Post on 07-Apr-2018
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Santa Fe Impact Structure, Santa Fe, New
MexicoTim McElvain
In the spring of 2004 I discovered shatter cones approximately 10
kilometers north east of the Historic Santa Fe Plaza on NM Highway
475.
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Location map of the Santa Fe Impact Structure in north central New Mexico Further
investigation revealed a road cut with a beautiful nest of shatter cones rivaling those of
Vredefort, Sudbury, and other well known shatter cone exposures. The road cut contains
shatter cones ranging in size from a few centimeters up to 2 meters in a large tabular lens
of resistant crystalline rock striking north south and dipping 65 degrees to the west. The
lens is composed of several rock types which are cut by a dominant fracture system
striking plus or minus 10 degrees from due north, dipping 65 degrees to the west. The
rocks in the lens are schist exhibiting varying degrees of schistosity and grain size. There is
a black, isotropic (except for some elongation of the grains), fine grained quartz,
hornblende, biotite schist exhibiting very little schistosity that produces the best nestled,
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convex, horsetail striations (shatter cones) with the sharpest detail. There is a soft, grey
schist exhibiting a high degree of schistosity which contains numerous, convex, horsetail
striations (shatter cones), but without the fine grained detail found in the hard black
schist. The schist is intruded by a granitic rock of at least three different grain sizes; very
fine grained granite, and fine to medium grained granite, and a pegmatite. There are
shatter cones developed in all these granites of varying grain sizes, but as with the schist
the finer the grain and more isotropic the rock the sharper and more precise the horsetail
striations are.
Nest of shatter cones in fine grained granitic rock; some of the cones are over 1.5 meters in
length.
Photo of a beautiful shatter cone in a black, hard, isotropic (except for some elongation of
the grains), fine grained quartz, hornblende, biotite schist exhibiting very little schistosity.
Photo of a small shatter cone in a fine grained granitic rock found approximately 1kilometer west of the above mentioned road cut verifying that the shatter cones were not
caused by blasting during road construction.
The discovery of Shatter Cones precipitated an investigation into their origin.
Siobhan P. Frackelman et. al. published the following paper:
Shatter cone and microscopic shock-alteration evidence for a post-
Paleoproterozoic terrestrial impact structure near Santa Fe, New
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Mexico, USA, Siobhan P. Fackelman, Jared R. Morrow, Christian
Koeberl, Thornton H. McElvain, 2008 Elsevier B.V. All rights
reserved. This paper verified that the horsetail striations are indeed
shatter cones and they also found Planar Deformation Features withinthe shatter cones confirming that they were caused by a bolide
impact. The authors speculate the age of the impact to be between
early Mississippian and Mesoproterozoic. My research which has
continued through 2008 and will continue, leads me to believe that
the impact event occurred in Mid-Tertiary. The balance of this page
is my interpretation of continuing research on the Santa Fe Impact
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Structure The morphological Santa Fe Impact Structure has yet to bedefined and may be completely destroyed; however, the following
oblique view downloaded from Google Earth is an elongated circular
structure that could represent the remnants of the Santa Fe ImpactStructure or a smaller slightly younger impact structure that helped
destroy an earlier larger impact structure that actually was responsible
for generating the nest of shatter cones.
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Marker 05021 is the location of the nest of shatter cones in the road
cut; I have found shatter cones all along the valley from the road up
to markers 05049, 05050 and 05051. The other markers are locations
where I have taken samples looking for planar microstructures.Markers 05056, 0fo57, 05058, 05060 are locations of samples of
Pennsylvanian and Mississippian sandstone where I have samples of
quartz grains with planar microstructures whose angles to the C-Axis
I have measured and indexed fitting the requirements for Planar
Deformation Features (see below).
I have found breccia, mega-breccia, melts, and probable
allochthonous slide blocks all containing quartz with planar
microstructures (PM's) that fit the scale of planar deformationfeatures (PDF's) and histograms of the angle of the pole of the planar
microstructure to the c-axis resemble those of known impact
structures. Waypoint Numbers on the following two maps 05055,
05057, and 05064.2 marks the location of samples of sandstone in
which I have found grains of quartz with planar microstructures.
Waypoint 05051 marks the location of the clastic dike described
below.
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The above map has my Waypoints plotted and the map below is of the same area with the
Santa Fe Geologic Map overlain on the western half of the picture. The Geologic map has
the only Phaneorzoic Units in the vicinity mapped.
