The Conterminous United States Mineral 

Appraisal Program: Background Information 

to Accompany Folio of Geologic, 

Geochemical, Geophysical, and Mineral 

Resource Maps of the Choteau 1 ° x 2° 

Quadrangle, Montana 

The Conterminous United States Mineral 

Appraisal Program: Background Information 

to Accompany Folio of Geologic, 

Geochemical, Geophysical, and Mineral 

Resource Maps of the Choteau 1 ° x 2° 

Quadrangle, Montana 

By Robert L. Earhart, David J. Grimes, Reinhard W. Leinz, and M. Dean Kleinkopf 

GEOLOGICAL SURVEY CIRCULAR 849 

1981 
United States Department of the Interior 

JAMES G. WATT, Secretary 

Geological Survey 

Doyle G. Frederick, Acting Director 

Library of Congress catalog-card No. 81-600053 

Free on application to Distribution Branch, Text Products Section, 

U. S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 
CONTENTS 

Page 

Abstract . . . . • . • • . . . . . . . . • . . • . . . . • • • • • . • . . . . . • • . . • . • • • • • • • • • • • . • • • • • • • • • • 1 

Introduction . . . . . . . . • • • • . . . . • . • • • • • . . . . • • . • • • • • • • • • • . . . • . . • . . . • • • . . • . • • • • 1 

Location and geography . • • • • • . • • . . . . . . • . . • . . . . . • • . . • . . . . . • • • . • • • • • • • • 1 

Sources of information . . . . . • • . • . . . . . . . • . . • . • • • • • • • • • • • • . . . . . • . . . • • • • • 2 

Present investigations . • . . . • • • • • • • • • . . • • . . . • • • . . • • • • • . • • • • • • • • • • • • • . • 2 

Descriptions of maps of the Choteau 1 °x 2° folio . . • • . • • • • • • . • • • • • • • • • • • • • • • • . 2 

Geologic maps • • • . • • . . . . • • • • • • • . . . . . . • . . • . • • • • • • • • • • • • • . • • • • • • . . . . . . 2 

Hydrocarbon potential map • . . . • • • . . . . . . . . . • . . • • • • • • • • • • . • • • . • . • • . . . . • 3 

Mineral resources map • • . • • • . • . . . . • . • • • • • • • • • • . • . • • • • • • • • • • • • • • • . . • . . 3 

Geochemical maps . • • . . . . . . • . . • • . . . . . . . . . . . . . . . . . . . . . . . • • • • • • • . • . . • • 3 

Aeromagnetic map . . • • • • • • . . . . . • . • • • . • . • . . . . . . . . . . . . . • . . • . • . • • • • . • • . 3 

Bibliography of the Choteau quadrangle . . . . . • • . . . • • • • • • • • • . • • • • • . . . . . . . . . . • • 3 

ll..LUSTRATION 

Figure 1. Index showing location of the Choteau and adjacent 

1 °x 2° quadrangles, Montana. • . . . . • • . • • • . • . . . . . . • . . • . . • . . . • . • . • • • • • • • • 1 

TABLE 

Table 1. Component maps of the Choteau quadrangle • • • • • • • • • • . . • • . . . . . • . . • • • 9 

III 

The Conterminous United States Mineral Appraisal Program: 

Background information to accompany folio of geologic, 

geochemical, geophysical, and mineral resource maps 

of the Choteau 1° x 2° Quadrangle, Montana 

By Robert L. Earhart, David J. Grimes, Reinhard W. leinz, and M. Dean Kleinkopf 

ABSTRACT 

The Choteau 1 °x 2° quadrangle in northwest 

Montana was studied by an interdisciplinary research 

team in order to appraise its mineral resource and 

hydrocarbon potential. The appraisal is based on field 

and laboratory investigations of the geology, geochemistry, and geophysics. The results of the investigations 

are published as a folio of maps, figures, tables, and 

accompanying discussions. This circular provides 

background information on the investigations and integrates the published components of the resource 

appraisal. A comprehensive bibliography cites both 

specific and general references to the geology, 

geochemistry, geophysics, and mineral deposits of the 

Choteau 1 °x 2° quadrangle. 

INTRODUCTION 

This circular, as well as a folio of separately 

published maps, is part of a series of U.S. Geological 

Survey reports that contain information on the mineral 

resources and mineral resource potential of the 

conterminous United States. The studies described in 

this circular include the Choteau 1 °x 2° quadrangle in 

Montana (fig. 1). This circular and the folio maps were 

compiled under the Conterminous United States Mineral Appraisal Program (CUSMAP). CUSMAP is 

intended to provide regional mineral appraisal 

information to assist in formulating a sound, longrange national minerals policy and to assist Federal, 

State, and local governments in making decisions that 

involve land-use planning. In addition, the products of 

CUSMAP are intended to increase geological, geochemical, and geophysical knowledge of the 

conterminous United States. In accomplishing these 

goals, the program provides a regional geologic and 

mineral resource framework for specific studies such 

as the mineral appraisal of wilderness areas and guidance for mineral exploration. 

Location and geography 

The Choteau 1 °x 2° quadrangle covers approximately 16,600 km 2 in northwestern Montana between 

1 

lat 47° and 48° N. and long 112° and 114° W. (fig. 1). 

The area straddles the front ranges of the northern 

Rocky Mountains; the eastern third is in the Great 

Plains physiographic province and the western twothirds is in the Northern Rocky Mountains province. 

The Continental Divide trends northerly through the 

approximate center of the quadrangle. Principal 

drainages east of the Divide are the Dearborn, Sun, 

and Teton Rivers; west of the Divide they are the West 

Fork Flathead, Blackfoot, and Swan Rivers. Altitudes 

within the quadrangle range from about 2, 700 m near 

the Continental Divide to about 1,100 m near the 

eastern boundary. The town of Choteau, the largest 

community in the quadrangle, is located on U.S. Highways 89 and 287 in the northeastern part. 

