NEW MEXICO BUREAU OF GEOLOGY AND MINERAL RESOURCES
NMBGMR Open-file Geologic Map 87
Last Modified 18 SEP 2007
A DIVISION OF NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY
106°32'30"W
106°35'0"W
106°37'30"W
357000
356000
355000
354000
A
Kbc
Qls
360000
359000
358000
Tpc
77 Kd
Tgea
Jm
8
27
15
Tgea
Tsto
Tgea
Qal
Alluvium (Quaternary) – unconsoilidated, clay, silt, sand, and gravel deposits up to 5 m
thick; includes locally organic-rich sediments.
Qc
Colluvium (Quaternary) – unconsolidated fine to coarse debris derived from local
volcanic and sedimentary rocks; up to 35 m thick.
3998000
Qbt
Qbo
Tgea
Qal
Tgea
Kd
Qbt
Qbt
25
Qco
Je
Jt
Ta
Tap
Pedernal Chert member – varicolored, white, blue to gray, black, cryptocrystalline,
massive chert, limey chert, and limestone containing nodular chert, conspicuous ledge
former, 2 to 8 m thick. The cert is locally interlayered with thin beds of arkosic sandstone
and conglomerate and is typically more limey at its base.
Tal
Lower conglomerate member – pinkish tan to gray, generally coarse arkosic conglomerate and fine- to medium-grained sandstone, slope forming, 300 to 400 ft (100 to 130 m)
thick. The lower conglomerate member is poorly sorted, weakly to moderately indurated,
calcareous, and characterized by well rounded pebble to boulder-size (up to 50 cm) clasts
composed of Precambrian quartzite, granite, pegmatite, gneiss and schist, as well as
fine-grained limestone and mudstone.
Qco
Qco
26
Tged 32
7.85
Explanation of Map Units
Qbt
Qbo
Qal
Qbo
Tgea
5 Qls
@cp
3998000
Qal
Qal
31
Kd
@cp
365000
14
Tr
Kd
Tgea
Tgea
Tged
Ta
@cu
Tgea
364000
363000
362000
361000
Ql
Landslide deposits (Quaternary) – unconsolidated unsorted, fine to coarse volcanic and
sedimentary debris with morphology suggestive of a landslide; up to 35 m thick.
Qb
Bandelier Tuff (1.6 Ma to 1.4 Ma) – pumiceous air-fall tephra, welded rhyolitic
ash-flow tuff, and local volcaniclastic sediments; divided into two members, from
younger to older:
Qls
Qc/Js+Jm
Qls
5
Tsto
Tgea
Qal
Qbt
A'
Qbo
15
Tpc
3997000
Kbc
23
3997000
Qbt
@cp
Qco
20 Ta
Kd
Qls
Qbt
Km
Qal
Je
Jt
Qal
Qal
Tgea
7.42(+-)0.01
Qco
70
8.75(+-)0.06
@cp
Qbo
Tsto
3996000
Tga
Qal
3996000
Tgea
@cp
Tga
Qal
Qls
Qco
Tga
Tghd
Tt
Qco
60
El Rito Formation (Eocene) – orange-red, hematitic, micaceous mudstone and siltstone
and lenses of fine- to medium-grained arkosic sandstone, slope forming, estimated 50 to
140 m thick. The El Rito Formation locally possesses a 2-to 10-m-thick basal conglomerate section made up of very well rounded Precambrian schist, gneiss, and hematitic
quartzite cobbles and boulders (up to 1 m) in a weakly indurated matrix of coarse sand.
Km
Mancos Shale (Late Cretaceous) – dark gray and brown, weakly consolidated, calcareous, carbonaceous shale and interlayered thin beds of fossiliferous limestone, slope
forming, 0 to 65 m thick. Lowermost part of the section only is locally present; upper
contact is an erosional unconformity of moderate relief.
Kd
Dakota Sandstone (Late Cretaceous) – white, gray, and tan, fine-grained quartzose
sandstone, well sorted, locally kaolinitic, conspicuous as a cliff former, 60 to 67 m thick.
The Dakota Sandstone is well sorted, thick bedded to massive, and locally contains thin
interbeds of black, carbonaceous shale. The basal contact with the underlying Morrison
Formation was arbitrarily determined as the lowest occurrence of carbonaceous matter
observed in the rock, whether sandstone or shale.