The above map plots the location of the sandstone samples on a geologic map of the Santa
Fe Impact Structure. The Geologic Map was cut and pasted from the Preliminary Geologic
Map of the Santa Fe Quadrangle Bauer, May, 2000 Last Revised: 8-October-2003
The formation symbols on the map are hard to read at this scale;
however, the buff yellow represents the Nambe Member of the
Tertiary Tesuque Formation, the blue represents the Paleozoic
Formations and the grey represents the Precambrian formations, all of
which are described below. The descriptions have been cut and
pasted from the Preliminary Geologic Map. Ttn Namb Member
(upper Oligocene(?) to lower Miocene) Poorly sorted sandy
pebble to cobble conglomerate, sandstone, and minor mudstone
composed of detritus eroded from pre-Tertiary rocks. Color is
typically red to pink but is locally white to very pale pink or buff.
Base is unconformable on Proterozoic or Pennsylvanian rocks
atvarious locations in the map area. Basal contact is highly irregular
in part because of erosional relief along the basal unconformity and
also because of interpreted deposition of lower parts of the member in
small half grabens. In the Big Tesuque watershed there are at least
400 m of Namb Member locally present below the Bishops Lodge
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Member. These lowest Namb strata are distinctive for their
abundance of Paleozoic clasts (25-60%, typically 50-60%). Namb
strata between Bishops Lodge volcaniclastic intervals in the
Bishops Lodge-Arroyo de la Piedra area contain 25-35% Paleozoicclasts and Namb beds above the Bishops Lodge Member contains
4 m across. Spiegel and
Baldwin portrayed a dip slope containing such clasts above
Proterozoic rocks on the north side of Big Tesuque Creek as
Pennsylvanian bedrock. Despite the large size of the Paleozoic clastsfound on that slope, there is no outcrop of such rocks and exposures
along the USFS Winsor Trail, at the southern end of that slope,
clearly show the large blocks to be in the basal Tesuque Formation.
The origin of these large clasts is unknown and is especially puzzling
in the absence of nearby Paleozoic outcrops. They may be a residual
lag of Pennsylvanian clasts resting on exhumed Precambrian outcrops
and then buried beneath Tesuque Formation. Otherwise, clast sizes in
the Namb Member are generally 2-20 cm, with Paleozoic limestone
and some Proterozoic granite clasts approaching 40-50 cm ineasternmost exposures. IPm Pennsylvanian Madera Group
undifferentiated Limestone, calcareous siltstone, shale, and minor
fine to medium grained sandstone, includes isolated thin outcrops of
Mississippian rocks and some coarse sandstones that may represent
Pennsylvanian Sandia Formation. Mu Mississippian (?) limestone
(undifferentiated) Approximately 10 m of brecciated gray
limestone, with red silty matrix in fractures, present only on a low
ridge about 0.6 km northeast of Bishops Lodge. Limestone overlies
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Proterozoic mylonite and wedges out to the south below a calcareous
siltstone more typical of basal Pennsylvanian strata seen elsewhere.
The crackle-breccia texture and red-silt fracture filling material is
suggestive of karst dissolution prior to deposition of the overlyingcalcareous siltstone. The brecciation and abrupt lateral pinchout of
the limestone strongly suggest that these strata are Mississippian,
rather than Pennsylvanian, in age. Madp Del Padre Member of the
Mississippian Espiritu Santo Formation a distinctive silica-
cemented white sedimentary quartzite sometimes seen in float along
the Paleozoic/Proterozoic unconformity Generally exposures are to
thin to differentiate on the map. Proterozoic Rocks Ymg
Megacrystic granitoid (Mesoproterozoic?)
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Coarse unfoliated granite contains quartz, biotite, and large (up
to 10cm) K-spar megacrysts. looks quite similar to the Sandia
Granite. High magnetic susceptibility suggests that this rock may
be responsible for pronounced magnetic highs in the SetonVillage quadrangle (Mark Hudson, personalcommunication,
2003). Yg Microcline-qtz-muscovite granitoid (Mesoproterozoic)
Fine to medium grained unfoliated to weakly foliated granitoid.
Ypeg Pegmatite (Mesoproterozoic?) Simple pegmatite veins and
pods, unfoliated Xgd Granodiorite to Diorite (Paleoproterozoic?)
Weakly to undeformed pods and irregularly shaped bodies of
intermediate intrusive rocks best exposed along the lower end of the
Ski Basin Road. Xd Granodiorite to Diorite (Paleoproterozoic?)
