Mineral Resources of the 

Devils Playground and 

Twin Buttes

Wilderness Study Areas, 

Sweetwater County, Wyoming

U.S. GEOLOGICAL SURVEY BULLETIN 1759-C
AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY

Instructions on ordering publications of the U.S. Geological Survey, along with the last offerings, are given in the current-year issues of 

the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publications released prior 

to the current year are listed in the most recent annual "Price and Availability List." Publications that are listed in various U.S. Geological 

Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" are no longer available.

Prices of reports released to the open files are given in the listing "U.S. Geological Survey Open-File Reports," updated monthly, which 

is for sale in microfiche from the U.S. Geological Survey Books and Open-File Reports Sales, Box 25425, Denver, CO 80225.

Order U.S. Geological Survey publications by mail or over the counter from the offices given below.

BY MAIL

Books

Professional Papers, Bulletins, Water-Supply Papers, Techniques of Water-Resources Investigations, Circulars, publications 

of general interest (such as leaflets, pamphlets, booklets), single 

copies of periodicals (Earthquakes & Volcanoes, Preliminary Determination of Epicenters), and some miscellaneous reports, including some of the foregoing series that have gone out of print at the 

Superintendent of Documents, are obtainable by mail from

U.S. Geological Survey, Books and Open-File Report Sales

Box 25425 

Denver, CO 80225

Subscriptions to periodicals (Earthquakes & Volcanoes and 

Preliminary Determination of Epicenters) can be obtained ONLY 

from

Superintendent of Documents

U.S. Government Printing Office

Washington, DC 20402

(Check or money order must be payable to Superintendent of 

Documents.)

Maps

For maps, address mail order to

U.S. Geological Survey, Map Sales

Box 25286 

Denver, CO 80225

Residents of Alaska may order maps from

U.S. Geological Survey, Map Sales

101 Twelfth Ave., Box 12

Fairbanks, AK 99701

OVER THE COUNTER

Books

Books of the U.S. Geological Survey are available over the 

counter at the following U.S. Geological Survey offices, all of 

which are authorized agents of the Superintendent of Documents.

 ANCHORAGE, Alaska-^230 University Dr., Rm. 101

 ANCHORAGE, Alaska-605 West 4th Ave., Rm G-84

 DENVER, Colorado-Federal Bldg., Rm. 169,1961 Stout St.

 LAKEWOOD, Colorado-Federal Center, Bldg. 810

 MENLO PARK, Califomia-Bldg. 3, Rm. 3128, 345

Middlefield Rd.

 RESTON, Virginia-National Center, Rm. 1C402, 12201 

Sunrise Valley Dr.

 SALT LAKE CITY, Utah-Federal Bldg., Rm. 8105,125 South 

State St.

 SAN FRANCISCO, California-Customhouse, Rm. 504, 555 

Battery St.

 SPOKANE, Washington-U.S. Courthouse, Rm. 678, West 

920 Riverside Ave.

 WASHINGTON, D.C.-U.S. Department of the Interior Bldg., 

Rm. 2650,1849 C St., NW.

Maps

Maps may be purchased over the counter at the U.S. Geological Survey offices where books are sold (all addresses in above list) 

and at the following Geological Survey offices:

 ROLLA, Missouri-1400 Independence Rd.

 FAIRBANKS, Alaska-New Federal Building, 101 Twelfth 

Ave.
Chapter C

Mineral Resources of the 

Devils Playground and 

Twin Buttes

Wilderness Study Areas, 

Sweetwater County, Wyoming

By RICHARD E. VAN LOENEN and W. ANTHONY BRYANT 

U.S. Geological Survey

MICHAEL E. LANE 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1759 

MINERAL RESOURCES OF WILDERNESS STUDY AREAS-
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government.

UNITED STATES GOVERNMENT PRINTING OFFICE: 1991

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

Van Loenen, Richard E.

Mineral resources of the Devils Playground and Twin Buttes Wilderness 

Study Areas, Sweetwater County, Wyoming/ by Richard E. Van Loenen, 

W. Anthony Bryant, and Michael E. Lane.

p. cm. (U.S. Geological Survey bulletin ; 1759-C) 

(Mineral resources of wilderness study areas miscellaneous states ; ch. C)

Includes bibliographical references.

Supt. of Docs, no.: I 19.3:1759C

1. Mines and mineral resources Wyoming Devils Playground 

Wilderness. 2. Mines and mineral resources Wyoming Twin Buttes 

Wilderness. 3. Devils Playground Wilderness (Wyo.). 4. Twin Buttes 

Wilderness (Wyo.). I. Bryant, W. Anthony. II. Lane, Michael E. 

III. Title. IV. Series. V. Series: Mineral resources of wilderness study 

areas miscellaneous states ; ch. C. 

QE75.B9 no. 1759c 

[TN24.W8] 

557.3 s dc20

[553'.09787'85] 91-26164

CIP
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 the Devils Playground (WY-040-401) and Twin Buttes (WY040-402) Wilderness Study Areas, Sweetwater County, Wyoming.