The eastern third of the quadrangle is accessible 

by numerous paved and graveled roads and the western 

part is accessible by a highway that follows the broad, 

Figure 1.-Index showing location of the Choteau and 

adjacent 1 °x 2° quadrangles, Montana. 
northerly trending Swan River-Clearwater River valley 

between the Swan and Mission Ranges. About onethird of the Choteau quadrangle is included in the 

National Wilderness Preservation System. The central 

part contains the Great Bear, Bob Marshall, and Scapegoat Wilderness Areas, in which access is permitted 

only by foot or horseback. The Mission Range, along 

the western boundary, includes the Mission Wilderness 

Area where use of motorized vehicles is also 

restricted. 

Sources of information 

The maps and interpretations included in the 

CUSMAP folio of the Choteau 1 °x 2° quadrangle (table 

1) are a product of numerous multidisciplinary studies 

conducted between 1957 and 1979. Studies prior to 

this period provided invaluable background information, particularly the geological reconnaissance studies 

of Chapman (1900), Walcott (1906; 1908; 1915), and 

Stebinger (1918). Numerous workers contributed to an 

understanding of the stratigraphy of the Paleozoic and 

Mesozoic rocks prior to 1957. Studies of the metalliferous deposits in the quadrangle by Pardee and 

Schrader (1933) provided the basis for many subsequent 

economic geology studies, and the mine production 

records which they compiled have been used along with 

more modern data on the mineral resource map in the 

Choteau folio (Earhart and others, 1980). 

Much of the information used in compiling the 

Choteau folio was generated from mineral resource 

studies by the U.S. Geological Survey and the 

U.S. Bureau of Mines of the wilderness and wildernesscandidate study areas. The wilderness studies began in 

1968 and were completed in 1978. 

Present investigations 

The present investigations began in 1957 with the 

geologic mapping of six 7 1/2-minute quadrangles in 

the Sun River Canyon area by Mudge (1965; 1966a; 

1966b; 1966c; 1967; 1968). The stratigraphy and structural geology of these quadrangles were discussd by 

Mudge (1972a; 1972b). Mudge (1968) conducted 

geological, geochemical, and geophysical studies in the 

southeastern part of the Lewis and Clark Range. 

Other mineral-resource studies from which much 

information is taken and incorporated in the CUSMAP 

studies include wilderness-related investigations 

(Mudge, Earhart, Watts and others, 1974; Mudge, 

Earhart, and Claypool, 1977; Mudge and Earhart, 1978; 

Mudge, Rice and others, 1978; Earhart and others, 

1977). Studies of the stratigraphy and structure of the 

northern Disturbed Belt were used in compiling the 

geologic and structural maps included in the folio 

(Mudge, Earhart, and Rice, 1977a; 1977b). The above 

investigations were supplemented with geological, 

geochemical, and geophysical studies in 1977 and 1978 

in order to provide complete coverage of the Choteau 

quadrangle. 

Aeromagnetic data were obtained by the U.S. 

Geological Survey in conjunction with regional studies 

in northwestern Montana (Mudge and others, 1968; 

Harrison and others, 1969; and Kleinkopf and Mudge, 

1972). These data were supplemented by aeromagnetic 

surveys flown in the southeastern part of the quadrangle in 1978 (U.S. Geological Survey, 1980a). 

2 

Gravity data were generated as a part of the 

mineral resource studies of wilderness areas (Mudge 

and others, 1975; Kleinkopf and others, 1978). These 

data were supplemented by the results of unpublished 

gravity surveys by D. M. Wilson throughout the 

remainder of the Choteau quadrangle. Although the 

gravity data are not included in the folio, unpublished 

interpretations of the gravity data were utilized in the 

preparation of the mineral resource map. 

DESCRIPTIONS OF MAPS OF THE CHOTEAU 

1°x 2° FOLIO 

Geologic maps-(OF-79-280, 79-863, and 79-719) 

The rocks in the Choteau quadrangle range from 

Proterozoic to Quaternary in age. Most of the rocks 

are of sedimentary origin. Locally the sedimentary 

rocks are intruded by stocks, dikes, and sills that range 

from Proterozoic to Tertiary in age. Glacial deposits 

of Pleistocene age cover large areas in the eastern 

part and occupy the major valleys elsewhere in the 

quadrangle. The western two-thirds of the quadrangle 

is structurally complex and contains numerous thrust 

faults, normal faults, and folds. 

The oldest rocks exposed are clastic and carbonate rocks assigned to the Belt Supergroup of 

Proterozoic age. The Belt rocks are regionally metamorphosed to the chlorite subfacies and are wiCiely 

distributed throughout the western two-thirds of the 

quadrangle. 

The Belt rocks are overlain by Paleozoic rocks 

that are predominantly limestone and dolomite. The 

Paleozoic rocks are best exposed along the Sawtooth 

Range which forms the mountain front in the eastcentral part of the quadrangle. They are also exposed 

at many places on and near the Continental Divide and 

along down-faulted blocks to the west of the Divide. 

Most of the eastern third of the quadrangle is 

underlain by Mesozoic rocks that consist mostly of 

mudstone, shale, and sandstone. The Mesozoic rocks 

are also exposed in north-trending narrow belts along 

the front range to as far west as the North Fork Sun 

River. 

