NEW MEXICO BUREAU OF GEOLOGY AND MINERAL RESOURCES
107°37'30"W
261000
262000
Description of Units
A DIVISION OF NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY
263000
107°35'0"W
264000
265000
266000
267000
107°32'30"W
268000
269000
270000
271000
These are mainly the field descriptions used during mapping with a few descriptions from Lipman et al. (1979). Cretaceous descriptions and a few volcanic descriptions are from the Lobos Springs Quad Goff et al, (2008)
107°30'0"W
272000
QUATERNARY
35°15'0"N
Qal
Tcptd
80
Tbctd
Tbhtd
Qtc
Tbhtd
Tbtd
Tpta
Thbi Thbi
Thbi
Tptd
Ttha
3903000
Tpta
Tptd
Tvs
Thi
Tptba
Tpta
Tdo
Tpcta
Tvs
65
Tr
Tthi
32
Qtc
Tr
Tvs
Qc
Qtc
Tvs
Tbhtd
Tr
Teta
Tr
Tcptd
Ttha
Ttha
50
40
Tvs
Ttha
Tcptd
Tdo
Tta Tr
Thbi Ttha
Tob
78 Tob
5
Qtc
Tcptd
Ttha
Qfy
Kuh
Qtc 13
Qtc
Tbhi
Tob
Ttdl
Kuh
3900000
Qal
Tta
18
Tbhtd
10
Kcg
Tbhtd
40
Qc
Qal
15
18
Trt
Qal
Tvs
3898000
Tvt
Tbb
Tvs
5
Tbb
Tpb
Ttd Tbhi
Tvs
Tta2
Tpb
Tvs
Tvs
Qtc
12
Tta
Kcg
Tbb
Tub
Qal
Tpb
33
3897000
Tpb
Qtc
Tpb
Ttd
Tub
Qal
Tta
Qal
Tubc
Ku
Tubi
Tubi
Tub
Tpb
30
Qal
Qtc
Qal
Qf3
Qal
Kmm
Tvs
Tub
Qa
Kmm
Kcd
Kcd
Tub
Qa
Qal
Tub
Qtc
Kcd
Tvs2
Tvs
Qa
Kcd
Kcs
Qal
Tpb
Kcd
Kmm
Kcs
Kcs
Kcd
Tvs
Tpb
Km
Kmm
4
Qtc
Kcs
Kmm
Kcdc Kcdc
8
Kcd Tpb
Tpb
Kmm
Qtc
Tptb
Tpb
Kmm
Km
Kgu
Qtc
Qa
Qtc
Kmm
Tpb
Kcg
Kgm
Qtc
Tphtd
Kgl
5
Kcs
Qtc
Kcs
Kmm
Kcd
Kmm
Kcd
Kcg
Kmm
Kcdc
Qal
Kmm
Tub
Km Kgu
Qal
Km
Km
Qt3 Qtc
3
Kgl
Qal
Qt3
Km
Kgu Kgl
Qf3
Km
Kgl
Qtc
Km
Kgu
Km
Kgl
Tptd
Qf3
Kgl
Qal
261000
262000
263000
264000
107°35'0"W
265000
266000
Qf3
Tphtd
Qtc
3890 000
Km
267000
268000
Qal
269000
107°32'30"W
Base map from U.S. Geological Survey 1957, from photographs taken 1955, field checked in 1957.
1927 North American datum, Polyocnic projection. Reprojected to UTM projection -- zone 13N
1000-meter Universal Transverse Mercator grid, zone 13, shown in red
QUADRANGLE LOCATION
This draft geologic map is preliminary and will undergo revision. It was produced
from either scans of hand-drafted originals or from digitally drafted original maps
and figures using a wide variety of software, and is currently in cartographic production.
It is being distributed in this draft form as part of the bureau's Open-file map series
(OFGM), due to high demand for current geologic map data in these areas where
STATEMAP quadrangles are located, and it is the bureau's policy to disseminate
geologic data to the public as soon as possible.
After this map has undergone scientific peer review, editing, and final cartographic
production adhering to bureau map standards, it will be released in our Geologic Map
(GM) series. This final version will receive a new GM number and will supercede
this preliminary open-file geologic map.