CONTENTS

Abstract Cl 

Summary Cl 

Introduction C2

Investigations by the U.S. Bureau of Mines C5 

Investigations by the U.S. Geological Survey C5 

Appraisal of identified resources C5 

Mining history C5 

Trona C5 

Zeolite C6 

Sand and gravel C6 

Collectible commodities C6

Assessment of potential for undiscovered resources C6 

Geologic setting C6 

Geochemistry C7 

Mineral and energy resources C7 

Oil and gas C7 

Oil shale C8 

Trona C8 

Zeolite C8 

Coal C8

Metallic minerals C9 

References cited C9

FIGURES

1. Map showing location of the Devils Playground and Twin Buttes Wilderness 

Study Areas, Sweetwater County, Wyoming, and major structural elements and 

subbasins of the Greater Green River basin C9

2. Summary map showing mineral and energy resource potential of the Devils 

Playground and Twin Buttes Wilderness Study Areas C9

TABLE

1. Data and analyses for the Twin Buttes #1 and the Buckboard Ranch #2 drill 

holes C5

Contents

MINERAL RESOURCES OF WILDERNESS STUDY AREAS MISCELLANEOUS STATES

Mineral Resources of the Devils Playground and 

Twin Buttes Wilderness Study Areas, 

Sweetwater County, Wyoming

By Richard E. Van Loenen and W. Anthony Bryant 

U.S. Geological Survey

Michael E. Lane 

U.S. Bureau of Mines

ABSTRACT

In 1990 the U.S. Geological Survey and the U.S. Bureau 

of Mines conducted a mineral resource appraisal of the 

Devils Playground (WY-040-401) and the Twin Buttes 

(WY-040-402) Wilderness Study Areas in Sweetwater County 

in southwest Wyoming. The study areas contain 1.2 billion 

tons of inferred resources of trona (a mineral used in making 

soda ash). The study areas have high mineral resource 

potential for additional deposits of trona, high energy resource 

potential for natural gas and oil shale, moderate mineral 

resource potential for zeolites, and low energy and mineral 

resource potential for oil, coal, and metallic minerals.

SUMMARY

The Devils Playground and Twin Buttes Wilderness 

Study Areas lie in southwest Wyoming about 25 rni (miles) 

south of Green River. Flaming Gorge Reservoir is about 3 rni to 

the east. The study areas are contiguous, totaling about 26,800 

acres, and unless specific mention is made to one or the other, 

the two areas are referred to as the "study areas" in this report. 

Access to the study areas is provided on the east by State 

Highway 530 and on the west by county highway 1 (fig. 1). 

The boundaries of the study areas are defined, for the most 

part, by jeep trails or four-wheel-drive roads.

The study areas are along the southeastern edge of the 

Green River basin. The topography of the study areas is 

dominated by two prominent landmarks called Twin Buttes 

and Black Mountain. Colorful badlands are carved in the 

slopes of these topographic highs and the badlands that formed

Manuscript approved for publication September 9, 1991.

on the slopes of Black Mountain are called Devils Playground. 

Nearly 1,500 ft (feet) of flat-lying sedimentary rocks of Eocene 

age are exposed in the study areas. These rocks belong to the 

Bridger Formation and consist mainly of poorly consolidated 

mudstone and fine sandstone interbedded with sandstone, 

siltstone, claystone, and tuff beds. Minor amounts of indurated 

ledge- forming, commonly siliceous dolostone units form 

conspicuous stratigraphic markers that locally hold up 

prominent topographic benches in the study areas. Pyroclastic 

material is abundant throughout the Bridger Formation. The 

study areas lie over the deepest parts of the Green River basin 

where Phanerozoic rock may be as much as 30,000 ft thick.

No mines, prospects, or mining claims are known in the 

Devils Playground and Twin Buttes Wilderness Study Areas. 

The study areas were withdrawn from mining claim location 

because of the rich oil shale deposits in the region. The study 

areas are also considered by the Minerals Management Service 

to have moderate development potential for sodium (trona). 

Study of drill hole data for this investigation indicates as much 

as 1.2 billion tons of inferred trona resources may be present in 

the Green River Formation at depths of 2,200 ft to just over 

3,000 ft beneath the study areas.

The study areas have a high resource potential for 

undiscovered natural gas in overpressured low-perrneability 

Cretaceous sandstone reservoirs. Favorable reservoir rock for 

gas such as the Cleverly and Frontier Formations is thought to 

be present. The older Paleozoic rock beneath the study areas is 

unfavorable for oil and gas due to the absence of structural 

traps in the deeper parts of the basin; production from 

structurally controlled reservoirs in these rock comes from the 

nearby arched and uplifted terrane.

The study areas have high energy resource potential for 

oil shale deposits in the Green River Formation, although at 

depths of several thousand feet below the surface. The surface

Mineral Resources, Devils Playground and Twin Buttes Wilderness Study Areas, Wyoming C1
rock contains some very thin and low grade oil shales.

In addition to areas of inferred resources of trona, the 

study areas have high mineral resource potential for additional 

undiscovered deposits of trona in the Green River Formation.

The Bridger Formation, the rock unit exposed on the 

surface of the study areas, was deposited in a favorable 

environment for the formation of zeolites; however, such 

deposits were found to be very thin and impure. All tuff beds 

and other conspicuous rocks were examined for zeolite 

content. Traces of clinoptilolite, a common zeolite mineral, 

were found in some of the sampled beds in the study areas and 

major amounts were found in thin beds along the northeast 

and northwest boundary of the Devils Playground study area. 

The study areas, therefore, have a moderate potential for 

undiscovered deposits of zeolite; the resource potential is not 

high because of the very thin and impure nature of the beds.

The study areas have low potential for coal resources. 

Coal-bearing strata are probably present in the subsurface but 

are at great depths.

The study areas have low mineral resource potential for 

undiscovered metallic minerals. The Bridger Formation in its 

present geologic setting in the Green River basin is not a 

favorable environment for these types of mineral resources.

INTRODUCTION

This report discusses the mineral and energy 

resources of 26,800 acres in the Devils Playground (WY040-401) and the Twin Buttes (WY-040-402) Wilderness 

Study Areas. The study areas are contiguous and unless 

specific mention is made to one or the other, the two areas 

are referred to as the "study areas" in this report. The study 

areas are in Sweetwater County in southwestern Wyoming 

about 25 mi (miles) south of Green River, Wyo., and 20 mi 

north of Manila, Utah (fig. 1). Flaming Gorge Reservoir is 

about 3 mi to the east. The boundaries of the study areas are 

defined, for the most part, by jeep trails or four-wheel-drive 

roads. These roads were built to serve, among others, 

livestock operations in the region, well-drilling projects, and 

pipeline maintenance. No established or marked hiking 

trails are within the study areas but bulldozer cuts traverse 

much of the terrain.

The road along the western boundary of the Devils 

Playground study area leads to Pine Springs. Pine Springs 

has been developed and a network of pipes connects the 

springs to water troughs several miles to the north. Pine 

Springs is also an important archaeological site that was 

examined by archaeologists from the University of Utah in 

the early 1960's. Their studies indicate that the site was 

occupied from 10,000 B.C. to A.D. 1,200.

