Santa Fe Impact Structure

8/4/2019 Santa Fe Impact Structure

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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.
http://www.impact-structures.com/http://www.impact-structures.com/


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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.pdf


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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.

Documents

Santa Fe Impact Structure