Generally mediumgrained dark, weakly foliated-to-unfoliatedmassive diorite. Forms pod-like bodies within surrounding gneisses
suggesting late emplacement. Cut by Ypeg. Xpg Pink Granitic
Gneiss (Paleoproterozoic) Fine-grained quartz-Kspar mylonitic
gneiss is distinctly pink in outcrop. This rock appears to be more
resistant to weathering than the coarser biotite-bearing gneisses and
forms the bulk of the Sunlit Hills. Xbg Biotite-rich granitic gneiss
(Paleoproterozoic) Coarse grained strongly foliated biotite-bearing
gneiss often contains microcline augen and appears to be less
resistant toweathering than Xpg. Forms much of the broad valley east
of the Sunlit hills that I- 25 travels along. Unit is broadly generalizeddue to poor exposure. Xqm Quartz muscovite schist
(Paleoproterozoic) Generally strongly foliated and often
crenulated quartz-muscovite schist. Muscovite is often very coarse
suggesting pervasive annealing similar to that seen in other nearby
uplifts. Xms Quartz biotite schist (Paleoproterozoic) Xa
Paleoproterozoic strongly foliated amphibolite and mafic schist,
may include Xd in places. Mafic units tend to weather poorly and are
often mantled by Yg and Xbg float. Consequently, Xa and other
mafic units are probably vastly under-represented on the map.
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Measurements of the Angle of the Pole of the
Planar Microstructure to the C-Axis
On the above maps I have plotted the GPS Waypoint number where
I collected the samples analyzed below of quarts grains with planar
micro structures.
Photomicrograph of a typical sandstone grain with Planar
Microstructures (PMs). The scale of the microstructures fits the scale
of Planar Deformation Features (PDFs), and the pole of the plane of
these microstructures fit the Low Miller Indices in more than 90
percentof the measurements that I have made. In my opinion the
PMs are PDFs.
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05064.2 Paleozoic sandstone collected at the contact
between the Precambrian and the Paleozoic formations.
05055 Paleozoic sandstone stringer about 300 meters higher in thesection than the Paleozoic Precambrian contact.
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The above histogram was made from measured planar feature in
grains from sample 05057 Sample of a Paleozoic clast in the basal
Nambe Member of the Tesuque Formation (Ttn). In my opinion the
Ttn Formation here is a mega breccia, containing large clasts of
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Paleozoic formation.
Clastic Dike
05051 (see map above) marks the location of a clastic dike
composed of Precambrian basement rocks (maroon) penetrating
upward into the Paleozoic limestone (buff color) formations. The
clastic dike is macroscopic evidence, but not proof, that the impact
event is post Paleozoic.
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Along the contact at the upper left hand corner of the photographthere is evidence of the fluidization and mixing of competent
limestone and basement rocks, the following photographs look
similar to me to illustrations found in the web site Ernston Claudin
Impact Structures, Azuara impact structure (Spain): Evidence of
shock fluidization of competent limestone, which can be seen on this
link - http://www.impactstructures.com/Archiv/archiv.html.
Varve like bedding of the Mississippian limestone broken and rotated
by the forceful intrusion of the clastic dike. The varve like bedding
indicates that the limestone was deposited in very quiet and sheltered
environments unlikely to have moved and caused soft sediment
deformation, which some geologists attribute this deformation to.
Photograph the contact of the clastic dike and the basement rock
where the friction caused by the movement and the confining
pressure plasticized or fluidized the limestone mixing it with pieces
of brownish red basement rock with flow structures mixing
competent limestone and basement rocks.
This and the following photograph are close-ups of the above contact
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zone of the clastic dike and the basement rock illustrating the flow
structure and mixing of the reddish brown basement rock and the
grey competent and fluidized limestone.
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Photograph of a clast of basement rock with a reaction rind within thefluidized zone.
Clasts of competent limestone and basement rock within the fluidized zone.
The above two photographs illustrate competent limestone and clasts
of basement rock within the clastic dike frozen within the fluidized
zone in finer and finer detail.
PHOTOMICROGRAPHS
The following photomicrographs are of quartz grains dissolved out ofthe fluidized limestone exhibiting up to three sets of planar
microstructures.
Tertiary Megabreccia mapped as the basal Nambe Member of the
Tertiary Tesuque Formation
Sample number 06055 (see map above) was collected from a
Paleozoic sandstone clast, most probably of Pennsylvanian age within
this megabreccia. Some of the larger clasts within this breccia are
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displayed in the photographs below. There is no road cut or streamchannel that exposes a clean cross section of the formation; however,
one can see in the following photographs that the makeup of this
breccia resembles a diamictite.
