size, bioturbation intensity, distribution of burrowing, and ethological interpretation.
3. Facies Description Based on the integration of lithology, primary sedimentary structures, bioturbation intensity, and ichnological suites, ten recurring facies have been identified from the Sparky, Waseca, and McLaren formations of the Mannville Group within the study area (F1 to F10 of Table 1). Evaluating bioturbation intensity has been used to help assess the relative rates of deposition and processes responsible for sedimentation. This technique was originally proposed by Reineck (1963) and involves a semi-quantitative measurement of the intensity of bioturbation in order to describe the destruction of primary bedding by biogenic activity (Reineck and Singh, 1980). Taylor and Goldring (1993) redefined this approach as “bioturbation index” (BI), based on a non-linear scale of BI 0 to BI 6.
a) Facies 1: Mudstone Facies 1 consists of 70 to 98% mudstone (silt and clay) with the remaining components consisting of thin bands of siltstone and sandstone. Based on sedimentological and ichnological features, Facies 1 has been subdivided into three subfacies.
Figure 1 - Correlation of Lower Cretaceous strata in eastern Alberta and western Saskatchewan (modified after Christopher, 2003); red dots indicate formations included in this study.
ALBERTA SASKATCHEWAN
ATHABASCA COLD LAKE LLOYDMINSTER
LOW
ER
MID
DLE
UP
PE
R
ALB
IAN
LOW
ER
CR
ETA
CE
OU
S
PELICAN FM VIKING FM VIKING FM
JOLI FOU FM JOLI FOU FMJOLI FOU
FM
GRAND RAPIDSFM
CLEARWATER FM
WABISKAW
A UNIT
B UNIT
C UNIT
D UNIT
MA
NN
VIL
LE G
RO
UP
LOW
ER
CO
LOR
AD
OG
RO
UP
WASECA
SPARKY
GENERAL PETROLEUMS
REX
CUMMINGS
LLOYDMINSTER
DINA
COLONYMcCLAREN
MCMURRAY FM
NE
OC
OM
IAN
-A
PTI
AN
WAB
AMUN
WIN
TERB
URN
WO
ODB
END
BEAV
ERHI
LL L
AKE
DEVONIAN
SOURIS RIVER
DUPEROW
THREE FORKS
SUCCESS FM (S2)
Saskatchewan Geological Survey 3 Summary of Investigations 2009, Volume 1
Fig
ure
2 - L
ocat
ion
of st
udy
area
in w
est-c
entr
al S
aska
tche
wan
and
eas
t-cen
tral
Alb
erta
. Red
dot
s on
the
deta
iled
map
indi
cate
loca
tions
of 7
3 w
ells
with
Man
nvill
e G
roup
co
res t
hat h
ave
been
exa
min
ed.
AB
SK
N
T49 T50 T51 T52 T53 T54 T55 T56 T57 T58 T59 T60
W3
Saskatchewan Geological Survey 4 Summary of Investigations 2009, Volume 1
Tabl
e 1
- Sum
mar
y of
dep
ositi
onal
faci
es. B
I, bi
otur
batio
n in
dex;
HC
S, h
umm
ocky
cro
ss-s
trat
ifica
tion;
and
SC
S, sw
aly
cros
s-st
ratif
icat
ion.
LIT
HO
LO
GY
PHY
SIC
AL
SE
DIM
EN
TA
RY
ST
RU
CT
UR
ES
BIO
GE
NIC
ST
RU
CT
UR
ES
B I
DE
POSI
ON
AL
PR
OC
ESS
ES
DE
POSI
TIO
NA
L S
ET
TIN
G
1a: F
issi
le
mud
ston
eTh
ick
dark
gre
y to
bla
ck
mud
ston
e, lo
cally
lam
inat
ed
fine-
grai
ned
sand
ston
e/si
ltsto
ne
inte
rlam
inat
ed. S
hale
98%
, sa
ndst
one/
silts
tone
2%
.
Rar
e os
cilla
tion
rippl
e la
min
atio
n.C
hond
rite
s, Pl
anol
ites,
navi
chni
a.0
to 1
Mud
ston
e de
posi
ted
thro
ugh
susp
ensi
on se
ttlin
g or
as f
locc
ulat
ed
mud
; sed
imen
t m
obili
zed
by
osci
llato
ry fl
ow.
Var
ious
dep
ositi
onal
setti
ngs,
aban
done
d ch
anne
l, ch
enie
r pla
in.
1b: B
urro
wed
si
lty
mud
ston
e
Mix
ture
of m
udst
one,
fine
- to
very
fine
-gra
ined
sand
ston
e an
d si
ltsto
ne; m
udst
one
70%
, sa
ndst
one/
silts
tone
30%
.
Rar
e pr
eser
vatio
n of
ph
ysic
al se
dim
enta
ry
stru
ctur
es, l
ocal
ly
osci
llatio
n rip
ples
, mic
ro-
HC
S (th
in-b
edde
d lo
w-
angl
e un
dula
tory
par
alle
l la
min
atio
n).
Teic
hich
nus,
Plan
olite
s, Pa
laeo
phyc
us, A
ster
osom
a,
Hel
min
thop
sis,
Phyc
osip
hon,
G
yrol
ithes
, Cyl
indr
ichn
us,
Skol
ithos
, Cho
ndri
tes,
fugi
chni
a, n
avic
hnia
.
2 to
5M
udst
one
depo
site
d th
roug
h su
spen
sion
settl
ing
or a
s flo
ccul
ated
m
ud;
sand
ston
e de
posi
ted
by
osci
llato
ry fl
ow.
