Mineral Resources of the

Mill Creek Canyon Wilderness Study Area,

Grand County, Utah ^

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Chapter E

Mineral Resources of the

Mill Creek Canyon Wilderness Study Area,

Grand County, Utah

By MICHAEL F. DIGGLES, JAMES E. CASE, 

HARLAN N. BARTON, and JOSEPH S. DUVAL 

U.S. Geological Survey

MICHAEL E. LANE 

U.S. Bureau of Mines

U.S. GEOLOGICAL SURVEY BULLETIN 1754

MINERAL RESOURCES OF WILDERNESS STUDY AREASUPPER COLORADO RIVER REGION, UTAH
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, WASHINGTON : 1990

For sale by the

Books and Open-File Reports Section

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Library of Congress Cataloging-in-Publication Data

Mineral resources of the Mill Creek Canyon Wilderness Study Area, Grand County, 

Utah / by Michael F. Diggles...[et al.].

p. cm. (Mineral resources of wilderness study areas Upper Colorado 

River region, Utah ; Ch. E) (U.S. Geological Survey bulletin ; 1754-E)

Includes bibliographical references (p. ).

Supt.ofDocs.no.: 119.3: 1754-E

1. Mines and mineral resources Utah Mill Creek Canyon Wilderness. 2. Mill 

Creek Canyon Wilderness (Utah) I. Diggles, M. F. II. Series. III. Series: U.S. 

Geological Survey bulletin; 1754-E.

QE75.B9 no. 1754-E 557.3 s dc20 90-14050 

[TN24.U8] [553'.09792'58] 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 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 Mill Creek Canyon Wilderness Study 

Area (UT-060-139A), Grand County, Utah.

CONTENTS

Summary El

Abstract El 

Character and setting El 

Identified mineral resources El 

Mineral resource potential E2 

Introduction E3

Location and physiography E3 

Procedures E3 

Previous studies E3 

Acknowledgments E6 

Appraisal of identified resources E6 

Mining history E6 

Appraisal of sites examined E6 

Energy resources E6 

Conclusions E6

Assessment of mineral resource potential E7 

Geology E7

Stratigraphy E7 

Structure E8 

Geochemistry E8

Methods and background E8 

Sample analysis E8 

Results and interpretation E9 

Geophysical studies E9

Aeromagnetic data E9 

Gravity data E9

Assessment of mineral resource potential E13 

References cited E14 

Appendixes E17

Definition of levels of mineral resource potential and certainty of

assessment E18

Resource/reserve classification E19 

Geologic time chart E20

FIGURES

1. Index map showing location of Mill Creek Canyon Wilderness Study Area, Grand 

County, Utah E2

2. Mineral resource potential and generalized geology of Mill Creek Canyon 

Wilderness Study Area, Grand County, Utah E4

3. Schematic contours on Precambrian surface in vicinity of Mill Creek Canyon 

Wilderness Study Area, Utah E10

4. Residual total-intensity aeromagnetic map of vicinity including Mill Creek Canyon 

Wilderness Study Area, Utah Ell

5. Bouguer anomaly map of region including Mill Creek Canyon Wilderness Study 

Area, Utah E12

6. Schematic gravity model across Spanish Valley and Mill Creek Canyon Wilderness 

Study Area, Utah E13

Contents

Mineral Resources of the

Mill Creek Canyon Wilderness Study Area,

Grand County, Utah

By Michael F. Diggles, James E. Case, Harlan N. Barton, and Joseph S. Duval 

U.S. Geological Survey

Michael E. Lane 

U.S. Bureau of Mines

SUMMARY

Abstract

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

approximately 9,780 acres of the Mill Creek Canyon Wilderness Study Area (UT-060-139A) was evaluated for identified 

mineral resources (known) and mineral resource potential 

(undiscovered). In this report, the area studied is referred to 

as the "wilderness study area" or "the study area." Fieldwork 

was conducted in 1988 to assess the mineral resources and 

resource potential of the study area. No mineral resources 

were identified in the Mill Creek Canyon Wilderness Study 

Area. Placer gold is present in the eastern part of the study 

area but not in sufficient quantity to be considered a resource. 

Eolian sand and sandstone occur in the study area, but it is 

unlikely these will be developed. Oil and gas leases cover a 

small part of the study area; no geothermal resources are 

known to exist in the study area.

The entire study area has high potential for undiscovered 

mineral resources of potash and halite, and areas underlain 

by the Navajo Sandstone (Lower Jurassic) also have high potential for resources of flagstone. The top of Wilson Mesa 

also has high resource potential for small deposits of placer 

gold. The entire study area has moderate potential for resources of uranium, thorium, copper, vanadium, oil and gas, 

and carbon dioxide gas and has low potential for resources of 

helium gas and for geothermal energy.

Character and Setting

The Mill Creek Canyon Wilderness Study Area covers 9,780 acres of canyons and mesas in Grand County,

Manuscript approved for publication, August 27, 1990.

Utah, 2 mi east of the town of Moab (fig. 1). The study 

area is bounded on the north by the dirt road that runs along 

the ridge between the North Fork of Mill Creek/Rill Creek 

drainage and Negro Bill Canyon. It is bounded on the 

south by Mill Creek and on the east by roads on Wilson 

Mesa. Access to the area is from U.S. Highway 191 on the 

southwest and from the Sand Flats Road on the north and 

east. In this semiarid region, vegetation on the mesas in the 

western parts of the study area consists of sagebrush and 

grasses; the steeper terrain in the east contains pifion pine 

and juniper with Mormon tea, sagebrush, squawbrush, and 

blackbrush. The study area is in the Paradox Basin fold 

and fault belt of the Colorado Plateau physiographic province. The exposed rocks consist of subhorizontal beds of 

Jurassic sandstone and minor amounts of shale and siltstone 

(see "Appendixes" for geologic time chart). The study area 

is on the northeastern limb of the Moab Valley-Spanish 

Valley salt anticline, which collapsed when the salt core 

was partially dissolved and removed by ground water. Remaining evaporite deposits in the underlying strata may host 

deposits of potash, halite, oil, and gas.

Identified Mineral Resources

No mineral resources were identified in the Mill Creek 

Canyon Wilderness Study Area. Analyses of placer samples 

collected in and near the eastern part of the study area show 

traces of gold in detrital material. Eolian sand and sandstone 

in the study area may be suitable as foundry, fracturing, or 

filtering sand, but they are not likely to be developed because 

similar deposits are readily available elsewhere nearer possible markets. Oil and gas leases cover only a very small 

part of the study area. No geothermal resources are known 

to exist in the study area.

Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand County, Utah El
Mineral Resource Potential

Potash and halite are present in the Paradox Member 

(Middle Pennsylvanian) of the Hermosa Formation (Middle 

and Upper Pennsylvanian), which is present at depth within 

the study area. The entire area is therefore considered to 

have high mineral resource potential for potash and halite 

(fig. 2). The Navajo Sandstone (Lower Jurassic) is presently 

being quarried for flagstone for building materials in the 

lower reaches of Mill Creek outside the study area. The 

resource potential is high for additional flagstone in areas 

underlain by the Navajo Sandstone in the western pan of 

the study area. Gold, which probably originated in the La 

Sal Mountains to the east, is present on Wilson Mesa in 

placer claims outside the study area; the host streams during 

the Pleistocene Epoch continued into the parts of the mesa

that are within the study area. The top of Wilson Mesa, 

therefore, has high resource potential for small placer deposits of gold. Uranium is mined in nearby areas from the 

Cutler (Lower Permian), Chinle (Upper Triassic), and 

Morrison (Upper Jurassic) Formations. Also produced from 

these areas are vanadium from vanadium silicates and copper 

from chalcopyrite, bornite, and chalcocite. The Chinle, 

Cutler, and Morrison are present at depth in the study area, 

and it is possible that additional ore-bearing zones may be 

present within these three units. The entire study area, 

therefore, has moderate mineral resource potential for uranium, thorium, copper, and vanadium. No evidence of the 

presence of other metals related to deposition, structure, or 

intrusions was observed. Oil is produced in the region 

from the Paradox Member of the Hermosa Formation and 

from the Lower Mississippian Leadville Limestone, both of

38° 

37' 

30H

109°30" 109°22'30"

ARCHES NATIONAL 

i 191 L MONUMENT

APPROXIMATE BOUNDARY

OF

c MILL CREEK CANYON 

 -""yon WILDERNESS STUDY AREA 

(UT-060-139A)

\:\v A 

%> %

38° 

30'

Figure 1. Index map showing location of Mill Creek Canyon Wilderness Study Area, Grand County, Utah.

E2 Mineral Resources of Wilderness Study Areas Upper Colorado River Region, Utah
which are known to be present at depth beneath the study 

area. The same porous rocks that could contain oil and gas 

also could contain carbon dioxide gas and, less likely, helium gas. The resource potential is moderate for oil and gas 

and for carbon dioxide gas and is low for helium gas in the 

entire study area. No geothermal springs or wells were 

observed or are known to be present in the study area, and 

no evidence of geothermal activity was seen. The National 

Oceanic and Atmospheric Administration (1980) reported 

that the regional heat flow over the area is low, and therefore 

the entire study area has low resource potential for geothermal energy.

Vegetation on the mesas in the western parts of the study 

area consists of sagebrush and grasses; sagebrush (Artemisia 

tridentatd) is the dominant species. The higher elevations 

to the east, including all ridges and canyons, are vegetated 

with a pifton-juniper climax community that consists of juniper (Juniper utahensis, J. scopulorum et spp.) and pifion 

pine (Pinus edulis et spp.). The zones between wooded areas 

support sparse grass, herbs, and small shrubs including 

Mormon tea (Ephedra sp.), sagebrush, blackbrush 

(Coleogyne sp. and Ceanothus greggi), and squawbrush 

(Rhus trilobata). Yucca (Yucca sp.) and cacti, including 

pricklypear (Opuntia sp.), are common.

INTRODUCTION

This mineral survey was requested by the U.S. Bureau of Land Management and is the result of a cooperative 

effort by the U.S. Geological Survey and the U.S. Bureau 

of Mines. An introduction to the wilderness review process, 

mineral survey methods, and agency responsibilities was 

provided by Beikman and others (1983). The U.S. Bureau 

of Mines evaluates identified resources at individual mines 

and known mineralized areas by collecting data on current 

and past mining activities and through field examination of 

mines, prospects, claims, and mineralized areas. Identified 

resources are classified according to a system that is a 

modification of that described by McKelvey (1972) and 

U.S. Bureau of Mines and U.S. Geological Survey (1980). 

U.S. Geological Survey studies are designed to provide a 

scientific basis for assessing the potential for undiscovered 

mineral resources by determining geologic units and structures, possible environments of mineral deposition, presence 

of geochemical and geophysical anomalies, and applicable 

ore-deposit models. Goudarzi (1984) discussed mineral assessment methodology and terminology as they apply to 

these surveys. See "Appendixes" for the definition of levels 

of mineral resource potential and certainty of assessment 

and for the resource/reserve classification.

Location and Physiography

The Mill Creek Canyon Wilderness Study Area is 

approximately 9,780 acres in size, and its western end is 2 

mi east of the city of Moab, Utah (fig. 1). The terrain is 

generally steep and rugged; elevations range from about 

7,300 ft near Wilson Mesa to about 4,800 ft at the mouth of 

Mill Creek canyon. Access to the study area is by U.S. 

Highway 191 on the southwest and the Sand Flats Road on 

the north and east. Access within the study area is by fourwheel-drive vehicle on the Mill Creek canyon jeep trail 

(Barnes, 1986), by mountain bicycle, and by foot The 

climate is semiarid; mean annual precipitation of 10 to 15 

in. falls mostly during thunderstorms that cause flash floods.

Procedures

The U.S. Geological Survey conducted detailed field 

investigations of the Mill Creek Canyon Wilderness Study 

Area in the summer of 1988. This work included making a 

detailed geologic map at the scale of 1:24,000, collecting 

geochemical and petrologic samples, and examining outcrops 

for evidence of mineralization. The generalized geology of 

the study area (fig. 2) is modified from Baker (1933).

U.S. Bureau of Mines personnel reviewed literature 

concerning mining and geology of the region. In addition, 

U.S. Bureau of Land Management records were reviewed 

for mining claim information and oil and gas leases and 

lease applications.

In September 1988, two U.S. Bureau of Mines geologists spent 11 days conducting a field examination in and 

within 1 mi of the study area. Surface workings and selected 

outcrops were sampled. A total of 7 samples was collected 

during the field investigation; five samples (MCC 3-7) were 

collected inside the study area and two (MCC 1-2) were 

collected just outside the east boundary. One sandstone 

sample (MCC 3) was analyzed for characteristics necessary 

for its use as an industrial material. The remaining samples 

were analyzed by neutron activation for 34 elements including gold and silver. Bondar-Clegg and Company, Lakewood, 

Colo., conducted the analyses.

Previous Studies

Overview geologic reports of the region and of nearby 

areas include Hintze's (1980) geologic map of Utah, geologic 

maps of Arches National Park (Doelling, 1985; Lohman, 

1975; Baars, 1983b), and geologic maps of Canyonlands 

National Park (Huntoon and others, 1982; Baars, 1983b). 

Other geologic reports on the region include those by 

McKnight (1940), Hemphill (1955), Baars (1983a), and 

Stokes (1969; 1987); geologic reports of local interest were 

published by Barnes (1978) and Vreeland (1976a, b). Reports on the stratigraphy include those by Stewart and others (1972a, b), Richmond (1962), and Padian (1989).

Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand County, Utah E3
109°30' 109°25'

.^1*3?" APPROXIMATE B,£>

. EXPLANATION I Area having high mineral resource potential (H) for potash and

halite, and for stone or gold where indicated, and moderate(M) or low (L) mineral resource potential for othercommodities as indicated

Levels of certainty of assessment

B Data only suggest level of potential C Data give good indication of level o 

D

Data only suggest level of potential

Data give good indication of level of potentialData clearly define level of potential
EXPLANATION Continued

Commodities

Au Placer gold 

K

CO2 Carbon dioxide gas O/G

Cu Copper StnGeo Geothermal energy U/ThHal Halite 

V

He Helium gas

Potash 

Oil and gas 

Building stone 

Uranium and thorium 

Vanadium

. i'

L

Correlation of map units

I Quaternary

n |

n3»r

t

I 

| 

n

i

Glen 

Canyon 

Group

Upper Jurassic

Middle Jurassic

Unconformity?

Jn

Jk

Jw

Lower Jurassic

Upper Triassic

> Middle(?) and Lower Triassic

Lower Permian

Upper 

Pennsylvanian

Description of map units

Qal Alluvium (Quaternary) Alluvial fan deposits and 

stream deposits of gravel, sand, silt, and clay

Jmsw Morrison Formation, Salt Wash Member (Upper 

Jurassic) Massive fine-grained sandstone

Jmt Morrison Formation, Tidwell Member (Upper Jurassic) Red shale and siltstoneJem Entrada Sandstone, Moab Tongue (Middle Jurassic) Massive white medium-grained friable 

sandstone

Jes Entrada Sandstone, Slick Rock Member (Middle 

Jurassic) Massive cross-bedded banded orange 

and white sandstone

J ed Entrada Sandstone, Dewey Bridge Member (Middle 

Jurassic) Red siltstone and shale

J n Navajo Sandstone (Lower Jurassic) Fine- to medium-grained cross-bedded quartz sandstoneJk Kayenta Formation (Lower Jurassic) Sandstone 

with minor conglomerate, siltstone, limestone, 

and shale

Jw Wingate Sandstone (Lower Jurassic) Fine-grained 

quartzose cross-bedded calcareous sandstone

"fcc Chinle Formation, undivided (Upper Triassic) Variegated clay-rich sandstone and siltstone"fcm Moenkopi Formation, undivided (Middle(?) and 

Lower Triassic) Reddish-brown ripple-marked 

cross-laminated siltstone and fine-grained sandstone

PC Cutler Formation (Lower Permian) Cherty chalky 

limestone, siltstone, anhydrite, claystone, conglomerate, and massive crossbedded arkosic sandstone interbedded with lenses of siltstone and 

sandy shale

IP hp Hermosa Formation, Paradox Member (Upper Pennsylvanian) Salts, anhydrite, and gypsum interbedded with black shales, undivided

Contact

 Fault Dashed where inferred

Figure 2. Mineral resource potential and generalized geology of Mill Creek Canyon Wilderness Study Area, Grand County, Utah. 

Base from U.S. Geological Survey, 1:62,500 quadrangles: Castle Valley, 1954; Moab, 1959, Utah. Contour interval 80 ft. Geology 

modified from Baker (1933).
Geophysical studies in the area include those by Byerly 

and Joesting (1959), Case and Joesting, (1972), Case and 

others (1963), Joesting and others (1966), and Hildenbrand 

and Kucks (1983). Structural geology of the area was studied by Hunt (1958), Williams (1964), and Baars and Doelling 

(1987).

Mineral and energy resources papers on the area include those by Baker (1933), Baker and others (1952), Williams (1964), Baars (1966), Dolton and others (1981), 

Molenaar and others (1982), and Molenaar and Sandberg 

(1983). Nearby wilderness study areas for which mineral 

resources papers have been published include Lost Spring 

Canyon Wilderness Study Area 25 mi to the north (Soulliere 

and others, 1988; Gese, 1987), Negro Bill Canyon Wilderness Study Area just to the northeast (Bartsch-Winkler and 

others, 1990), and Behind The Rocks Wilderness Study Area 

5 mi to the southwest across Spanish Valley (Patterson and 

others, 1988; Thompson, 1988).

Land-use management reports that pertain to the study 

area include the Resource Management Plan (U.S. Bureau 

of Land Management, 1985a) and its final environmental 

impact statement (U.S. Bureau of Land Management, 1983) 

as well as the statewide wilderness report (draft) (U.S. Bureau of Land Management, 1985b).

Acknowledgments

The authors greatly appreciate the cooperation of Peter 

Christensen, Lynn Jackson, Brent Northrup, Terry 

McParland, David Minor, Max Day, and Russell Van Koch 

of the U.S. Bureau of Land Management who gave support 

and use of their facilities. Fran Barnes provided information 

on local field conditions and access. Christine TurnerPeterson helped by discussing uranium resources. Information supplied by Philip Gramlich of Moab concerning gold 

occurrences in alluvium along the east boundary of the study 

area is greatly appreciated.

APPRAISAL OF IDENTIFIED RESOURCES

By Michael E. Lane 

U.S. Bureau of Mines

Mining History

No signs of mining activity were found in the Mill 

Creek Canyon Wilderness Study Area; two small pits are 

adjacent to the east boundary. The nearest mining district 

is about 7 mi northeast of the study area in the La Sal 

Mountains. Lode mining claims extend into the western 

part of the study area. Placer claims along Mill Creek 

cover a large part of the study area (Lane, 1989).

Appraisal of Sites Examined

Gold was detected in six samples from detrital material that consists of alluvial gravels and eolian sand and silt 

along the east edge of the Mill Creek Canyon Wilderness 

Study Area. Sample MCC 1 contains 675 parts per billion 

(ppb) gold (0.020 ounces per short ton, oz/st) and sample 

MCC 4 contains 575 ppb gold (0.017 oz/st). The other 

samples contain between 14 and 86 ppb gold. These gravels 

are only present along the east edge of the study area, and 

significant concentrations of gold are not likely to be present 

elsewhere (Lane, 1989). The gold-bearing gravels are between 6 in. and 30 ft thick (Philip Gramlich, oral commun., 

1988) and extend about 1,000 ft between the east boundary 

and the canyon rim. Detailed measurements of the thickness 

of the gravels by trenching or drilling would be required to 

determine if gold resources are present. Eolian sand deposits are abundant in the study area (Richmond, 1962) but are 

not considered economic because similar deposits occur 

closer to possible markets.

A sandstone sample (MCC 3) collected in the study 

area was determined to be protoquartzite (containing 75-95 

percent silica, SiO2). This sandstone is not suitable as glass 

sand because the SiO2 content is too low and the amounts 

of iron (FeO2) and aluminum (ALp^ oxides are too high 

(Lane, 1989). Glass sand generally requires an SiO2 content 

of at least 93 to 99 percent, an FeO2 content of 0.06 percent 

or less, and an ALO3 content between 0.1 and 0.5 percent 

(Bates, 1960; Coope and Harben, 1977). Sand to be used 

as foundry sand requires an SiO2 content of at least 88 percent (Coope and Harben, 1977).

Sandstone in the Mill Creek Canyon Wilderness Study 

Area may be suitable for use as foundry, fracturing, or filtering sand; however, characteristics for these uses vary. 

The sandstone is unlikely to be developed because similar 

deposits occur nearer to possible markets.