0.5
1000
0
1
Magnetic Declination
April, 2007
10º 5' East
At Map Center
0
1000
0.5
2000
3000
1 MILE
4000
5000
6000
0
270000
271000
CONTOUR INTERVAL 20 FEET
NATIONAL GEODETIC VERTICAL DATUM OF 1929
107°30'0"W
May 2009
7000 FEET
1 KILOMETER
272000
Geologic map of the Mount Taylor
quadrangle, Cibola County, New Mexico
1:24,000
1
by
G.R. Osburn , S.A. Kelley , F. Goff 3, P.G. Drakos 4, and C.A. Ferguson
1
2
1
Earth and Planetary Science Department, Washington University, St. Louis, MO, 63130
New Mexico Bureau of Geology and Mineral Resources, New Mexico Tech, Socorro, NM, 87801
3
Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM, 87131
4
Glorieta Geoscience Inc., Santa Fe, NM, 87502
5
119 North Fork Rd., Centennial, WY, 82055
2
New Mexico Bureau of Geology and Mineral Resources
Open-file Map Series
OFGM 186
COMMENTS TO MAP USERS
DRAFT
Tt
trachyte—fine grained dark lava. Few recognizable phenocrysts.
Intrusions
Thbi
Trachydacite intrusions—Gray to pink rocks containing 15 to 20 phenocrysts of plagioclase, hornblende and
biotite. Most common around the center of Mt Taylor.
Thi
Trachydacite to Trachyandesite intrusions—Gray rocks containing obvious plagioclase and hornblende
phenocrysts but not biotite
CRETACEOUS
Crevasse Canyon Formation
Kcg
(Kgi) Gibson Coal Member—Interbedded black to brown siltstone, thin to medium bedded tan, golden-yellow,
brown, and greenish gray sandstone, and black coal. The sandstones are composed of well to moderately sorted,
very fine- to medium-grained angular to subrounded quartz grains with < 10% mafic minerals and <1% clay
(litharenite). The sandstone beds are cross-bedded, ranging from trough cross-beds to large-scale, low amplitude planar cross-beds. Ripple marks are locally preserved. Mud clast conglomerates frequently occur at the
base of the sandy intervals. Bioturbation is rare. Elliptical to spherical fractured siderite to goethite concretions
with calcite (or more rarely, barite) fill fractures and are present throughout the unit (Figure 10). Petrified wood
fragments are common; logs up to 10 cm in diameter and 0.5 m long are locally preserved (Figure 11). The coal
beds are generally < 0.5 m thick. A volcanic ash bed that is 2 to 4 cm thick is interbedded with coal at UTM
coordinates 254819 3901134 (NAD27)(Figure 12). The lower contact is gradational with the underlying Dalton
Sandstone Member; the top is not exposed. Maximum exposed thickness is roughly 350 m.
Kcd
(Kd) Dalton Sandstone Member—Forms two prominent cliffs, a lower yellowishorange cliff and an upper white
cliff with an intervening short slope (doublet). The basal sandstone near the contact with the underlying Mulatto
Tongue of the Mancos Shale often has thin beds containing abundant pelecypods casts and molds. The carbonate-cemented basal sandstone is composed of well-sorted, very fine-grained angular quartz grains with < 5%
mafic minerals and <1% clay. The weakly cemented upper sandstone consists of well sorted, fine-grained, angular to subrounded quartz grains with <1% lithics and 7 to 10% feldspar. The upper and lower contacts are
gradational with the overlying Gibson Coal Member of the Crevasse Canyon Formation and the underlying
Mulatto Tongue of the Mancos Shale. Maximum exposed thickness is ≤25 m.
Kcs
(Ks, Kst) Stray Sandstone Member—Forms two prominent reddish-orange cliffs with an intervening short slope
(doublet). On a fresh surface, this medium-bedded, planar cross- bedded sandstone is white to yellowish gray.
This sandstone is composed of well to moderately sorted, very fine- to medium-grained angular quartz grains
with < 1% mafic minerals and <1% clay. The top of the Stray Sandstone is a thin (<1 m) conglomerate with
pebbles to cobbles of quartzite, chert, and quartz. The upper and lower contacts are gradational with the overlying Mulatto Tongue of the Mancos Shale and the underlying Dilco Coal Member of the Crevasse Canyon Formation. Maximum exposed thickness is ≤40 m.
Kcdc
(Kdi) Dilco Coal Member—Interbedded black to brown siltstone, thin to medium bedded tan, brown, and olivegreen sandstone, and black coal. The sandstones are composed of well to moderately sorted, very fine- to finegrained angular quartz grains with < 5% mafic minerals, 1 to 5% muscovite, and 1-5 % potassium feldspar altered to clay. The sandstones are cross-bedded to ripple laminated. Elliptical to spherical fractured siderite to
goethite concretions, with calcite (or more rarely, barite) filling the fractures are present throughout the unit.