Fully
mar
ine
depo
sitio
n be
low
stor
m
wav
e-ba
se o
r set
tings
shel
tere
d fr
om
stor
ms,
slow
con
tinuo
us d
epos
ition
, ox
ygen
ated
con
ditio
ns.
1c: P
inst
ripe
mud
ston
eD
ark
grey
or b
lack
mud
ston
e w
ith v
ery
thin
inte
rbed
ded
silts
tone
or v
ery
fine-
grai
ned
sand
ston
e.
Pins
tripe
lam
inat
ion,
no
rmal
gra
ding
, syn
eres
is
crac
ks.
Plan
olite
s, C
ylin
dric
hnus
, Sk
olith
os, T
eich
ichn
us,
Gyr
olith
es,
navi
chni
a.
0 to
2M
udst
one
depo
site
d th
roug
h su
spen
sion
settl
ing
or a
s mud
; se
dim
ent m
obili
zed
by o
scill
ator
y flo
w.
Var
ious
dep
ositi
onal
setti
ngs.
Poss
ible
hyp
erpy
cnal
and
/or
hypo
pycn
al c
ondi
tions
.
2a: L
entic
ular
-be
dded
m
udst
one
Gr e
y, si
derit
ic si
lty m
udst
one
with
ver
y fin
e to
fine
gra
ined
rip
pled
sand
ston
e, lo
cally
bi
otur
bate
d. M
udst
ones
>7
0%.
Osc
illat
ion
rippl
e cr
oss-
lam
inat
ion,
con
volu
te
bedd
ing,
nor
mal
ly g
rade
d be
ds, s
harp
con
tact
s.
Plan
olite
s, Sk
olith
os,
Cyl
indr
ichn
us, T
eich
ichn
us,
fugi
chni
a, n
avic
hnia
.
0 to
2A
ltern
atio
n be
twee
n tra
ctio
n tra
nspo
rt an
d su
spen
sion
sedi
men
t de
posi
tion.
Var
ious
dep
ositi
onal
setti
ngs,
com
mon
in
shal
low
, sub
tidal
to
inte
rtida
l env
ironm
ents
.
2b: B
urro
wed
m
udst
one
and
sand
y si
ltst o
ne
Het
erol
ithic
, int
erbe
dded
m
udst
one
and
very
fine
- to
fine-
grai
ned
sand
ston
e.
Mud
ston
es >
70%
.
Osc
illat
ion
rippl
e cr
oss-
lam
inat
ion,
loca
l mic
ro-
HC
S, sy
nere
sis c
rack
s, no
rmal
gra
ding
.
Plan
olite
s, Sk
olith
os,
Gyr
olith
es, T
eich
ichn
us,
Thal
assi
noid
es,
Pala
eoph
ycus
, Ros
selia
, Rh
izoc
oral
lium
, Ter
ebel
lina,
C
hond
rite
s, fu
gich
nia,
na
vich
nia.
1 to
5M
udst
one
depo
site
d th
roug
h su
spen
sion
settl
ing
or a
s flo
ccul
ated
m
ud, s
edim
ent m
obili
zed
by
osci
llato
ry fl
ow. C
lay
shrin
kage
fro
m sa
linity
fluc
tuat
ions
.
Dep
ositi
on w
ithin
fair-
wea
ther
wav
e-ba
se. F
luct
uatin
g sa
linity
, low
rate
of
sedi
men
tatio
n, a
nd p
erio
dic-
even
t se
dim
enta
tion.
3a:
Spor
adic
ally
to
mod
erat
ely
burro
wed
in
terb
edde
d sa
ndst
one
and
mud
ston
e
Het
erol
it hic
mud
ston
e an
d sa
ndst
one;
shar
p co
ntac
ts,
loca
lly b
iotu
rbat
ed.
Sand
ston
e/m
udst
one
prop
ortio
ns a
ppro
xim
atel
y su
bequ
al.
Osc
illat
ion
rippl
e, v
ery
rare
cu
rrent
ripp
les,
sand
-fille
d sy
nere
sis c
rack
s.
Plan
olite
s, Sk
olith
os,
Gyr
olith
es, C
ylin
dric
hnus
, C
hond
rite
s, Te
ichi
chnu
s, na
vich
nia,
?Ar
enic
olite
s, fu
gich
nia.
0 to
2M
udst
one
depo
site
d by
susp
ensi
on
settl
ing
or a
s flo
ccul
ated
mud
; sa
ndst
one
depo
site
d by
un
idire
ctio
nal f
low
and
osc
illat
ion,
sa
linity
-indu
ced
and
clay
shrin
kage
.
Dep
osite
d ab
ove
stor
m w
ave-
base
but
be
low
fair-
wea
ther
wav
e-ba
se,
fluct
uatin
g sa
linity
.
3b:
Mod
erat
ely
to
perv
asiv
ely
burro
wed
i n
terb
edde
d sa
ndst
one
and
mud
ston
e
Het
erol
ithic
mud
ston
e an
d sa
ndst
one;
con
tact
s are
bi
otur
bat e
d.
Sand
ston
e/m
udst
one
prop
ortio
ns a
ppro
xim
atel
y su
bequ
al.
Rar
e os
cilla
tion
and
curre
nt
rippl
es.
Plan
olite
s, C
ylin
dric
hnus
, Sk
olith
os, T
eich
ichn
us,
Pala
eoph
ycus
, Th
alas
sino
ides
, Ros
selia
, C
hond
rite
s, As
tero
som
a,
Gyr
olith
es,
navi
chni
a,
fugi
chni
a.