Tertiary sedimentary rocks underlie small areas 

in the southern and western parts of the quadrangle 

and mostly consist of mudstone, shale, and conglomerate. Widespread glacial deposits of Pleistocene age 

are derived from continental glaciers in the eastern 

third of the area and from mountain glaciers to the 

west. Quaternary unconsolidated alluvial and colluvial 

deposits are widely distributed throughout the 

quadrangle. 

Igneous rocks occur locally throughout the quadrangle, but are most abundant in the southeastern 

part. Andesite and diorite sills of Proterozoic 1:1ge 

locally crop out in the western two-thirds of the quadrangle and are the oldest igneous rocks exposed in the 

area. Trachyandesite sills of Cretaceous age crop out 

in the central and north-central parts of the area, and 

Tertiary stocks, dikes, and sills, mostly of monzonitic 

to rhyolitic composition, crop out in the southeastern 

part. Volcanic and volcanic-sedimentary rocks of Cretaceous and Tertiary ages are also present in the 

southeast part. 

The dominant structural features in the Choteau 

quadangle are thrust faults, normal faults, and folds 

which are a part of the Northern Disturbed Belt-a 
north to northwesterly striking belt of highly deformed 

rocks that extends from the southeastern corner of the 

quadrangle through the east-central part to the north 

boundary. The rocks to the west of the Disturbed Belt 

contain broad, open folds and numerous normal 

faults. To the east, the rocks dip gently easterly. 

Hydrocarbon Potential Map (OF-80-24) 

Oil and gas are produced from wells to the north 

and east of the quadrangle. Gas has been located in 

the Northern Disturbed Belt in the north part of the 

quadrangle, and the results of present studies indicate 

a high potential for additional discoveries. 

Mineral Resources Map (MF-858A) 

Past mineral production in the Choteau quadrangle mostly consisted of base and precious metals and 

totaled about $25 million, all from the southeastern 

part. As of 1980, there were no producing mines in the 

quadrangle. A copper-molybdenum porphyry-type 

deposit in the southeastern part of the quadrangle is 

reported to be of economic size and grade (Miller and 

others, 1973), and the surrounding area has a high potential for the discovery of similar deposits. Occurrences of stratabound copper and silver are widespread 

in the Proterozoic rocks in the western two-thirds of 

the quadrangle. Silver-copper ore was produced from 

one stratabound deposit in the southern part, but the 

other known occurrences are of submarginal grade. 

Other mineral occurrences in the quadrangle include 

stratabound and replacement deposits of lead and zinc, 

base and precious metals in vein deposits, and strataform titaniferous magnetite deposits. 

Geochemical Maps (MF-858B, C, D, E, F) 

The geochemical maps contain data from geochemical surveys conducted by the U.S. Geological 

Survey in the Choteau quadrangle from 1968-1979. 

These data show the distribution and abundance of 

selected elements and delineate areas with anomalous 

concentrations. 

The geochemical studies consisted of the collection and analyses of 3,329 rock and 2,235 streamsediment samples and of the compilation and interpretation of the analytical data. All of the major rock 

types that crop out in the quadrangle were sampled. 

They include fresh unaltered rocks, which were analyzed in order to determine normal trace-element 

populations, and mineralized and altered rocks. 

Stream sediments were collected from most of the 

streams in the quadrangle from the finest-grained sediment available; where possible, they were taken from 

the most active part of the stream. 

All samples were prepared and analyzed by the 

U.S. Geological Survey in mobile laboratories at field 

camps or in laboratories in Golden, Colo. The rock 

samples were crushed, split, and ground to 0.1 mm in a 

pulverizer equipped with ceramic plates. The stream 

sediments were air dried and sieved to minus 0.18 mm 

in stainless-steel sieves. Most samples were analyzed 

for 30 elements by an optical emission-spectrographic 

method, for gold by an atomic absorption method, and 

for mercury by a vapor detector technique. 

3 

Geochemical data sets were merged and manipulated by a computer located at the U.S. Geological 

Survey Computer Center in Denver, Colo. The 

combined data set contains multi-element analyses and 

locations of all samples (Grimes and others, 1980), and 

is available on computer tape from the National Technical Information Service (McDanal and others, 1980). 

Data reduction, which eliminated duplicate sample 

sites and samples that were collected too close 

together to plot at a 1:250,000-map scale, was accomplished by dividing the quadrangle into a grid with 0.5-

km-square cells and selecting the maximum value for 

each chemical element and sample location within the 

cell. The resultant minor deviations in some of the 

sample locations are considered insignificant at the 

scale of the folio maps and have negligible effect on 

the delineation of anomaly patterns in the 

quadrangle. All of the geochemical distribution and 

abundance plots were produced on a flatbed plotter 

from the condensed rock and stream-sediment data 

sets and were plotted on a screened topographic and 

generalized geologic base map. The elements shown 

on these maps were selected on the basis of their 

associations with the types of mineral deposits that 

may occur in the quadrangle as suggested by the geology, and on the availability of analytical data from 

previous geochemical studies. 

Aeromagnetic Map (MF-858G) 

The aeromagnetic map of the Choteau quadrangle is a mosaic of six separate surveys flown by the 

U.S. Geological Survey to study regional structure and 

the magnetic character of the rocks in the upper part 

of the Earth's crust (Kleinkopf and Mttdge, 1972; U.S. 

Geological Survey, 1969; 1979; 1980a; 1980b). Aeromagnetic data support geologic mapping, and they 

provide a basis for the assessment of mineral resource 

potential in the subsurface. The configuration and location of buried intrusive bodies and the delineation of 

major faults and shear zones in the subsurface are 

interpreted from the magnetic data. Some of these 

features are reflected by magnetic trends associated 

with known mineralized localities. In the southeastern 

part of the quadrangle magnetic data are interpreted 

to reflect near-surface apophyses of buried intrusions 

that may contain porphyry-type, copper-molybdenum 

deposits. 