Jm
Morrison Formation (Late Jurassic) – shown on the map as an undivided unit, three
members are recognized in the map area with combined total thickness of 220 to 250 m
as measured in sec. 27 and 34, T. 23 N. R. 4 E. and sec. 3, T. 21 N. R. 3 E. (Lawrence,
1979). From younger to older, the subunits are:
Otowi Member – tan-colored, crystal- and lithic-bearing tuff, weakly to partly welded,
locally with up to 30% xenoliths of dacite and other intermediate to mafic volcanic rocks;
0-100 m thick. Basal pumiceous tephra deposits of the basal Guaje Pumice Bed not
observed.
Tschicoma Fornmation (3 Ma to 7 Ma) – includes andesites and local dacites occur
ring as massive lavas, domes, vents, and shallow intrusives on La Grulla Plateau;
informally divided into two members:
Qco
Tpc
Ter
Tshirege Member – primarily light pinkish gray, crystal tuff, weakly to moderately
welded with phenocrysts of quartz, sanidine, and pyroxene and pumice fragments in a
fine-grained matrix of vitric ash; up to 70 m thick; includes basal white pumiceous tephra
deposits (1-2 m thick) of the Tsankawi Pumice Bed. Cerro Toledo tuffaceous and volcaniclastic sediments not observed.
Ta
B
Kbc
Tga
Qal
Tr
Qbt
3995000
Ttd
3995000
Qbo
Qco
Qal
Qbt
Qco
Tghd
Qco
7
4
36°5'0"N
Qls
Tga
36°5'0"N
3994000
Tb
Qco
Kd
3994000
Tga
18
70
40
Ter
Qls
Tta
Fo
vo ur
H
ce lcan ills
nt ic
er
53
Qal
Tga
Tr
Tga
Qbt
Tga
Qbo
Qco
Tga
7.35
Tr
Tsto
Tga
Tb
30
Tl
Tld
3993000
Qco
3993000
Tghd
Qbt
Tr
Qco
Qbt
Qbt
5
Tla
Qal
Qco
Tsto
Qbo
Kbc
Tga
Kd
Qco
Tga
Qal
Qco
6
Tpc
Qal
15
Qco
Tb
Basalt (unassigned) (late Miocene to Pliocene) – weakly porphyritic, fine-grained
olivine-phyric basalt exposed in thin flows within Santa Fe Group sandstone on Canones
Creek. Also observed in boulder subcrop where deposited on lower Abiquiu Formation
conglomerate in the Four Hills area.
Qco
Tsto
5
Kd
Qbo
Qco
Qbt
Qco
Qbo
4
22
Tpc
Ttd
17
44
Qco
Qbt
Ttd
Tga
Qal
Qbo
Qco
Qal
Qco
5
3990000
Qal
Qal
Tpc
Qco
3989000
Qal
Qbt
Ta
Ta
Upper Shale Member (also known as the Petrified Forest Member) – maroon and
gray-green, micaceous shale, minimum 100 m thick.
Abiquiu Formation (early Miocene) – informally divided into three subunits including,
from younger to older:
@p
Poleo Sandstone – yellow-brown to maroon-gray, medium- to fine-grained, micaceous,
quartzose sandstone and interbedded reddish brown shaley sandstone, locally cross
bedded; minimum 50 m thick.
Upper sandstone member – white, light gray, and buff-colored fine- to medium-grained,
tuffaceous and volcaniclastic sandstone and mudstone, locally conglomeratic, estimated
100 to 130 m thick. The upper sandstone is a slope-forming unit comprised of moderately
sorted, moderately indurated volcanic detritus representing diverse lithologies including
pumice, basalt, and welded tuff.
3989000
Correlation of Map Units
Unconsolidated Sediments
Tpc
Qal
Ttd
Qbt
Qco
Qc
Qbo
Qbt
10
Qco
3988000
Qco
Qbt
Qal
Qbo
Tghd
unconformity
Ttd
Qbt
Qbo
3987000
QUATERNARY
Pleistocene
unconformity
Qbt
Tta
Tga
10
Qal
Holocene
and/or
Pleistocene
Ql
Volcanic Rocks
3988000
Qal
7.81
Qbo
unconformity
Tga
Qbt
Qbt
Ttd
Tld
3987000
Pliocene
Tla
unconformity
Qbt
Qbo
Tpa
Qco
Qal
Ttd
7.63
TERTIARY
unconformity
Sedimentary Rocks
Qbo
Tsf
Tghd
Qco
Qal
Tau
Tga
3986000
Qco
Qal
3986000
Qco
Qal
Qbo
Tap
unconformity
Tga
Ter
Tghd
Qco
7.8
Qal
Qbt
Kd
Tgbhd
Tgb
Jm
3985000
Qbt
Tpa
Qls
Qbt
MESOZOIC
3985000
Jt
36°0'0"N
36°0'0"N
355000
Upper
Cretaceous
and Upper
Jurrasic
Km
Qco
354000
Eocene (?)
