Mineral Resources of the 

Antelope Wilderness Study Area, 

Socorro County, New Mexico

U.S. GEOLOGICAL SURVEY BULLETIN 1734-B

NEW MEXICO

Chapter B

Mineral Resources of the 

Antelope Wilderness Study Area, 

Socorro County, New Mexico

By DONALD H. RICHTER and RICHARD W. SALTUS 

U.S. Geological Survey

STANLEY L. KORZEB 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1734

MINERAL RESOURCES OF WILDERNESS STUDY AREAS 

WEST-CENTRAL NEW MEXICO
DEPARTMENT OF THE INTERIOR 

DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1987

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center

Box 25425

Denver, CO 80225

Library of Congress Cataloging-in-Publication Data

Richter, Donald H.

Mineral resources of the Antelope Wilderness Study Area, Socorro 

County, New Mexico.

(Mineral resources of wilderness study areas west-central New 

Mexico ; ch. B)(U.S. Geological Survey bulletin ; 1734-B)

Bibliography: p.

Supt. of Docs, no.: I 19.3:1734-6

1. Mines and mineral resources New Mexico Antelope Wilderness 

Area. 2. Antelope Wilderness Area (N.M.). I. Saltus, R.W. (Richard 

W.) II. Korzeb, Stanley L. III. Title. IV. Series. V. Series: U.S. 

Geological Survey bulletin ; 1734-B.

QE75.B9 no. 1734-B 

[TN24.N6]

557.3 s 

[553'.09789'62]

87-600184
STUDIES RELATED TO WILDERNESS

Bureau of Land Management Wilderness Study Areas

The Federal Land Policy and Management Act (Public Law 94-579, October 21, 

1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral 

surveys on certain areas to determine the mineral values, if any, that may be present. Results 

must be made available to the public and be submitted to the President and the Congress. 

This report presents the results of a mineral survey of a part of the Antelope (NM-020-053) 

Wilderness Study Area, Socorro County, New Mexico.

CONTENTS

Summary 1 

Introduction 1

Investigations by the U.S. Bureau of Mines 5 

Investigations by the U.S. Geological Survey 5 

Appraisal of identified resources 5 

Assessment of potential for undiscovered resources 5 

Geology 5 

Geophysics 6

Gravity data 6 

Aeromagnetic data 6 

Aerial radiometric survey data 9 

Mineral and energy resource potential 10 

Coal 10 

Metals 10 

Oil and gas 10 

Sand 10

References cited 10 

Appendix 13

FIGURES

1. Map showing mineral resource potential and geology of the Antelope Wilderness 

Study Area and vicinity 2

2. Index map showing location of the Antelope Wilderness Study Area 4

3. Isostatic residual gravity map of the Antelope Wilderness Study Area and vicinity 7

4. Depth to Paleozoic basement below Santa Fe Group rocks in the Antelope Wilderness Study Area and vicinity 8

5. Aeromagnetic map of the Antelope Wilderness Study Area and vicinity 9

Contents V

MINERAL RESOURCES OF WILDERNESS STUDY AREAS WEST-CENTRAL NEW MEXICO

Mineral Resources of the 

Antelope Wilderness Study Area, 

Socorro County, New Mexico

By Donald H. Richter and Richard W. Saltus 

U.S. Geological Survey

Stanley L. Korzeb 

U.S. Bureau of Mines

SUMMARY

The USBM (U.S. Bureau of Mines) and USCS (U.S. 

Geological Survey) studied 9,892 acres of the Antelope 

(NM-020-053) Wilderness Study Area to appraise the 

mineral resources and assess the mineral resource potential. These investigations revealed (1) no identified 

mineral resources, (2) a high mineral resource potential 

for undiscovered sand in the southeastern part of the 

study area and a low resource potential for undiscovered 

sand in the rest of the study area, (3) a moderate mineral 

resource potential for undiscovered coal in the northern 

one-third of the study area and a low resource potential 

for undiscovered coal in the rest of the study area, and 

(4) a low mineral resource potential for undiscovered 

metals and oil and gas in the entire study area (fig. 1).