The coal beds are < 0.5 m thick and are usually in the lower part of the unit. The upper and lower contacts are
gradational with the overlying Stray Sandstone of the Crevasse Canyon Formation and the underlying main
body of the Gallup Sandstone. Maximum exposed thickness is ≤150 m.
Mapping of this quadrangle was funded by a matching-funds grant from the STATEMAP program
of the National Cooperative Geologic Mapping Act, administered by the U. S. Geological Survey,
and by the New Mexico Bureau of Geology and Mineral Resources, (Dr. Peter A. Scholle,
Director and State Geologist, Dr. J. Michael Timmons, Geologic Mapping Program Manager).
New Mexico Bureau of Geology and Mineral Resources
New Mexico Tech
801 Leroy Place
Socorro, New Mexico
87801-4796
[505] 835-5490
http://geoinfo.nmt.edu
This and other STATEMAP quadrangles are (or soon will be) available
for free download in both PDF and ArcGIS formats at:
http://geoinfo.nmt.edu/publications/maps/geologic/ofgm/home.html
Gallup Sandstone
Kgm
Main body—Yellowish gray, white, or golden yellow, medium to thick-bedded, cross-bedded sandstone. The
sandstone consists of moderately sorted, fine to very fine-grained angular to subrounded quartz grains with <
5% mafic minerals, 1 to 2% muscovite, plant debris, and potassium feldspar altered to clay (10 to 30%). Often
the sandstone beds are bioturbated with ~1.0 cm diameter cylindrical, vertically oriented burrows. Carbonaceous shale is intercalated with the sandstone. Locally contains fossiliferous (Innocermid) beds near the top.
Faint, very low angle trough cross beds occur locally in sets less than 0.25 m thick, with azimuth of 010°
(northerly flow). Beds are primarily planar-tabular or laminated. The lower contact is gradational with Mancos
Shale and the upper contact is gradational with the Dilco Coal Member of the Crevasse Canyon
Kgu
Upper tongue—White medium-bedded, cross-bedded to tabular sandstone that is locally capped by wellcemented, fractured, brown-weathering, planar crossbedded sandstone. The brown sandstone is carbonate cemented; the weakly cemented white sandstone does not react to hydrochloric acid. The sandstone consists of
well-sorted, fine-grained angular quartz grains with < 5% mafic minerals and potassium feldspar altered to clay
(15 to 25%). The white arkosic sandstone has no muscovite, but the brown capping sandstone has trace amounts
of muscovite and biotite. Trough cross beds occur in sets less than 0.5 m thick and have azimuths of 025°
(northeastern flow direction). Cross beds are moderately steeper than those in unit Kgi (described below). Local
internal scour surfaces are present. Hematitic concretions and stained surfaces occur throughout unit. The upper
and lower contacts are gradational with Mancos Shale. Maximum exposed thickness is ≤30 m.
Kgl
Lower tongue—White medium-bedded, cross-bedded to tabular sandstone that is locally capped by wellcemented, fractured, brown-weathering, planar crossbedded sandstone. Brown sandstone is carbonate cemented; the weakly cemented white sandstone does not react to hydrochloric acid. The sandstone is composed
of well to moderately sorted, fine to very fine-grained angular quartz grains with < 5% mafic minerals and potassium feldspar altered to clay (10 to 15%). The white subarkosic sandstone has no muscovite, but the brown
capping sandstone has trace amounts of muscovite. Cross bed sets are 0.5 meters thick, low angle trough cross
beds, with azimuths of 150° (southeastern flow direction). The top of unit is locally conglomeratic with sandstone clasts and sharks teeth. The upper and lower contacts are gradational with Mancos Shale. Maximum exposed thickness is ≤15 m.
Mancos Shale
Kmm
Mulatto Tongue—Golden yellow, thin-bedded, tabular to ripple-laminated sandstone and black shale. Burrows
and scattered pelecypod molds are common in the sandstone beds. Moderately to well sorted, very fine-grained
angular to very well-rounded quartz grains with < 1% mafic minerals, ~1% muscovite, and abundant clay
(~30%). Coarse to very coarse sandstone beds near the basal contact with the Stray Sandstone and lenses of
conglomerate with well-rounded pebbles of black and white chert and black quartzite are locally present. Upper
and lower contacts are gradational with the Dalton and Stray Sandstone members of the Crevasse Canyon Formation. Maximum exposed thickness is ≤50 m.
Km
Main body—Black to dark brown shale and silty shale intercalated with finely laminated to cross-bedded thinly
bedded sandstone. The sandstones are wellsorted, fine-grained quartz arenites. Upper and lower contacts are
gradational. Small tongues of Main Mancos are interbedded within the Gallup Sandstone units. Maximum exposed thickness of Main Mancos beneath Gallup Sandstone is ≤50 m. Maximum drilled thickness including
Bridge Creek Limestone (described below) is roughly 145 m (Table 2).