2 to
4M
udst
one
depo
site
d by
susp
ensi
on
settl
ing
or a
s flo
ccul
ated
mud
, sa
ndst
one
depo
site
d by
un
idire
ctio
nal f
low
and
osc
illat
ion.
Dep
osite
d ab
ove
stor
m w
ave-
base
but
be
low
fair-
wea
ther
wav
e-ba
se, s
low
er
depo
sitio
n th
an F
acie
s 3a.
4a:
Inte
rbed
ded
mud
ston
e a n
d rip
pled
sa
ndst
ones
Het
erol
ithic
mud
ston
e an
d sa
ndst
one.
Dar
k m
udst
one
drap
es o
f cen
timet
re to
m
illim
etre
scal
e, o
rgan
ic
detri
tus;
sand
ston
es c
entim
etre
to
dec
imet
re sc
ale
(>60
%).
Osc
illat
ion
rippl
e cr
oss-
lam
inat
ion
s yne
resi
s cra
cks,
mic
ro-H
CS,
mud
ston
e dr
apes
, co n
volu
te b
eddi
ng,
norm
ally
gra
ded
beds
.
Plan
olite
s, Sk
olith
os,
Gyr
olith
es, C
ylin
dric
hnus
, fu
gich
nia,
nav
ichn
ia.
0 to
2M
udst
one
depo
site
d m
ainl
y fro
m
susp
ensi
on se
ttlin
g, o
scill
ator
y flo
w,
poss
ible
hyp
erpy
cnal
and
hyp
opyc
nal
cond
ition
s. C
lay
shrin
kage
from
sa
linity
fluc
tuat
ions
.
Fair
wea
ther
and
rare
stor
m
cond
ition
s. Fl
uvia
l sed
imen
t inp
ut in
th
e co
asta
l reg
ime.
4b:
Bio
turb
ated
in
terb
edde
d m
udst
one
and
rippl
ed
sand
ston
es
Het
erol
ithic
mud
ston
e an
d sa
ndst
one.
Dar
k m
udst
one
drap
es c
entim
etre
to
mill
imet
re sc
ale,
org
anic
de
tritu
s; sa
ndst
ones
cen
timet
re
to d
ecim
etre
scal
e (>
60%
).
Osc
illat
ion
rippl
e cr
oss-
lam
inat
ion
syne
resi
s cra
cks,
mic
ro-H
CS,
mud
ston
e dr
apes
, co n
volu
te b
eddi
ng,
norm
ally
gra
ded
beds
.
Plan
olite
s, Sk
olith
os,
Gyr
olith
es, C
ylin
dric
hnus
, C
hond
rite
s, Te
ichi
chnu
s, Pa
laeo
phyc
us, L
ocke
ia,
Thal
assi
noid
es,
fugi
chni
a,
navi
chni
a.
2 to
4M
udst
one
depo
site
d fro
m
susp
ensi
on, s
ands
tone
ent
rain
ed b
y w
aves
. Cla
y sh
rinka
ge fr
om sa
linity
flu
ctua
tions
.
Fair-
wea
ther
and
rare
stor
m w
aves
. V
aria
ble
wat
er sa
liniti
es, p
ossi
ble
fluvi
al se
dim
ent i
nput
.
Fine
-gra
ined
sand
ston
e,
orga
nic
detri
tus,
loca
l m
udst
one
drap
es.
Wav
y pa
ralle
l lam
inat
ion.
Skol
ithos
, Cyl
indr
ichn
us,
Cho
ndri
tes,
fugi
chni
a.0
to 2
Sedi
men
t mob
ilize
d by
wav
es.
Sedi
men
t dep
osite
d ab
ove
fair-
wea
ther
wav
e-ba
se.
Ver
y fin
e-gr
aine
d, e
rosi
onal
ly
amal
gam
ated
sand
ston
e, ra
re
mud
ston
e d r
apes
.
HC
S, S
CS,
osc
illat
ion
rippl
e cr
oss-
lam
inat
ion.
fugi
chni
a0
to 1
Eros
iona
l am
alga
mat
ion,
pro
duce
d by
stor
m w
aves
.H
CS
and
SCS,
dep
osite
d un
der
stric
tly o
scill
ator
y st
orm
con
ditio
ns.
S edi
men
t dep
osite
d ab
ove
fair-
wea
ther
wav
e-ba
se o
r bel
ow fa
ir-w
eath
er w
ave-
base
, but
abo
ve st
orm
w
ave-
base
.Fi
ne- t
o m
ediu
m-g
rain
ed
sand
ston
e w
ith so
me
inte
rstit
ial m
ud a
nd
biot
urba
ted
fabr
ic, a
ltern
atin
g w
ith th
in, s
harp
-bas
ed
lam
inat
ed sa
nd b
eds.
Loca
lly H
CS
and
osci
llatio
n rip
ples
Dom
inat
ed b
y bi
ogen
ical
ly
mot
tled
fabr
ic;
Plan
olite
s, Sk
olith
os, P
alae
ophy
cus,
Aste
roso
ma,
Cho
ndri
tes,
?A
reni
colit
es, C
ylin
dric
hnus
.
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out f
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urat
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.
