Mineral Resources of the

Owl Creek Wilderness Study Area,

Hot Springs County, Wyoming

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Chapter D

Mineral Resources of the

Owl Creek Wilderness Study Area,

Hot Springs County, Wyoming

By DANAJ. BOVE, ROBERT R. CARLSON, and 

DOLORES M. KULIK 

U.S. Geological Survey

WILLIAM LUNDBY 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1756

MINERAL RESOURCES OF WILDERNESS STUDY AREAS NORTHERN WYOMING
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L Peck, Director

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For sale by the

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Library of Congress Cataloging-in-Publication Data

Mineral resources of the Owl Creek Wilderness Study Area, Hot Springs 

County, Wyoming.

(Mineral resources of wilderness study areas northern Wyoming ; ch. D) 

(U.S. Geological Survey bulletin ; 1756-D)

Bibliography: p.

Supt. of Docs, no.: I 19.3:1756-0

1. Mines and mineral resources Wyoming Owl Creek Wilderness. 

2. Owl Creek Wilderness (Wyo.) I. Bove, Dana. II. Series. III. Series': U.S. 

Geological Survey bulletin ; 1756-D.

QE75.B9 no. 1756-D 557.3 S [553'.09787'43] 88-607933 

UN24.W8]
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 Owl Creek (WY-010-104 A/B/C) 

Wilderness Study Area, Hot Springs County, Wyoming.

CONTENTS

Abstract Dl 

Summary Dl

Character and Setting Dl 

Identified Mineral Resources Dl 

Mineral Resource Potential D4 

Introduction D5

Investigations by the U.S. Bureau of Mines D5 

Investigations by the U.S. Geological Survey D5 

Appraisal of Identified Resources D5

Mining and Exploration History, and Identified Resources D5 

Appraisal of Industrial Mineral Resources D5 

Assessment of Potential for Undiscovered Resources D6 

Geology D6 

Geochemistry D7 

Geophysics D7

Mineral and Energy Resources D9 

Metallic Deposits D9 

Oil and Gas D10 

Coal Dll 

Zeolites D12 

Geothermal Energy D12 

References Cited D12 

Appendix D15

FIGURES

1. Map showing mineral resource potential and geology of the Owl Creek 

Wilderness Study Area, Wyoming D2

2. Map showing location of the Owl Creek Wilderness Study Area, 

Wyoming D3

3. Index map of the Owl Creek Wilderness Study Area, Wyoming, showing 

location of oil and gas leases D4

4. Chart showing terminology for members of the Wiggins Formation used in this 

report D6

5. Bouguer anomaly and generalized structure map of the Owl Creek Wilderness 

Study Area and surrounding area D8

6. Residual-intensity aeromagnetic anomaly and generalized structure map of the 

Owl Creek Wilderness Study Area and surrounding area DIG

Contents

MINERAL RESOURCES OF WILDERNESS STUDY AREAS-NORTHERN WYOMING

Mineral Resources of the

Owl Creek Wilderness Study Area,

Hot Springs County, Wyoming

By Dana J. Bove, Robert R. Carlson, and

Dolores M. Kulik

U.S. Geological Survey

William Lundby 

U.S. Bureau of Mines

ABSTRACT

At the request of the U.S. Bureau of Land Management, 

710 acres of the Owl Creek Wilderness Study Area 

(WY-010-104 A/B/C) were studied for mineral endowment. 

Field and laboratory studies were conducted by the U.S. 

Geological Survey and the U.S. Bureau of Mines. A search of 

U.S. Bureau of Land Management, State, and county 

records showed no current or previous mining claim activity 

and, other than common-variety sand and gravel, no mineral 

resources were identified during field examination of the 

study area. Sand and gravel is classified as an inferred 

subeconomic resource; however, the remoteness of the area 

precludes much usage of this material. About two-thirds of 

the study area is under lease for oil and gas. The entire study 

area has moderate resource potential for undiscovered oil 

and gas and low resource potential for undiscovered metals, 

coal, zeolites, and geothermal energy.

SUMMARY 

Character and Setting

The Owl Creek (WY-010-104 A/B/C) Wilderness Study 

Area comprises 710 acres in the southeastern Absaroka 

Range, Hot Springs County, Wyo. (figs. 1,2). The Owl Creek 

Wilderness Study Area is adjacent to the 703,961 -acre Washakie Wilderness, Shoshone National Forest. The study area 

lies in relatively remote country, about 30 mi (miles) west of 

the town of Hamilton Dome and about 45 mi west of

Manuscript approved for publication, December 29, 1988.

Thermopolis. Due to the small size and proximity of parcels 

A, B, and C, they will be referred to collectively as the 

"wilderness study area," or simply the "study area;" these 

parcels will be referred to individually if a more specific 

geographic notation is required.

The Absaroka Range is the largest Eocene volcanic 

field in the northern Rocky Mountains (9,000 mi2) and 

straddles northwestern Wyoming and adjacent parts of Montana. The rocks of the range are predominately Eocene (see 

geologic time chart in Appendix) lava flows and volcaniclastic 

rocks. Rocks of the Absaroka volcanic plateau coverthewest 

flank of the Bighorn basin, where they conceal Paleozoic and 

Mesozoic sedimentary strata (Brittenham and Tadewald, 

1985). A thick sequence of middle Eocene volcaniclastic 

rocks [as much as 4,000 ft (feet); K.A. Sundell, Ram Oil, 

Corp., unpub. data] covers the entire study area. The Tepee 

Trail Formation, which is the oldest volcaniclastic unit 

exposed in the study area, typically consists of olive-gray, 

well-bedded volcanic sandstone and conglomerate, lesser 

amounts of volcanic breccia, and minor siltstone. The Tepee 

Trail Formation is overlain by the Wiggins Formation, which is 

characterized by white to light-colored tuffaceous volcanic 

conglomerate and sandstone and contains massive, 

unsorted landslide-debris flow breccias. Although no 

intrusions have been identified within the study area, the 

Washakie Needles, which are the topographic expression of 

a 38-m.y. (million year old) porphyritic dacite plug (Love and 

others, 1976), crop out about 1 mi north of parcel A (fig. 1).