unconformity
Qbt
Qbo
Miocene
Tal
7.27
Qbo
Mid-Miocene
to Pliocene
Tb
unconformity
Tghd
Qbt
Qbt
356000
360000
359000
358000
357000
362000
361000
363000
364000
Upper
Jurrasic
and Upper
Triassic
Je
106°32'30"W
106°35'0"W
106°37'30"W
@u
@p
Base from U.S.Geological Survey 1953, photorevised 1977
1927 North American datum, Universal Transverse Mercator Projection
1000- meter UTM grid ticks, zone 13, shown in red
1:24,000
ARROYO
DEL AGUA
JAROSA
SEVEN
SPRINGS
YOUNGSVILLE
Cerro
del
CERRO
DEL
Grant
GRANT
VALLE SAN
ANTONIO
Chinle Formation (Late Triassic) – two members occur in the map are, from younger to
older:
@u
Qbt
Qco
Qbo
@c
Ojo Caliente Formation of the Santa Fe Group (late Miocene to Pliocene) – pink to
tan-colored, well-sorted, fine-grained feldspathic and quartzo-feldspathic sandstone of
eolian origin; up to 100 m thick.
10
Qal
Qbo
Entrada Sandstone (Late Jurassic) – white, pink, and yellowish tan, fine- to very
fine-grained quartzose sandstone, well sorted, moderately indurated, exhibits large-scale
eolian dunal cross-bedding, cliff former, 60 to 67 m thick.
36°2'30"N
Qco
Qco
Qal
Je
Qal
Tpc
Qbt
Todilto Formation (Late Jurassic) – white to gray, dominantly fine-grained, massive
gypsum, sloping-forming unit; with a 2- to 3-m-thick basal section of gray, laminated,
fissile limestone; total unit thickness 15 to 27 m. A gray, crusty “popcorn” texture typically develops on erosional surfaces of Todilto gypsum.
Qbo
Tpc
Ta
Tpc
Qbt
Qal
Ta
Qco
Ta
Jt
Qal
Ttd
Qco
3990000
Ttd
36°2'30"N
Tpc
Tau
10
Tghd
Tpc
Ta
Qbo
Qbo Qco
Qco
Qbo
Qal
9
Tr
Qbo
55
Ter
Ter
Tpc
Tsf
3991000
Qbt
3991000
Recapture Shale Member – conspicuously banded, gray and maroon, white to gray very
fine grained quartzose to subarkosic sandstone and interlayered maroon-colored sandy to
silty shale, slope forming, 72 m thick. The basal 12 m of this unit consists of white to
light gray, fine- to very fine grained quartzose sandstone, thin-bedded, fissile, containing
small-scale ripple marks.
Tschicoma andesite (Pliocene) – dark gray, weakly porphyritic, fine-grained,
plagioclase-pyroxene-olivine basaltic-andesite and andesite exposed in a series of flows
with pyroclastic interlayers associated with a shield cone at Encino escarpment; includes
remnant andesite lavas and pyroclastic debris on Banco Largo; at least 70 m thick.
Paliza Canyon andesite (8 Ma) – dark gray, coarsely porphyritic, pyroxene andesite;
locally strongly altered; exposed in limited outcrop on the northern Valles caldera rim;
thickness undetermined.
20
Kbc
Lobato Dacite (Pliocene, <7.85 Ma) – weakly porphyritic, plagioclase-augitehypersthene ± biotite dacite exposed as an endogenous dome at Encino Escarpment and
dike on Banco Largo; up to 100 m thick.
Tpa
3992000
Tga
Tga
3992000
Brushy Basin Member – banded, dark reddish brown and light tan to ochre-colored,
interlayered dark-colored sandy to silty shale and light-colored very fine grained subarkosic to feldspathic sandstone, slope forming, 110 m thick.
Qbo
Tghd
Qbt
Jackpile Sandstone Member – white to tan, fine-grained, kaolinitic, quartzose sandstone, well indurated, conspicuous cliff-forming unit, thick bedded to massive, 57 to 67m
thick. Contains abundant thin beds of quartz pebble conglomerate and locally exhibits
medium-scale cross bedding.