Kmb
Bridge Creek Limestone—Finely laminated, fossiliferous, light gray limestone interbedded with thin black
shale below the Main body of the Mancos Shale. Identified only in narrow horst on east side of exposed core of
San Fidel dome where it overlies Twowells Sandstone; in fault contact with other units. Correlative with the
Greenhorn Limestone. Contains abundant invertebrate fossils including Pycnodonte aff. P. kellumi, Exogyra
levis, Plicatula cf. P.hydrotheca, cf. Caryocorbula and Turritella sp. (Barry Kues, University of New Mexico,
personal communication). Unit is moderately hornfelsed from subjacent magmatic intrusions and displays minor hydrothermal alteration, particularly along fractures and planer zones of permeability. Maximum exposed
thickness is ≤25 m.
K
Ku Cretaceous Rocks Undivided or uncategorized. (Kus— unidentified sandstone), (Kuh—hornfelsed siltstone and shales)--
Porphyritic Intrusive Rocks—subdivided based on phenocryst mineralogy, in particular presence of hornblende
and biotite. Mapped as Tplu where exposure or time prevented separation.
Trachyandesite, undivided—
Multiple flows of gray to blue-gray, porphyritic lavas that originate from
near the summit of Mount Taylor. Phenocrysts consist of resorbed plagioclase, potassium feldspar, oxidized
clinopyroxene, hypersthene, sparse biotite, sparse oxidized hornblende, and magnetite in a pilotaxitic groundmass containing microphenocrysts of plagioclase, clinopyroxene, apatite, opaque oxides, and devitrified glass.
May contain rare, small (≤5 mm) hornblende megacrysts. Some specimens show minor Fe-oxide alteration.
Overlies small flow of Tytb and flows of hornblende trachyandesite (That). Interbedded with volcaniclastic
sedimentary deposits (Tvs). Underlies flow of Tytb on upper north side of Rinconada Canyon. Flow near summit of Mount Taylor is dated at 2.60 ± 0.05 Ma (Perry et al., 1990). Exposed thickness is >215 m.
Trachydacite to Trachyandesite lavas –Gray to tan moderately porthyritic rocks with phenocryst assembledge
coarse phenocrysts dominated by plagioclase with no obvious biotite or hornblende and little visible pyroxene.
Tbhtd Biotite bearing Trachydacite—Tan to gray rocks with abundant plagioclase phenocrysts and visible biotite.
Often also contain hornblende Usually more porphyritic and lighter colored than Tta or Tptd.
35°7'30"N
107°37'30"W
Porphyritic Intermediate Lavas
3891 000
Km
Qc
Qtc
Qal
Qtc
Qf2 Qf1
Km
Basaltic intrusions-- Dark gray to black fine grained intrusive equivalents of Tub or other extrusive lavas.
Qf4
Qf4
Qf3
Tbi
Tta
Qal
Kgm
Tuffs and tuffaceous sediments—Tan to white ash flow tuffs, tephra, pumice falls, sandstones, conglomerates
located below Tpb or stratigraphic equivalent. Where well exposed along Water Canyon ash flow and tephra
deposits are common, perhaps dominant in this interval.
Qf4
Km
Qtc
Tvt
Tplu
Qtc
Volcaniclastic sedimentary rocks—Gray to tan to white debris flows, fluvial deposits and interbedded tuffs shed
from the Mount Taylor stratovolcano during growth. Boulders form a lag deposit on surface of debris flows to
the extent that the true mix of facies is usually unknown.. Fluvial component contains rounded to subrounded
cobbles including a higher proportion of basaltic clasts, especially to SW. Tuffs consist mostly of thin beds and
lenses of fall deposits with vesiculated pumice having phenocrysts of plagioclase, clinopyroxene ± hornblende
± biotite. Unit is interbedded with practically all lavas on southwest side of Mount Taylor and Horace Mesa.
Overlies pyroxene basaltic trachyandesite (Tbta) east of Rinconada Basin and basanite (Tbb). Maximum exposed thickness is >200 m.
Plagioclase basalt--Distinctive flows of coarsely porphyritic basalt , containing 10-20 percent phenocrysts of
plagioclase in tablets as much as 2 cm in diameter and sparse smaller phenocysts of olivine and pyroxene. Usually interbedded in Tvs. Probably erupted from one or more vent areas near the top of Mount Taylor.