Energy Resources

The study area is in a terrane rated as having medium 

potential for the occurrence of oil and gas (Molenaar and 

Sandberg, 1983). Oil and gas leases cover a very small part 

of the study area. The region was investigated thoroughly 

for uranium occurrences during the uranium boom of the 

1950's; no uranium occurrences were found. No geothermal activity is known in the wilderness study area.

Conclusions

No mineral resources were identified in the Mill Creek 

Canyon Wilderness Study Area. Analysis of the samples 

collected in and near the study area show gold in detrital 

material in the eastern part. Additional fieldwork including

E6 Mineral Resources of Wilderness Study Areas Upper Colorado River Region, Utah
possible trenching or drilling is needed to determine if a 

resource exists.

Eolian sand and sandstone occur in the study area and 

may be suitable as foundry, fracturing, or filtering sand. It 

is unlikely these will be developed because similar deposits 

are readily available elsewhere nearer possible markets.

Oil and gas leases cover only a very small pan of the 

study area. No geothermal resources are known to exist in 

the study area.

ASSESSMENT OF MINERAL RESOURCE 

POTENTIAL

By Michael F. Diggles, James E. Case, 

Harlan N. Barton, and Joseph S. Duval 

U.S. Geological Survey

Geology

The Mill Creek Canyon Wilderness Study Area is 

within the Paradox Basin fold and fault belt of the Colorado 

Plateau physiographic province. It is underlain by the 

northeastern limb of the Moab Valley-Spanish Valley salt 

anticline that collapsed when the upper pan of the salt core 

was dissolved and removed by ground water (Baars and 

Doelling, 1987). The rock units exposed within the study 

area consist mainly of subhorizontal beds of Jurassic sandstone and minor amounts of shale and siltstone (fig. 2). 

Sedimentary rock units as old as Cambrian may underlie 

the area at depth. The Precambrian basement beneath the 

study area is probably about 7,000 ft below sea level.

Stratigraphy

Although no rock units older than Early Jurassic crop 

out within the study area, older subhorizontal rocks crop 

out in the general region and (or) underlie the study area at 

depth. The oldest of these rocks are Precambrian igneous 

and metamorphic basement rocks. The oldest strata overlying the basement rocks consist of Cambrian quartzite and 

shale, Devonian limestone, dolomite, siltstone, shale, and 

sandstone, and Mississippian limestone and dolomite. The 

Cambrian rocks consist of the Ignacio Quartzite and Ophir 

Shale. The Devonian rocks consist of the Aneth and Elbert 

Formations and the Ouray Limestone (Gustafson, 1981). 

The Aneth is a dark-gray siltstone that includes lighter colored dolomites and is as thick as 200 ft. The Elbert consists 

of a basal sandstone and an upper dolomite, green and red 

shale, and sandstone; the combined thickness is as much as 

600 ft. The Ouray is a massive limestone and dolomite that 

has some thin green shale and is as thick as 150 ft. The 

Lower Mississippian Leadville Limestone is a light-colored 

limestone and dolomite that is as thick as 1,000 ft where

Late Mississippian to Early Pennsylvania!! erosion has left 

it intact (Gustafson, 1981).

The oldest of the post-Mississippian rocks, the Paradox Member of the Middle and Upper Pennsylvanian 

Hermosa Formation, is exposed near the study area (fig. 2). 

The Paradox Member consists of salts, anhydrite, and gypsum interbedded with black shales (Baars, 1983b). It ranges 

in thickness from 0 to 10,000 ft. This unit is being mined 

for potash by solution methods down river from Moab.

Permian rocks in the region are represented by the 

Cutler Formation (Lower Permian) and equivalent units; 

uranium has been mined from units within the Cutler. The 

Elephant Canyon Formation (equivalent to the lower part of 

the Cutler) consists of gray, cherty, chalky limestone, bluegray siltstone, and thin beds of anhydrite. It ranges in 

thickness from 400 to 1,500 ft. The Cutler Formation contains the Halgaito Tongue, Cedar Mesa Sandstone Member, 

Organ Rock Shale Member, and White Rim Sandstone 

Member. The Halgaito consists of reddish-brown and purple 

arkosic sandstone, red siltstone, claystone, and conglomerate and ranges in thickness from 400 to 700 ft The Cedar 

Mesa Sandstone Member consists of white to pale-reddishbrown massive crossbedded sandstone interbedded with 

lenses of red, gray, green, and brown sandstones. It ranges 

in thickness from 200 to 1,200 ft. The Organ Rock Shale 

Member consists of reddish-brown siltstone and sandy shale 

and ranges in thickness from 250 to 400 ft. The White Rim 

Sandstone Member consists of light-gray to yellowish-gray 

fine-grained crossbedded sandstone as thick as 250 ft It 

forms overhanging cliffs in Canyonlands National Park 

southwest of the study area (Baars, 1983b).

Triassic rocks exposed nearby but present only at depth 

beneath the study area consist of the Moenkopi Formation 

(Lower and Middle? Triassic) and the Chinle Formation 

(Upper Triassic) (O'Sullivan and MacLachlan, 1975). The 

Moenkopi Formation consists of the Hoskinnini Member, 

an unnamed lower slope-forming member, the Sinbad Limestone Member, a ledge-forming member, and an upper slopeforming member. The Moenkopi is generally reddish-brown, 

evenly bedded, ripple-marked cross-laminated siltstone and 

fine-grained sandstone. It ranges in thickness from 200 to 

500 ft. The Chinle Formation locally consists of the Moss 

Back Member, Petrified Forest Member, Owl Rock Member, 

and Church Rock Member. The Chinle Formation is generally variegated red, purple, green, and yellow bentoniticclay-rich sandstone and siltstone. Uranium has been mined 

from this formation.

The oldest rocks exposed at the surface within the 

study area are Jurassic in age and are about 900 ft thick. 

The oldest Jurassic units are in the Lower Jurassic Glen 

Canyon Group (Pipiringos and O'Sullivan, 1978), which 

consists of the Wingate Sandstone, the Kayenta Formation, 

and the Navajo Sandstone. The Wingate is a reddish-brown, 

massive, crossbedded, fine-grained, well-sorted sandstone 

that ranges in thickness from 30 to 435 ft. The uppermost

Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand County, Utah E7
part of the Wingate Sandstone is exposed in creek bottoms 

in the central part of the study area. This unit appears to be 

particularly resistant to erosion, and so its gentle westward 

dip tends to determine the gradient of the lower reaches of 

the creeks. Above the Wingate is the Kayenta Formation, 

which consists of reddish-brown to lavender, fine- to medium-grained sandstone with minor amounts of conglomerate, siltstone, limestone, and shale. It ranges in thickness 

from 200 to 260 ft. Padian (1989) reported fossils of the 

dinosaur Scelidosaurus (Jurassic) in the Kayenta from 

northern Arizona. The Kayenta is overlain by the Navajo 

Sandstone, a buff to pale-orange, well-sorted, fine- to medium-grained crossbedded sandstone that is about 300 ft 

thick. This unit is quarried for flagstone just west of the 

study area near Moab.