Identified Mineral Resources

In addition to field examination, the U.S. Bureau of 

Mines (USBM) conducted a literature search for geologic

Owl Creek Wilderness Study Area D1
109° 12'30" 109° 10'

APPROXfMATE BOUNDARY Of

OWL CREEK WILDERNESS

STUbY AREA (WY-010-104)

B

c

D

EXPLANATION

Geologic terrane having moderate mineral resource 

potential for oil and gas. with a certainty level of D

Geologic terrane having low mineral resource potential 

for coal, zeolites, and geothermal energy, with a certainty level of B

Geologic terrane having low mineral resource potential for all metals, with a certainty level of C 

Levels of Certainty

Available information suggests the level of mineral

resource potential 

Available information gives a good indication of the

level of mineral resource potential 

Available information clearly defines the level of min- _

eral resource potential

Qal 

Qf

Ti

Twiu

Twc

Twa

Tt

Alluvium (Quaternary) 

Debris fan deposits (Quaternary) 

Tertiary intrusive rocks (Oligocene) 

Wiggins Formation (middle Eocene)

Upper member

Chaos member

Allochthonous member 

Tepee Trail Formation (middle Eocene)

Contact Dashed where inferred

Figure 1. Mineral resource potential and geology of the Owl Creek Wilderness Study Area, Wyoming. Geology modified 

from K.A. Sundell (Ram Oil, Corp., unpub. map).

information and locations of patented and unpatented mining State, and County records showed no current or previous

claims, mineral leases, and oil and gas leases in and near the mining claim activity and, other than common-variety sand

study area. A search of U.S. Bureau of Land Management, and gravel, no mineral resources were identified during field

D2 Mineral Resources of Wilderness Study Areas Northern Wyoming
109°00'

Margin of Absaroka 

Volcanic Supergroup

/oil field xtf Hamilton 

Dome

APPROXIMATE 

BOUNDARY OF 

OWL CREEK 

WILDERNESS 

STUDY AREA

HOT SPRINGS CO

Circle Ridge 

oil field

Figure 2. Location of the Owl Creek Wilderness Study Area, Wyoming. Parcels identified by letters (A, B, C). Open circles 

show location of drill holes.

examination. Sand and gravel is classified as an inferred 

subeconomic resource; however, the remoteness of the area 

precludes much usage of this material. About two-thirds of 

the study area is under lease for oil and gas, but no evidence 

of drilling was found there (fig. 3).

The study area, which is situated in the southwestern 

Bighorn basin (Sundell, 1982,1986), is underlain by many of 

the same Mesozoic and Paleozoic sedimentary rocks that

produce oil and gas in the Bighorn and Wind River basins to 

the east and south, respectively (fig. 2) (Sundell, 1982; Bailey 

and Sundell, 1986; Br'rttenham and Tadewald, 1985). Three 

holes drilled less than 5 mi to the east of the study area (fig. 

2) penetrated anticlinal structures in known oil-producing 

formations including the Madison, Amsden, Tensleep, and 

Phosphoria Formations (Bailey and Sundell, 1986; Sundell, 

1982; K.A. Sundell, Ram Oil, Corp., unpub. data). Although

Owl Creek Wilderness Study Area D3
109°07'30"

WYOMING

1

R 103 W R 102 W 

2 MILES

EXPLANATION

Oil and gas leases

Approximate boundary of Owl Creek Wilderness Study Area

Figure 3. Index map of the Owl Creek Wilderness Study Area, Wyoming, showing location of oil and gas leases 

and drill holes. Lease information from U.S. Bureau of Land Management: current as of 1986.

asphaltum and oil and gas shows were recorded in all three 

drill holes, the holes were economically nonproducing and 

were abandoned (Bailey and Sundell, 1986; Sundell, 1986).

Mineral Resource Potential

Stream-sediment samples were collected by the U.S. 

Geological Survey (USGS) in and adjacent to the study area 

for geochemical analysis. Examination of analytical results 

from these samples revealed no anomalous amounts, 

groupings, or patterns of elements commonly associated 

with ore deposits, other than barium. In the absence of other 

anomalous elements that indicate hydrothermal activity, 

barium probably present in the mineral barite is thought 

to be of sedimentary origin.

Gravity and magnetic studies are largely of a reconnaissance nature and are adequate only to define regional 

features with respect to the subsurface distribution of rock 

masses and the structural framework of the area. Gravity data 

suggest that the study area lies near the leading edge of one 

or more thrust faults in an area where anticlines commonly

form during fault-related deformation; these anticlines could 

be traps for oil and gas.

The mineral resource potential for all undiscovered 

metals is low in the study area (fig. 1). The geologic environment for metal deposits is unfavorable; mineralized rock was 

not seen at the surface; and there are no anomalous element 

concentrations in the geochemical data indicative of metal 

deposits.