Kgu
Qf4
Qf4
Qf1
Km
Km Kgl
Km
Kgu
Qtc
Kgu
Qtc
Qf3
Kgm
Km
Km
Km
3892 000
Qf2
Km
Kgu
Kgu
Qf4
Qal
Tub
Kmm
Qf4
Tub
Kgl
Kcdc
7
Qf4
Kcdc
12
Kgl Km
Qf4
Km Kgu
Kcdc
Kgm
Kgm
Km
Pyroxene basaltic trachyandesite—Gray, fine-grained flow and red to black cinder deposits (Tbtc) containing
conspicuous, large (≤1.5 cm), resorbed, very dark green clinopyroxene megacrysts (Lipman et al., 1979).
Phenocrysts consist of plagioclase, olivine, clinopyroxene, and orthopyroxene in an intersertal groundmass containing plagioclase, olivine, clinopyroxene, opaque oxides, and glass. Many specimens contain quartz
xenocrysts. Eroded cinder cone is located west Mt Taylor quadrangle and contains rare blocks of fine- to medium-grained olivine-pyroxene gabbro. Underlies Tvs but overlies Totb, Topta, Upper Cretaceous Dalton Sandstone (Kcd) and the Mulatto Member of the Mancos Shale (Kmm). Unit is not dated. Maximum exposed thickness is about 80 m.
Tpb
Km
Qtc
Qal
Km
Kgu
Kmm
Qc
Km
Kcdc
Qf1
Kgm
Qf4
Km Km Km
Qf4
3
Qf4
6
3893 000
Qtc
Kgm
Kcdc
Km
Qtc
Kmm
6
Km
Qtc
Kgl
Qal
Kmm
Km
Km
Qtc
80
20
Kgl
Qt3
Tub
Kgu Qt2
Qt3
Tub
5
Qtc
Km
Kgm
Km
Km
Qf4
14
Qt1
Qf3
Qtc
Qal
Tvs
Qf4
Kcs
Kcd
Kmm Qa
Kmm
Kgm
Kcdc Tvs Qtc
Qtc
Kgu
Km
Kgm
Kcs
Kgm
Qt2
Kcd
Tpb
4
Qtc
Qtc
Kcdc Kcdc
Kcd
Kmm
Kcdc
Qtc
Tubi
Kmm
Qa Tubi
Tubc
Qt2
Kgm
Tphtd
25
Kmm
Tvs
Qf4
Tvt
Kgm
Qtc
3894 000
Kgm
Kmm
Tubi
Tvs
Kgm
Kcd Qtc
Tvs
Kcd
Kmm
Kcs
Kmm
Kcdc
Kgm Kcd
Tpb
Tubc
Qtc
Qtc
Tpb
Kcdc
Qf4
Kcdc
Kmm
Qtc
Kcd
Tpb
Tub
35°10'0"N
Tbb
Kmm
Qtc
Tvs
Tvs
Kmm
Kmm
Qtc
Kmm
Tvs
Qa
Tvs
Tvs
Kmm
Ku
Qtc
Qtc
Tvs Qtc
Kmm
3
Kcdc
Kmm
Tub
Tvs
cinder deposits (Totc) having sparse olivine and plagioclase phenocrysts in intersertal groundmass containing
microphenocrysts of plagioclase, augite, olivine, opaque oxides and glass. Some flows have rare orthopyroxene
microphenocrysts. Some flows have tiny (<1 mm) ovoid patches very rich in glass and opaque oxides. All flows
may have rare quartz xenocrysts. Eroded cone on east side of Rinconada Basin has NNE-trending dike and fissure. Eroded cone on SE side of Horace Mesa contains NE-trending feeder dike.
Tbta
Kcdc
Kcd
Kmm
Tpb
3893000
Kmm
Tvs
Qt4
Qal
Tvs2
Qf3
Kcdc
Qf3
Kcg
Tub
Qtc
Totc
Qtc
Kcd
Qtc
Qt4
Qtc
Tpb
Ter
Tub
Older trachybasalt—Black to dark gray, fine-grained basalt and red to black
Qal
Ku
Tub
Tptb
Totb
3895 000
Kmm
Tvs
Tpb
Tub
Tvs2
35°7'30"N
Tvs
Tpb
Qal
Upper Basalt (Lipman)--Fine grained dense alkalic basalt and basaltic scoria (Tubc). Sometimes has scattered
pyroxene phenocrysts to 1 cm. Several local vent areas, marked by scoria cones, occur around the southern
lower flank of Mt Taylor present in this map area. One
scoria cone contains intrusive areas (Tubi) Locally contains interlayers of similar lithology to TPb. These have been observed in a few areas to be gradational
in contact and not interleaved flows.