Overlying the Glen Canyon Group is the Entrada 

Sandstone (Middle Jurassic) that ranges in thickness from 

225 to 350 ft and contains three members: the Dewey 

Bridge Member, Slick Rock Member, and Moab Tongue. 

The Dewey Bridge Member is a red siltstone and shale; the 

Slick Rock Member is a salmon to white, fine-grained 

crossbedded sandstone; and the Moab Tongue is a massive 

white medium-grained friable sandstone.

Unconformably overlying the Entrada Sandstone is 

the Upper Jurassic Morrison Formation, which locally has 

three members. Only the lower two, the Tidwell and Salt 

Wash Members, are present in the study area. The Tidwell 

Member consists of reddish-brown, thin-bedded, ripplelaminated muddy sandstone and siltstone that ranges in 

thickness from 20 to 90 ft. The Salt Wash Member is a 

massive fine-grained sandstone, but only a thin remnant of 

it remains on top of the plateaus in the eastern pan of the 

study area. Uranium has been mined from the Salt Wash 

Member elsewhere, but no uranium was detected in this 

unit within the study area. Younger strata are not present in 

the study area due to erosion.

Quaternary deposits in the area consist of alluvium 

and talus. Along streams these sediments are poorly sorted 

mixtures of clay, silt, sand, and gravel. On the plateaus in 

the eastern pan of the study area, they include talus, alluvial 

fans, and fluvial deposits. Stream deposits on the east side 

of the study area were eroded from granitic rocks in the La 

Sal Mountains to the east and include local gold placers.

Structure

The Precambrian basement in the region of the study 

area was transected by northwest-trending faults and rifts 

about 1,700 million years ago (Ma). Cambrian through 

Mississippian strata were deposited in low-lying parts of 

the region. In Pennsylvania!! time, the Uncompahgre Highland was uplifted east of the study area, and the adjacent 

Paradox basin held a sea into which sediments including 

salt were deposited. Accumulating clastic overburden from 

the east caused the salt to flow against the basement structures and upward along the basement fault blocks to form 

salt anticlines (Elston and others, 1962). Subsequent diapirism caused the salt to rise as much as 10,000 ft The 

overlying strata collapsed when 3,000 to 6,000 ft of the 

evaporites were dissolved and removed by the action of 

ground water (Baars and Stevenson, 1981). Moab Valley 

and Spanish Valley were formed by the collapse of the 

Moab Valley-Spanish Valley salt anticline, and Castle Valley was formed by the collapse of the Castle Valley salt 

anticline.

Geochemistry

Methods and Background

A reconnaissance geochemical survey was conducted 

in Mill Creek Canyon Wilderness Study Area during May 

1988 to aid in the mineral resource assessment Minus-80- 

mesh stream sediments, heavy-mineral panned concentrates 

derived from stream sediments, and rocks were selected as 

sample media. Stream-sediment samples represent a composite of rock and soil exposed in the drainage basin upstream. Their analysis provides information that helps 

identify those basins containing unusually high concentrations of elements that may be related to mineral occurrences. 

Chemical analysis of heavy minerals concentrated from 

stream sediments provides information about the chemistry 

of certain high-density, resistant minerals eroded from rocks 

exposed in the drainage basin upstream. The removal of 

most of the rock-forming silicates, clays, and organic material allows determination of some elements in the concentrate 

that are often not detectable in bulk stream sediments by 

the analytic methods available. Some of these elements can 

be constituents of minerals related to ore-forming processes.

Four rock samples were collected to provide information on geochemical background concentrations and to check 

for possible mineralization. Visibly altered and mineralized 

samples that might disclose suites of elements associated 

with mineralization were not found.

Bulk stream-sediment and heavy-mineral-concentrate 

samples were collected from active alluvium from 19 firstor second-order ephemeral streams within drainage basins 

ranging from 0.2 to 2.0 mi2 in area. Sample-collection sites 

were selected in Mill Creek, North Fork of Mill Creek, Rill 

Creek, Burkholder Draw, and their tributary streams.

Sample Analysis

Stream-sediment, heavy-mineral-concentrate, and rock 

samples were all analyzed using a semiquantitative emission spectrographic method (Grimes and Marranzino, 1968) 

for the following 37 elements: antimony, arsenic, barium, 

beryllium, bismuth, boron, cadmium, calcium, chromium, 

cobalt, copper, gallium, germanium, gold, iron, lanthanum,

E8 Mineral Resources of Wilderness Study Areas Upper Colorado River Region, Utah
lead, magnesium, manganese, molybdenum, nickel, niobium, 

palladium, phosphorous, platinum, scandium, silver, sodium, 

strontium, thorium, tin, titanium, tungsten, vanadium, 

yttrium, zinc, and zirconium. In addition, stream-sediment 

and rock samples were analyzed for antimony, arsenic, bismuth, cadmium, gold, thorium, uranium, and zinc by specific chemical and instrumental methods (Centanni and 

others, 1956; Thompson and others, 1968; Motooka and 

Grimes, 1976; O'Leary and Meier, 1986; Crock and others, 

1987). Analytical data, locations of sample-collection sites, 

analysis method references, detection limits, and a detailed 

description of the sampling and analytical techniques are 

given in a report by Bullock and others (1990).

Results and Interpretation

Anomalous values, defined as being above the upper 

limit of normal background values, were determined for 

each element by inspection of the analytical data rather 

than by statistical techniques. Only 14 stream-sediment 

and heavy-mineral-concentrate samples and 4 rock samples 

were collected, and many elements had only a few measurable occurrences. For some elements (silver, gold, molybdenum, tin, tungsten) any occurrence above the detection 

limit would be considered anomalous.

The Jurassic sedimentary rocks exposed in the study 

area are barren, and the geochemical survey did not disclose 

any near-surface metallic mineralization. Only two heavymineral-concentrate samples contain anomalous concentrations of elements; both are from sites outside the wilderness 

study area. The concentrate from site NB035 contains 100 

parts per million (ppm) gold. This site is at the head of the 

North Fork of Mill Creek and the site of a recent gold-placer 

operation. It is approximately 0.5 miles east of the wilderness 

study area in the Manti-La Sal National Forest A second 

concentrate contains minor amounts of copper (70 ppm) and 

lead (1,000 ppm). This site, NB037, is at the head of a 

tributary to Burkholder Draw and east of the road on Wilson 

Mesa. No stream-sediment or rock samples from within the 

study area contain anomalous concentrations of elements.

Geophysical Studies

By combining data from deep drill holes and depth 

estimates from aeromagnetic data, a map was prepared mat 

shows schematic contours of the Precambrian basement in 

the region including the Mill Creek Canyon Wilderness 

Study Area (fig. 3; Bartsch-Winkler and others, 1990, fig. 