The proximity of the study area to large oil and gas 

fields in the Bighorn and Wind River basins, the presence of 

reservoir-quality sedimentary rocks of Paleozoic age and live 

oil and gas shows in the subsurface in drill holes within 5 mi, 

and the possibility of anticlinal structures and stratigraphic 

traps as indicated by drill-hole and regional gravity data 

indicate a moderate resource potential for undiscovered oil 

and gas in the study area (fig. 1).

The study area has low resource potential for undiscovered coal, geothermal energy, and zeolites (fig. 1). 

Although these commodities occur elsewhere in similar 

geologic environments, geologic investigations during this 

study, and studies of the adjacent Washakie Wilderness to 

the north (Ketner and others, 1966), indicate that these

D4 Mineral Resources of Wilderness Study Areas Northern Wyoming
resources either are not present in the study area or, if 

present, are deeply buried.

INTRODUCTION

At the request of the U.S. Bureau of Land 

Management (BLM), 710 acres of the Owl Creek 

Wilderness Study Area (WY-01G-104 A/B/C) were 

studied for mineral endowment. The study area is in the 

southeastern Absaroka Range, Wyoming, which is a 

150-mi-long northwest-trending mountain range in 

northwestern Wyoming that extends into southwestern 

Montana. The study area, which is located about 45 mi 

west of Thermopolis, is accessed by driving 8 mi 

northwest from Thermopolis along State Highway 120 

and continuing 25 mi westward along State Highway 170 

to the end of the pavement and about 12 mi along dirt 

roads and trails leading to the confluence of the South 

Fork of Owl Creek and Rock Creek (fig. 2). The study 

area is bounded by Rock Creek to the northeast and 

South Fork to the southwest; elevations range from 

about 9,400 to 11,000 ft above sea level.

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 Bureau of Mines (USBM) and 

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

are classified according to the system of the U.S. Bureau 

of Mines and the U.S. Geological Survey (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 resources). It is classified according to 

the system of Goudarzi (1984) and is shown in the 

Appendix. Undiscovered resources are studied by the 

USGS.

Investigations by the 

U.S. Bureau of Mines

The USBM examined BLM records of mining 

claims and oil and gas leases in and adjacent to the study 

area. Field studies were conducted during the summer of 

1987 to examine, map, and sample all known mines, 

prospects, and mineralized zones in and near the study 

area in order to inventory past production, reserves, and 

subeconomic resources. Results of these studies have 

been published by the USBM (Lundby, 1988).

Investigations by the 

U.S. Geological Survey

From 1987 to 1988 the USGS conducted field and 

laboratory studies to evaluate the potential for undiscovered mineral resources in the Owl Creek Wilderness 

Study Area (WY-010-104 A/B/C). The USGS (1) fieldchecked previous mapping (K.A. Sundell, Ram Oil, 

Corp., unpub. data; Sundell, 1986), made revisions in 

previous interpretation, and added Quaternary geology 

to the unpublished map by Sundell; (2) examined and 

sampled rock units within potentially mineralized areas; 

(3) collected stream-sediment samples for geochemical 

analysis (Malcolm and Carlson, in press); (4) conducted 

gravimetric and aeromagnetic studies; and (5) searched 

for previously published and unpublished data on the 

geology and mineral resources in and adjacent to the 

study area.

Acknowledgments. We thank Kent A. Sundell of 

Ram Oil, Corp., for providing invaluable information on 

the local and regional geology, furnishing unpublished 

geologic maps of the area, and allowing access to critical 

drill-hole information.

APPRAISAL OF IDENTIFIED RESOURCES

By William Lundby 

U.S. Bureau of Mines

Mining and Exploration History, and 

Identified Resources

No mining claims are on record with the BLM 

(August 1987), and no evidence of mining or prospect 

excavating was found in the study area during the field 

examination.

Parcels B and C of the study area are under lease 

(post-Federal Land Policy and Management Act of 

1976) for oil and gas, but no holes have been drilled 

within the boundaries of the study area (fig. 3). Two 

exploratory oil and gas wells, about 3 mi east of the study 

area, were drilled and abandoned (fig. 2) (Lundby, 

1988).

Appraisal of Industrial Mineral Resources

Sand and gravel deposits present in the study area 

along stream channels can be classed as inferred subeconomic resources. The remoteness of the study area 

would preclude usage of this material except for local 

needs.

Owl Creek Wilderness Study Area D5
Petrified wood stumps have been described in all 

units of the Wiggins Formation and are reported as most 

abundant about 20 mi west-northwest of the study area 

(Ketner and others, 1966). Such material is of interest to 

collectors and can be used for decorative purposes. No 

petrified wood was found in the study area during the 

field examination.

ASSESSMENT OF POTENTIAL FOR 

UNDISCOVERED RESOURCES

By Dana J. Bove, Robert R. Carlson, and

Dolores M. Kulik

U.S. Geological Survey

Geology

The study area lies in the southeastern portion of 

the Absaroka Range. The Absaroka Range is the largest 

Eocene-age volcanic field in the northern Rocky 

Mountains (9,000 mi2) and straddles northwestern Wyoming and adjacent parts of Montana. The geology of the 

range is predominately lava flows and volcaniclastic 

rocks. Rocks of the Absaroka volcanic plateau cover the 

west flank of the Bighorn basin, where they conceal 

Paleozoic and Mesozoic sedimentary strata (fig. 2) (Brittenham and Tadewald, 1985). The Absaroka Range is 

bounded on the east by the Bighorn basin, on the 

northeast by the Beartooth Mountains, on the northwest 

by the Madison and Gallatin Ranges, on the west by the 

Yellowstone plateau, and on the south by the Wind River 

basin.