Photograph of a large megabreccia sized limestone clast in the
Nambe member of the Tertiary Tesuque Formation.
Sandstone clast similar to the one that I sampled and found Planar
Microstructures (PMs) in. These mega clasts appear to be rounded,
but because of their fragile, bedded nature I do not believe they
would survive stream transport. Kord Ernston and Fernando Claudin
in their web site, Ernstson Cladin Impact Structures, The Perlarda
Formation, http://www.impact-structures.com/ show examples of
clasts rounded and polished in the excavation stage of an impact
crater.
Photograph of another megabreccia calcareous areniteclast located further to the north in Big Tesuque CreekCanyon that also seems to have been rounded duringexcavation.
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GALISTEO FORMATION OUTCROP AT ARROYO
HONDO, NM
Tertiary Galisteo Formation outcrops approximately 14 kilometers
southwest of the shatter cone outcrop. I believe this formation
mapped as Tertiary Galisteo Formation (?) is an impact melt and
melt breccia. This formation is mapped in the Arroyo Hondo
Canyon just down stream from where I-25 crosses the canyon. The
Formation consists of a reddish orange, hematite rich melt breccia
with siltstone sized angular quartz clasts and feldspar phenocrysts
resting on the basement, some of the quartz clasts have planar
microstructures. The melt is overlain and incised by a melt breccia
gravity slide and reworked breccia, composed of pebble up to
cobble size clasts with a melt matrix in which I found phenocrysts
of feldspar.
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Topographic map illustrating the relationship between the shattercone area and the outcrop of the Tertiary Galisteo Formation (?)
which I am mapping as consisting of a melt, melt breccia, fallback
crater fill and reworked breccia.
The Tg? Symbol and purple color in the center of the map has been
mapped as the Tertiary Galisteo Formation primarily because of its
stratigraphic position underlying the Tertiary Espinosa Formation.
There is a question mark after the symbol because the Galisteo
formation is usually sandwiched between the Paleozoic formationsand the Espinosa Formation. Here the breccia is deposited directly
upon the basement rocks, and appears to come to a feather edge to the
east.
In this photograph the fine grained glass melt rests directly upon the
granite and has been channeled into and overlain by a gravity slide
melt breccia that channeled into the impact melt.
In this photograph the dark maroon basement rocks are about 1 meter
below the feet of the two geologists, overlain by the light orange red
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impact melt glass, which in turn is overlain by the coarser grainedgravity slide melt breccia.
Close up of the impact melt illustrating ball and pillow structure.
Close up of a pillow with indentations and impressions caused by
plastic deformation.
Photomicrograph of the impact melt with the angular siltstone sized
clasts of quartz and feldspars in a glassy matrix highly stained with
hematite, photomicrograph has a larger quartz crystal that has been
embayed by melt, and a phenocryst of feldspar illuminated by plain
polarized light.
Same photomicrograph as above illuminated with crossed polarized
light illustrating the glassy nature of the matrix. These
photomicrographs and the description of the impact melt is very
similar to the photo and description of a lithic breccia in Bevan M.
Frenchs book Traces of Catastrophe on page
71.
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Traces of Catastrophe
A Handbook of Shock-Metamorphic Effects in
Terrestrial Meteorite Impact Structures
Bevan M. French
Research Collaborator Department of Mineral Sciences, MRC-119
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Smithsonian Institution WashingtonDC20560 LPI Contribution No.
954
Figure 23
5.4.2. Lithic Breccias (Allogenic)
Melt-free breccias (lithic breccias) form a common and
distinctlithology in both large and small impact structures (Figs. 3.7and 3.13).In small impact structures, e.g., Brent(Canada) (Dence,1968; Grieve and Cintala, 1981), lithic breccias may form unitshundreds of metersthick that extendover much of the final crater.
At the larger RiesCrater (Germany), a distinctive allogenic polymictlithicbreccia [the Bunte (colored) Breccia] occurs beneath the
overlyingmelt-bearing suevite breccias both inside and outside thecrater (Hrz, 1982; Hrz et al., 1983), with a sharp contact betweenthe twounits. In some impact structures, especially those formed incarbonate target rocks, lithic breccias may be the only type ofcrater-fill materialpresent (Roddy,1968; Reiff, 1977). Lithic brecciasconsist of rock andmineral fragments in a clastic matrix of finer-
grained similar material(Fig. 5.8). The breccias are poorly sorted;fragment sizes generallyrange from
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Partially melted and quenched crystal within the impact melt
illuminated with plane polarized light.