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udst
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d w
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s.N
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ssils
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argi
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Faci
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sand
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e
Faci
es 8
: Mas
sive
(a
ppar
ently
st
ruct
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sa
ndst
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FAC
IES
Facies 1: Mudstone Facies 2: Mudstone-dominated heterolithics
Faci
es 9
: Cur
rent
- rip
ple
to tr
ough
cr
oss-
stra
tifie
d sa
ndst
one
Faci
es 1
0: C
oal
Facies 3: : Subequal sandstone and mudstone heterolithics Facies 4: Sandstone-dominated heterolithics
Faci
es 5
: Wav
y an
d pl
anar
par
alle
l-la
min
ated
sand
ston
eFa
cies
6: L
ow-a
ngle
un
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par
alle
l- la
min
ated
sand
ston
e
Saskatchewan Geological Survey 5 Summary of Investigations 2009, Volume 1
Facies 1a: Fissile Mudstone
This facies consists of massive dark grey to black mudstone, locally laminated. Siderite-cemented bands or nodules occur sporadically throughout the facies. Very fine-grained sandstone and siltstone comprise 3 to 5% of the facies, and locally show normal grading, and oscillation ripples (Figures 3A and 3B). Facies 1a displays BI 0 to BI 1 and is sporadically bioturbated. Trace fossils include Planolites, Chondrites, and navichnia (mantle-and-swirl structures).
We interpret that muds have been deposited through suspension settling or as flocculated mud, and silts and sands transported by oscillatory waves. The graded beds indicate sediment emplacement by sudden, waning-energy density underflows. Low bioturbation intensities are probably the result of high sedimentation rates. The presence of diminutive Chondrites suggests that marine conditions prevailed.
Facies 1b: Burrowed Silty Mudstone
Facies 1b consists of up to 70% mudstone with intercalated layers of fine-grained sandstone/siltstone. It is pervasively bioturbated, although rare preservation of physical sedimentary structures such as oscillation ripples and micro-hummocky cross-stratification occurs within some siltstone and sandstone layers. Carbonaceous detritus is locally common. Bioturbation intensities within the facies commonly reach BI 5 and locally range down to BI 2 where primary sedimentary structures are preserved (Figures 3C and 3D). Trace fossils include Teichichnus, Planolites, Palaeophycus, Asterosoma, Helminthopsis, Phycosiphon, Gyrolithes, Cylindrichnus, Skolithos, Chondrites, fugichnia (escape structures), and navichnia.
We interpret Facies 1b to have been deposited in a well oxygenated and more normal marine setting, probably lying below fair-weather wave-base and largely sheltered from storms. Facies 1b contains distinctively marine trace fossils (e.g., Asterosoma, Helminthopsis, and Phycosiphon) and corresponds to a slightly stressed expression of the Cruziana Ichnofacies.
Facies 1c: Pinstripe Mudstone
Facies 1c is characterized by abundant millimetre- to centimetre-thick, sharp-based, locally normally graded siltstone or very fine-grained sandstone layers interlaminated with fissile mudstone. Interlaminae within the pinstripes are commonly parallel laminated and locally are wavy rippled. Syneresis cracks and siderite nodules are common elements of the facies. Bioturbation intensities at the bed scale range from BI 0 to BI 2 (Figures 3E and 3F). Trace-fossil diversities are typically low. Trace-fossil suites are dominated by deposit-feeding structures, with subordinate dwelling structures of inferred suspension-feeding organisms. Trace fossils include Planolites, Cylindrichnus, Skolithos, Teichichnus, Gyrolithes, and navichnia.
The low bioturbation intensity of the facies suggests that sedimentation rates were high. Reduced trace-fossil diversities, diminutive ichnogenera, and locally common syneresis cracks indicate that the salinities were variable and commonly brackish (Beynon and Pemberton, 1992; Gingras et al., 2005; MacEachern and Gingras, 2007).
b) Facies 2: Mudstone-dominated Heterolithic Facies Facies 2 comprises mudstone-dominated heterolithic intervals wherein mudstone comprises at least 70% of the facies, with the remaining components consisting of siltstone and sandstone layers. Facies 2 has been subdivided into two subfacies on the basis of sedimentological and ichnological features.
Facies 2a: Lenticular-bedded Mudstone
Facies 2a comprises dark grey to black mudstone interbedded with abundant oscillation-rippled siltstone and sandstone stringers. Mudstone and siltstone bedsets are typically 1 to 3 cm thick and may reach up to 5 cm; the surfaces between them are commonly sharp and undulating. Facies 2a shows low bioturbation intensities (BI 0 to BI 2, with BI 1 most common); this weakly burrowed character distinguishes it from Facies 2b. Biogenic structures are typically diminutive, and suites show low diversity (Figure 4A). Trace fossils include Planolites, Skolithos, Cylindrichnus, Teichichnus, fugichnia, and navichnia.
Facies 2a is interpreted to have been deposited due to autogenic alternations between traction-sediment reworking by waves and suspension-sediment deposition. Low-diversity trace-fossil suites, diminutive ichnogenera, and a predominance of facies-crossing elements suggest an environment in which water salinities were persistently brackish (e.g., Beynon and Pemberton, 1992; Gingras et al., 2005; MacEachern et al., 2005; MacEachern and Gingras, 2007). The trace-fossil suite contains elements of both the Skolithos and Cruziana ichnofacies. Facies 2a corresponds to sediments deposited in brackish-water bays, and bay-head deltas.