BffiLIOGRAPHY OF THE CHOTEAU t 0 x 2° 

QUADRANGLE 

*indicates reports of the CUSMAP project 

Alden, W. C., 1932, Physiography and glacial geology 

of eastern Montana and adjacent areas: U.S. 

Geological Survey Professional Paper 17 4, 133 p. 

Alpha, A. G., 1956, The Genou Trend of north-central 

Montana, in American Association of Petroleum 

Geologists-Rocky Mountain Section Geological 

Record, Feb. 1955: World Oil, v. 142, no. 1, p. 

79-82, 84. 

Armstrong, R. L., 1974, Magnetism, orogenic timing, 

orogenic diachronism in the Cordilleran from 

Mexico to Canada: Nature, v. 27, p. 348-351. 

Barksdale, J. D., 1951, Cretaceous glassy welded tuffs, 

Lewis and Clark County, Montana: American 

Journal of Science, v. 249, no. 6, p. 439-443. 
Berg, R. R., 1969, Bentonite in Montana: Montana 

Bureau of 1\Iines and Geology Bulletin 7 4, 34 p. 

Bevan, A. C., 1929, Rocky Mountain front in 

Montana: Geological Society of America 

Bulletin, v. 40, no. 2 p. 427-456. 

Brenner-Tourtelot, E. F., Meier, A. L., and Curtis, 

C. A., 1978, Lithium in rocks from the Lincoln, 

Helena, and Townsend areas, Montana: U.S. 

Geological Survey Open-File Report 78-430, 29 

p. 

Burchfiel, B. C., and Davis, G. A., 1975, Nature and 

controls of Cordilleran orogenesis, Western 

United States-Extensions of an earlier 

synthesis: American Journal of Science, v. 275-

A, p. 363-396. 

Chamberlin, R. T., 1945, Basement control in Rocky 

Mountain deformation: American Journal of 

Science, v. 243-A (Daly volume), p. 98-116. 

Chapman, R. H., 1900, Notes on the structure of the 

Rocky Mountains in the Lewis and Clark timber 

reserve, Montana: American Institute of Mining 

Engineers Transactions, v. 29, p. 153-156. 

Chelini, J. M., 1963, Metallic and industrial mineral 

resources-Stone, in Mineral and water resources 

of Montana: u.s:- 88th Congress, 1st session, 

Committee Print, p. 111-112. 

Clapp, C. H., 1932, Geology of a portion of the Rocky 

Mountains of northwestern Montana: Montana 

Bureau of Mines and Geology Memoir 4, 30 p. 

Clapp, C. H, and Deiss, C. F., 1931, Correlation of 

Montana Algonkian formations: Geological Society of America Bulletin, v. 42, no. 3 p. 673-696. 

Cobban, W. A., 1945, Marine Jurassic formations of 

Sweetgrass Arch, Montana: American 

Association of Petroleum Geologists Bulletin, v. 

29, no. 9, p. 1262-1303. 

1955, Cretaceous rocks of northwestern Montana: 

--Billings Geological Society 6th Annual Field Conference Guidebook, p. 107-119. 

Cobban, W. A., Erdmann, C. E., Lemke, R. W., and 

Maughan, E. K., 1959, Colorado group on Sweetgrass Arch, Montana: Billings Geological Society 

lOth Annual Field Conference Guidebook, p. 89-

92. 

__ 1959b, Revision of Colorado group on Sweetgrass 

Arch, Montana: American Association of Petroleum Geologists Bulletin, v. 43, no. 12, p. 

2786-2796. 

Coney, P. J., 1972, Cordillera tectonics and North 

American plate motion: American Journal of 

Science, v. 272, no. 7, p. 603-628. 

Connor, J. J., 1980, Geochemistry of copper-silver 

bearing sandstone in the Spokane Formation (Belt 

Supergroup), Rogers Pass area, western Montana 

abs. : Geological Society of America Abstracts 

with Programs. 

Defense Mapping Agency Aerospace Center, 1974, 

World relative gravity reference network, North 

America, Part 2: DMAAC Reference Publication 

25, with supplement updating gravity values to 

the International Gravity Standardization Net 

1971, 1635 p. 

Deiss, C. F., 1933, Paleozoic formations of northwestern Montana: Montana Bureau of Mines and 

Geology Memoir 6, 51 p. 

__ 1938, Cambrian formations and sections in part of 

Cordilleran trough: Geological Society of 

America Bulletin, v. 49, no. 7, p 1067-1168. 

4 

1939, Cambrian stratigraphy and trilobites of 

-- northwestern Montana: Geological Society of 

America Special Paper 18, 135 p. 

__ 1943a, Stratigraphy and structure of southwest 

Saypo quadrangle, Montana: Geological Society 

of America Bulletin, v. 54, no. 2, p. 205-262. 

1943b, Structure of central part of Sawtooth 

--Range, Montana: Geological Society of America 

Bulletin, v. 54, no. 8, p. 1123-1167. 

Dobbin, C. E., and Erdmann, C. E, 1955, Structure 

contour map of the Montana plains: U.S. Geological Survey Oil and Gas Investig-ations Map OM178A, scale 1:500,000. 

Earhart, R. L., 1975, Andesite sills in the Red 

Mountain area, Scapegoat Wilderness, Lewis and 

Clark County, Montana: U.S. Geological Survey 

Journal of Research, v. 3, no. 4, p. 415-424. 

1978, A geologic and geochemical evaluation of 

--the mineral resources of the Bob Marshall 

Wilderness and study areas, Chapter C in Mineral 

resources of the Bob Iviarshall Wilderness and 

study areas, Lewis and Clark, Teton, Pondera, 

Flathead, Lake, Missoula, and Powell Counties, 

Montana: U.S. Geological Survey Open-File 

Report 78-295, p. 61-104. 