Volcanic rocks of the Absaroka Range, which are 

known as the Absaroka Volcanic Supergroup (Smedes 

and Prostka, 1972) and were derived from local volcanic 

centers, erupted episodically during Eocene time. The 

primary volcanic rocks were rapidly and continuously 

reworked to form a complex assemblage of primary-vent

and alluvial-facies rocks derived from multiple source 

areas (Sundell, 1986). The Eocene volcanics unconformably overlie Precambrian, Paleozoic, Mesozoic, and 

lower Tertiary rocks that were folded and faulted 

primarily during the Laramide orogeny (Keefer, 1957; 

Love, 1934; Sundell, 1986; Brittenham and Tadewald, 

1985).

A thick sequence of middle Eocene volcaniclastic 

rocks (as much as 4,000 ft; K.A. Sundell, Ram Oil, Corp., 

unpub. data) cover the entire study area. The Tepee Trail 

Formation (unit Tt, fig. 1), which is the oldest of these 

units exposed in the study area, typically consists of 

olive-gray, well-bedded volcanic sandstone and conglomerate, lesser amounts of volcanic breccia, and minor 

siltstone. The Tepee Trail Formation is overlain unconformably by the Wiggins Formation, which is characterized by white to light-colored tuffaceous volcanic 

conglomerate and sandstone and contains massive, 

unsorted landslide-debris flow breccia. The Wiggins 

Formation was subdivided into four units by Sundell 

(1982) for mapping purposes. Figure 4 compares the 

units of Sundell (1982) with the informal nomenclature 

used in this report. All units but the lower member of the 

Wiggins are present in the study area. Two bodies of the 

allochthonous member crop out just outside the study 

area; one body is in Needle Creek, north of parcel A, and 

the other body is above Rock Creek, northwest of parcel 

C (fig. 1). The allochthonous member consists of large, 

detached plates of well-bedded Wiggins lithologies (Sundell, 1982, 1986). Conspicuous, reworked white and 

lime-green tuff beds ("Sugar loaf tuff beds"; Sundell, 

1982) are present in the allochthonous member in the 

study area and have been used as a key stratigraphic 

marker throughout the region. The chaos member, which 

unconformably overlies the allochthonous member and 

the Tepee Trail Formation, is interpreted as large-scale 

landslide or debris-flow deposits and consists of large 

blocks and contorted masses of andesitic breccia in an 

unsorted, boulder- to clay-size matrix. The upper member caps the rocks of the study area and unconformably 

rests upon the chaos member. Strata of the upper 

member of the Wiggins consist of volcanic conglomerate,

Sundell (1982) This report

Wiggins 

Formation

upper Wiggins

Castle Rocks chaos

allochthonous Wiggins

lower Wiggins

Wiggins 

Formation

upper member

chaos member

allochthonous member

lower member

Figure 4. Chart showing terminology for members of the Wiggins Formation used in this 

report (modified from Sundell, 1982).

D6 Mineral Resources of Wilderness Study Areas Northern Wyoming
sandstone, laharic breccia, and tuff beds. Clasts of the 

chaos member are abundant at the base of the upper 

member.

Although no intrusions have been identified within 

the study area, the Washakie Needles, which are the 

topographic expression of a 38-m.y. porphyritic dacite 

plug (unit Ti, fig. 1) (Love and others, 1976), crop out 

about 1 mi north of parcel A.

The study area, which is situated in the southwestern Bighorn basin (Sundell, 1982,1986), is underlain 

at depth by many of the same Paleozoic and Mesozoic 

sedimentary rocks that are present in the Bighorn and 

Wind River basins to the east and south, respectively 

(fig. 2) (Sundell, 1982; Bailey and Sundell, 1986; Brittenham and Tadewald, 1985). Wells drilled less than 5 mi to 

the east of the study area (fig. 2) penetrated the Madison, 

Amsden, Tensleep, and Phosphoria Formations (Bailey 

and Sundell, 1986; Sundell, 1982; K.A. Sundell, Ram Oil, 

Corp., unpub. data). An isopach map of the Tensleep 

Sandstone that was constructed on the basis of drill-hole 

and seismic data indicates that this unit occurs beneath 

the study area at an elevation of about 6,000-7,000 ft 

above sea level (K.A Sundell, Ram Oil, Corp., oral 

commun., 1987).

Quaternary rocks in and adjacent to the study area 

are confined to locations in and around present streams 

(Rock Creek, South Fork, and Cabin Creek) and consist 

of alluvial sand and gravel (unit Qal) and relatively small 

debris fans (unit Qf) (fig. 1).

Geochemistry

A reconnaissance geochemical survey was 

conducted in the Owl Creek Wilderness Study Area in 

July 1987. Stream sediments and panned concentrates 

were collected at 11 sites and were subsequently 

prepared and analyzed as minus-80-mesh sediments and 

nonmagnetic heavy-mineral concentrates, respectively. 

These sample media represent a composite of rock and 

soil materials exposed in the drainage basin upstream of 

each sample site. The minus-80-mesh sediment gives the 

general chemical signature of the drainage basin, with 

some enhancement of elements that tend to be adsorbed 

by clay minerals. The heavy-mineral concentrate enhances the detection of mineral deposits that may occur 

in the drainage basin.