Access to the study areas is provided on the east by 

State Highway 530 and on the west by county highway 1 

(fig. 1). Roads to the study areas branch off of these 

highways at several different locations. The boundary roads, 

with the exception of the Pine Springs road, are in very poor 

condition.

The study areas are along the southeastern edge of the 

Green River basin, one of several basins in the Greater 

Green River basin of southwestern Wyoming (fig. 1). The 

topography of the study areas is dominated by two prominent landmarks called Twin Buttes and Black Mountain. 

They are capped by a hard and very resistant conglomerate 

that preserves the softer underlying rock. Colorful badlands 

are carved in the softer rock underlying Twin Buttes and 

Black Mountain. Nearly 1,500 ft (feet) of flat-lying 

sedimentary rocks of various shades of red, green, and gray 

are exposed in a picturesque landscape.

The study areas have a desert climate with most of the 

precipitation resulting from a few storms in summer and 

winter. All streams are ephemeral and drain eastward into 

Flaming Gorge Reservoir on the Green River. Drainage 

from the areas include Buckboard Wash, Squaw Hollow, 

Anvil Wash, Butte Wash, and several tributaries to Henry's 

Wash, which is south of the map of figure 2. Numerous 

small dams, many of which are within the study areas, have 

been built on the smaller tributaries for stock ponds. Strong 

winds are common in the region, but sparse patches of 

native grasses and sagebrush tend to stabilize older sand 

dunes and the thin veneer of soil that is characteristic of this 

type of terrain. The badlands are protected from wind 

erosion by a thin coating of a loosely cemented mixture of 

clay, fine sand, and rock fragments. Pinon pine and juniper 

are sparse and there is a grove of spruce trees at Pine 

Springs.

No mines, prospects, or mining claims are in the 

study areas, but rock and fossil collecting has taken place. 

Chert beds are common and some of it is prized by 

collectors for its banded appearance. These beds were the 

source of chert used by the Indians at Pine Springs for 

thousands of years.

Many famous collecting sites for vertebrate fossils are 

in the Green River basin. The study areas are classic sites of 

vertebrate fossil collecting and have yielded specimens now 

found in the collections of the American Museum of Natural 

History, the United States National Museum, and the Yale 

Peabody Museum. Thousands of fossil specimens have 

been collected for study. Fossil mammals include primates, 

carnivores, rodents, insectivores, marsupials, and ungulates; 

fossil amphibians are represented by salamanders; and fossil 

reptiles include snakes, lizards, turtles, alligators, and 

crocodiles. In addition to the terrestrial vertebrate faunas, 

fossil aquatic animals include gastropods, pelecypods, 

ostracodes, and fish. Fossil wood, leaf, and algal remains 

also occur. The fossil vertebrate mammal faunas provided 

the basis for the recognition and definition of the North 

American middle Eocene Bridgerian land-mammal age 

(Wood and others, 1941).

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 U.S. Bureau of Mines (USBM) and 

the U.S. Geological Survey (USGS). Identified resources

C2 Mineral Resources of Wilderness Study Areas Miscellaneous States
110° 109 108C 107°

43° 

HOGBACK 

BASIN

APPROXIMATE BOUNDARY

OF THE GREATER 

GREEN RIVER BASIN

i __._._.__.__

GREAT DIVIDE 

BASIN

SWEETWATER

WAMSUTTER ARCH cRock

Springs SPRINGS 

DEVILS 1530 UPLIFT

LAYGROUND 

ILDERNESS . DY AREA/1 n Flaming

TWIM RI ITTPQ i WY-040-401/(f\\( Gorge TWIN BUTTES I 7J I \\ k Rpcpr,,0ir 

WILDERNESS K fT IKeseruoir 

STUDY AREA

WASHAKIE I BASIN

WYOMING CHEROKEE

UINTA MOUNTAINS SAND WASH 

BASIN

DUCHESNE 

40

RIO I BLANCO

41

0 10 20 30 40 50 MILES

I I ________________

EXPLANATION

[ * Anticline Arrows show direction of plunge 

A A Thrust fault Sawteeth on upper plate

Figure 1. Map showing location of the Devils Playground and Twin Buttes Wilderness Study Areas, Sweetwater 

County, Wyoming, and major structural elements and subbasins of the Greater Green River basin.

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, 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. The potential for undiscovered resources is 

studied by the USGS.

Mineral Resources, Devils Playground and Twin Buttes Wilderness Study Areas, Wyoming C3
r 109 47'30" 

151

109°37'30"

Buckboard 

Ranch #2

Flaming

Gorge

Reservoir

APPROXIMATE BOUNDARY OF 

THE DEVILS PLAYGROUND 

WILDERNESS STUDY AREA 

(WY-040-401)

APPROXIMATE BOUNDARY

OF THE TWIN BUTTES

WILDERNESS STUDY AREA

(WY-040-402)

EXPLANATION

Geologic terrane having high resource potential for natural gas, oil 

shale, and trona Applies to both areas

Geologic terrane having moderate resource potential for zeolite 

Applies to both areas

Geologic terrane having low resource potential for coal and metallic 

metals Applies to both areas

Geologic terrane having low resource potential for oil Applies to 

both areas

Tbi Bishop Conglomerate

Tb Bridger Formation

 Drill Holes Refer to table 1

Figure 2. Summary map showing mineral and energy resource potential of the Devils Playground and Twin Buttes 

Wilderness Study Areas.

C4 Mineral Resources of Wilderness Study Areas Miscellaneous States
Investigations by the U.S. Bureau of Mines

Appraisal of identified resources in the Devils 

Playground and Twin Buttes Wilderness Study Areas 

included literature searches and field work. A detailed 

literature search was made for geologic and mining 

information pertinent to the study areas, and BLM records 

were examined for mining claims, land status, and oil and 

gas leases. Two USBM geologists spent 7 days in the field 

in June 1990 in and near the study areas.