The Antelope Wilderness Study Area is 25 mi south 

of the city of Socorro in Socorro County, central New 

Mexico (fig. 2). The area overlies an extensive and relatively flat alluvial plain perched a few hundred feet above 

the modern flood plain of the Rio Crande. The alluvial 

deposits, which may be as much as 100 ft thick, cover 

sedimentary and volcanic rocks ranging from the 

fanglomerate of the Tertiary and Quaternary Santa Fe 

Croup to the limestone of the Pennsylvanian Magdalena 

Croup. Coal-bearing strata of the Cretaceous Mesaverde 

Croup sandstone beds may underlie the northern part 

of the wilderness study area at relatively shallow depths.

There has been no mineral production in the study 

area, nor are there any mineral prospects or claims. The 

study area has no identified mineral resources. The 

Carthage coal field, about 5 mi northeast of the study 

area, has produced high-volatile A bituminous coal. 

Similar rocks crop out within 2 mi of the northern part 

of the study area, and they may be present within a few 

hundred feet of the surface in the northern part of the

study area. The northern one-third of the wilderness 

study area therefore has a moderate mineral resource 

potential for coal. The southeastern part of the study 

area contains active sand dunes. These areas have a high 

resource potential for sand. The rest of the study area 

has a low resource potential for sand. The entire wilderness study area has a low mineral resource potential for 

metals (including sedimentary uranium deposits) and oil 

and gas.

INTRODUCTION

The USGS and the USBM studied 9,892 acres of 

the Antelope Wilderness Study Area (NM-020-053) in 

1985. The study of this acreage was requested by the 

BLM (U.S. Bureau of Land Management). In this report 

the studied area is referred to as the "wilderness study 

area" or simply the "study area."

The wilderness study area is approximately 25 mi 

south of the city of Socorro in central New Mexico, on 

the east side of the Rio Grande, contiguous to the Bosque 

del Apache National Wildlife Refuge (fig. 2). Access is 

by an occasionally improved dirt road that services remote 

ranches in the area; passage can be difficult during periods 

of inclement weather. The access road extends south from 

U.S. 380 about 6 mi east of the small town of San 

Antonio.

The wilderness study area is entirely within the Rio 

Grande rift valley. It overlies a broad plain, 4,700-4,900 

ft in elevation, perched about 300 ft above the modern 

flood plain of the Rio Grande. The plain is completely 

overlain by alluvial and eolian deposits. The plain is underlain by older alluvial deposits of the upper Tertiary

Antelope Wilderness Study Area B1
106°50' 106°45'

33° 

BO33' 

45

APPROXIMATE BOUNDARY OF THE 

ANTELOPE WILDERNESS 

STUDY AREA (MM-020-053)

Qab

\

Base from U S. Geological Survey 1.62,500, Carthage, 

Gran|ean Well, San Antonio, and Val Verde, 1948

R. 1 E. R. ? E.

2 MILES 

J

Geology by 0 H Richier and S.O Ludmgton, 1985 

Geology ol the northern Little San Pascual 

Mountains modified after Geddes (1963) Surlicial 

geology from aerial pnoiographs and G.R. Osburn 

(unpublished geologic map of Socorro County, 

N. Mex.)

Figure 1 (above and facing page). Map showing mineral resource potential and geology of the Antelope Wilderness 

Study Area and vicinity, Socorro County, New Mexico.

B2 Mineral Resources of Wilderness Study Areas West-Central New Mexico
L/B

B 

C

EXPLANATION OF MINERAL 

RESOURCE POTENTIAL

Geologic terrane having high mineral resource 

potential for sand, with certainty level C

Geologic terrane having moderate mineral resource potential for coal, with certainty 

level B

Geologic terrane having low mineral resource 

potential for metals (including sedimentary 

uranium deposits), oil and gas, coal (except 

as noted above), and sand (except as noted 

above), with certainty level B Applies to 

entire study area

Certainty levels

Data indicate geologic environment and suggest level of resource potential 

Data indicate geologic environment and resource potential but do not establish activity of resource-forming processes

Qab

CORRELATION OF MAP UNITS

Surficial deposits

Qa

Sed

vol

1

Qaf

ue

Qab <

mcntary and 

canic rocks

QTs

TV

Tb

Pa

Pm

*

. Holocene 

 Pleistocene

, Pleistocene - 

to Miocene

* Oligocene 

 Eocene(?)