4; Case and Joesting, 1972). Southwest of the Moab Valley-Spanish Valley anticline, drill holes bottomed in Mississippian to Cambrian strata at depths ranging from 1,515 

to 2,520 ft below sea level; a drill hole in the Spanish 

Valley salt anticline bottomed in Mississippian rocks at 3,523 

ft below sea level. A drill hole just north of the study area

bottomed in Devonian rocks at 5,882 ft below sea level, 

and a drill hole on the northeast flank of Castle Valley salt 

anticline penetrated about 3,000 ft of evaporites and bottomed in Cambrian strata at 6,905 ft below sea level.

Because the deep Mississippian to Cambrian stratigraphy is relatively well known from many drill holes to the 

south and west, it is possible to estimate the elevation of the 

Precambrian surface. Thickness of Mississippian to Cambrian strata in the Lisbon Valley area, 30 mi southeast of the 

study area, ranges from 1,675 to 1,855 ft. The Precambrian 

surface dips northwestward in the region at depths of 3,000 

to 10,000 ft below sea level (fig. 3). In the study area, the 

Precambrian basement is probably about 7,000 ft below sea 

level. The well on the southwest flank of Spanish Valley 

penetrated about 5,800 ft of the Paradox Member of the 

Pennsylvanian Hermosa Formation, presumably evaporites 

with some shale and limestone, above Mississippian strata.

Aeromagnetic Data

Aeromagnetic surveys over the Mill Creek Canyon 

Wilderness Study Area and vicinity were flown at two different flight elevations: the eastern part was flown at an 

elevation of about 12,500 ft, flightline spacing about 1 mi 

(Case and others, 1963). The western part was flown at an 

elevation of about 8,500 ft, flightline spacing about 1 mi 

(Joesting and others, 1966). Four flightlines cross the study 

area. Subsequently, the magnetic data in the western part 

were continued mathematically upward to 12,500 ft, and a 

map was prepared (fig. 4; Hildenbrand and Kucks, 1983).

Anomalies on the original map, flown at 8,500 ft, 

diminish somewhat in amplitude when continued upward to 

12,500 ft, but they retain their shapes. Comparison of figures

3 and 4 shows the intrabasement (Precambrian) origin -for 

most of the magnetic anomalies of the region. High-amplitude, steep-gradient anomalies in the eastern part of figure

4 are produced by the Late Cretaceous-early Tertiary 

laccolithic intrusions of the La Sal Mountains. No sources 

of magnetic anomalies in the Phanerozoic sedimentary sequence have been identified.

The magnetic field is relatively smooth over the study 

area itself: contours show a south-plunging positive nose 

over the central part of the study area and negative reentrants over the eastern and western parts of the area. Values increase northward by 20 to 30 gammas across the 

study area. These magnetic features are probably related to 

a much larger closed magnetic high about 12 to 15 mi 

northeast of the study area. This high is most likely produced by a very deep (10,000 ft below sea level, or more) 

magnetic body within the Precambrian basement.

Gravity Data

Few gravity stations were established in the study 

area, but stations north and south of the area provide control

Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand County, Utah E9
on the regional gravity anomaly field and trends of anomalies 

across the study area (fig. 5). The gravity data were reduced assuming a reduction density of 2.5 grams per cubic 

centimeter (g/cm3); terrain corrections were calculated to a 

distance of 4.1 mi or farther. Details are provided in reports 

by Case and others (1963), Joesting and others (1966), and 

Hildenbrand and Kucks (1983). Gravity anomalies are regarded as accurate to about 2 milligals (mGal) with respect 

to the local base network.

The southwest side of the study area parallels the 

edge of relative negative anomalies over the northeastern 

pan of the Spanish Valley salt anticline; the eastern part of 

the study area coincides with part of a positive gravity nose 

between the northwest-trending lows over the Castle Valley

APPROXIMATE BOUNDARY

OF

MILL CREEK CANYON 

\ WILDERNESS STUDY AREA , 0< 

(UT-060-139A)

38°15'

Figure 3. Schematic contours on Precambrian surface in vicinity of Mill Creek Canyon 

Wilderness Study Area, Utah. Circles indicate drill holes that bottomed in Pennsylvanian or 

older rocks (Case and Joesting, 1972). Numbered circles indicate bottom depth of holes and 

age of rocks at bottom: , Cambrian; D, Devonian; M, Mississippian. Contour interval 1,000 

ft, datum is mean sea level. Heavy dashed lines show approximate boundaries of salt 

anticlines. E-E' is line of section for fig. 6; Bartsch-Winkler and others (1990).

E10 Mineral Resources of Wilderness Study Areas Upper Colorado River Region, Utah
and Moab Valley-Spanish Valley salt anticlines. Two-dimensional gravity models were previously constructed along 

two lines near the study area: one line 2 mi northwest of 

the study area crosses the Moab Valley salt anticline, and 

the other starts at the north edge of the study area and 

crosses the Castle Valley salt anticline (Bartsch-Winkler 

and others, 1990, fig. 6; Case and Joesting, 1972). The salt 

core of the Moab Valley salt anticline has a vertical amplitude of about 9,000 ft on the model, assuming a mean density contrast of - 0.35 g/cm3 between the salt and the adjacent strata. Subsequent drill data suggest that the amplitude 

varies from about 6,000 to 8,000 ft. The amplitude of the 

salt core of Castle Valley anticline is about 8,000 ft, assuming a density contrast of- 0.3 g/cm3.

A schematic gravity model across the Spanish Valley 

salt anticline has been constructed using the available drill 

holes as a partial control on salt thickness (fig. 6). Because 

only a few gravity stations were established near the line of

109°30'

38°30'

APPROXIMATE BOUNDAR

Of

MILL CREEK CANYON

WILDERNESS STUDY AREA

(UT-060-139A)

1090 15'

38°15'

Figure 4. Residual total-intensity aeromagnetic map of vicinity including Mill Creek Canyon 

Wilderness Study Area, Utah. Contour interval 10 gammas. Hachures indicate closed areas 

of lower magnetic intensity. Original magnetic data were continued mathematically upward 

to elevation of 12,500 ft From Hildenbrand and Kucks (1983) and Patterson and others 

(1988).

Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand County, Utah Ell
section, anomaly values were taken from the contour maps. 

The following assumptions were made in construction of the 

model: the evaporite sequence has a mean density contrast of 

- 0.35 g/cm3; the base of the evaporite sequence is planar (an 

unlikely assumption because drilling and geophysical data for 

large presalt structures for other salt anticlines of the Paradox 

basin do not indicate planar bases); and the residual anomalies 

were produced by subtracting a planar regional field from the 

Bouguer anomaly field. Some larger discrepancies between 

the residual anomalies and the calculated anomalies, southwest of Spanish Valley and at the northeast end of the section, may be due to presalt structures, to intrabasement density 

contrasts, or to variations in density contrasts within the salt 

itself or within the overlying sedimentary sequence. Note, 

however, that these differences are generally less than 2 mGal, 

the probable error in the residual Bouguer anomalies.