Tga
7.35
Qco
Tschicoma andesite (Pliocene) – mainly coarsely porphyritic, 2-pyroxene andesites that
occur as massive flows, domes and shallow intrusives on the west-central parts of La
Grulla Plateau; 70 10 150 m thick. Includes local dark gray, fine-grained, weakly porphyritic andesite containg pyroxene and minor olivine.
Lobato Formation (7 Ma to 14 Ma) – includes andesites and local dacite occurring as
lavas, domes, and vents exposed in the escarpment of Encino Lookout, on Banco Largo,
and on the north end of La Grulla Plateau; informally divided into two members:
B'
25
Qbo
Tschicoma dacites (7.35 Ma) – includes hornblende- and hornblende-biotite porphyritic
rocks of diverse texture and lithology that overlie Tschicoma andesites and are consentrated in domes and lavas of limited aerial extent along the east edge of La Grulla
Plateau; 0-150 m thick. Both coarsely porphyritic and fine-grained,, flow-banded, weakly
porphyritic dacites are present.
1
CANONES
NEW MEXICO
0.5
1000
0
0
1000
2000
3000
1 MILE
4000
5000
6000
Geologic map of the Cerro Del Grant quadrangle,
Rio Arriba and Sandoval Counties, New Mexico.
VALLE
TOLEDO
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.
DRAFT
A
WEST
7000 FEET
May 2004
POLVADERA
PEAK
1
Magnetic Declination
September, 2002
10º 28' East
At Map Center
0.5
0
by
Lawrence, J.R. , Kelley, S. 2, and Rampey M. 3
CONTOUR INTERVAL 20 FEET
Banco Largo
10,000
feet ASL
1 KILOMETER
1
9,000’
Kd
Je
@u
Km
Jt
Kd
Jt
@u
6,000’
Km
Tla
Rito
Encino
Ta
Qc
Ta
Ter
Kd
Jt
Je
Ter
Kd
Kd
Kd
Jm
Jm
Jm
Tld Jt
Ta
Je
Je
@u
@u
Je
@u
9,000’
Tla
Qbt
Tsf
Qbo
Ter
Kd
Jt
Jt
Qc
Ta
Kd
Jt
@u
Tsf
Ta
Ter
Tla
Tla
Tsf
Ta
10,000
feet ASL
Tla
Tsf
Tla
Tsf
Jm
Jm
Je
OFGM 87
Ter
Ta
Ter
Jm
7,000’
Tla
Qc
Tsf
8,000’
Lawrence GeoServices, Ltd. Co., 2321 Elizabeth Street NE, Albuquerque, NM 87112.
2
New Mexico Bureau of Geology, 801 Leroy Place, Socorro, NM, 87801.
3
Dept. of Geology, Queen's College, Cambridge Univ., CB39ET, United Kingdom.
Tla
Qc
A’
EAST
La Grulla Plateau
Qc
1
NATIONAL GEODETIC VERTICAL DATUM OF 1929
New Mexico Bureau of Geology and Mineral Resources
Open-file Map Series
Encino
Lookout
Jm
8,000’
Tsf
Ta
Jm
Ter
Kd
Je
Ta
@u
Je
Qbo
Ter
Kd
Jm
7,000’
6,000’
COMMENTS TO MAP USERS
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
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.
Cerro
Valdez
B
WEST
La Grulla Plateau
Mesa Lagunas
10,000
feet ASL
Tla
Qc
9,000’
9,000’
Ter
Ta
Km
8,000’
8,000’
@u
Kd
Ql
Jm
Je
7,000’
7,000’
@u
Ter
Kd
Km
Ta
Km
Ter
Kd
Ter
Kd
Jm
Jm
Je
Je
@u
Jt
Je
@u
Ta
Tsf
Ta
Jm
Jt
@u
6,000’
6,000’
Tsf
Ta
Kd
Ter
Kd
Jm
Jt
Je
Jm
Je
@u
Jt
@u
EAST
10,000
feet ASL
Qc
Qc
Tla
Tsf
Ta
Tta
Qc
Tta
B’
Four Hills
Tta
Ter
9,000’
Qbt
Qc
Qbo
Tta
Tsf
Tsf
Jm
Ttd
Jt
Je
@u
8,000’
Ta
Ter
Kd
Jm
Ta
Kd
Ter
7,000’
Jm
6,000’