 QUATERNARY

 TERTIARY

 PERMIAN 

 PENNSYLVANIAN

DESCRIPTION OF MAP UNITS

Qe Eolian deposits (Holocene) Active sand dunes.

Maximum thickness about 25 ft 

Alluvial fan deposits

Qa Alluvium of Rio Grande flood plain (Holocene) Chiefly sand, silt, and mud May include some coarser alluvium in fan deposits 

of side arroyos. Thickness unknown

Qaf Alluvium in broad fans (Holocene and Pleistocene) Deposits marginal to upland areas 

consisting chiefly of rounded and poorly 

sorted sand, gravel, and boulders. Deposits 

locally reworked by small, intermittent streams. 

Maximum thickness about 100 ft

QTs

TV

Tb

Pa

Pm

62

Alluvium of closed basins (Holocene and 

Pleistocene) Chiefly poorly indurated mudstone, siltstone, and sandstone. Gradational 

laterally into alluvial fan deposits (unit Qaf) 

and downward into younger deposits of the 

Santa Fe Group (unit QTs). Deposits locally 

veneered by eolian sands. Maximum thickness about 200 ft

Santa Fe Group, undivided (Pleistocene to 

Miocene) Chiefly flood-plain deposits of 

the ancestral Rio Grande and fanglomerate 

shed into Rio Grande valley from adjacent 

highlands. Deposits consist of buff, reddishbrown, and gray, moderately to poorly indurated conglomerate, sandstone, and minor 

siltstone and mudstone. Maximum exposed 

thickness about 100 ft; maximum thickness 

underlying wilderness study area may be as 

much as 2,000 ft

Volcanic rocks (Oligocene) Medium-gray to 

grayish-red, porphyritic, high-potassium, calcalkaline andesite flows and shallow intrusives. 

Rocks contain 30-40 percent phenocrysts (2- 

5 mm) of plagioclase (15-25 percent), clinopyroxene (5-10 percent), hypersthene (0-5 

percent) altered to serpentine, and opaque 

minerals (1-3 percent) in a pilotaxitic groundmass of feldspar laths and mafic minerals. 

Probably equivalent to the Datil Group (Osburn 

and Chapin, 1983). Maximum thickness 

about 200 ft

Baca Formation (Eocene?) Reddish-brown 

coarse conglomerate, reddish-brown and 

very light gray sandstone, and reddish-brown 

siltstone and mudstone. Conglomerate beds 

contain pebble- to cobble-size rounded clasts 

of Paleozoic limestone and sandstone and 

Precambrian crystalline rocks. Maximum exposed thickness about 1,000 ft

Abo Formation (Permian) Red, maroon, and 

dark-reddish-brown, fine-grained sandstone, 

siltstone, and mudstone. Maximum exposed 

thickness about 500 ft

Magdalena Group, undivided (Pennsylvanian) 

Chiefly light-gray to greenish-gray, thin- to 

massive-bedded limestone and minor interbeds of greenish-gray shale and sandstone. 

Maximum thickness about 1,500 ft

Contact Known and approximate; dashed

where inferred 

Fault Dotted where concealed Ball and bar on

downthrown side 

Strike and dip of beds

Antelope Wilderness Study Area B3
107°00' 

34°07'30"

106°33'30"

33°40'30"

COUNTY

\\ CARTHAGE COAL FIELD

7\ r

I

I

BOSQUE / DEL APACHE

APPROXIMATE BOUNDARY OF THE 

ANTELOPE WILDERNESS STUDY 

AREA (NM-020-053)

NEW MEXICO

Figure 2. Index map showing location of the Antelope Wilderness Study Area, New Mexico. Dashes indicate unimproved roads.

B4 Mineral Resources of Wilderness Study Areas West-Central New Mexico
and Quaternary Santa Fe Group (see geologic time chart 

in Appendix for explanation of relative ages); no bedrock 

(pre-Santa Fe Group) is exposed in the wilderness study 

area.