From the combined drill-hole and gravity data, it appears that the Spanish Valley salt anticline is asymmetrical, 

having a steeper northeastern flank. The geophysical data 

and interpretations, especially the gravity data, are pertinent

MILL CREEK CANYON 

WILDERNESS STUDY AREA

(UT-060

109°15'

38°30'

38° 15'

Figure 5. Bouguer anomaly map of region including Mill Creek Canyon Wilderness Study 

Area, Utah. Contour interval 2 milligals. Hachures show closed areas of lower gravity 

values. Dots indicate locations of gravity stations. Some surficial structural features are 

shown. Modified from Hildenbrand and Kucks (1983) and Patterson and others (1988). 

Gravity model along E-E' shown in figure 6.

El 2 Mineral Resources of Wilderness Study Areas Upper Colorado River Region, Utah
to evaluation of the potential resources for potash and oil 

and gas of the study area; however, they provide little information about near-surface metallic mineral deposits.

Assessment of Mineral Resource Potential

Potash and halite are present in the Paradox Member 

of the Hermosa Formation. This member is present at a 

depth of more than 8,000 ft (fig. 6) within the study area. 

Solution mining of potash from this unit is presently underway at the Cane Creek mine, down river from Moab (Nigbor, 

1982). At that site, however, the water necessary for such 

mining is abundant. Finding a water supply for such an 

operation within the study area may present a problem. 

There is, nonetheless, high mineral resource potential, 

certainty level C, for potash and halite in the entire study 

area. Gypsum and bentonite are also produced from the 

Paradox but only where the unit can be mined by direct 

access rather than by solution mining.

The Navajo Sandstone is presently being quarried for 

flagstone for building materials in the lower reaches of Mill 

Creek outside the study area (Terry McParland, U.S. Bureau of Land Management, Moab District Office Geologist, 

oral commun., 1988). The resource potential is high, certainty level D, for flagstone in low-lying areas underlain by 

the Navajo within the study area.

Gold is present in placer claims east of the study area 

on Wilson Mesa and is in gravel deposits derived from 

granitic terrane of the La Sal Mountains 4 mi to the east. In 

Pleistocene time, the host streams crossed parts of what is 

now Wilson Mesa within the study area. The top of Wilson 

Mesa, therefore, has high resource potential, certainty level 

D, for small placer deposits of gold.

Uranium is mined in nearby areas from the Cutler, 

Chinle, and Morrison Formations. Part of the Morrison is 

present in the upper pan of the plateaus in the eastern part 

of the study area, and the other two units are present at 

depth beneath the study area. No uranium was reported 

from the limited drill data in and near the study area, and

Southwest

E

Northeast

-16

-24

6000

Sea

level

-6000 -.

Cane Creek anticline Spanish Valley Mill Creek Canyon 

Wilderness Study Area

Pre-Paradox sedimentary rocks

'.'?i^'~}/'< o'^vri-M&O.-ffi Vrr'oV^'.^i>" .^/V/'r /j'r1 /- 77 L'fr"ir'CriyjVx^oVo.V\-"^ -1. -^u ^.V/aT-r^T^'r^

16 24 32 40 48

FEET, IN THOUSANDS

56 64 72 80 86

Figure 6. Schematic gravity model and section across Spanish Valley and Mill Creek Canyon Wilderness Study Area, Utah. 

Model along line £-£' of figure 3; +, point of surface at which gravity anomaly was calculated. Drill holes and extent of study area 

projected to line £-£'. Gravity effects of thickened salt were not calculated at southwest end of section.

Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand County, Utah El 3
no uranium or thorium was detected in geochemical samples 

from the surface streams in the study area or from testing 

with a scintillometer during field mapping. However, it is 

possible that uranium- and (or) thorium-bearing zones within 

the three units may be present below the surface. Zones 

from which uranium is mined typically have also produced 

vanadium from vanadium silicates and copper from chalcopyrite, bornite, and chalcocite. Therefore, the entire study 

area has moderate mineral resource potential, certainty level 

C, for uranium, thorium, copper, and vanadium.

Oil is produced in the region from the Middle and Upper 

Pennsylvania!! Paradox Member of the Hermosa Formation 

and from the Lower Mississippian Leadville Limestone, both 

of which are known to be present at depth beneath the study 

area. No oil and gas is known to be present beneath the study 

area, but leases cover part of it The same porous rocks that 

could contain oil and gas could also contain carbon dioxide 

gas and, less likely, helium gas. A well in Lisbon Valley 

contains trace amounts of helium, and other wells there contain 

moderate amounts of carbon dioxide gas. Due to the underlying strata and to the proximity to those wells, the resource 

potential of the entire study area is moderate, certainty level 

B, for oil and gas and for carbon dioxide gas and is low, 

certainty level B, for helium gas.

No evidence of the presence of other metals related to 

deposition, structure, or intrusions was observed. No geothermal springs or wells were observed or are known to be 

present in the study area, and no evidence of geothermal 

activity was seen. The National Oceanic and Atmospheric 

Administration (1980) reported that the regional heat flow 

over the area is low. The entire study area has low resource 

potential, certainty level B, for geothermal energy.

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policy: American Scientist, v. 60, p. 32-40.

McKnight, E.T., 1940, Geology of area between Green and Colorado Rivers, Grand and San Juan Counties, Utah: U.S. Geological Survey Bulletin 908,147 p., 13 plates.

Molenaar, C.M., and Sandberg, CA., 1983, Petroleum potential 

of wilderness lands in Utah, in Miller, EM., ed., Petroleum 

potential of wilderness lands in the Western United States: 

U.S. Geological Survey Circular 902-K, 14 p.

Molenaar, CA., Sandberg, C A, and Powers, R.B., 1982, Petroleum 

potential of wilderness lands, Utah: U.S. Geological Survey 

Miscellaneous Geologic Investigations Map 1-1545, scale 

1:1,000,000.

Motooka, J.M., and Grimes, D.J., 1976, Analytical precision of 

one-sixth order semiquantitative spectrographic analysis: U.S. 

Geological Survey Circular 738,25 p.

National Oceanic and Atmospheric Administration, 1980, Geothermal resources of Utah, [compiled from data provided by 

the Utah Geological and Mineralogical Survey]: U.S.

Department of Energy, Division of Geothermal Energy, scale 

1:1,000,000.

Nigbor, M.T., 1982, State of the art of solution mining for salt, 

potash, and soda ash: U.S. Bureau of Mines Open-File Report 

142-82,90 p.

O'Leary, R.M., and Meier, A.L., 1986, Analytical methods used 

in geochemical exploration, 1984: U.S. Geological Survey 

Circular 948,48 p.

O'Sullivan, RJJ., and MacLachlan, M.E., 1975, Triassic rocks of 

the Moab-White Canyon area, southeastern Utah: Four Corners Geological Society, 8th Field Conference, Canyonlands 

National Park, Utah, Guidebook, p. 129-141.

Padian, Kevin, 1989, Presence of the dinosaur Scelidosaurus indicates Jurassic age for the Kayenta Formation (Glen Canyon 

Group, northern Arizona): Geology, v. 17, p. 438-441.

Patterson, C.G., Toth, M.I., Case, J.E., Green, G.N., Barton, H.N., 

and Thompson, J.R., 1988, Mineral resources of the Behind 

the Rocks Wilderness Study Area, Grand and San Juan 

Counties, Utah: U.S. Geological Survey Bulletin 1754-B, 

p.Bl-B18.