Same as above but illuminated with cross polarized light.
Photomicrograph of a phenocryst of feldspar within the impact melt.
Silt sized quartz crystal with planar microstructures that fit the scale
of planar deformation structures within the impact melt.
Silt sized quartz crystal with planar microstructures that fit the scale
of planar deformation structures within the impact melt.
Photomicrograph of the melt breccia composed of angular fragments
of quartz and feldspar illuminated with plane polarized light.
Photomicrograph of the same section of the melt breccia showing the
glassy matrix along with some carbonate cement illuminated with
cross polarized light.
Blob of diaplectic glass within the impact melt breccia under plain
polarized light.Blob of impact melt within the melt breccia illuminated by cross polarized light.
Phenocryst of feldspar within the melt breccia illuminated with plane
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polarized light.Phenocryst of feldspar within the melt breccia illuminated with
cross polarized light.
DISTAL EJECTA
The Los Dos Quartzite, Los Dos Subdivision, Santa Fe, County,
New Mexico
The most recent published description of Tesuque Formation and theLos Dos Quartzite is found in the following description, cut and
pasted from the digital copy of the: Preliminary Geologic Map of
the Horcado Ranch Quadrangle, Santa Fe County, New Mexico
by, Daniel J. Koning and Florian Maldonado, May, 2001, New
Mexico Bureau of Geology and Mineral Resources
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Open-file Digital Geologic Map OF-GM 44
Lower mixed Lithosome A-B, fine-grained (middle Miocene)
Sandstone, siltstone, and claystone with 1-15% conglomeratebeds. Conglomerate is commonly pinkish-gray (7.5YR 7/2), clast
supported, and consists of pebbles with subordinate cobbles.
Conglomerate beds are very thin to medium, lenticular, and
commonly indurated by calcium carbonate to form resistant
ledges up to about 2 m thick. Within a bed there may be cross-
lamination or planar lamination. Conglomerate clasts are
granitic with 1-5% amphibolite, 3-15% yellowish Paleozoic
siltstone and sandstone, trace 10% grayish to yellowish Paleozoic
limestone, trace-5% muscovite- schist, 1-5% brownish chert, and
up to 40% quartzite. Coarse to very coarse pebbles and cobbles
are rounded to subrounded; very fine to medium pebbles are
subangular to subrounded. Conglomerate clasts are moderately
to poorly sorted within a bed. Siltstone and claystone beds are
very thin to thick, tabular, and range in color from brown (7.5YR
5/4), reddish-brown (2.5YR-5YR 46/3-4), light-reddish-brown
(5YR 6/4), light yellowish-brown (10YR 6/4), light-brown (7.5YR
6/3-4) to pink (7.5YR 7/3-4). Sandstone and silty sandstone are
light-brown (7.5YR 6/3-4), pink (7.5YR 7/4), or reddish-yellow
(10YR 6/6). Sandstone is commonly in very thin to thick, tabularor lenticular beds. Sandstone is very fine- to very coarse-grained,
subrounded to subangular, mostly well sorted with some
moderate sorting, and arkosic. Within 3 km of the south border
of the quadrangle, the sediment is more reddish, sandy, and the
clasts more granitic (with 5-10% quartzite) than to the north.
The non-gravelly sediment is weakly to moderately consolidated.