This report presents an evaluation of the mineral 

endowment (identified resources and mineral resource potential) of the study area and is the product of several 

separate studies by the USBM and the USGS. Identified 

resources are classified according to the system of the 

USBM and USGS (1980), which is shown in the Appendix of this report. Identified resources are studied by the 

USBM. Mineral resource potential is the likelihood of occurrence of undiscovered metals and nonmetals, of industrial rocks and minerals, and of undiscovered energy 

sources (coal, oil, gas, oil shale, and geothermal sources). 

It is classified according to the system of Goudarzi (1984) 

and is shown in the Appendix of this report. Undiscovered 

resources are studied by the USGS.

Investigations by the U.S. Bureau of Mines

The USBM reviewed Socorro County and BLM records for information regarding patented and unpatented 

claims, as well as federal mineral and oil and gas leases 

in or near the study area. No mineralized areas were found 

during the three days of field investigations in 1985; no 

samples were taken. Details of the study are provided in 

Korzeb (1986).

Investigations by the U.S. Geological Survey

Field investigations by the USGS in 1985 consisted 

of three days of geologic mapping and rock sampling of 

the wilderness study area and vicinity. No geochemical 

studies were undertaken. The lack of bedrock in the area, 

as well as the absence of alluvium known to be locally 

derived, ruled out the feasibility of a stream-sediment 

geochemical investigation. Large-scale gravity and aeromagnetic maps of the wilderness study area and vicinity 

were prepared from gravity data used for regional gravity 

maps of New Mexico and from a wide-spaced aeromagnetic survey flown for the NURE (National Uranium Resource Evaluation) program. No new geophysical data 

were acquired for this resource evaluation.

Acknowledgments. Personnel of the BLM in 

Socorro, N. Mex., especially geologist Roy Dean, were 

extremely helpful in providing both background information on the wilderness study area and air photos of the 

area. Special thanks are also due to Glenn R. Osburn 

of the New Mexico Bureau of Mines and Mineral Resources in Socorro for providing a preliminary copy of 

the geologic map of Socorro County. A report on the 

geology, energy, and mineral resources of the Armendaris 

area, New Mexico (Krason, Jan, Wodzicki, Antoni, and 

Cruver, S.K., 1982, unpub. data) prepared for the BLM 

was a very useful guide for this assessment.

APPRAISAL OF IDENTIFIED RESOURCES

By Stanley L. Korzeb 

U.S. Bureau of Mines

No mining has been done in the Antelope Wilderness Study Area nor are there any known deposits of 

either locatable or leasable minerals. The study area contains no identified resources. The Carthage coal field (Osburn, 1983), which was active from about 1856 to 1967, 

is approximately 5 mi northeast of the wilderness study 

area (fig. 2). Production from 1899 to 1960 was more 

than a million metric tons of high-volatile A bituminous 

coal. The minable coal occurs in a single bed, 5-6 ft 

thick, in the lower part of the Upper Cretaceous Crevasse 

Canyon Formation, a part of the Mesaverde Group. The 

coal bed dips 12-35° and is locally highly faulted. No 

detailed geologic mapping has been done in the coal field, 

and the coal resource is not known.

Sand and gravel occur in the study area, but the 

current likelihood of development is low. Similar deposits 

are more readily available elsewhere in the Rio Grande 

river valley.

ASSESSMENT OF POTENTIAL FOR 

UNDISCOVERED RESOURCES

By Donald H. Richter and Richard W. Saltus 

U.S. Geological Survey

Geology

The wilderness study area is almost entirely underlain by alluvial and eolian deposits of Quaternary age; 

no bedrock older than late Tertiary in age (pre-Santa Fe 

Group) is exposed. However, Cenozoic to Paleozoic rocks 

do crop out in three areas, 1-3 mi outside of the wilderness study area: (1) northeast of the study area, shale and 

sandstone of the Upper Cretaceous Mesaverde Group, 

sandstone and conglomerate of the Eocene(?) Baca Formation, and volcanic rocks of Oligocene age dip moderately

Antelope Wilderness Study Area B5
both to the east and west; (2) at Sand Mountain about 

1 mi east of the study area, Oligocene volcanic rocks 

are exposed; and (3) southwest of the study area in the 

northern part of the Little San Pascual Mountains, Paleozoic limestone (Magdalena Group) and Permian red beds 

(Abo Formation) dip steeply to the east.