Investigations by the U.S. Geological Survey

Assessment of the potential for undiscovered mineral 

and energy resources in the Devils Playground and Twin 

Buttes Wilderness Study Areas is based largely on the 

geologic setting, geochemical data from rocks and stream 

sediments, and consideration of the production history of 

similar rocks in the surrounding areas. The field work for 

this assessment was done in July 1990. No new information 

or data were obtained during this study for the subsurface 

geology. Information used in assessing oil and gas potential 

is taken largely from Spencer (1983) who rated the petroleum potential of Wyoming, Law and others (1989) who 

discussed hydrocarbon plays and estimated gas resources in 

the Greater Green River basin, Root and others (1973) who 

summarized the mineral resources of Sweetwater County, 

and Bradley (1964) who provided a comprehensive 

description of the Eocene rocks in the Green River basin.

APPRAISAL OF IDENTIFIED RESOURCES

By Michael E. Lane 

U.S. Bureau of Mines

Mining History

No mines, prospects, or mining claims are in the 

Devils Playground and Twin Buttes Wilderness Study 

Areas. There are no mining claims in the study areas as of 

June 1990. Both study areas were withdrawn from mining 

claim location because oil shale deposits occur at depth in 

the Green River basin (Executive Order 5327, May 20, 

1930, and Public Land Order 45, 1967). The study areas are 

almost entirely within the boundaries of the Green River 

Basin Known Sodium Leasing Area as delineated by the 

Minerals Management Service (MMS) and are considered 

by the MMS to have moderate development potential for 

sodium (trona).

The only mines in the region are trona mines about 

25 mi northwest of the study areas near Green River, Wyo., 

and coal mines around the Rock Springs uplift to the 

northeast and in the Henrys Fork coal field to the south.

Table 1 . Data and analyses for the Twin Buttes #1 and the 

Buckboard Ranch #2 drill holes

[na, not analyzed; ?, not known. BLM file data, Rock Springs District 

Office]

Depth to 

top of 

bed (ft)

Bed

number

Thickness 

of bed 

(ft)

% Trona

Twin Buttes #1 drill hole

2664

2710

2762

2781

2836

2854

2881

2902

2951

3008

3020

3034

3079

18

17

16

15

14

7

13

12

9

4

3

2

1

3

4.5

10

6.5

11

3

10

6

9

2.5

3

2

3

na

na

na

na

na

na

na

na

na

na

na

na

na

Buckboard Ranch #2 drill hole

2222

2259

2311

2329

2381

18

17

16

15

14

6

11

9

14

10

na

81.9

42.5

21.5

46.1

Several drill holes are near the wilderness study areas. 

Two holes are adjacent to or within the present study area 

boundaries; the Twin Buttes #1 (T. 14 N., R. 109 W., 

sec. 33) and the Buckboard Ranch #2 (T. 15 N., R. 109 W., 

sec. 32), intercepted trona beds in the Green River 

Formation at 2,664 ft and 2,222 ft, respectively (BLM file 

data) (fig. 2). The Buckboard Ranch #2 hole was drilled for 

trona by Joseph Perkins in July 1959, five trona beds were 

intersected (table 1; 14, 15, 16, 17, and 18). The Twin 

Buttes #1 hole was drilled in July 1975 by Farmers Union 

Central Petroleum Company to search for oil and gas. 

Twelve trona beds (1, 2, 3, 4, 9, 12, 13, 14, 15, 16, 17, and 

18) were encountered. The Twin Buttes #1 hole was not 

cored or analyzed. (See Lane, 1990.)

Trona

Trona (Na2CO3NaHCO3 »H2O) is an evaporite mineral formed in nonmarine alkaline lakes and marshes. These 

types of deposits are rarely economic (Lefond, 1983, 

p. 1188); however, the world's largest trona deposits are 

being mined west of Green River (U.S. Bureau of Mines, 

1989, p. 149). These deposits occur as numerous beds in the 

Wilkins Peak Member of the Green River Formation 

(Eocene). Culbertson (1966) assigned numbers to 25 trona 

beds that exceeded 3 ft in maximum thickness and have an 

areal extent of 100 sq mi or more; these reference numbers 

are used in this report. Trona bed 17 is being mined by FMC 

Corporation and is 8-14 ft thick, about 1,600 ft deep, and

Mineral Resources, Devils Playground and Twin Buttes Wilderness Study Areas, Wyoming C5
has purity of 80-90 percent trona and 10-20 percent halite 

and insolubles (shale stringers and other impurities) (Dave 

Hutcheson, FMC Corporation, oral commun., 1990).

Trona is readily processed to form soda ash (sodium 

bicarbonate). Soda ash is mostly used in making glass and 

paper, but it is also used in soaps, detergents, and pharmaceuticals. Thirteen trona beds, projected to extend 

beneath the wilderness study areas, have been identified 

from drill-hole data (table 1). The beds range in thickness 

from 2 to 14 ft. Using drill-hole data and computergenerated isopach maps supplied by the BLM, about 1.2 

billion tons of inferred trona resources were calculated for 

beds 17, 14, and 12 underlying the wilderness study areas. 

These calculations do not contain purity estimates because 

of limited data. The calculations were done using a tonnage 

factor of 15 ft3 per ton and maps that showed outlines and 

thicknesses of projected trona beds. Additional data, 

including drilling, would be needed to verify and more 

accurately delineate trona beds and determine the quality of 

the resources. Table 1 shows drill-hole data for the two drill 

holes. Existing trona reserves under lease, in the region, are 

projected to meet market demands for hundreds of years 

(U.S. Bureau of Land Management, 1982); thus, development of trona beds in the near future beneath the study areas 

is unlikely.

Zeolite

Occurrences of zeolite in the study areas have been 

reported by Harris and others (1985), but no zeolite 

resources were identified in the study areas.

Sand and Gravel

The Bishop Conglomerate (Oligocene) on Black 

Mountain is considered a major gravel deposit (Root and 

others, 1973); however, it is not accessible. The State 

Highway Department has developed two gravel pits along 

the west boundary of the study areas (Root and others, 

1973). Material from these pits was used locally for road 

construction. This and similar material in the study areas is 

very common in the region and it possesses no special 

qualities.

Collectible Commodities

With the exception of fossil turtles, the vertebrate 

fossils that were abundant on or near the surface in the past 

have been largely removed by collectors from the study 

areas. Nonmarine invertebrates and plant fossils are common throughout the Bridger Formation (Eocene), which is 

exposed in the study area. Black, brown, and banded cherts, 

common in outcrop and as float in the study areas are prized 

by rock collectors.