Earhart, R. L., Grimes, D. J., and Leinz, R. W., 1977, 

Mineral resources of the proposed additions to 

the Scapegoat Wilderness, Powell and Lewis and 

Clark Counties, Montana, with a section on Geophysical surveys by Donald L. Peterson: U.S. 

Geological Survey Bulletin 1430, 62 p. 

*Earhart, R. L., Mudge, l\1. R., Whipple, J. TN., and 

Connor, J. J., 1980, Mineral resource and ~eneralized geologic maps of the Choteau 1 x 2° 

quadrangle, Montana: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-858A, scale 

1:250,000. 

Eaton, G. P., Wahl, R. R., Prostka, H. J., Mauey, 

D. R., and Kleinkopf, I\:1. D., 1978, Regional 

gravity and tectonic patterns; their relation to 

late Cenozoic epeirogeny and lateral spreading in 

the Western Cordillera, in Cenozoic tectonics 

and regional geophysics of the Western 

Cordillera: Geological Society of America 

Memoir 152, p. 51-91. 

Fabiano, E. B., and Peddie, N. W., 1980, Magnetic declination in the United States-Epoch 1980: U.S. 

Geological Survey Miscellaneous Geologic Investigations Map I-1283. 

*Grimes, D. J., and Leinz, R. W., 1980a, Geochemical 

and generalized geologic maps showing the distribution and abundance of copper in the Choteau 

1 °x 2° quadrangle, Montana: U.S. Geological 

Survey Miscellaneous Field Studies Map MF8588, scale 1:250,000. 

* 1980b, Geochemical and generalized geologic 

--maps showing the distribution and abundance of 

silver in the Choteau 1 °x 2° quadrangle, 

Montana: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-858C, scale 1:250,000. 

*Grimes, D. J., Leinz, R. W., Hopkins, R. T., 1980, 

Spectrographic and chemical analyses and sample 

location maps of stream sediment and rocks from 

the Choteau 1 °x 2° quadrangle, Montana: U.S. 

Geological Survey Open-File Report 80-1258. 

Grimes, D. J., Leinz, R. W., and Smith, R. J., 1976, 

Magnetic tape containing spectrographic and 

chemical analyses of stream sediments and rocks 
from the proposed additions to the Scapegoat 

Wilderness, Powell and Lewis and Clark 

Counties, Montana: U.S. Geological Survey 

Report USGS-GD-76-007, 4 p.; available only 

from U.S. Department of Commerce National 

Technical Information Service, Springfield, Virginia 22161, as Report PB-253 190/AS. 

Hammond, C. R., and Trapp, Henry, Jr., eds., 1959, 

Sawtooth-Disturbed Belt area Mont. : Billings 

Geological Society lOth Annual Field Conference 

Guidebook, 208 p. 

Harris, F. G., III, 1963, Geology of the Dry Creek area, 

Lewis and Clark Counties, Montana: University 

of Missouri M.A. thesis, 114 p. 

Harrison, J. E., 1972, Precambrian belt basin of northwestern United States; Its geometry, 

sedimentation, and copper occurrences: Geological Society of America Bulletin, v. 83, no. 5, p. 

1215-1240. 

Harrison, J. E., Griggs, A. B., and Wells, J. D., 1974, 

Tectonic features of the Precambrian Belt Basin 

and their influence on post-Belt structures: 

United States Geological Survey Professional 

Paper 866, 15 p. 

Harrison, J. E., Reynolds, M. W., Kleinkopf, M. D., and 

Pattee, E. C., 1969, Mineral resources of the 

Mission Mountains Primitive Area, Missoula and 

Lake Counties, Montana: U.S. Geological Survey 

Bulletin 1261-D, 48 p. 

Hoffman, J., Hower, J., and Aronson, J. L., 1976, Radiometric dating of time of thrusting in the 

Disturbed Belt of Montana: Geology, v. 4, no. 1, 

p. 16-20. 

Hurley, G. W., 1959, Overthrust faulting and Paleozoic 

gas prospects in Montana's Disturbed Belt: 

Billings Geological Society lOth Annual Field 

Conference Guidebook, p. 98-108. 

__ 1962, Distribution and correlation of Upper 

Devonian formations, Sweetgrass Arch area, 

northwestern Montana: Billings Geological 

Society 13th Annual Field Conference 

Guidebook, p. 23-32. 

Imlay, R. W., 1945, Occurrence of Middle Jurassic 

rocks in Western Interior United States: American Association of Petroleum Geologists 

Bulletin, v. 29, no. 7, p. 1019-1027. 

1952a, Correlation of the Jurassic formations of 

-- North America, exclusive of Canada: Geological 

Society of America Bulletin, v. 63, no. 9, p. 953-

992. 

__ 1952b, Summary of Jurassic history in the 

Western Interior of the United States: Billings 

Geological Society 3d Annual Field Conference 

Guidebook, p. 79-85. 

1953, Callovian (Jurassic) ammonites from the 

-- United States and Alaska, in Part 1, Western 

Interior United States: U.S-:-Geological Survey 

Professional Paper 249-A, p. 1-39. 

__ 1962, Jurassic (Bathonian or early Callovian) 

ammonites from Alaska and Montana: U.S. Geological Survey Professional Paper 37 4-C, p. ClC32. 

1967, Twin Creek Limestone (Jurassic) in the 

--western interior of the United States: U.S. Geological Survey Professional Paper 540, 105 p. 