Pipiringos, G.N., and O'Sullivan, R.B., 1978, Principal 

unconformities in Triassic and Jurassic rocks, western interior United States a preliminary survey: U.S. Geological 

Survey Professional Paper 1035-A, p. A1-A29.

Richmond, G.M., 1962, Quaternary stratigraphy of the La Sal 

Mountains, Utah: U.S. Geological Survey Professional Paper 

324,135 p., 6 plates.

Soulliere, S.J., Lee, O.K., Case, J.E., and Gese, D.D., 1988, Mineral resources of the Lost Spring Canyon Wilderness Study 

Area, Grand County, Utah: U.S. Geological Survey Bulletin 

1754-C, 12 p.

Stewart, J.H., Poole, F.G., and Wilson, R.F., 1972a, Stratigraphy 

and origin of the Chinle Formation and related Upper Triassic 

strata in the Colorado Plateau region: U.S. Geological Survey Professional Paper 690,336 p.

 1972b, Stratigraphy and origin of the Triassic Moenkopi 

Formation and related strata in the Colorado Plateau region: 

U.S. Geological Survey Professional Paper 691,195 p.

Stokes, W.L., 1969, Scenes of the plateau lands and how they came 

to be: Salt Lake City, Utah, Starstone Publishing Co., 66 p.

 1987, The geology of Utah: Utah Museum of Natural 

History Occasional Paper 6,280 p.

Thompson, C.E., Nakagawa, H.M., and Van Sickle, G.H., 1968, 

Rapid analysis for gold in geologic materials, in Geological 

Survey Research 1968: U.S. Geological Survey Professional 

Paper 600-B, p. B130-B132.

Thompson, J.R., 1988, Mineral investigation of the Behind the 

Rocks Wilderness Study Area, Grand and San Juan Counties, 

Utah: U.S. Bureau of Mines Open-File Report MLA 2-88, 

25 p.

U.S. Bureau of Land Management, 1983, Proposed Resource 

Management Plan and Final Environmental Impact Statement 

for the Grand Resource Area, Moab District, Utah: Washington, D.C., Government Printing Office, 269 p.

 1985a, Grand Resource Area Resource Management Plan: 

Washington, D.C., Government Printing Office, 106 p.

 1985b, Mill Creek Canyon WSA, in U.S. Bureau of Land 

Management, Utah BLM Statewide Wilderness Draft Environmental Impact Statement, Volume V, Southeast region: 

Washington, D.C., Government Printing Office, 26 p.

Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand County, Utah El 5
U.S. Bureau of Mines and U.S. Geological Survey, 1980, Prin- 1976b, Nature's bridges and arches. Volume 5, Vicinity of

ciples of a resource/reserve classification for minerals: U.S. Moab, Utah: Westminster, Calif., Robert H. Vreeland, 99 p.

Geological Survey Circular 831,5 p. Williams, P.L., 1964, Geology, structure, and uranium deposits of

Vreeland, R.H., 1976a, Nature's bridges and arches, Volume 1, the Moab quadrangle, Colorado and Utah: U.S. Geological

General information: Westminster, Calif., Robert H. Vreeland, Survey Miscellaneous Geologic Investigations Map 1-360,

64 p. scale 1:250,000.

El 6 Mineral Resources of Wilderness Study Areas Upper Colorado River Region, Utah
APPENDIXES
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.

IZ

LU

o

LU

A

U/A

UNKNOWN POTENTIAL

B

H/B

HIGH POTENTIAL

M/B

MODERATE POTENTIAL

UB

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, 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.

El 8 Mineral Resources of Wilderness Study Areas Upper Colorado River Region, Utah
RESOURCE/RESERVE CLASSIFICATION

ECONOMIC

MARGINALLY 

ECONOMIC

SUBECONOMIC

IDENTIFIED RESOURCES

Demonstrated

Measured

Resc

Indicated

:rves

Marginal 

Reserves

Demonstrated 

Subeconomic

Resources

i

Inferred

Inferred 

Reserves

Inferred 

Marginal 

Reserves

Inferred 

Subeconomic 

Resources

UNDISCOVERED RESOURCES

Probability Range

Hypothetical Speculative

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

Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand County, Utah El 9
GEOLOGIC TIME CHART

Terms and boundary ages used by the U.S. Geological Survey in this report

EON

Phanerozoic

Proterozoic

/Aid ICall

pre-Archean2

ERA

Cenozoic

Mesozoic

Paleozoic

Late Proterozoic

Middle Proterozoic

Early Proterozoic

Late Archean

Middle Archean

Early Archean

PERIOD

Quaternary

Neogene

Subperiod

Tertiary ,

ralcUgcnf?

Cretaceous

Jurassic

Triassic

Permian

Pennsylvanian 

Carboniferous

Mississippian

Devonian

Silurian

Ordovician

Cambrian

.......... (3800?)- - -

EPOCH

Holocene

Pleistocene

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Late

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

Late 

Middle 

Early

AGE ESTIMATES OF 

BOUNDARIES IN 

MILLION YEARS (Ma)

 0.010

 1.7

 5

 24

 JO

 55

 66

96

1 1Q

 205

~7/in

f^3\l

 -330

 360

 410

"f J»J

tJ\J\J

tj/ \j

j\j\j

I bUU

A*tJ\J\f

 3000

J*tV/W

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

Informal time term without specific rank.

E20 Mineral Resources of Wilderness Study Areas Upper Colorado River Region, Utah
Mineral Resources of

Wilderness Study Areas 

Upper Colorado River Region, Utah

This volume was published as separate chapters A-E

U.S. GEOLOGICAL SURVEY BULLETIN 1754
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director
CONTENTS

[Letters designate the separately published chapters]

(A) Mineral Resources of the Indian Creek, Bridger Jack Mesa, and Butler Wash

Wilderness Study Areas, San Juan County, Utah, by Charles G. Patterson, Margo I. 

Toth, James E. Case, Harlan N. Barton, Gregory N. Green, Russell A. Schreiner, 

and John R. Thompson.

(B) Mineral Resources of the Behind the Rocks Wilderness Study Area, Grand and San 

Juan Counties, Utah, by Charles G. Patterson, Margo I. Toth, James E. Case, 

Gregory N. Green, Harlan N. Barton, and John R. Thompson.

(C) Mineral Resources of the Lost Spring Canyon Wilderness Study Area, Grand 

County, Utah, by Sandra J. Soulliere, Greg K. Lee, James E. Case, and Diann D. 

Gese.

(D) Mineral Resources of the Negro Bill Canyon Wilderness Study Area, Grand

County, Utah, by Susan Bartsch-Winkler, James E. Case, Harlan N. Barton, Joseph

S. Duval, and Michael E. Lane. 

(E) Mineral Resources of the Mill Creek Canyon Wilderness Study Area, Grand

County, Utah, by Michael F. Diggles, James E. Case, Harlan N. Barton, Joseph S.

Duval, and Michael E. Lane.



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