Unit correlates to the Skull Ridge Member of Galusha and Blick
(1971). Smith (2000b) has interpreted the Skull Ridge Member to
represent an alluvial slope environment fed by drainages in the
Sangre de Cristo Mountains, and we concur. The age of the Skull
Ridge Member on this quadrangle is interpreted to be 15.1 to 16
Ma based on its Barstovian fossil assemblage and paleomagnetic
correlations (Galusha and Blick, 1971; Barghoorn, 1981; Tedford
and Barghoorn, 1993) in 40 39 addition to Ar/ Ar dates of ash
beds (Izett and Obradovich, 2001). Total thickness is
approximately 250-430 m. Silica cementation of quartz-rich
sandstone Within 0.5 km of the south boundary of the
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quadrangle, local silica-cementation of gravel and sand of unit
Tts1has been observed at three locations. These locations are noted
on the map (see "explanation of map symbols" below). The
cementation has resulted in a very well-indurated, pebble- andcobble-conglomerate and sandstone that looks like the sediment of
unit Tts1 except that these rocks have low amounts of feldspar grains
and lack granitic clasts; instead, quartz grains and quartzite clasts
dominate. These well-indurated and erosionally resistant rocks
generally form angular blocks up to 3 m in diameter, some of which
are still in place (based on their geometry and consistent attitudes
between the beds within these blocks and the surrounding strata of
the Tesuque Formation). Calcium carbonate nodules (1-7 cm in
diameter) may coat the outside of the in-situ blocks. The clastlithology is: 85-90% quartzite and quartz, 10% yellow, green, and
black chert, and trace to 5% schist and amphibolite. Sand grains are
estimated (using a hand lens) to have 75% quartz and 25% feldspar
and are generally medium to very coarse. Granitic clasts are generally
not observed except near the margins of the in-situ blocks, where
they comprise approximately 1% of the clasts. These silica-indurate
rocks commonly occur along a north-south or northwest-southeast
trend. In an exposure located in the extreme southeast corner of the
quadrangle (NW1/4, NE1/4 of Section 32, T. 18 N., R 9 E.; UTM
coordinates: 3,956, 810N 408, 975 E, zone 13), silica cementationoccurs adjacent to a fault that strikes N10W and similar faults may
be located adjacent to the other outcrops as well. The authors agree
with the interpretations by Borton (1979) that these outcrops are not
from an upthrown fault block. Rather, we speculate that quartz-rich,
mud-free sand beds of relatively high permeability were
preferentially cemented by silica-rich fluids that flowed up from
relatively deep depths adjacent to faults. A somewhat similar, silica-
indurated, sandstone dike occurs on the northeast corner of Pueblo
Road and
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U.S. 84/285 (3-5 mi south of Espanola and 8 mi north of Pojoaque).Los Dos Quartzite Pile Waypoint number10002, the largest of the 8 quartzite piles found
in the Los Dos Subdivision, Santa Fe County, NM
This enigmatic quartzite is also described by Robert L Borton in a paper published 1n
the New Mexico Geological Society Guidebook, 30thField Conference, Santa Fe
County, 1979. Dr. Bolton in his article proved that the quartzite
piles are not rooted, but resting on about 3 thousand feet of
Tesuque Formation, which they do not resemble at all
lithologically nor is the cementation and Overgrowth of the quartz
grains similar. He also drew attention to the partially polished
boulder found in Quartzite Pile10004. I interpret the origin and
meaning of the Tesuque Formation and the associated Los Dos
Quartzite (Silica cementation of quartz-rich sandstone) differently
from the above authors. I believe that the Tesuque Formation
-Lower mixed Lithosome A-B, fine-grained (middle Miocene)
including the Los Dos Quartzite is either direct or reworked distal
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Photo of the Tesuque Formation with rounded clasts that indicate fluvial erosion and
rounding; however, rounding can also be caused by the excavation and transportation of
ejecta.
Photo of the Tesuque Formation with angular clasts indicative of a breccia and the fact that
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an angular clast is found approximately 8 miles from the source indicates to me that it is
an impact ejecta breccia.
Photo of a massive sandstone lens within the Tesuque Formation, this sandstone is thick
and massive enough to be cemented with silica and resemble the Los Dos Quartzite;
however it is an arkosic arenite whereas the Los Dos Quartzite is a quartz arenite.
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Close up of the above massive sandstone lens with both angular and rounded clasts.
The Los Dos Quartzite consists of large enigmatic clasts, boulders or slabs of quartz
arenite that lie approximately 8 miles west of the shatter cone outcrop associated with
the Santa Fe Impact Structure.
Map illustrating the relative location of the Los Dos Quartzite Piles in relation to otherevidence of the Santa Fe Impact Structure that I have found in the area.
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I have attempted to contour the elevations of the quartzite piles and
their elevation appears to place them on the same depositional
sequence time line one would expect when the projected strike and
dip (N-60-E, 10 degrees NW) of the sandstone lens located in the
immediate vicinity of the Los Dos quartzite pile elevation 6682, see
photograph of the sandstone lens below.
On the following illustration I have projected the locations of thequartzite piles onto the cross section published in the above captioned
Horcado Ranch Quadrangle on a rough guess of the sequence time
line.
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The black dots represent my projection of the quartzite piles on my
estimation of the depositional sequence line in the Tesuque (Tts1)
Formation.