Imlay, R. W., Gardner, L. S., Rogers, C. P., Jr., and 

Hadley, H. D., 1948, Marine Jurassic formations 

5 

of Montana: United States Geological Survey Oil 

and Gas Investigations Preliminary Chart 32, 

scale 1:1,200. 

International Association of Geodesy, 1967, Geodetic 

reference system, 1967: International Association of Geodesy Special Publication 3, 7 4 p. 

Johns, W. M., 1970, Geology and mineral deposits of 

Lincoln and Flathead Counties, Montana: 

Montana Bureau of Mines and Geology Bulletin 

79, 182 p. 

*Kleinkopf, M. D., 1980, Aeromagnetic and 

generalized geologic map of the Choteau 1 °x 2° 

quadrangle, Montana: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-858G, scale 

1:250,000. 

Kleinkopf, M. D., and Mudge, M. R., 1972, Aeromagnetic, Bouguer gravity, and generalized geologic 

studies of the Great Falls-Mission Range area, 

northwestern Montana: U.S. Geological Survey 

Professional Paper 726-A, p. 1-19. 

Kleinkopf, M. D., Mudge, M. R., and Harrison, J. E., 

1968, Aeromagnetic and gravity studies across 

the Northern Disturbed Belt in northwestern 

Montana abs. : American Geophysical Union 

Transactions, v. 49, no. 1, p. 330. · 

Kleinkopf, M. D., Wilson, D. M., and Peterson, D. L., 

1978, Aeromagnetic and gravity studies of the 

Bob Marshall Wilderness and study areas, 

Chapter B in Mineral resources of the Bob Marshall Wilderness and study areas, Lewis and 

Clark, Teton, Pondera, Flathead, Lake, Missoula, 

and Powell Counties, Montana: U.S. Geological 

Survey Open-File Report 78-295, p. 52-60. 

Knapp, G. F., 1963, A diorite sill in the Lewis and 

Clark Range, Montana: Massachusetts University M.S. thesis. 

*Leinz, R. W., and Grimes, D. J., 1980a, Geochemical 

and generalized geologic maps showing the distribution and abundance of lead in the Choteau 

1 °x 2° quadrangle, Montana: U.S. Geological 

Survey Miscellaneous Field Studies Map MF858D, scale 1:250,000. 

* 1980b, Geochemical and generalized geologic 

--maps showing the distribution and abundance of 

zinc in the Choteau 1 °x 2° quadrangle, 

Montana: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-858E, scale 1:250,000. 

*Leinz, R. W ., and Grimes, D. J., 1980c, Geochemical 

and generalized geologic maps showing the distribution and abundance of m ercury6 arsenic, and 

molybdenum in the Choteau 1 °x 2 quadrangle, 

Montana: U.S. Geological Survey Miscellaneous 

Field Studies Map MF-858F, 2 sheets, scale 

1:250,000. 

Mabey, D. R., Zietz, Isidore; Eaton, G. P., and Kleinkopf, M. D., 1978, Regional magnetic patterns in 

part of the Cordillera in the Western United 

States, in Cenozoic tectonics and regional geophysics of the Western Cordillera: Geological 

Society of America Memoir 152, p. 93-106. 

Marks, L. Y., 1978, Economic appraisal of the Bob 

Marshall Wilderness and study areas, Chapter E, 

in Mineral resources of the Bob Marshall Wilderness and study area, Lewis and Clark, Teton, 

Pondera, Flathad, Lake, Missoula, and Powell 

Counties, Montana: U.S. Geological Survey 

Open-File Report 78-295, p. 141-187. 
McDanal, S. K., Grimes, D. J., Leinz, R. W., and 

Hopkins, R. T., 1980, Magnetic tape containing 

spectrographic and chemical analyses of rock and 

stream-sediment samples from the Choteau 1 °x 

2° quadrangle, Montana: U.S. Geological Survey 

Report ERT-030; available only from U.S. 

Department of Commerce National Technical 

Information Service, Springfield, Virginia 22151. 

McDanal, S. K., and Wilch, L. 0., 1977, Magnetic tape 

containing analyses of rock and stream-sediment 

samples from the Bob Marshall Wilderness and 

adjacent study areas, Flathead, Lake, Lewis and 

Clark, Missoula, Pondera, Powell, and Teton 

Counties, Montana: U.S. Geological Survey 

Report ERT-77-014; available only from U.S. 

Department of Commerce National Technical 

Information Service, Springfield, Virginia 22151. 

McGill, G. E., and Sommers, D. A., 1967, Stratigraphy 

and correlation of the Precambrian Belt Supergroup of the southern Lewis and Clark Range, 

Montana: Geological Society of America 

Bulletin, v. 78, no. 3, p. 343-351. 

McMannis, W. J., 1965, Resume of depositional and 

structural history of western Montana: 

American Association of Petroleum Geologists 

Bulletin, v. 49, no. 11, p. 1801-1823. 

Miller, R. N., Shea, E. P., Goddard, C. C., Potter, 

C. W ., and Brox, G. B., 1973, Geology of the 

Heddleston copper-molybdenum deposit, Lewis 

and Clark County, Montana: American Institute 

of Mining, Metallurgical, and Petroleum 

Engineers, Inc., Pacific Northwest Metals and 

Minerals Conference, Couer d'Alene, Idaho, 1973, 

Proceedings, p. 1-33. 

Mudge, M. R., 1959, A brief summary of the geology of 

the Sun River Canyon area Mont. : Billings Geological Society lOth Annual Field Conference 

Guidebook, p. 18-22. 

__ 1965, Bedrock geologic map of the Sawtooth 

Ridge quadrangle, Teton and Lewis and Clark 

Counties, Montana: U.S. Geological Survey 

Geologic Quadrangle Map GQ-381. 