Kcg
Qtc
Kcd
Tvs2
Rhyolite flow or dome. Light gray to white rocks containing 10 to 20 percent quartz, potassium feldspar and
biotite phenocrysts. Sugary texture near margins and in western exposure but more altered and denser to east..
Center of exposures are coarser grained, lack quartz and have a distinctively porphyritic texture (Tod). Exposures are very poor in general. Occurs in core of Mount Taylor cone and forms the first volcanic unit that can be
observed in the volcanic sequence
Talus/Colluvium--Slope wash, talus, coarse colluvium, and landslide material where morphology not obvious.
Tub
Kcg
Qtc
Qal
Qa
Kcs
Tpb
Tubc
Qal
Landslides—Poorly sorted debris that has moved chaotically down steep slopes; slumps or block slides (toreva
blocks) partially to completely intact, that have moved down slope; slumps and block slides usually display
some rotation relative to their failure plane; thickness varies considerably depending on the size and nature of
the landslide.
Kcg
Qal
3894000
Qls
3896 000
Tbh
Tvs Qt4
Tvs
Deposits underlying Qf3 fan surfaces—Part of fan complex at the mouth of Water, Timber, and Castillo Canyons; Qf3 surfaces form part of the modern piedmont. Deposits of sandy pebble to boulder gravel of mixed volcanic lithologies and subordinate sandstone clasts greater than 3 m thick; base of deposit poorly exposed. Soils
are partially eroded, but exhibit Stage II to III carbonate morphology, Bt horizon with 5YR to 7.5YR color
(Figure 2, Table 1). Likely middle Pleistocene.
Basaltic Rocks
Tbb
Tpb
2
Tpb
Tr
Hawaiite lava.—medium gray mafic lavas. Sheen on weatered broken surface. Occur beneath the basanite
lavas in southeastern portion of quadrangle.
Colluvium—Poorly sorted slope wash and mass wasting deposits from local sources; mapped only where extensive or where covering critical relations; thickness can locally exceed 15 m. Locally buries terrace surfaces and
underlying alluvium along the sides of narrow canyons, including Water, Timber, and Seco canyons.
Kcd
Qfy
Tvt Ku
Ku
35°10'0"N
3890000
Qtc
Qtc
Qls
Tvs
Totc
3891000
Kcg
Kcg
Tvs
Ku
Kcd
Tpb
Totb
Tbb
Tpb
Qt4
Older Dacite-- light gray to white moderately porphyritic rock containing feldspar, hornblende and biotite.
Often has a distinctive blocky textured plagioclase. May be more mafic component of Tr dome or a separate
dome or intrusion.
TERTIARY
Qfy
Ttd
Qal
Tubi
Qal
Tvt
Qtc
Tvs
Tvs
Tub
16
Qa
TubiTubi
Tdo
Tbh
Qc
Qtc
Tbh
Tbb
Qtc Kcg
Qtc
porphyritic mixed lava --Distinctive bulbous flow or intrusion on southwest side of Mt Taylor cone. Dark gray
to black rock which contains abundant porphyritic enclaves of more mafic rock or magmas Similar to Tel but
enclaves are very abundant in every sample.
Alluvium underlying Qt1 terrace surfaces—Deposits of sandy cobble to boulder size gravel underlying terrace
surfaces located approximately 35 to 40 m above local base level. Forms fill terraces with deposit thickness
ranging from 6 to 8 m or more. Soils are stripped (eroded). Early Pleistocene?
Qal
Tbhtd
14
Tder
Basanite lava. Single flow of dark gray to black basaltic lavas. Contains a few obvious phenocrysts of olivine.
Underlies Tpb and overlies Tbh in Southeastern portion of the quadrangle. Flow decreases in elevation northward and may have been erupted to the south flowing north before Mt Taylor became an edifice.
Deposits underlying Qf1 fan surfaces—Deposits of subrounded to subangular sandy pebble to boulder gravel
underlying remnant fan surfaces at mouth of Castillo canyon. Deposit is 5 to 10 m thick, with upper 2 m comprising basalt boulder gravel. Qf1 fan surfaces are 15 to 20 m above local base level. Soils are stripped; however, clasts eroding from deposit exhibit continuous carbonate coatings. Early Pleistocene?
3897 000
Tbh
Tpb
Ttd
Tpb
Ter
Qtc
Tpb
Qal
Tpb
Enclave rich Trachydacite to trachyandesite –gray to brown rocks containing plagioclase, and hornblende
phenocrysts but also containing abundant (nearly every hand sample) enclaves of more mafic rocks or magmas.