Saskatchewan Geological Survey 6 Summary of Investigations 2009, Volume 1
Figure 3 - Mudstone facies (Facies 1): A) Fissile mudstone (Facies 1a) with locally millimetre-scale silt laminations; trace fossils include Planolites (P); well 07-03-054-25W3, 443.6 m. B) Unburrowed fissile mudstone from Facies 1a; well 08-30-051- 19W3, 478.1 m. C) Facies 1b showing pervasively bioturbated (BI 5) sandy mudstone; trace-fossil suite includes Skolithos (S), Teichichnus (T), Planolites (P), Cylindrichnus (Cy), Palaeophycus (Pa), and Chondrites (Ch); well 07-03-054-25W3, 490.2 m. D) Pervasively bioturbated (BI 4 to BI 5) silty mudstone from Facies 1b with vestiges of oscillation-ripple lenses; trace fossils include Planolites (P), Teichichnus (T), Chondrites (Ch), Asterosoma (As), Helminthopsis (H), Palaeophycus (Pa), Cylindrichnus (Cy), and fugichnia (Fu); well 13-01-052-27W3, 472.8 m. E) and F) Pinstripe mudstone from Facies 1c; note the thin lenses of fine-grained sandstone/siltstone; trace fossils include Planolites (P), Chondrites (Ch), Cylindrichnus (Cy), Gyrolithes (G), Teichichnus (T), and navichnia (Na); well 11-20-051-19W3, 486.5 m and well 15-35-058-21W3, 315.5 m.
Saskatchewan Geological Survey 7 Summary of Investigations 2009, Volume 1
Figure 4 - A) Weakly burrowed lenticular-bedded mudstone from Facies 2a; note the syneresis cracks (syn) in the middle of the photograph; trace fossils include Planolites (P); well 07-08-052-23W3, 444.2 m. B) Facies 2b showing oscillation-rippled sandstone and siltstone encased in mudstone; trace-fossil suite includes Planolites (P), Cylindrichnus (Cy), and Rhizocorallium (Rh); well 07-29-051-25W3, 511.5 m. C) Facies 2b showing heterolithic laminated to burrowed silty mudstone interbedded with thin wavy parallel-laminated sandstone; trace fossils include Planolites (P), Cylindrichnus (Cy), Skolithos (S), Gyrolithes (G), Asterosoma (As), Chondrites (Ch), Palaeophycus (Pa), and Phycosiphon (Ph); well 05-06-051-20W3, 452.2 m. D) Moderately bioturbated mudstone interbedded with sandstone of Facies 2b; note the disruption of sandstone due to bioturbation; trace-fossil suite consists of Planolites (P), Cylindrichnus (Cy), Skolithos (S), Chondrites (Ch), and Teichichnus (T); well 13-14-050-25W3, 529.8 m. E) Sporadically bioturbated interbedded mudstone and sandstone of Facies 3a showing oscillation ripples; note the syneresis cracks (syn); trace-fossil suite includes Cylindrichnus (Cy), and Planolites (P); well 07-10-052-23W3, 421.6 m. F) Interbedded mudstone and oscillation-rippled sandstone of Facies 3a; trace-fossil suites are dominated by Gyrolithes (G), which are mud filled and penetrate both mudstone and sandstone with rare, isolated Cylindrichnus (Cy) and Arenicolites (Ar); well 04-16-050-19W3, 455.8 m.
Saskatchewan Geological Survey 8 Summary of Investigations 2009, Volume 1
Facies 2b: Burrowed Mudstone and Sandy Siltstone
The heterolithic units of Facies 2b comprise 70% mudstone that is commonly bioturbated. Individual mudstone beds range from 1 to 10 cm thick. Thin, intervening siltstone and fine-grained sandstone beds (1 to 3 cm thick) contain rare oscillation ripples, small-scale hummocky cross-stratification, and current ripple laminae. The facies locally contains syneresis cracks and normal grading. Bioturbation values vary at the bed scale from BI 1 to BI 5 but typically average BI 3 (Figures 4B, 4C, and 4D). Trace-fossil diversities are typically low and are characterized by diminutive forms. Trace fossils include Planolites, Skolithos, Gyrolithes, Teichichnus, Thalassinoides, Palaeophycus, Rosselia, Rhizocorallium, Terebellina, Chondrites, fugichnia, and navichnia.
We interpret Facies 2b to reflect deposition in a standing body of water within fair-weather wave-base. The environment was characterized by a low (though variable) rate of deposition subject to periodic-event sedimentation. Salinity appears to have fluctuated but was generally higher than in Facies 2a. Trace-fossil suites are dominated by deposit-feeding structures and lesser dwellings of inferred filter-feeding organisms, and corresponds to a stressed expression of the archetypal Cruziana Ichnofacies.
c) Facies 3: Subequal Sandstone and Mudstone Heterolithic Facies Facies 3 consists of regularly interbedded sandstone and mudstone, forming heterolithic composite bedsets. Sandstone and mudstone each constitute approximately 50% of the facies. Facies 3 has been subdivided into two subfacies on the basis of sedimentological and ichnological features.
Facies 3a: Sporadically to Moderately Burrowed Interbedded Sandstone and Mudstone
Facies 3a consists of low-angle, parallel-laminated to oscillation-rippled sandstones intercalated with moderately bioturbated mudstone. These form composite bedsets that correspond to wavy bedding. Soft-sediment deformation structures and syneresis cracks are locally present. Internal laminae are locally marked by carbonaceous detritus or spherulitic siderite. Bioturbation intensities range from BI 0 to BI 2, and trace fossils are sporadically distributed (Figures 4E and 4F). Mudstone beds commonly possess higher bioturbation intensities. Ichnogenera include Planolites, Skolithos, Gyrolithes, Cylindrichnus, Chondrites, Teichichnus, Arenicolites, navichnia, and fugichnia. Locally within this facies, suites are monogeneric and dominated by one of Gyrolithes, Cylindrichnus, or Planolites.