__ 1966a, Geologic map of the Patricks Basin quadrangle, Teton and Lewis and Clark Counties, 

Montana: U.S. Geological Survey Geologic Quadrangle Map GQ-453, scale 1:24,000. 

__ 1966b, Geologic map of the Pretty Prairie quadrangle, Lewis and Clark County, Montana: U.S. 

Geological Survey Geologic Quadrangle Map GQ454, scale 1:24,000. 

__ 1966c, Geologic map of the Glenn Creek quadrangle, Lewis and Clark and Teton Counties, 

Montana: U.S. Geological Survey Geologic Quadrangle Map GQ-499, scale 1:24,000. 

__ 1967, Geologic map of the Arsenic Peak 

quadrangle, Teton and Lewis and Clark Counties, 

Montana: U.S. Geological Survey Geologic Quadrangle Map GQ-597, scale 1:24,000. 

__ 1968, Bedrock geologic map of the Castle Reef 

quadrangle, Teton and Lewis and Clark Counties, 

Montana: U.S. Geological Survey Geologic Quadrangle Map GQ-711, scale 1:24,000. 

__ 1970, Origin of the Disturbed Belt in northwestern 

Montana: Geological Society of America 

Bulletin, v. 81, no. 2, p. 377-392. 

__ 1972a, Pre-Quaternary rocks in the Sun River 

6 

Canyon area, northwestern Montana: U.S. Geological Survey Professional Paper 663-A, 142 p. 

1972b, Structural geology of the Sun River -- Canyon and adjacent areas, northwestern 

Montana: U.S. Geological Survey Professional 

Paper 663-B, 52 p. 

*Mudge, M. R., Clayton, J. L., and McNichols, K., 

1980, Hydrocarbon potential and structure 

contour map of the Choteau 1 °x 2° quadrangle, 

Montana: U.S. Geological Survey Open-File 

Report 80-24, scale 1:250,000. 

Mudge, M. R., and Earhart, R. L., 1978, Geology of the 

Bob Marshall Wilderness and study areas, 

Chapter A in Mineral resources of the Bob Marshall Wilderness and study areas, Lewis and 

Clark, Teton, Pondera, Flathead, Lake, Missoula, 

and Powell Counties, Montana: U.S. Geological 

Survey Open-File Report 78-295, p. 1-60. 

1980, The Lewis thrust fault and related 

--structures in the Disturbed Belt, northwestern 

Montana: U.S. Geological Survey Professional 

Paper 1174, 18 p. 

Mudge, M. R., Earhart, R. L., and Claypool, G. E., 

1977, An evaluation of the hydrocarbon potential 

of the proposed Great Bear Wilderness area, 

Flathead, Teton, and Pondera Counties, 

Montana: U.S. Geological Survey Open-File 

Report 77-773, 33 p. 

Mudge, M. R., Earhart, R. L., and Rice, D. D., 1977a, 

Preliminary bedrock geologic map of part of the 

Northern Disturbed Belt, Lewis and Clark, Teton, 

Pondera, Glacier, Flathead, and Powell Counties, 

northwest Montana: U.S. Geological Survey 

Open-File Report 77-25. 

1977b, Northeast-trending lineaments in the 

-- Northern Disturbed Belt, northwest Montana 

abs. : Geological Society of America, Northwest Meeting, Missoula, Montana. 

Mudge, M. R., Earhart, R. L., Watts, K. C., Jr., 

Tuchek, E. T ., Rice, W. L., and Peterson, D. L., 

1974, Mineral resources of the Scapegoat Wilderness, Powell and Lewis and Clark Counties, 

Montana: U.S. Geological Survey Bulletin 1385-

B, 82 p. 

*Mudge, M. R., Earhart, R. L., Whipple, J. W ., and 

Harrison, J. E., 1979a, Geologic map of the Choteau 1 °x 2° quadrangle, Lewis and Clark, Teton, 

Powell, Missoula, Lake, Flathead, and Cascade 

Counties, Montana: U.S. Geological Survey 

Open-File Report 79-280. 

1979b, Structure and structure contour maps of 

--the Choteau 1 °x 2° quadrangle, Lewis and Clark, 

Teton, Powell, Missoula, Lake, Flathead, and 

Cascade Counties, Montana: U.S. Geological 

Survey Open-File Report 79-863. __ l}n press], Geologic and structure maps of the 

Choteau 1 °x 2° quadrangle, Lewis and Clark, 

Teton, Powell, Missoula, Lake, Flathead, and 

Cascade Counties, Montana: U.S. Geological 

Survey Miscellaneous Investigations Series Map 1-

1300, scale 1:250,000. 

Mudge, M. R., Erickson, R. L., Kleinkopf, M. D., 

Curtin, G. C., Marranzino, A. P ., and Zartrr.an, 

R. E., 1968, Reconnaissance geology, geophysics, 

and geochemistry of the southeastern part of the 

Lewis and Clark Range, Montana: U.S. Geological Survey Bulletin 1252-E, 35 p. 
Mudge, M. R., Rice, D. C., Earhart, R. L., and Claypool, G. E., 1978, Petroleum evaluation of the 

Bob Marshall Wilderness and study areas, 

Chapter D in Mineral resources of the Bob Marshall Wilderness and study areas, Lewis and 

Clark, Teton, Pondera, Flathead, Lake, Missoula, 

and Powell Counties, Montana: U.S. Geological 

Survey Open-File Report 78-295, p. 106-137. 

Mudge, M. R., Robinson, G. D., and Eaton, G. P., 1966, 

Preliminary report on regional aeromagnetic 

anomalies in northwestern Montana, in Geological Survey Research 1966: U.S. Geological 

Survey Professional Paper 550-B, p. 111-B114. 