Seven of the sampled sites were on first-order 

(unbranched) streams that drain the study area; these 

samples represent a sampling density of one site per 

0.5 mi2 . In addition, two sampled sites were located on 

Rock Creek (a second-order stream) and two sampled 

sites were located on the South Fork of Owl Creek (at 

second- and third-order localities); these streams flank 

the study area ridge on the northwest and southwest

sides. These last four sites were sampled to yield 

information on the general geochemical setting of the 

study area.

The stream sediments and nonmagnetic heavymineral concentrates were analyzed for 35 and 37 

elements, respectively, by a semiquantitative emission 

spectrographic method (Grimes and Marranzino, 1968). 

The analytical data, a description of the sampling and 

analytical techniques used, and a sample locality map are 

in the files of M J. Malcolm and R.R. Carlson (USGS, 

Lakewood, Colo.).

Examination of analytical results for the sites on 

streams that drain the study area, and comparison to the 

results for the four sites of the general area, showed no 

anomalous concentrations, groupings, or patterns of 

elements associated with mineral deposits, other than 

barium. The pattern of barite occurrence in the 

mineralogical split of the nonmagnetic heavy-mineral 

concentrates indicates that the source of the barium is 

the Tepee Trail Formation. However, in the absence of 

other anomalous elements that indicate hydrothermal 

activity, the barite is considered to be of authigenic 

sedimentary origin.

Geophysics

Gravity and magnetic studies were undertaken as 

part of the mineral resource assessment of the Owl Creek 

Wilderness Study Area and to provide information on the 

subsurface distribution of rock masses and the structural 

framework. The gravity and magnetic data are of a 

reconnaissance nature and are adequate only to define 

regional features; however, the regional structural 

features defined by geophysics and geology are pertinent 

to an evaluation of the potential for oil and gas beneath 

the study area.

The gravity data were obtained in and adjacent to 

the study area in 1987. These data were supplemented by 

data maintained in the files of the U.S. Defense Mapping 

Agency, Aerospace Center (1974), of the Department of 

Defense; along the western map margin (fig. 5) by 

unpublished data of the USGS; and in the northwest 

corner of the map (fig. 5) by data from Long (1982). 

Stations measured during this study were established 

using a Worden Model W-177 gravimeter. The data 

were tied to the International Gravity Standardization 

Net 1971 (U.S. Defense Mapping Agency, Aerospace 

Center, 1974) at base station ACIC 1661-1 at Shoshone, 

Wyo. Station elevations were obtained from benchmarks, spot elevations, and estimates from 1:24,000- and 

l:62,500-scale topographic maps and are accurate to 

±20 and ±40 ft, respectively. The error in the Bouguer 

value is less than 2.5 mGal (milligals) for errors in 

elevation control. Bouguer gravity values were computed

Owl Creek Wilderness Study Area D7
44C 

00'

43° 

15'

109"00' 

I

10

I

20 MILES

Figure 5 (above and facing page). Bouguer anomaly and generalized structure map of the Owl Creek Wilderness Study Area 

and surrounding area. Contour interval, 5 milligals. Contours dashed where inferred; hachures indicate closed lows. Letters 

identify features discussed in text. Geology and structure from Love and others (1955).

using the 1967 gravity formula (International Asso- corrections were made by computer for a distance of 100

ciation of Geodesy, 1967) and a reduction density of 2.67 mi from the station using the method of Plouff (1977).

g/cm3 (grams per cubic centimeter). Mathematical The data are shown in figure 5 as a complete Bouguer

formulas are given in Cordell and others (1982). Terrain gravity map with contour interval of 5 mGal.

D8 Mineral Resources of Wilderness Study Areas Northern Wyoming
*

" 

EXPLANATION

Owl Creek Wilderness Study Area

| Anticline

Thrust or reverse fault Sawteeth on upper plate; dashed

where covered or inferred 

Thrust or reverse fault Sawteeth on upper plate; inferred

from gravity data 

Gravity station location measured for this study

Gravity station from U.S. Defense Mapping Agency, Aerospace Center (1974) 

Gravity station from Long (1982)

Gravity station from U.S. Geological Survey unpublished data

Precambrian rocks

A major gravity high (A) is associated with the Owl 

Creek uplift and extends north across the flank of the 

uplift to the edge of the Bighorn basin (fig. 5). It is caused 

by relatively dense Precambrian crystalline rocks in the 

core of the uplift and in the shallow subsurface on its 

north flank. Another gravity high (B) is associated with 

relatively dense Precambrian rocks of the Wind River 

Range in the southwest corner of the map area. A gravity 

low (C) is associated with a thick section of sedimentary 

rocks in the Wind River basin. The extension of gravity 

low C over the south edge of the Owl Creek uplift 

suggests that the crystalline rocks are thin in the area of 

the gravity low and that the underlying thrust fault dips at 

a low angle to the north. Northwest-trending thrust faults 

bring Precambrian rocks to the surface in the uplift in the 

eastern part of the map area. These faults occur on the 

south flank of gravity high A. The steep gravity gradient 

and higher gravity values here suggest that the northwesttrending faults segment the crystalline rocks of the upper 

plate and that the low-density sedimentary rocks of the 

Wind River basin do not extend beneath these parts of 

the faults. The northwest-trending faults that have been 

mapped do not coincide with the gravity gradient and are, 

therefore, probably confined to the thin leading edge of 

the upper plate. The major gravity gradient reflects the 

juxtaposition of thicker Precambrian rocks in the core of 

the uplift with the lower density sedimentary rocks that 

wedge out beneath the uplift.