ASSESSMENT OF POTENTIAL FOR 

UNDISCOVERED RESOURCES

By Richard E. Van Loenen and 

W. Anthony Bryant 

U.S. Geological Survey

Geologic Setting

The Devils Playground and Twin Buttes Wilderness 

Study Areas are within the deepest part of Green River 

basin, a deep structural and sedimentary basin containing 

over 25,000 ft of Phanerozoic rock. The structural and 

stratigraphic history of the Greater Green River basin began 

near the end of the Cretaceous Period, at the onset of the 

Laramide orogeny. Paleocene sediments that now comprise 

the Fort Union Formation were deposited in the basin. 

These sediments were derived from the newly formed 

mountain ranges surrounding the basin, and the sediments 

were deposited on flood plains in fluvial, lacustrine, and 

paludal (marsh) environments. Late Paleocene swamps 

were especially dominant, and later formed coal beds. These 

coal beds have been mined around the margin of the Rock 

Springs uplift where Fort Union rocks are exposed. The Fort 

Union is not exposed in the study areas but is present in the 

subsurface at depths exceeding 5,000 ft.

Downwarping of the basin and uplift of the adjoining 

mountain ranges continued through Paleocene and into 

Eocene time. Sediments of the Wasatch Formation were 

deposited on the Fort Union in a depositional environment 

similar to that of the Fort Union. The Wasatch also contains 

coal.

During the early and middle Eocene, prehistoric Lake 

Gosiute flooded the basin several times resulting in the 

deposition of an alternating sequence of lacustrine and 

fluvial sediments. These sediments now comprise the Green 

River Formation, which contains rich oil shale and trona 

deposits. The Green River Formation is present at depths of 

100 to 3,000 ft beneath the study areas.

During middle Eocene time, the prevailing lacustrine 

environment changed back to mainly fluvial with the 

deposition of the Bridger Formation. Nearby volcanic 

centers also supplied voluminous pyroclastic material to the 

basin during this time. The material makes up much of the 

Bridger Formation, and it is also the source rock for zeolite.

About 1,400 ft of the middle and upper parts of the 

Bridger Formation are exposed in the study areas. This 

includes strata of the uppermost part of the Blacks Fork and 

Twin Buttes Members as recognized by Wood (1934) and 

the Cedar Mountain Member of West and Hutchison (1981). 

The rocks are mostly poorly consolidated mudstone and fine 

sandstone with the amount of pyroclastic material increasing upward in the section. Indurated ledge-forming, commonly siliceous dolostone units are minor, but conspicuous

C6 Mineral Resources of Wilderness Study Areas Miscellaneous States
stratigraphic markers that locally hold up prominent topographic benches in the study areas. Coarse sandstone, 

siltstone, claystone, and tuff beds are interbedded throughout the section in lesser amounts. Some of the more 

pronounced light-colored beds, referred to in previous 

studies as "white layers," are used as time- stratigraphic 

marker beds. The clastic sedimentary rocks, as exposed in 

the steep slopes and cliffs, are green, gray, olive, and red; 

and these sediments were deposited in fluvial flood plain, 

channel, and marginal lacustrine settings. The indurated 

carbonate rocks are pale brown, light gray, grayish orange, 

and grayish black; and they represent lacustrine deposition.

In this area the uppermost part of the Bridger was 

removed by erosion, and later the Bishop Conglomerate was 

deposited during the Oligocene. The Bishop Conglomerate, 

the youngest formation in the study areas, consists of coarse 

debris derived mainly from the Uinta Mountains. Erosion 

has since removed all but a few small remnants of Bishop 

Conglomerate that cap Twin Buttes and Black Mountain. 

On both mountain slopes large blocks of Bishop Conglomerate have broken loose and have been rafted downslope on the Bridger Formation.

The Bishop Conglomerate is 75-100 ft thick and is 

comprised of loosely cemented bouldery, cobbly conglomerate and coarse- to medium-grained, poorly sorted, 

pebbly, friable sandstone. The Bishop is light gray, light 

brown, red, and white; it was probably deposited as part of 

a continuous alluvial slope around the flanks of the Uinta 

Mountains and was subsequently eroded. Faults and fold 

structures are absent in the rock exposed in the study areas; 

the beds dip gently to the west at about 3 degrees, exposing 

older rock along the east side of the study areas.

Geochemistry

Six stream-sediment samples were collected and 

analyzed for forty-six elements, including base and precious 

metals, arsenic, uranium, and thorium. These samples represent material derived from sedimentary rock exposed in the 

study areas and deposited by the major streams. Analysis of 

these samples did not reveal any anomalous concentrations 

of any important elements indicative of mineral resources. 

The samples were analyzed for 44 elements that included 

base and precious metals by the ICP method by P.H. Briggs 

and for uranium and thorium by delayed neutron counting 

by R.E. McGregor and D.M. McKown of the U.S. 

Geological Survey. These data are available for public 

inspection at the U.S. Geological Survey, MS 973, 25046 

Federal Center, Denver, CO 80225, under job no. UB76.

The tuffaceous rocks in the study areas are known to 

contain zeolite, and 35 rock samples were collected and 

analyzed to evaluate this potential resource. The samples 

were analyzed for zeolite by X-ray diffraction methods. The 

zeolite content of the samples was estimated by comparing 

X-ray traces of the samples to X-ray traces of samples

containing known amounts of zeolites. Ten samples contain 

clinoptilolite (a common zeolite mineral) ranging from trace 

amounts to 10 percent, with one sample containing as much 

as 80 percent. No other zeolite minerals were detected. 

Other material in the samples consists of varying amounts 

of quartz, micas, feldspars, clays, and carbonate minerals. 

The locations of the clinoptilolite-bearing samples are on 

plate 1 of Lane (1990).

Mineral and Energy Resources

The geologic setting of the study areas is not 

favorable for metallic mineral resources, and the strata 

exposed there are not known to contain such resources 

anywhere in the region. The study areas are, however, 

within a large natural gas province; and oil shale, coal, and 

evaporite minerals (trona) occur at depth beneath the study 

areas.