The Quaternary alluvial and eolian deposits, which 

underlie the wilderness study area, may be as much as 

100 ft thick and consist of unconsolidated alluvium in 

closed basins, broad fans marginal to upland areas, and 

sand dunes. These surficial deposits overlie perhaps between 1,000 and 4,000 ft of older alluvial deposits of 

the upper Tertiary and Quaternary Santa Fe Group, which 

were deposited in the tectonically active Rio Grande rift 

valley. Rocks of the Santa Fe Group are moderately indurated fanglomerate and sandstone containing abundant volcanic debris, and unconformably overlie rocks ranging in 

age from middle Tertiary to Paleozoic. Oligocene volcanic 

rocks, along the east side of the study area, consist of 

flows and shallow intrusives chiefly of high-potassium andesitic composition. The volcanic rocks show no evidence 

of hydrothermal alteration. As much as 1,000 ft of conglomerate and sandstone of the Eocene(?) Baca Formation 

may be present between the Oligocene volcanic rocks and 

the sandstone, shale, and coal of the Upper Cretaceous 

Mesaverde Group. The Paleozoic rocks exposed in the 

Little San Pascual Mountains southwest of the wilderness 

study area are faulted and strongly folded. Dips at the 

north end of the Little San Pascual Mountains are steep 

to the east.

The complex structures apparent in the pre-Santa 

Fe Group rocks near the wilderness study area indicate 

that the distribution and attitude of these strata beneath 

the study area can be inferred in only a very general way. 

Paleozoic limestone undoubtedly underlies the entire study 

area, but depth to these rocks may vary from 2,000 ft 

to as much as 6,000 ft (fig. 4). Mesaverde Group rocks 

may occur within a few hundred feet of the surface in 

the northern one-third of the study area, based on bedding 

attitudes measured entirely on exposures outside the study 

area.

Geophysics

Gravity Data

An isostatic residual gravity map of an area encompassing the wilderness study area is shown on figure 3. 

This map was compiled using data from about 600 gravity 

stations assembled and edited for regional gravity maps 

of New Mexico by Cordell and others (1982), and emphasizes the gravity effect of density distributions in the 

upper crust (Simpson and others, 1986).

The wilderness study area is situated on the northern 

end of an elongate north-trending gravity high. This high 

is flanked on the west by steep gravity gradients leading 

down into the Rio Grande rift zone. On the east side 

of the high the gravity field drops to a very large closed 

gravity low (40 milliGals below the high) centered about 

10.5 mi east of the wilderness study area.

The anomalies on the gravity map are probably 

primarily due to the relief on the contact between the relatively low density Santa Fe Group sedimentary rocks at 

the surface and the underlying higher density Paleozoic 

carbonate rocks. Thus, the central gravity ridge indicates 

a shallow depth to the Paleozoic rocks and the large 

closed low to the east is caused by a relatively thick Santa 

Fe section. If the Paleozoic limestone is assumed to have 

a bulk density of 2.7 grams per cubic centimeter, the 

largest reasonable density contrast between the Paleozoic 

rocks and the Santa Fe Group is probably 0.5 grams per 

cubic centimeter. Using this density contrast and the 

method of Cordell and Henderson (1968), a map showing 

minimum depth to Paleozoic basement has been derived 

from the gravity map (fig. 4). The map shows that the 

Paleozoic basement is within 1,600 ft of the surface near 

the wilderness study area but is at least 10,000 ft deep 

under the gravity low to the east.

The very steep gradient just west of the wilderness 

study area (best defined by a line of closely spaced gravity 

stations on fig. 3) is probably associated with graben 

faulting along the Rio Grande rift to the west.

Aeromagnetic Data

An aeromagnetic map of the wilderness study area 

and vicinity is shown on figure 5. Data for the map were 

obtained as part of the NURE program in 1982 (Berry 

and others, 1982). The survey was flown at an altitude 

of 400 ft above ground along flight lines spaced 3 mi 

apart. Because the flight lines are so widely spaced, shortwavelength features cannot be contoured reliably from line 

to line. In order to avoid false correlation of these features 

by automatic contouring, a grid was produced from the 

original data using the method of minimum curvature 

(Briggs, 1974) and was then continued upward 1,600 ft 

to remove the short-wavelength features.