Tbb
Qf1
Kcg
Tbb
15
Tpb
Tel
Qtc
Qal
Qtc
Tvs
Tql of Lobo Springs-- Coarse porphyritic trachydacite—Pale pink to tan, very coarse porphyritic lava containing large (≤ 3 cm) phenocrysts of potassium feldspar. Unit superficially looks like granite and makes a distinctive fine gravelly soil. Smaller phenocrysts consist of magnetite, potassium feldspar, plagioclase, oxidized clinopyroxene, and apatite in a hyalopilitic groundmass of tiny felted plagioclase, potassium feldspar, clinopyroxene, opaque oxides and devitrified glass. Unit shows minor Fe-oxide alteration. Unit underlies Tta and probably
That in extreme NE corner of quadrangle. Relations with other units in Mount Taylor stratovolcano are unclear.
Unit is not dated. Maximum observed thickness is about 80 m.
basaltic lavas—Dark gray to black basalts, usually altered. These flows occur in the center of the Mt Taylor
crater area and are some of the earliest rocks from this vent area.
Qf2
Deposits underlying Qf2 fan surfaces—Deposits of subrounded to subangular sandy pebble to boulder
gravel underlying remnant fan surfaces at mouth of Timber and Castillo canyons. Deposit is 10 to 15 m or
more thick. Qt2 fan surfaces are 10 to 12 m above local base level. Soils are stripped; however, clasts eroding
from deposit exhibit continuous carbonate coatings. Early to middle Pleistocene?
3898 000
Tbb
Tvs
3892000
Tpb
Tcptd
Tbo
Qf2
Qal
Tub
15
8
3895000
35°12'30"N
Tvs
Qal
7
Ku
3899 000
Ttd
30
Tptd
3896000
Qal
Tvs
Qal
Ttha
15
Tta
Qf3
Tvs
Tvs
Tpb
Qt4
Tvs
Trt
Ttha
Tbhtd
Tvs
Ttdl
Tvs
Tbhi
50
Tbhtd
Tub
Ttdc
Tub
75
80
Qal
Bedded tuff deposites. Underlie Tphtd at one locality along western edge of quadrangle. Mostly light colored
medium to fine pumice fall deposits in this exposure.
Alluvium underlying Qt2 terrace surfaces—Deposits of sandy pebble to boulder size gravel underlying terrace
surfaces located 12 to 18 m above local base level. Deposit thickness ranges from 4 to 10 m or more. Where
preserved, soils are well developed, exhibit Stage II to III carbonate morphology, Bt horizon .with 5YR color.
Likely middle to late Pleistocene in age.
Deposits underlying Qf4 fan surfaces—Part of fan complex at the mouth of Water, Timber, and Castillo Canyons; Qf4 surfaces form part of the modern piedmont. Deposits of fine sand to coarse gravel; typically interbedded fine to medium sand and imbricated cobble-to-boulder-size gravel with individual gravel beds 1-3m thick.
Qf4 deposits often bury Qf3 deposits and include buried soils (Figure 1). Total thickness 3 to 10 m or more.
Where present, Qf3 buried soils are 1 to 5 m below the Qf4 surface. Qf4 soils are characterized by A-Bw-C or
A-Bk-C profiles with maximum Stage I carbonate morphology (Table 1), locally include buried A horizons.
Middle to late Holocene.
Tbhi
Tvs
Alluvium underlying Qt3 terrace surfaces—Deposits of sandy pebble to boulder size gravel underlying terrace
surfaces located approximately 7 m above local base level. Typically forms fill terraces with deposit thickness
of 7 m or more. Poorly preserved; soil properties not described.
Qf4
Tub
Qtc
Alluvium underlying Qt4 terrace surfaces—Deposits of sandy pebble to boulder size gravel underlying terrace
surfaces located approximately 3 to 5 m above local base level. Deposit thickness ranges from 2 to greater than
6 m. Soils developed in deposits underlying Qt4 surfaces are weakly developed, with 10YR color, minimal
horizon development, none to minimal carbonate accumulation, and lack of Bt horizon development (Table 1).
Late Holocene in age.
Young Alluvial fans—Typically fan-shaped deposits of coarse bouldery gravel and sand, silt, and clay that emanate from tributary drainages along axis of major drainages. Grades into alluvial deposits along main channels;
probable late Holocene age; maximum exposed thickness about 10 m.
Tvt
Tta
Tpta
Tbhtd
3900 000
Tpb
Tvs
Alluvium-- flat areas of upland alluvium not associated with any obvious valley or piedmont slopes. Usually
fine grained and perhaps of eolian origin.