Oil and Gas

The Greater Green River basin is considered an oil 

and gas producing province. Oil and gas have been 

produced from many fields in different stratigraphically and 

structurally controlled reservoirs throughout the province. 

The major producing reservoirs are Cretaceous and Tertiary 

sandstones, but production has also come from Cambrian 

sandstone, Mississippian carbonate rocks, Pennsylvanian 

carbonate rocks and sandstone, and Jurassic sandstone 

(Spencer, 1983). The majority of the oil and gas fields in 

Sweetwater County are along the crest and the eastern flank 

of the Rock Springs uplift, some 50 to 75 mi east of the 

study areas. The Church Buttes field on the Moxa Arch is 

about 20 mi northwest and the Clay basin field is about 

25 mi to the southeast of both study areas. All land 

adjoining the study areas is currently under lease for oil and 

gas and approximately 20 percent of the study areas are 

covered by oil and gas leases (Lane, 1990). Bulldozercuttrails, which were probably used for seismic surveys, are 

evident throughout much of the study areas. These surveys 

illustrate past interest for oil and gas by private companies. 

Two holes, one to a depth of 5,000 ft and one to nearly 

20,000 feet, were drilled prior to 1975 within the study 

areas. The locations of these holes were not determined. The 

deeper well recovered gas from Jurassic and Cretaceous 

reservoirs, but it is currently shut in (U.S. Bureau of Land 

Management, 1988).

The study areas were rated by Spencer (1983) as 

having high potential for gas in Cretaceous and Tertiary 

sandstones and low potential for structurally controlled oil 

and gas accumulations in Jurassic sandstone and Permian 

and Pennsylvanian sandstones and carbonates. Recent 

studies by Law and others (1989) have shown that much of 

the Greater Green River basin contains large amounts of

Mineral Resources, Devils Playground and Twin Buttes Wilderness Study Areas, Wyoming C7
Znatural gas in overpressured low-permeability Cretaceous 

and Tertiary sandstone reservoirs. Generation and accumulation of gas in low-permeability rock at rates greater than 

the gas can escape causes overpressuring. Natural gas is 

generated from organic matter in the interbedded coal, 

marine shale, and carbonaceous lithologies contained in the 

Cretaceous and Tertiary rock (Law and others, 1989; 

McPeek, 1981). These gas-bearing sandstones occupy the 

deeper parts of the basins. Five stratigraphic plays were 

assessed in the Greater Green River basin by Law and 

others (1989) and these include Cloverly-Frontier, Mesaverde, Lewis, Fox Hills-Lance, and Fort Union Formations. 

Of these the only play that may be present beneath the 

Devils Playground/Twin Buttes study areas is the CloverlyFrontier. The other formations are either absent from the 

study areas or they lack the basic attributes required for gas 

accumulation (Law and others, 1989).

The study areas, therefore, have a high energy 

resource potential, with a certainty level C, for undiscovered 

natural gas and a low potential for oil at a C level of 

certainty. The older Paleozoic rock are unfavorable for oil 

and gas due to the absence of structural traps in the deeper 

parts of the basin; production from structurally controlled 

reservoirs in these rock comes from the arched and uplifted 

terrane.

Oil Shale

Oil shale is widespread in Eocene lacustrine sediments of the Green River basin. Oil shales are typically 

finely laminated, brown, kerogen- bearing calcareous sedimentary rocks. They occur, in descending order, in the 

Laney, Wilkins Peak, and Tipton Shale Members of the 

Green River Formation. H.W. Roehler (written commun., 

1990) estimated oil yields for beds in the three members in 

the Green River basin as ranging from 2-30 gallons of oil 

per ton (gpt).

The depth to the oil shales in the top of the Laney 

Member ranges from 1,000 to 3,000 ft below the surface of 

the study areas and with greater depths to the lower oil 

shale-bearing members. Oil shales occur on the surface in 

the Bridger Formation in the study areas, but they are thin 

and of low grade. The Bridger was not deposited in a 

favorable environment for the accumulation of rich or high 

grade oil shales. The study areas have high energy resource 

potential for oil shale deposits in the Green River Formation, although at depths that would require in-situ 

methods of extraction. This assessment is made with a C 

level of certainty.

Trona

Trona occurs in the Wilkins Peak Member of the 

Green River Formation. Drill-hole data confirm the presence of trona in the subsurface of the study areas (table 1

and Lane, 1990). In addition to areas of inferred resources 

of trona, the study areas have high mineral resource 

potential for undiscovered deposits of trona, with certainty 

level C.

Zeolite

Zeolites are hydrous aluminosilicate minerals, many 

of which have commercial applications as they have the 

ability to selectively remove specific ions from solutions to 

which they are exposed, either by absorption, by ion 

exchange, or by acting as molecular sieves. Most zeolites of 

commercial importance occur as authigenic minerals in 

sediments of saline and alkaline lakes. The minerals form 

from vitric volcanic ash that has been deposited by air fall 

or by streams in lakes. The ash is devitrified or altered 

during diagenesis, by saline and alkaline waters, to clay and 

other minerals including zeolites. Commercial deposits of 

zeolite can form if the volcanic ash occurs in significant 

quantities, is not greatly diluted with other detrital material, 

and if the composition of the enclosing water is maintained 

long enough to convert the ash to zeolite.

Zeolite minerals are common in the middle and upper 

Eocene rocks of the Greater Green River basin (R.A. 

Sheppard, written commun., 1990). These rocks include the 

Bridger Formation, which is exposed in most of the study 

areas. During deposition of the Bridger Formation, large 

amounts of pyroclastic material, supplied from nearby 

volcanic centers, were added to the basin. Although most of 

this volcanogenic material was probably reworked and 

deposited along with other material in a fluvial environment, some ash fell and accumulated in more favorable 

lacustrine (lake) deposits. Trace amounts of clinoptilolite (a 

common zeolite mineral) were found in selected samples of 

the Bridger Formation in the study areas, and major 

amounts occur in thin beds along the northeast and northwest boundary of the Devils Playground study area. The 

geologic setting is, therefore, favorable for the occurrence 

of zeolites, but the resource potential is not high because the 

zeolite-bearing beds are usually thin and impure. Thus, the 

study areas have moderate mineral resource potential for 

zeolite minerals with a certainty level of C.