The gravity low over the Wind River basin narrows 

and decreases northwestward across a gravity saddle and 

again broadens and decreases at D at the western edge of 

the map area. The thrust fault that bounds the Owl Creek 

uplift on the south bends northward and probably 

continues as the Buffalo Fork thrust fault (Antweiler and 

others, 1983) west of the map area. Gravity low D is part 

of a more extensive low that is interpreted as being 

associated with a sedimentary basin beneath the volcanic 

rocks of the Absaroka Volcanic Supergroup (Kulik,

1981; Antweiler, and others, 1983). Volcanic rocks occur 

in the area of moderate gravity values east, west, and 

north of the study area. Part (gradient F) of this more 

extensive gravity low continues for a short distance along 

a mapped fault just southeast of the study area. Another 

part (gradient G) of this more extensive gravity low 

trends north about 10 mi north-northwest of the study 

area. These gradients may be continuous across the area 

of no data and may be caused by a fault that is concealed 

beneath volcanic cover. A saddle (H) in the gravity low 

west of gradient G suggests that a fault splay may also 

occur beneath cover here. The interpreted faults are 

identified by the dashed traces with the letter "G" on 

figure 5. The gravity contours (I) northeast of the study 

area suggest that the southward-dipping fault northeast 

of the study area and its associated anticline may 

continue westward just north of the study area. The study 

area lies near the leading edge of one or both interpreted 

thrust faults in an area where anticlines commonly form 

during thrusting.

Magnetic data are from U.S. Department of 

Energy (1982). Flight lines were flown east-west at 

2-5-mi intervals and 400 ft above the ground elevation. 

Magnetic data commonly reflect variations in magnetic 

susceptibility in basement rocks, although shortwavelength anomalies may be caused by volcanic rocks 

near the surface. Magnetic highs A and B on figure 6 

appear to be associated with exposed Precambrian rocks 

of the Owl Creek uplift. Another short-wavelength 

magnetic high (C) has no correlation with crystalline 

rocks at the surface; it may be caused by Precambrian 

rocks that do not crop out and (or) by an intrusive body 

at a shallow depth. Magnetic high D is partially coincident 

with the edge of a thrust fault that may have brought 

Precambrian rocks near the surface. Other magnetic 

anomalies in the map area probably represent variations 

in the susceptibility of the basement rocks. No identifiable magnetic signature is associated with the surface 

volcanic rocks in the area shown in figure 6.

Mineral and Energy Resources

Metallic Deposits

The mineral resource potential for all undiscovered metals in the wilderness study area is low (fig. 1). 

The geologic environment is unfavorable; mineralized 

rock was not seen at the surface during field studies; and 

there were no anomalous element concentrations, other 

than barium, in the geochemical data. These findings are 

supported by studies of the adjacent Washakie Wilderness (Ketner and others, 1966). The entire study area has 

been assessed to have low mineral resource potential for 

all undiscovered metals, with a certainty level of C.

Owl Creek Wilderness Study Area D9
109°00'

Figure 6 (above and facing page). Residual-intensity aeromagnetic anomaly and generalized structure map of the Owl Creek 

Wilderness Study Area and surrounding area. Contour interval, 100 nanoteslas. Hachures indicate closed lows. Letters identify 

features discussed in text. Geology and structure from Love and others (1955).

Oil and Gas western margin of the Bighorn basin and portions of the

northwestern Wind River basin. The majority of

Rocks of the Absaroka volcanic field unconform- petroleum from the Bighorn basin (over 2.3 billion 

ably overlie oil- and gas-producing formations on the barrels of oil; Brittenham and Tadewald, 1985) has been

D10 Mineral Resources of Wilderness Study Areas Northern Wyoming
,_t EXPLANATION

Owl Creek Wilderness Study Area

Anticline

Thrust or reverse fault Sawteeth on upper plate; dashed

where covered or inferred 

Thrust or reverse fault Sawteeth on upper plate; inferred

from gravity data

Precambrian rocks

produced from strata on anticlines with large amounts of 

structural closure. Principal reservoir rocks include 

carbonates of the Mississippian Madison Formation, the 

Pennsylvanian Tensleep Sandstone, and carbonates of 

the Lower Permian Phosphoria Formation. However, 

minor production has occurred from Cambrian, Ordovician, Triassic, and Cretaceous rocks (Stone, 1967; 

Brittenham and Tadewald, 1985). Two major oil fields, 

Hamilton Dome and Grass Creek, occur along the 

eastern margin of the Absaroka volcanic field in the 

southwestern Bighorn basin, about 20 mi east and 

northeast of the study area, respectively. Total production from both fields has exceeded 400 million barrels 

of oil and 7 trillion cubic feet of natural gas (Sundell, 

1982). The principal producing formations from these 

fields include the Upper Cretaceous Frontier Formation, 

Upper Triassic Crow Mountain Formation of the Chugwater Group, Lower Permian Phosphoria Formation, 

Pennsylvanian Tensleep Sandstone, Upper Mississippian 

Darwin Sandstone Member of the Amsden Formation, 

Mississippian Madison Formation, and Upper and 

Middle Ordovician Bighorn Dolomite. The Circle Ridge 

oil field (more than 20 million barrels of oil; Stone, 

1967), located about 11 mi to the south of the study area 

in the northwestern Wind River basin, produces from 

near-surface rocks in a dome, primarily from the Madison and Phosphoria Formations.