Facies 3a is interpreted to have been deposited subaqueously, above storm wave-base but below fair-weather wave-base. Low-diversity trace-fossil suites, diminutive ichnogenera, and locally monogeneric suites suggest an environment in which water salinities were persistently brackish (e.g., Beynon and Pemberton, 1992; Gingras et al., 2005; MacEachern et al., 2005; MacEachern and Gingras, 2007). Low-intensity bioturbation may indicate a combination of stressed conditions and elevated deposition rates. Such settings are typical of shallow, sheltered, brackish-water bays with river-sediment input along their landward margins.
Facies 3b: Moderately to Pervasively Burrowed Interbedded Sandstone and Mudstone
Facies 3b is sedimentologically similar to Facies 3a, but is more pervasively burrowed (Figure 5A). Bedding contacts are pervasively bioturbated and only locally sharp. Bioturbation intensities range from BI 2 to BI 4. Trace fossils include Planolites, Cylindrichnus, Skolithos, Teichichnus, Palaeophycus, Thalassinoides, Rosselia, Chondrites, Asterosoma, Gyrolithes, navichnia, and fugichnia.
Facies 3b is interpreted to have been deposited subaqueously above storm wave-base but below fair-weather wave-base, similar to Facies 3a, but in higher salinity environments. This is particularly well indicated by the presence of Asterosoma, Chondrites, and Rosselia, as well as the higher diversity suites. The elevated bioturbation indicates generally slower rates of deposition than for Facies 3a. Facies 3b is interpreted to have been deposited in shallow bay settings that were subject to less pronounced depositional stresses. Such bays are generally less restricted, and/or have fewer fluvial channels draining into their landward margins.
d) Facies 4: Sandstone-dominated Heterolithic Facies Facies 4 comprises sand-dominated heterolithic successions. Sand beds constitute significantly greater than 50% (generally 60 to 80%) of the interval. The facies is, therefore, intergradational between Facies 3 and Facies 5. It can be separated into two subfacies, which have distinctive ichnological characteristics but are sedimentologically similar.
Saskatchewan Geological Survey 9 Summary of Investigations 2009, Volume 1
Figure 5 - A) Sandstones and interbedded mudstones of Facies 3b largely reworked by Planolites (P), Thalassinoides (Th), Cylindrichnus (Cy), and Palaeophycus (Pa); note the syneresis cracks (syn) at the top of the photograph; well 13-02-051-22W3, 480 m. B) Sporadically bioturbated rippled sandstone mantled by mudstone (Facies 4a); note the syneresis cracks (syn) in the middle of the photograph; trace-fossil suite consists of Skolithos (S), Gyrolithes (G), Cylindrichnus (Cy), Planolites (P), Palaeophycus (Pa), and Thalassinoides (Th); well 12-24-052-27W3, 441.4 m. C) and D) Wavy parallel-laminated sandstone interbedded with moderately to intensely bioturbated muddy sandstone beds (Facies 4b). Trace-fossil suite comprises Skolithos (S or Sk), Gyrolithes (G), Planolites (P), Cylindrichnus (Cy), Palaeophycus (Pa), Teichichnus (T or Te), Asterosoma (As), Phycosiphon (Ph), and Helminthopsis (H); well 13-02-052-27W3, 431.5 m and 429.2 m. E) Erosionally amalgamated oscillation-rippled sandstone (Facies 5); trace fossils include Cylindrichnus (Cy); well 13-02-052-27W3, 433.2 m. F) Hummocky cross-stratified sandstone (Facies 6); note the escape structure (fu); well 07-03-054-25W3, 480.2 m.
Saskatchewan Geological Survey 10 Summary of Investigations 2009, Volume 1
Facies 4a: Interbedded Mudstone and Rippled Sandstones
Sandstones within Facies 4a commonly contain oscillation-ripple lamination, and less commonly possess hummocky cross-stratification. Intervals comprise composite bedsets that range from wavy bedding to flaser bedding. Mudstone layers are thin and may contain normal grading and syneresis cracks. They commonly drape the rippled sandstone beds. Many are dark and unburrowed (Figure 5B). Facies 4a intervals are weakly and sporadically burrowed, showing BI 0 to BI 2. Trace-fossil suites are low diversity, commonly diminutive, and generally dominated by facies-crossing structures such as Planolites, Skolithos, Gyrolithes, Cylindrichnus, fugichnia, and navichnia.
Facies 4a reflects the interplay of fluctuating wave-energy conditions and variable sedimentation rates in a subaqueous environment. The dominance of sand and low bioturbation intensities within the subfacies suggests generally high sedimentation rates. Mudstone deposition appears to have occurred under low-energy conditions by suspension settling and clay flocculation, but also at rates sufficiently high to impede larval recruitment of endobenthos. The domination of facies-crossing trace fossils, diminutive sizes of the ichnogenera, and the presence of syneresis cracks indicate persistently (and probably fluctuating) brackish-water conditions. Trace-fossil suites are dominated by dwellings of suspension-feeding and surface-detritus-feeding organisms, typical of stressed expressions of the Skolithos Ichnofacies, and common to salinity-stressed environments (MacEachern and Gingras, 2007).
Facies 4b: Bioturbated Interbedded Mudstone and Rippled Sandstones
Facies 4b generally displays higher BI values than Facies 4a, although their physical sedimentological characteristics are similar. It locally contains syneresis cracks, soft-sediment deformation features, and some normally graded mud drapes. Bioturbation intensities, though high, are nevertheless variable, and typically range from BI 2 to BI 4 at the bed scale (Figures 5C and 5D). Ichnogenera include Planolites, Skolithos, Gyrolithes, Cylindrichnus, Chondrites, Teichichnus, Palaeophycus, Lockeia, Thalassinoides, fugichnia, and navichnia.