Coal

Coal occurs in the Fort Union and Wasatch Formations and in several Upper Cretaceous formations in 

Sweetwater County. Coal is mined from these rocks where 

they are exposed or occur near the surface around the Rocks 

Springs uplift and about 10 mi south of the study areas in 

the Henrys Fork coal field. Coal-bearing Fort Union and 

Wasatch rocks are probably present beneath the study areas 

but at great depths. Due to the depth of burial, the study 

areas have low energy potential for coal with a certainty 

level of D.

C8 Mineral Resources of Wilderness Study Areas Miscellaneous States
Metallic Minerals

No evidence, such as mineralization, rock alteration, 

or geochemical anomalies, was found that indicates the 

presence of base or precious metal resources in the study 

areas. Furthermore, the Bridger Formation in its present 

geologic setting in the Green River basin is not a favorable 

environment for these types of mineral resources. Therefore, the study areas have low mineral resource potential for 

undiscovered metallic minerals, with a certainty level of D.

REFERENCES CITED

Bradley, W.H., 1964, Geology of the Green River Formation and 

associated Eocene rocks in southwestern Wyoming and 

adjacent parts of Colorado and Utah: U.S. Geological 

Survey Professional Paper 486-A, 86 p.; pi. 1, scale 

1:250,000.

Culbertson, W.B., 1966, Trona in the Wilkins Peak Member of the 

Green River Formation, southwestern Wyoming, in Geological Survey Research 1966, Chapter B: U.S. Geological 

Survey Professional Paper 550-B, 225 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.

Harris, R.E., Hausel, D.W., and Meyer, I.E., 1985, Metallic and 

industrial minerals map of Wyoming: The Geological 

Survey of Wyoming, Map Series 14, scale 1:500,000.

Lane, M.E., 1990, Mineral Resources of the Devils Playground 

(WY-040-401) and Twin Buttes (WY-040-402) Wilderness Study Areas, Sweetwater County, Wyoming: U.S. 

Bureau of Mines Mineral Land Assessment Open File 

Report MLA 7-90, 12 p.

Law, B.E., Spencer, C.W., Charpentier, R.R., Crovelli, R.A., Mast, 

R.F., Dolton, G.L., and Wandrey, C.J., 1989, Estimates of 

gas resources in overpressured low-permeability of 

Cretaceous and Tertiary sandstone reservoirs, Greater Green

River Basin, Wyoming, Colorado, and Utah: Wyoming 

Geological Association Guidebook, 40th Annual Field 

Conference, p. 39-61.

McPeek, L.A., 1981, Eastern Green River Basin A developing 

giant gas supply from deep, overpressured Upper Cretaceous sandstones: American Association of Petroleum 

Geologists Bulletin, v. 65, p. 1078-1098.

Root, F.K., Glass, G.B., and Lane, D.W., 1973, Sweetwater 

County, Wyoming, geologic map atlas and summary of 

economic mineral resources: Geological Survey of 

Wyoming County Resources Series no. 2, 9 sheets.

Spencer, C.W., 1983, Petroleum potential of Wilderness Lands in 

Wyoming, in Miller, B.W., ed., Petroleum potential of 

wilderness lands in the western United States: U.S. 

Geological Survey Circular 902-M, p. M1-M10.

U.S. Bureau of Land Management, 1982, Draft Rock Springs 

District Wilderness Environmental Impact Statement: U.S. 

Department of the Interior, Bureau of Land Management, 

Rock Springs District, p. 323-332.

____ 1988, Revised draft wilderness environmental impact 

statement for the Rock Springs District, Wyoming: U.S. 

Department of the Interior, Bureau of Land Management, 

Rock Springs District, 161 p.

U.S. Bureau of Mines, 1989, Mineral commodities summaries 

1989: Washington, D.C., 191 p.

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, 5 p.

West, R.M., and Hutchison, J.H., 1981, Geology and paleontology 

of the Bridger Formation, southern Green River Basin, 

southwestern Wyoming; Pt 6, The fauna and correlation of 

Bridger E: Milwaukee Public Museum Contributions in 

Biology and Geology, no. 46, 8 p.

Wood, H.E., 1934, Revision of the Hyrachyidae: Bulletin of the 

American Museum of Natural History, v. 67, art. 5, p. 181- 

295.

Wood, H.E., Chancy, R.W., Clark, J., Colbert, E.H., Jepsen, G.L., 

Reeside, J.B., Jr., and Stock, C., 1941, Nomenclature and 

correlation of the North American continental Tertiary: 

Geological Society of America Bulletin, v. 52, p. 1-48.

Mineral Resources, Devils Playground and Twin Buttes Wilderness Study Areas, Wyoming C9

APPENDIX
DEFINITION OF LEVELS OF MINERAL RESOURCE POTENTIAL 

AND CERTAINTY OF ASSESSMENT

LEVELS OF RESOURCE POTENTIAL

H 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.

M 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 reasonable likelihood for resource accumulation, and (or) where an application of mineral-deposit models 

indicates favorable ground for the specified type(s) of deposits.

L 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 permissive. This broad category embraces 

areas with dispersed but insignificantly mineralized rock, as well as areas with little or no indication of having 

been mineralized.

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

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

moderate/ or high level of resource potential.