The Aspen Creek and Dickie Creek oil fields, 

located within the southeastern Absaroka volcanic field, 

indicate that oil fields can be located beneath the Tertiary 

volcanic rocks in the same formations and along similar 

structures as discussed above. The oil-producing Aspen 

Creek anticline was recurrently uplifted after deposition 

of the overlying Tertiary volcanic rocks (Love, 1985) 

indicating post-Laramide deformation. Other studies 

also document prominent surface anticlines in the volcanics, which may reflect underlying structures critical to 

oil and gas targets in the underlying Paleozoic and 

Mesozoic rocks (Brittenham and Tadewald, 1985; KA. 

Sundell, Ram Oil, Corp., oral commun., 1987).

To date no holes have been drilled within the study 

area, although three holes (Federal 4-1, High Island 

Ranch 33-1, Rock Creek State 16-1; K.A. Sundell, Ram 

Oil, Corp., unpub. data; Bailey and Sundell, 1986) were

drilled less than 5 mi to the east and southeast (fig. 2). 

Two of these holes (Federal 4-1 and High Island Ranch 

33-1) were drilled at the crest of a northwesterly trending 

anticlinal structure, which is about 8 mi long and 2 mi 

wide (K.A. Sundell, Ram Oil, Corp., unpub. data). The 

anticline, which is mappable in the Tertiary volcanics, is 

expressed in the underlying Paleozoic and Mesozoic 

strata as evidenced by seismic and drill-hole data (K.A. 

Sundell, Ram Oil, Corp., unpub. data; Bailey and Sundell, 1986). Both drill holes penetrated about 3,400 ft of 

volcanics and as much as 875 ft of Paleozoic rocks 

including the Lower Triassic Dinwoody, Phosphoria, and 

Tensleep Formations. Asphalt, averaging 1-2 percent of 

the total cuttings, was present in both holes from about 

2,000 to 3,700 ft and occurred as dikes and fracturefilling veins. Shows of wet gas, heavy oil, and traces of 

hydrogen sulfide were also encountered in both holes 

from about 1,200 ft to the bottom of the hole (Bailey and 

Sundell, 1986; ICA. Sundell, Ram Oil, Corp., unpub. 

data). The best oil shows were reportedly present in the 

Phosphoria Formation.

Favorable aspects in regards to oil and gas 

resources within the study area include the proximity of 

the study area to large oil and gas fields in the Bighorn 

and Wind River basins, the likelihood of anticlinal 

structures occurring in the study area as suggested by 

regional geophysical studies, and the presence of asphaltum and live oil and gas shows in nearby drill holes that 

penetrate anticlinal structures in known oil- and gasproducing Paleozoic rocks. The criterion considered 

unfavorable for oil and gas resources in the study area is 

the absence of proven, overlying sealing rocks, such as 

Cretaceous rocks, which are present in oil fields to the 

east (Spencer, 1981). The angular unconformity between 

the Tertiary volcanics and underlying Paleozoic rocks has 

been proposed as a barrier to upward migration of 

hydrocarbons from reservoir rocks (Sundell and Bailey, 

1986); however, the presence of asphaltum in Tertiary 

rocks in nearby drill holes suggests that these rocks are 

too brittle to form an effective seal (C.W. Spencer, oral 

commun., 1987). Considering all the above data, the 

entire study area has been assessed to have moderate 

potential for undiscovered oil and gas resources, with a 

certainty level of D (fig. 1).

Coal

Due to the absence of Cretaceous rocks beneath 

the study area (Bailey and Sundell, 1986; K.A. Sundell, 

Ram Oil, Corp., unpub. data), which are known to 

contain low-quality coal deposits in parts of northwestern 

Wyoming (Ketner and others, 1966), the entire study 

area has been assessed to have low resource potential for

Owl Creek Wilderness Study Area D11
undiscovered coal, with a certainty level of B (fig. 1). The 

Washakie Wilderness to the north of the study area also 

was documented to have low resource potential for coal 

(Ketner and others, 1966).

Zeolites

Altered lime-green and white rhyolitic tuff beds 

within a block of the allochthonous member of the 

Wiggins Formation north of parcel C contains zeolites, 

identified by X-ray diffraction as heulandite. However, 

the tuff beds, which occur only in the small block of the 

allochthonous member (fig. 1), are generally less than 

100 ft thick, and zeolite content is estimated to be 

significantly less than 50 percent of the rock. There is no 

evidence that zeolites occur elsewhere in the study area. 

The entire study area has been assessed to have low 

resource potential for undiscovered zeolites, with a certainty level of B (fig. 1).

Geothermal Energy

No thermal springs are present in or near the study 

area, although hot springs are present at Thermopolis 

about 45 mi east of the study area. The entire study area 

has been assessed to have low potential for undiscovered 

geothermal resources, with a certainty level of B (fig. 1).

REFERENCES CITED

Antweiler, J.C., Williams, F.E., Jinks, J.E., and Light, T.D. 

1983, Preliminary report on the mineral resource 

potential of the Teton Wilderness, Teton, Fremont, and 

Park Counties, Wyoming: U.S. Geological Survey OpenFile Report 83-470, 64 p.

Bailey, M.H., and Sundell, K.A., 1986, Preliminary results of 

wildcat drilling in Absaroka volcanic rocks, Hot Springs 

County, Wyoming [abs.]: American Association of 

Petroleum Geologists Bulletin, v. 70, no. 8, p. 1030-1031.

Brittenham, M.D., and Tadewald, B.H., 1985, Detachment and 

basement involved structures beneath the Absaroka 

Range, in Greis, R.R., and Dyer, R.C., eds., Seismic 

exploration of the Rocky Mountain region: Rocky 

Mountain Association of Geologists, p. 31-44.

Cordell, L., 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 Series Map GP-949, scale 

1:1,000,000.