The aeromagnetic map is dominated by a large 

semicircular closed low with a triangle-shaped high 

indenting it from the west. These broad long-wavelength 

features are probably due to relief on the contact between 

the Precambrian basement and the relatively nonmagnetic

B6 Mineral Resources of Wilderness Study Areas West-Central New Mexico
107°00' 106°30'

33°45'

33°30'

Figure 3. Isostatic residual gravity map of the Antelope Wilderness Study Area (shaded) and vicinity, New Mexico. 

Contour interval 2 milliCals. Hachures indicate closed gravity low. Gravity station indicated byo. Reduction density 

2.67 grams per cubic centimeter.

Antelope Wilderness Study Area B7
106°52'30' 106°37'30"

33°45' -

33030' _

Figure 4. Depth to Paleozoic basement below Santa Fe Group rocks in the Antelope Wilderness Study Area (shaded) 

and vicinity, New Mexico. Contour interval 200 (650 ft) meters.

rocks above. A two-dimensional model constructed along 

two flight lines crossing the broad low gives an estimated 

depth of about 20,000 ft to the Precambrian under the 

low part of the anomaly along the east edge of the wilderness study area. This model assumes a 0.001 emu/cm3

(electromagnetic units per cubic centimeter) intensity of 

magnetization for a normally polarized basement. The 

same model yields depths of about 7,000 ft to Precambrian basement under the magnetic highs flanking the west 

edge of the wilderness study area.

B8 Mineral Resources of Wilderness Study Areas West-Central New Mexico
107°00' 106°30'

33°45'

33°30'

Figure 5. Aeromagnetic map of the Antelope Wilderness Study Area (shaded) and vicinity, New Mexico. Dashed 

lines indicate flight lines. Contour interval 10 nanoTesla. H, aeromagnetic high; L, aeromagnetic low.

Aerial Radiometric Survey Data

The Antelope Wilderness Study Area has low overall radioactivity. The aerial radiometric survey indicated 

values of 1.3-1.8 ppm (parts per million) equivalent uranium, 3.5-5.0 ppm equivalent thorium, and 1.6-2.1 percent potassium (J.S. Duval, USGS, written commun., 

1986). No anomalous radioactivity values are within or 

near the study area.

Antelope Wilderness Study Area B9
Mineral and Energy Resource Potential

Coal

The inactive Carthage coal field (Osburn, 1983), 5 

mi northeast of the Antelope Wilderness Study Area, has 

produced high-volatile A bituminous coal from a 4- to 

6-ft coal bed in the lower part of the Crevasse Canyon 

Formation, a formation of the Mesaverde Group of Late 

Cretaceous age. Mesaverde Group rocks crop out within 

2 mi of the northern part of the study area, and their 

attitudes and those of the overlying rocks of the Baca 

Formation suggest that Mesaverde strata may be present 

within a few hundred feet of the surface in parts of the 

study area. The northern one-third of the study area is 

therefore given a moderate potential for coal resources, 

with certainty level B. The rest of the study area has 

a low potential for coal resources, with certainty level 

B.

Metals

Occurrences of uranium minerals are occasionally 

found in upper Tertiary and Quaternary sedimentary rocks 

of the Santa Fe Group throughout New Mexico (Hilpert, 

1965). These deposits have been small and too low grade 

to mine. In the uranium assessment of the Tularosa, N. 

Mex., 1°X2° quadrangle, Berry and others (1982) indicated that the Santa Fe Group is unfavorable for either 

uraniferous calcrete or sandstone uranium deposits. Despite these negative aspects, we believe that the presence 

of known deposits, adequate source terrane (Tertiary volcanic rocks), and local accumulations of organic debris 

in the host sediments are criteria that suggest locally 

favorable geologic environments, especially for sandstonehosted deposits. In addition, the Baca Formation of Eocene(?) age, which probably underlies most of the northern part of the study area, locally hosts uranium minerals 

to the north and west of the study area (S.L. Moore, 

USGS, written commun., 1986) and should be considered 

a potential uranium source. The entire study area is given 

a low potential for uranium resources, with certainty level 

B. The study area lacks the rocks and geologic environment favorable for metallic mineral deposits, and no 

mineralized areas were observed. The study area is therefore given a tow mineral resource potential for metals, 

with certainty level B.