LEVELS OF CERTAINTY

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

B Available information only 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.

iLU

U

on

LU

o

A

U/A

UNKNOWN POTENTIAL

B

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

L/B

LOW POTENTIAL

C

H/C

HIGH POTENTIAL

M/C

MODERATE POTENTIAL

L/C

LOW POTENTIAL

D

H/D

HIGH POTENTIAL

M/D

MODERATE POTENTIAL

L/D

LOW POTENTIAL

N/D

NO POTENTIAL

LEVEL OF CERTAINTY

Abstracted with minor modifications from:

Taylor, R.B., and Steven, TA., 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.5. Geological Survey Open-File Report 84-0787, p. 7, B.
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured Indicated

1 

Reserves

1

1

Marginal Reserves

 _!___

Demonstrated 

Subeconomic Resources

Inferred

Inferred Reserves

Inferred 

Marginal Reserves

Inferred 

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

 (or) 

Hypothetical i Speculative

1

J_

1

1

1

Major elements of mineral resource classification, excluding reserve base and inferred reserve base. Modified from McKelvey,1972, Mineral 

resource estimates and public policy: American Scientist, v.60, p.32-40, and 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 by the U.S. Geological Survey in this report

EON

Phanerozote

Proterozoic

Archean

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Quaternary

Tertiary

Neogene 

Subperiod

Paleogene 

Subperiod

Cretaceous

Jurassic

Triassic

Permian

Carboniferous 

Periods

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

pre-Archean3

OQrtrtO

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

Lake 

Middle 

Early

Late 

Middle 

Early

______

AGE ESTIMATES 

OF BOUNDARIES 

(Ma1 )

- 0.010 

 1.7

 5

 24

OO

- 55

OO

_ flft

nfi

 205

- -240

oqn

_ vtn

"ien

- 410

f\nn

_ ~*570

 onn

 1600

ocn/i

 win

 3400

4550

1 Millions of years prior to A.D. 1950.

2Rocks older than 570 m.y. also called Precambrian, a time term without specific rank.

informal time term without specific rank. *U.S. GOVERNMENT PRINTING OFFICE: 1991-673-049/46018
Mineral Resources of Wilderness Study 

Areas Miscellaneous States

This volume was published

as separate chapters A, B, and C

CONTENTS

[Letters designate the chapters]

(A) Mineral Resources of the Cross Mountain Wilderness Study Area, Moffat 

County, Colorado, by Karl V. Evans, James G. Frisken, Dolores M. Kulik, and 

John R. Thompson

(B) Mineral Resources of the Fiddler Butte (East) Wilderness Study Area, Garfield 

County, Utah, by Russell F. Dubiel, Gregory K. Lee, Paul P. Orkild, and Diann 

D. Gese

(C) Mineral Resources of the Devils Playground and Twin Buttes Wilderness Study 

Areas, Sweetwater County, Wyoming, by Richard E. Van Loenen, W. Anthony 

Bryant, and Michael E. Lane

Volume Contents III

SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICATIONS

Periodicals

Earthquakes & Volcanoes (issued bimonthly). 

Preliminary Determination of Epicenters (issued monthly).

Technical Books and Reports

Professional Papers are mainly comprehensive scientific reports 

of wide and lasting interest and importance to professional scientists and 

engineers. Included are reports on the results of resource studies and of 

topographic, hydrologic, and geologic investigations. They also include 

collections of related papers addressing different aspects of a single scientific topic.

Bulletins contain significant data and interpretations that are of 

lasting scientific interest but are generally more limited in scope or geographic coverage than Professional Papers. They include the results of 

resource studies and of geologic and topographic investigations; as well 

as collections of short papers related to a specific topic.

Water-Supply Papers are comprehensive reports that present significant interpretive results of hydrologic investigations of wide interest 

to professional geologists, hydrologists, and engineers. The series covers 

investigations in all phases of hydrology, including hydrology, availability of water, quality of water, and use of water.

Circulars present administrative information or important scientific information of wide popular interest in a format designed for distribution at no cost to the public. Information is usually of short-term interest.

Water-Resources Investigations Reports are papers of an interpretive nature made available to the public outside the formal USGS publications series. Copies are reproduced on request unlike formal USGS 

publications, and they are also available for public inspection at depositories indicated in USGS catalogs.

Open-File Reports include unpublished manuscript reports, maps, 

and other material that are made available for public consultation at depositories. They are a nonpermanent form of publication that maybe cited in other publications as sources of information.

Maps

Geologic Quadrangle Maps are multicolor geologic maps on topographic bases in 7 1/2- or 15-minute quadrangle formats (scales mainly 1:24,000 or 1:62,500) showing bedrock, surficial, or engineering 

geology. Maps generally include brief texts; some maps include structure 

and columnar sections only.

Geophysical Investigations Maps are on topographic or planimetric bases at various scales, they show results of surveys using geophysical techniques, such as gravity, magnetic, seismic, or radioactivity, which 

reflect subsurface structures that are of economic or geologic significance. Many maps include correlations with the geology.

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also includes 7 1/2-minute quadrangle photogeologic maps on planimetric 

bases which show geology as interpreted from aerial photographs. The 

series also includes maps of Mars and the Moon.

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, 

stratigraphy, and structural relations in certain coal-resource areas.

Oil and Gas Investigations Charts show stratigraphic information for certain oil and gas fields and other areas having petroleum potential.

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology in relation to specific mining or mineral-deposit problems; post-1971 maps 

are primarily black-and-white maps on various subjects such as environmental studies or wilderness mineral investigations.

Hydrologic Investigations Atlases are multicolored or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; the principal 

scale is 1:24,000, and regional studies are at 1:250,000 scale or smaller.

Catalogs

Permanent catalogs, as well as some others, giving comprehensive 

listings of U.S. Geological Survey publications are available under the 

conditions indicated below from the U.S. Geological Survey, Books and 

Open-File Reports Sales, Box 25425, Denver, CO 80225. (See latest 

Price and Availability List.)

"Publications of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a set 

microfiche.

"Publications of the Geological Survey, 1962-1970" may be purchased by mail and over the counter in paperback book form and as a set 

of microfiche.

"Publications of the U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche.

Supplements for 1982, 1983, 1984, 1985, 1986, and for subsequent years since the last permanent catalog may be purchased by mail 

and over the counter in paperback book form.

State catalogs, "List of U.S. Geological Survey Geologic and Water-Supply Reports and Maps For (State)," may be purchased by mail and 

over the counter in paperback booklet form only.

"Price and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet 

form only.

Selected copies of a monthly catalog "New Publications of the 

U.S. Geological Survey" is available free of charge by mail or may be 

obtained over the counter in paperback booklet form only. Those wishing 

a free subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 National Center, Reston, VA 22092.

Note.-Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect Therefore, the prices 

charged may differ from the prices in catalogs, announcements, and publications.