Goudarzi, G.H., compiler, 1984, Guide to preparation of 

mineral survey reports on public lands: U.S. Geological 

Survey Open-File Report 84-797, 42 p.

Grimes, D.J., and Marranzino, A.P., 1968, Direct-current arc 

and alternating-current spark emission spectrographic 

field methods for the semiquantitative analysis of geologic materials: U.S. Geological Survey Circular 591, 6 p.

International Association of Geodesy, 1967, Geodetic reference system, 1967: International Association of 

Geodesy Special Publication 3, 116 p.

Keefer, W.R., 1957, Geology of the Du Noir area, Fremont 

County, Wyoming: U.S. Geological Survey Professional 

Paper 294-E, p. 155-221.

Ketner, K.B., Keefer, W.R., Fisher, F.S., Smith, D.L., and 

Raabe, R.G., 1966, Mineral resources of the Stratified 

Primitive Area, Wyoming: U.S. Geological Survey 

Bulletin 1230-E, 56 p.

Kulik, D.M., 1981, Gravity interpretation of subsurface 

structures in overthrust and covered terrains, in Sedimentary tectonics, principles and applications: University 

of Wyoming Circular 33, 30 p.

Long, C.L., 1982, Principal facts for gravity stations in the south 

Absaroka Wilderness, Wyoming: U.S. Geological Survey 

Open-File Report 82-1034, 12 p.

Love, J.D., 1934, The geology of the western end of the Owl 

Creek Mountains, Wyoming: Geological Survey of Wyoming Bulletin 24, 33 p.

___ 1985, Oil and gas potential of the Washakie (south 

Absaroka) Wilderness and adjacent study areas, Wyoming: Wyoming Geological Survey Report of Investigations 33, p. 10.

Love, J.D., Weitz, J.L., and Hese, R.K., 1955, Geologic map of 

Wyoming: U.S. Geological Survey, scale 1:50,000.

Love, L.L., Kudo, A.M., and Love, D.W., 1976, Dacites of 

Bunsen Peak, the Birch Hills and Washakie Needles, 

northwest Wyoming, and their relationship to the Absaroka volcanic field, Wyoming-Montana: Geological 

Society of America Bulletin, v. 87, p. 1455-1462.

Lundby, William, 1988, Mineral investigation of the Owl Creek 

Wilderness Study Area (WY-010-104), Hot Springs 

County, Wyoming: U.S. Bureau of Mines Open File 

Report MLA 12-88, 10 p.

Plouff, D.M., 1977, Preliminary documentation for a Fortran 

program to compute gravity terrain corrections based on 

topography digitized on a geographic grid: U.S. Geological Survey Open-File Report 77-535, 45 p.

Smedes, H.W., and Prostka, H.J., 1972, Stratigraphic 

framework of the Absaroka Volcanic Supergroup in the 

Yellowstone National Park region: U.S. Geological 

Survey Professional Paper 729-C, 33 p.

Spencer, C.W., 1981, Petroleum potential of wilderness lands in 

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

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

Geological Survey Circular 902-A-P, p. M1-M9.

Stone, D.S., 1967, Theory of Paleozoic oil and gas accumula 

tion in Big Horn Basin, Wyoming: American Association 

of Petroleum Geologists Bulletin, v. 51, no. 10, 

p. 2056-2114.

Sundell, K.A., 1982, Geology of the headwater area of the 

North Fork of Owl Creek, Hot Springs County, Wyoming: Wyoming Geological Survey Report of investigations 15, 51 p.

___ 1986, The Castle Rocks chaos A gigantic Eocene 

landslide-debris flow in the southeastern Absaroka 

Range, Wyoming: Santa Barbara, University of California, Ph. D. dissertation, 132 p.

D12 Mineral Resources of Wilderness Study Areas Northern Wyoming
U.S. Bureau of Mines and U.S. Geological Survey, 1980, America, Part 2: Defense Mapping Agency Aerospace

Principles of a resource/reserve classification for min- Center Reference Publication 25, 1,635 p.

erals: U.S. Geological Survey Circular 831, 5 p. U.S. Department of Energy, 1982, Thermopolis quadrangle:

U.S. Defense Mapping Agency, Aerospace Center, 1974, Residual Intensity Anomaly Contour Map GJM-099,

World Relative Gravity Reference Network, North pi. 4.

Owl Creek Wilderness Study Area D13

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

t

<

tuI

8LU 

DC

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.
RESOURCE/RESERVE CLASSIFICATION

IDENTIRED RESOURCES

Demonstrated

Measured Indicated

Inferred

UNDISCOVERED RESOURCES

Probability Range 

Hypothetical j Speculative

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

Reserves Inferred Reserves

Marginal Reserves

Demonstrated 

Subeconomic Resources

Inferred 

Marginal Reserves

Inferred

Subeconomic

Resources

+

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

resource estimstes and public policy: American Scientist, v.60, p.32-40, and U.S. Bureau of Mines and U.S. Geological Survey, 1980, 

Principlea of s 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 Archesn 

hean*

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 

Eerly

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Lste 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

 -

BOUNDARY AGE 

IN 

MILLION YEARS

-0.010

- 1.7

- 5

*)A

-55

-66

- 96

-138

_ OAK

-A. 240

- 290 

-~ 330

_ tttn

- 410

- HO9

- 500 

./* 570'

9UU

 1600

_ Ocrtrt

owv

- 3400 -

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

* Informal time term without specific rank.

rU.S. GOVERNMENT PRINTING OFFICE: 1989-673-047/66090
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