Facies 4b reflects fluctuating wave-energy conditions in a subaqueous setting, with variable sedimentation rates. Sand-bed emplacement occurred under higher energy and higher deposition rates than those for the intervening muds. Muds may, however, record both rapid clay flocculation and slow suspension-sediment settling. The generally higher bioturbation intensity attests to the reduced sedimentation rates compared to Facies 4a. The trace-fossil suite contains numerous facies-crossing elements, characteristic of environmental stress, but with intercalated ichnogenera typical of higher salinity conditions (e.g., Chondrites). The subfacies probably indicates shallow brackish-bay depositional environments which were less restricted, and/or were subject to reduced freshwater input along the bay margins.
e) Facies 5: Wavy and Planar Parallel-laminated Sandstone The sandstone beds within the Facies 5 are dominated by thin zones of low-angle planar parallel lamination, interpreted as hummocky cross-stratification and micro-hummocky cross-stratification, with associated oscillation-ripple lamination. Sand beds are typically erosionally amalgamated (Figure 5E) and generally range from 20 cm to 1 m in thickness. Mudstone layers are typically less than 1 centimetre thick and comprise less than 10% of the facies. Soft-sediment deformation is also present as convolute bedding and rare micro-faults, especially where thin beds of mud are intercalated. Bioturbation intensities are typically BI 0 to BI 2 at the bed scale. Trace fossils include Skolithos, Cylindrichnus, Chondrites (in the muds), and fugichnia.
Facies 5 is interpreted to have been deposited subaqueously above fair-weather wave-base where prevailing energy levels were high. Oscillatory processes both during fair-weather shoaling and during storms dominate the preserved expression of the facies. Mud layers, though rare, typically reflect drapes on the laminated sand indicating rapid clay flocculation and settling onto the sandy substrates. The paucity of burrowing in the muds indicates rapid deposition or accumulation under conditions of wave shoaling (e.g., mobile fluid mud). The trace-fossil suite comprises a low-diversity and probably stressed expression of the Skolithos Ichnofacies, but is dominated by facies-crossing dwelling structures that may reflect both suspension-feeding and surface-detritus-feeding organisms. Such suites are typical of higher energy sandy bays exposed to storms and wave energy, and with locally turbid water columns. Environments that possess such features occur in sandy bays and delta fronts of bay-head deltas.
f) Facies 6: Low-angle Undulatory Parallel-Laminated Sandstone Facies 6 consists of erosionally amalgamated very fine-grained, low-angle undulatory parallel-laminated sandstone beds. Laminae are delicate (millimetre scale) and form both concave upward and convex upward inclinations (Figure 5F). Rare oscillation-rippled sandstones are locally interbedded. Bioturbation is absent or very low (BI 0 to BI 1).
Saskatchewan Geological Survey 11 Summary of Investigations 2009, Volume 1
Facies 6 is interpreted as hummocky cross-stratification to swaly cross-stratification deposited in a subaqueous setting and reflecting sediment emplacement during storms. The amalgamated nature of sandstone beds in Facies 6 suggests increased storm frequency and heightened storm intensity, which reduced infaunal colonization windows for larvae and favoured erosional removal of fair-weather beds, respectively. Such conditions are typical of deposition above fair-weather wave-base in a subaqueous setting exposed to strong storms. They occur in more open sandy bays and in storm/wave-dominated delta fronts and bay-head delta fronts. The overall marine character of this facies can only be assessed in the context of the overlying and underlying facies with which it is associated.
g) Facies 7: Bioturbated Sandstone Facies 7 comprises fine- to medium-grained sand, in which primary stratification has been disrupted due to the activity of infaunal organisms (Figure 6A). Locally, oscillation ripples and small-scale tempestites (wavy-parallel laminae attributable to hummocky cross-stratification) are preserved within the facies. At the bed scale, bioturbation intensities range from BI 0 to BI 5, averaging BI 3. Common ichnogenera include Planolites, Skolithos, Palaeophycus, Asterosoma, Chondrites, Arenicolites, Cylindrichnus, and fugichnia.
The sediments of Facies 7 are interpreted to have been subaqueously deposited above fair-weather wave-base, influenced by waves and storms, but with slow and generally continuous accumulation of sand. Trace-fossil suites within this facies are characterized by a mixture of sessile deposit-feeding structures and dwelling structures attributed to suspension-feeding organisms, surface-detritus feeders and/or carnivores. The low-diversity suite attests to generally reduced salinities, but which were nonetheless sufficiently high to permit the presence of diminutive Asterosoma and Chondrites. This is consistent with sheltered open-bay environments with little or no direct fluvial sediment influx.
h) Facies 8: Massive (Apparently Structureless) Sandstone Facies 8 comprises very fine- to medium-grained, massively bedded (structureless) sandstone displaying high degrees of oil saturation and a paucity of visible sedimentary structures. Locally, low-angle planar lamination may be detected in some zones. Bioturbation is either absent, or the intense oil saturation has obscured the biogenic structures (Figures 6B and 6C).