If the Los Dos Quartzite Piles were deposited on the same
depositional sequence time line it would indicate that the piles were
all deposited at the same time, which would give credence to them
being ejecta from one of the larger multi-impact events in the Santa
Fe area.
Except for quartzite pile 10002 all the quartzite piles consist ofrandomly placed boulders of 1 to 10 feet of coarsely weathered
quartzite.
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surfaces are there or they are passed off as sandblasting by wind
action. The other blocks in the pile are not polished and there is not
good reason why the wind would select this boulder and not the
adjacent ones. If the polishing was not caused by man there is
evidence in other impact craters that polishing can occur during theexcavation phase of an impact event by particles in the cloud of
material or be glazed by the heat generated by the impact.
Close up of one of the highly polished or glazed surfaces on the large
boulder in Pile 10004
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view of the sole marks as shown in the following photograph.
The above photograph illustrates the sole marks in cross section;
there is little or no change in lithology from the edge of the sole
marks and the interior of the quartzite.
I do not believe these casts or sole marks would have been formed by water
circulating through an in situ lens of Tesuque sandstone.
Microscopic Evidence
In thin section the composition of the Los Dos Quartzite appears tome to be about 95% quartz and 5% feldspar and other minerals.
Thin sections of the Los Dos Quartzite do not look like sandstone
metamorphosed into a quartzite, it is very porous, permeable, and
well cemented with silica cement. The overgrowth on individual
rounded grains has grown in such a way that the rounded grains
have grown into small crystals with regular crystal faces and
terminations.
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The above photomicrograph of a quartz grain illustrates the original
rounded edge of the quartz grain and the straight edge of the crystal
resulting from the overgrowth. The 2 following photomicrographs
illustrate the same phenomenon.I have been told that this overgrowth and cementation process
requires much more time than the rapid cementation from percolating
silica rich spring water as discussed in USGS Quadrangle Map of the
Horcado Ranch Quadrangle, which prompts me to look for older
sandstone formations. Next summer I intend to compare thin sections
of the Dakota sandstone outcropping closest to the Los Dos Quartzite,
Cambrian and Proterozoic sandstone in Colorado and Utah. In
addition any water flowing up through a fault zone from depth would
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have to pass through approximately 2,500 feet of limestone rich
Paleozoic formations that lie beneath the Quartzite Piles. The Yates
Petroleum, La Mesa No.2, Sec. 24, T17N, R8E, Santa Fe County,
New Mexico well was drilled to the basement about 4 miles southwestof the Los Dos Quartzite piles and in situ Paleozoic rock rich in
limestone can be seen on the Schlumberger Litho Density
Compensated Neutron GR Log between the depths of 5021 feet and
7536 feet. Further interpretation of the stratigraphy penetrated by this
well was published in August 2006, The Stratigraphic analysis of the
Yates #2 La Mesa well and implications for southern Espaola Basin
tectonic history, Caroline Myer* and Gary A. Smith, Department of
Earth and Planetary Sciences, University of New Mexico,
Albuquerque, New Mexico 87131, *Current address: Department ofGeology, Utah State University, Logan, Utah 84322-4505 Can be
downloaded
athttp://geoinfo.nmt.edu/publications/periodicals/nmg/downloads/
28/n3/ nmg_v28_n3_p75.pdf
http://geoinfo.nmt.edu/publications/periodicals/nmg/downloads/28/n3/nmg_v28_n3_p75.pdfhttp://geoinfo.nmt.edu/publications/periodicals/nmg/downloads/28/n3/nmg_v28_n3_p75.pdfhttp://geoinfo.nmt.edu/publications/periodicals/nmg/downloads/28/n3/nmg_v28_n3_p75.pdfhttp://geoinfo.nmt.edu/publications/periodicals/nmg/downloads/28/n3/nmg_v28_n3_p75.pdfhttp://geoinfo.nmt.edu/publications/periodicals/nmg/downloads/28/n3/nmg_v28_n3_p75.pdf8/4/2019 Santa Fe Impact Structure
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This much limestone would have changed the chemistry of the
water percolating through and would have most probably
cemented the quartz grains with calcite instead of silica.
Planar Microstructures in the Los Dos Quartzite
There are a few quartz grains in the Los Dos Quartzite and in the
Tesuque Formation with Planar Microstructures that fit the scale
of PDFs.
The above photomicrograph of a quartz grain with 2 sets of planar
microstructures that fit the scale of planar deformation features.