Qfy
Ttdc
80
Tvs
35
35°12'30"N
3899000
Tta
Tbhi
Qtc
20
Tvs
Qal
Thrtd
60
Tbhi
40
30
Thbi
5
Qtc
Thrtd
Tpb
Tpta
70 24
Qt1
Ttdl
Tpb
Tt
Ttder
60
Tvt
Tub
65
45
3901 000
Ttder
Qtc
Tpb
Tub
Qtc
Tvs
Qtc
Tvt
Tpta
Tbhtd
Teta
Qtc
Qfy
Thli
Tob
Qt2
Ttder
Tvt
Tbi
Tplu
Tbhtd
Tt
30
Thli
35
Qal
Tob
Tdo
Tta
55
Ku
45
Teta
Qal
Qt4
Tr
Qt3
Tvt
Tvs
Thli
Thbi
Tta
3902 000
Tpta
Qtc
Ku Ku
Tob
Ku Tpbi
Thi
70
Tob
Tpbi
Tr
Tpbi Tob
Tdo
Qal
Qal
Qal
Tob Tr
Tcg
Ku
55
71
Tpb
Tvs
Tvs
75
Qt4
Tbtdl
Tr
Tta
Qa
Qtc
80
80
3903 000
Tbtd
Tr
Ttha
Tvs
Ttder
15
Qtc
Tplu
3902000
3901000
Tpta
25
Tr
Tta
Qal
Qal
Tvs
Tptai
Tvs
35°15'0"N
Ttder
55
Qtc
Qal
Tr
Thbi
Qc
Tr
Tpcta Tbi
Tub
Tvs
Qal
Tpta
Tpb
Tbtd
Alluvium—Deposits of sand, gravel and silt in main valley bottoms; locally includes stream terraces, alluvial
fans, and canyon wall colluvium; Late Holocene in age; maximum thickness of various alluvium deposits is
uncertain but may exceed 10 m. Alluvium in canyon bottoms and along major drainages is typically coarsegrained, cobble to boulder size sandy gravel of mixed volcanic lithologies and subordinate sandstone clasts.
Alluvium in embayments adjacent to main drainages is typically finer-grained, silt and sand dominated deposits
with pebble-gravel lenses and minor interbedded gravel beds. Valley floor alluvium and low terrace deposits
are characterized by weakly-developed soils with 10YR-2.5Ycolor, none to minimal carbonate accumulation,
and lack of Bt horizon development. Locally includes small areas of colluvium, terrace and fan deposits to
small to map separately.
Trt
A geologic map displays information on the distribution, nature, orientation, and age relationships
of rock and deposits and the occurrence of structural features. Geologic and fault contacts are
irregular surfaces that form boundaries between different types or ages of units. Data depicted
on this geologic quadrangle map may be based on any of the following: reconnaissance field
geologic mapping, compilation of published and unpublished work, and photogeologic interpretation.
Locations of contacts are not surveyed, but are plotted by interpretation of the position of a given
contact onto a topographic base map; therefore, the accuracy of contact locations depends on the
scale of mapping and the interpretation of the geologist(s). Any enlargement of this map could cause
misunderstanding in the detail of mapping and may result in erroneous interpretations. Site-specific
conditions should be verified by detailed surface mapping or subsurface exploration. Topographic
and cultural changes associated with recent development may not be shown.
Cross sections are constructed based upon the interpretations of the author made from geologic
mapping, and available geophysical, and subsurface (drillhole) data. Cross-sections should be used as
an aid to understanding the general geologic framework of the map area, and not be the sole source
of information for use in locating or designing wells, buildings, roads, or other man-made structures.
The map has not been reviewed according to New Mexico Bureau of Geology and Mineral Resources
standards. The contents of the report and map should not be considered final and complete until
reviewed and published by the New Mexico Bureau of Geology and Mineral Resources. The views and
conclusions contained in this document are those of the authors and should not be interpreted as
necessarily representing the official policies, either expressed or implied, of the State of New Mexico, or
the U.S. Government.
5
porphyritic hornblende trachydacite—Pale gray to tan, massive to sheeted porphyritic lava with conspicuous
large (≤1 cm) phenocrysts of plagioclase, some with apparent rapakivi texture. Additional phenocrysts are hornblende and clinopyroxene. Equivalent to porphyry of San Jose Canyon (Lipman et al., 1979). Intrudes Tbta and
Topta on SW edge of Mount Taylor quadrangle. Unit is not dated. Thickness of poorly exposed flow on SE
edge of Lobo Springs quadrangle is about 20m.