Interpretation of Facies 8 is problematic. The apparently structureless nature of the sandstone may be due to oil saturation which has obscured primary physical sedimentary structures and biogenic structures. Alternatively, the sands may have been deposited very rapidly without forming stratification (e.g., Bhattacharya and MacEachern, 2009). Such a mechanism would require high-energy density underflows capable of transporting the sand in suspension (e.g., grain flows, hyperpycnites, or turbidites). Intercalated low-angle planar lamination supports the possibility that oil saturation masks the structures, although interpretation of the facies is best made in the context of over- and underlying facies.
i) Facies 9: Current-ripple to Trough Cross-stratified Sandstone Facies 9 encompasses fine-grained to medium-grained sandstones that are dominated by current-generated structures. The most common structures are trough cross-stratification and current-ripple lamination (Figures 6D and 6E). Combined flow ripples and aggradational current ripples are present locally. Bioturbation intensities are generally low, and range from BI 0 to BI 2 at the bed scale. Trace-fossil suites consist of Skolithos, Cylindrichnus, Planolites, and fugichnia.
Deposition of Facies 9 reflects conditions of quasi-steady unidirectional flow with high sedimentation rates, and high- to moderate-energy hydrodynamic regimes. The bulk of the facies reflects asymmetric bedforms of dune and ripple scale that migrate in response to current flow. The trace-fossil suite is low diversity and markedly consists of facies-crossing forms. The paucity of burrowing should not be taken as an indication of reduced salinity, however, as mobile bedforms such as dunes are difficult to colonize unless they are moribund for extended periods of time. Facies 9 probably records channel environments (e.g., estuarine, tidal, distributary, etc.), but could also correspond to proximal delta-front settings (approximate upper shoreface equivalents) of bay-head deltas or open-coast deltas. The context of the intervals with over- and underlying facies is required in order to make such determinations.
j) Facies 10: Coal Facies 10 comprises coal and highly carbonaceous mudstones. Facies 10 units tend to be black to dark grey in colour, depending upon the amount of interstitial silt and sand (Figure 6F). This facies is locally associated with underlying rooted zones, confirming its in situ condition. No trace fossils are associated with this facies.
Facies 10 is interpreted to have been formed as a result of accumulation of plant material and organic matter on the coastal plain, probably as swamps, bogs and forested zones. Micro-lithotype analysis would be required in order to
Saskatchewan Geological Survey 12 Summary of Investigations 2009, Volume 1
Figure 6 - A) Thoroughly bioturbated (BI 4 to BI 5) muddy sandstone (Facies 7), with Planolites (P), Chondrites (Ch), Cylindrichnus (Cy), and Palaeophycus (Ph); well 11-26-055-26W3, 540.3 m. B) Apparently structureless sandstone (Facies 8); lack of visible structure is probably due to high oil saturation; well 04-24-053-24W3, 431.2 m. C) Structureless sandstone with abundant organic detritus (Facies 8); well 13-01-052-27W3, 480 m. D) Cross-stratified sandstone indicating dune-scale bedforms generated by current flow (Facies 9); note the siderite cementation; well 13-11-054-25W3, 482.4 m. E) Current-rippled sandstone (Facies 9); note the erosional contacts of ripples and a climbing ripple in the lower part of the photograph; well 11-20-051-19W3, 491.4 m. F) Well-bedded coal (Facies 10); well 05-06-051-20W3, 443.1 m.
A
Saskatchewan Geological Survey 13 Summary of Investigations 2009, Volume 1
ascertain the particular coal-forming environment. In coastal regimes, the preservation of coal is commonly associated with elevated and/or rising water tables. As such, coals may mark the early onset of transgression in the coastal regime.
4. Conclusions Preliminary study of ichnology and sedimentology from the Lower Cretaceous (Lower to Middle Albian) Sparky, Waseca, and McLaren formations of the upper Mannville Group in west-central Saskatchewan has resulted in the recognition of ten recurring facies. Sedimentary structures record a predominance of oscillatory depositional regimes (shoaling waves and storms) with limited influence by currents. This supports reduced tidal energies in the setting, and widespread dominance of subaqueous conditions. Low-diversity suites, the prevalence of facies-crossing elements and the diminutive character of ichnogenera within the recognized facies indicate that the environment was generally subject to physico-chemical stress. The most likely stress was one of reduced and fluctuating salinity, although the magnitude of salinity reduction was variable. The local occurrence of more marine ichnogenera (e.g., Asterosoma, Phycosiphon, Chondrites, Rhizocorallium, and Helminthopsis) within the succession may suggest that elevated salinities occurred periodically within the study area.
This interpretation suggests that the facies within the study area correspond to mainly coastal-margin subaqueous settings (e.g., shallow bays), with local bay-head deltas and estuaries feeding into them. Within the formations, the Sparky and McLaren show more diverse suites, whereas the Waseca Formation shows less diversity and is more heterolithic. Storm-generated structures such as hummocky cross-stratification to swaly cross-stratification are more common in the Sparky and Waseca formations as are current-generated structures.
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Bhattacharya, J.P. and MacEachern, J.A. (2009): Hyperpycnal rivers and prodeltaic shelves in the Cretaceous Seaway of North America; J. Sediment. Resear., v79, p184-209.
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Saskatchewan Geological Survey 14 Summary of Investigations 2009, Volume 1
Reineck, H-E. and Singh, I.B. (1980): Depositional Sedimentary Environments with Reference to Terrigenous Clastics, Springer-Verlag, Berlin, 549p.
Taylor, A.M. and Goldring, R. (1993): Description and analysis of bioturbation and ichnofabric; J. Geol. Soc. Lon., v150, issue 1, p141-148.
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Wickenden, R.T.D. (1948): The Lower Cretaceous of the Lloydminster Oil and Gas Area, Alberta and Saskatchewan; Geol. Surv. Can., Pap. 48-21, 15p.