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Photomicrograph of a quartz grain with 1 set of planar
microstructures that fit the scale of both planar deformation features
and planar fractures.
The above photomicrograph is of a quartz grain with 1 set of planar
microstructures that fit the scale of both planar deformation features
and planar fractures.
The above photomicrograph is of a quartz grain with 1 set of planar microstructures that fit
the scale of both planar deformation features and planar fractures.
The above photomicrograph is of a quartz grain with 1 set of planar
microstructures that fit the scale of planar deformation features that
has subsequently been fractured and plastically deformed.
The above photomicrograph is of a quartz grain with one set of planar
microstructures that fit the scale of planar fractures.
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The following photomicrographs of quartz grains with planar
microstructures were found in the Tesuque Formation in the vicinity
of the Los Dos Quartzite. The microstructures fit the scale of planar
deformation features, but the grains have been plastically deformedresulting in either curviplanar microstructures, or they are Bohm
Lamellae. In either case there has not been enough tectonic heat and
pressure for these features to have been formed from tectonic action,
meaning they have most probably been caused by an impact event. I
hope to do more microscope work on this formation and find better
examples. If there is evidence of shock metamorphism in the Tesuque
Formation it would indicate to me that this formation is some sort of
sedimentary breccia.
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In Summery
The very large clasts of the Los Dos Quartzite, if you want to call
them clasts, they look like outliers or Klippe of a sandstone formation
that has been thrust out away from the outcrop similar to Heart
Mountain in NW Wyoming. In this case, however, the quartzite piles
would have been propelled by the energy released by the Santa Fe
Impact Structure, the blocks of sandstone formation gliding on the
unconsolidated and fluidized ejecta (Lower mixed Lithosome). The
thickness of the quartzite piles could represent a thick massive
sandstone formation, or could have been formed by thinner bedded
sandstone that was thrust over itself forming a pile of slabs at the end
of its trajectory. If I tried to fit these quartzite piles into myhypothesis of the mid-Tertiary Impact Event the Lower mixed
Lithosome member of the Tesuque Formation represents the settling
of a very dense ejecta cloud caused by multiple and successive bolide
impacts with numerous cross currents and various compositions of
material graded into beds of sandstone, siltstone, claystone and
conglomerate which could mimic fluvial deposition. The large clasts
of quartzite would represent ejecta from a large bolide impact timed
toward the end of the series of impacts from the space rubble or dirty
snowball impact event.
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Los Dos Quartzite Possible depositionscenarios:
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The two above photographs of large blocks of the Dakota Formation
were taken south of Las Vegas NM along the canyon carved by the
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Gallinas River above Sa Augustine NM. The grain size is similar to
the Los Dos Quartzite and the rounded quartz grains are covered by
an overgrowth covering the grains forming a facetted crystal. The
formation is well cemented but not quite as well as the Los DosQuartzite, and the formation has similar weathering characteristics,
but the chert, vein quartz, and schist clasts are missing. The Dakota
Formation here also has much more distinct bedding.
The clasts could form in the Dakota Formation if a transgressive sea
began The above photographs are of an outcrop of the Dakota
Sandstone eroding a Burro Canyon Formation conglomerate similar
to the conglomerate in the following photograph. The Burro Canyon
conglomerate was photographed about 15 kilometers north of
Blanding UT and contains all the required conglomeratic clasts and
sandstone of about the correct grain size. The photograph is not very
clear because at the time I was not considering illustrating this
scenario. The eroded Burro Canyon material would then be cleaned,
washed and rounded by wave action eliminating all the clay and other
fines. The same depositional environment could be caused by a river
eroding the Burro Canyon or some other source and dumping the
material in a marine environment and reworked by wave action and
long shore currents.
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Burro Canyon sandstone photographed at the same location as the
conglomerate.
The Dakota Formation is not normally described as coming in direct contact with the
Burro Canyon Formation, but the above photograph shows a turbulent sort of contact
between the yellow Dakota Sandstone and the grey Burrow Canyon formation. This
photograph was taken higher up in the Abajo Mountains and may not represent an
erosional contact. I believe the Abajo Mountains represent the central uplift of a large
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impact crater which could drastically impact the contact between the two formations.I have not found an outcrop of the Dakota Formation that fits the Los Dos Quartzite, and
the Dakota Formation may be the wrong place to look. There are other older quartzites
that could be the source of the Los Dos Quartzite which I intend to explore.