Oil and Gas

The wilderness study area is underlain at depth by 

upper Paleozoic sandstone and limestone that are highly 

productive reservoir and source rocks in southeastern New 

Mexico. However, in the Rio Grande rift valley these 

rocks have been structurally disturbed and intruded by

igneous rocks, factors that do not enhance the rocks' ability to hold significant quantities of oil and gas. Three 

exploratory holes testing the Paleozoic section have been 

drilled about 6 mi west of the study area; all were dry 

(U.S. Geological Survey, 1981). The entire study area 

is assessed as having a low potential for oil and gas resources, with certainty level B.

Sand

The southeastern part of the study area contains active sand dunes with a maximum thickness of 25 ft. These 

areas have a high resource potential for sand, with certainty level C. The other Quaternary deposits in the area 

are heterogeneous and poorly sorted; they have a low mineral resource potential for sand, with certainty level B.

REFERENCES CITED

Berry, V.P., Nagy, P.A., Spreng, W.C., Barnes, C.W., and 

Smuse, DeForrest, 1982, Tularosa quadrangle, New Mexico 

(National Uranium Resource Evaluation): U.S. Department 

of Energy, GJQ-014(82), 22 p.

Briggs, I.C., 1974, Machine contouring using minimum curvature: Geophysics, v. 39, no. 1, p. 39-48.

Cordell, Lindrith, and Henderson, R.G., 1968, Iterative threedimensional solution of gravity anomaly data using a digital 

computer: Geophysics, v. 33, no. 4, p. 596-601.

Cordell, Lindrith, Keller, G.R., and Hildenbrand, T.G., 1982, 

Bouguer gravity map of the Rio Grande Rift, Colorado, 

New Mexico, and Texas: U.S. Geological Survey Geophysical Investigations Map GP-949, scale 1:1,000,000.

Geddes, R.W., 1963, Structural geology of Little San Pasqual 

Mountain and the adjacent Rio Grande Trough: Socorro, 

N. Mex., New Mexico Institute of Mining and Technology, 

M.S. thesis, 62 p.

Goudarzi, G.H., 1984, Guide to preparation of mineral survey 

reports on public lands: U.S. Geological Survey Open-File 

Report 84-787, 42 p.

Hilpert, L.S., 1965, Uranium, in Mineral and water resources 

of New Mexico: U.S. 89th Congress, 1st Session, Senate 

Committee on Interior and Insular Affairs, p. 209-226; reprinted 1982, New Mexico Bureau of Mines and Mineral 

Resources Bulletin 87, 437 p.

Korzeb, S.L., 1986, Mineral investigations of the Antelope Wilderness Study Area (NM-020-053), Socorro County, New 

Mexico: U.S. Bureau of Mines Open-File Report MLA 17- 

86, 6 p.

Osburn, J.C., 1983, Coal resources of Socorro County, New 

Mexico, in Chapin, C.E., and Callender, J.F., eds., Socorro 

region II: New Mexico Geological Society, 34th Field Conference Guidebook, p. 223-226.

Osburn, G.R., and Chapin, C.E., 1983, Nomenclature for Cenozoic rocks of northeast Mogollon-Datil volcanic field, New 

Mexico: New Mexico Bureau of Mines and Mineral Resources, Stratigraphic Chart SC-1.

B10 Mineral Resources of Wilderness Study Areas West-Central New Mexico
Simpson, R.W., Jachens, R.C., Blakely, R.J., and Saltus, U.S. Bureau of Mines and U.S. Geological Survey, 1980, PrinR.W., 1986, A new isostatic residual gravity map for the ciples of a resource/reserve classification for minerals: U.S. 

conterminous United States with a discussion on the signifi- Geological Survey Circular 831, 5 p. 

cance of isostatic anomalies: Journal of Geophysical Re- U.S. Geological Survey, 1981, Energy resources of New 

search, v. 91, no. B8, p. 8348-8372. Mexico: U.S. Geological Survey Miscellaneous Investigations Series Map 1-1327, scale 1:500,000.

Antelope Wilderness Study Area B11

APPENDIX
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

Definitions of Mineral Resource Potential

LOW mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics define a geologic environment in which the existence of resources is unlikely. This broad 

category embraces areas with dispersed but insignificantly mineralized rock as well as areas with few 

or no indications of having been mineralized.

MODERATE mineral resource potential is assigned to areas where geologic, geochemical, and geophysical 

characteristics indicate a geologic environment favorable for resource occurrence, where interpretations 

of data indicate a reasonable likelihood of resource accumulation, and (or) where an application of 

mineral-deposit models indicates favorable ground for the specified type(s) of deposits.

HIGH mineral resource potential is assigned to areas where geologic, geochemical, and geophysical characteristics indicate a geologic environment favorable for resource occurrence, where interpretations of 

data indicate a high degree of likelihood for resource accumulation, where data support mineral-deposit 

models indicating presence of resources, and where evidence indicates that mineral concentration has 

taken place. Assignment of high resource potential to an area requires some positive knowledge that 

mineral-forming processes have been active in at least part of the area.

UNKNOWN mineral resource potential is assigned to areas where information is inadequate to assign low, 

moderate, or high levels of resource potential.

NO mineral resource potential is a category reserved for a specific type of resource in a well-defined 

area.

Levels of Certainty

U/A

UNKNOWN

POTENTIAL

H/B

HIGH POTENTIAL

M/B 

MODERATE POTENTIAL

L/B

LOW

POTENTIAL

H/C

HIGH POTENTIAL

M/C 

MODERATE POTENTIAL

L/C

LOW

POTENTIAL

H/D

HIGH POTENTIAL

M/D 

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

O in

LU 

CC.

B C 

LEVEL OF CERTAINTY

A. Available information is not adequate for determination of the level of mineral resource potential.

B. Available information suggests the level of mineral resource potential.

C. Available information gives a good indication of the level of mineral resource potential.

D. Available information clearly defines the level of mineral resource potential.

Abstracted with minor modifications from:

Taylor, R. B., and Steven, T. A., 1983, Definition of mineral resource potential: Economic Geology,

v. 78, no. 6, p. 1268-1270. 

Taylor, R. B., Stoneman, R. J., and Marsh, S. P., 1984, An assessment of the mineral resource potential

of the San Isabel National Forest, south-central Colorado: U.S. Geological Survey Bulletin 1638, p.

40-42. 

Goudarzi, G. H., compiler, 1984, Guide to preparation of mineral survey reports on public lands: U.S.

Geological Survey Open-File Report 84-0787, p. 7, 8.
ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

RESOURCE/RESERVE CLASSIFICATION

IDENTIFIED RESOURCES

Demonstrated

Measured Indicated

1

Reserves

Marginal Reserves

Demonstrated 

Subeconomic Resources

Inferred

Inferred Reserves

Inferred 

Marginal Reserves

Inferred

Subeconomic

Resources

UNDISCOVERED RESOURCES

Hypothetical

Probability Range 

 (or)-

Speculative

+

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from 

U. S. Bureau of Mines and U. S. Geological Survey, 1980, Principles of a resource/reserve classification for 

minerals: U. S. Geological Survey Circular 831, p. 5.
GEOLOGIC TIME CHART 

Terms and boundary ages used in this report

EON

Phanerozoic

Proterozoic

Archean

pre-Arc

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean 

hean 2

PERIOD

Quaternary

Tertiary

Neogene 

Subperiod

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Carboniferous 

Periods

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

 3800? -

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

 -

BOUNDARY AGE 

IN 

MILLION YEARS

- 0.010

- 1.7

- 5

- 24

OQ

- 55

CC

- 96

1 OO 

one

-/v 240

-~ 330

oert

- 410

- 500 

- ~ 570 1

- 900 

- 1600

- 2500

- 3000 

- 3400

dBBO.

' Rocks older than 570 m.y. also called Precambrian, a time term without specific rank. 

2 Informal time term without specific rank.

U.S. GOVERNMENT PRINTING OFFICE: 1987 773-047/46,056 REGION NO. 8