Mudge, M. R., Sando, W. J., and Dutro, J. T., Jr., 1962, 

Mississippian rocks of Sun River Canyon area, 

Sawtooth Range, Montana: American Association of Petroleum Geologists Bulletin, v. 46, no. 11, p. 2003-2018. 

Mudge, M. R., and Sheppard, R. A., 1968, Provenance 

of igneous rocks in Cretaceous conglomerates in 

northwestern Montana, in Geological Survey Research 1968: U.S. Geological Survey Professional 

Paper 600-D, p. D137-D146. 

Obradovich, J. D., and Peterman, Z. E., 1968, Geochronology of the Belt Series, Montana: 

Canadian Journal of Earth Science, v. 5, no. 3, 

pt. 2, p. 737-747. 

Pardee, J. T., and Schrader, F. C., 1933, Metalliferous 

deposits of the greater Helena mining region, 

Montana: U.S. Geological Survey Bulletin 842, 

318 p. 

Perry, E. S., 1929, The Kevin-Sunburst and other oil 

and gas fields of the Sweetgrass Arch: Montana 

Bureau of Mines and Geology Memoir 1, 41 p. 

Peterson, J. A., 1966, Sedimentary history of the 

Sweetgrass Arch: Billings Geological Society 

17th Annual Field Conference Guidebook, p. 112-

134. 

Powers, Sidney, and Shimere, H. W., 1914, Notes on 

the geology of the Sun River district, Montana: 

Journal of Geology, v. 22, p. 556-559. 

Reeside, J. B., Jr., 1957, Paleoecology of the Cretaceous seas of the western interior of the United 

States, Chapter 18 in Ladd, H. S., ed., Paleoecology v. 2 of Treatise on marine ecology and 

paleoecology: Geological Society of America 

Memoir 67, p. 505-542. 

Reynolds, M. W ., and Kleinkopf, M. D., 1977, The 

Lewis and Clark Line, Montana-Idaho-A major 

intraplate tectonic boundary abs. : Geological 

Society of America Abstracts with Programs, v. 9, no. 7, p. 1140-1141. 

Rice, D. D., 1977, Petroleum evaluation of the Bob 

Marshall Wilderness and adjacent study areas, 

Lewis and Clark, Teton, Pondera, Flathead, 

Lake, Missoula, and Powell Counties, Montana: 

U.S. Geological Survey Open-File Report 77-542. 

Sahinen, U. M., 1959, Metalliferous deposits in the 

Helena area, Montana: Billings Geological 

Society lOth Annual Field Conference 

Guidebook, p. 129-140. 

1963, Metallic and industrial mineral resources-

--Clays, in Mineral and . water resources of 

, Montana: U.S. 88th Congress, 1st session, 

Committee Print, p. 60-62. 

Sahinen, U. M., and Crowley, F. A., 1959, Summary of 

Montana mineral resources: Montana Bureau of 

Mines and Geology Bulletin no. 11, 51 p. 

7 

Sahinen, U. M., Smith, R. I., and Lawson, D. C., 1958, 

Progress report on clays of Montana: Montana 

Bureau of Mines and Geology Information 

Circular no. 23, 41 p. 

Schmidt, R. G., 1963, Preliminary geologic map and 

sections of the Hogan 4 Southeast Wolf Creek 

quadrangle, Lewis and Clark County, Montana: 

U.S. Geological Survey Miscellaneous Geologic 

Investigatons Map 1-379, scale 1:24,000. 

1966, Preliminary geologic map of the Comb Rock 

--quadrangle, Lewis and Clark County, Montana: 

U.S. Geological Survey Miscellaneous Geologic 

Investigations Map 1-468, scale 1:24,000. 

1972a, Geologic map of the Wolf Creek 

--quadrangle, Lewis and Clark County, Montana: 

U.S. Geological Survey Geologic Quadrangle Map 

GQ-974, scale 1:24,000. 

1972b, Geologic map of the Coburn Mountain 

-- quadrangle, Lewis and Clark and Cascade 

Counties, Montana: U.S. Geological Survey Geologic Quadrangle Map GQ-975, scale 1:24,000. 

1972c, Geologic map of the Comb Rock 

--quadrangle, Lewis and Clark County, Montana: 

U.S. Geological Survey Geologic Quadrangle Map 

GQ-976, scale 1:24,000. 

1978 1979 , Rocks and mineral resources of the 

--Wolf Creek area, Lewis and Clark and Cascade 

Counties, Montana: U.S. Geological Survey Bulletin 1441, 91 p. 

Schmidt, R. G., and Strong, C. P., Jr., 1968, Preliminary geologic map of the Roberts Mountain 

quadrangle, Lewis and Clark County, Montana: 

U.S. Geological Survey Miscellaneous Geologic 

Investigations Map 1-564, scale 1:24,000. 

1972, Geologic map of the Roberts Mountain 

--quadrangle, Lewis and Clark County, Montana: 

U.S. Geological Survey Geologic Quadrangle Map 

GQ-977, scale 1:24,000. 

Schmidt, R. G., Swanson, D. A., and Zubovic, Peter, 

1964, Preliminary geologic map and sections of 

the Hogan 4 Northeast Coburn Mountain quadrangle, Lewis and Clark and Cascade Counties, 

Montana: U.S. Geological Survey Miscellaneous 

Geologic Investigations Map 1-409, scale 

1:24,000. 

Scholten, R., 1968, Model for evolution of Rocky 

Mountains east of the Idaho Batholith: Tectonophysics, v. 6, no. 2, p. 109-126. 

Sloss, L. L., 1950, Paleozoic sedimentation in Montana 

area: American Association of Petroleum Geologists Bulletin, v. 34, no. 3, p. 423-451. 

Sloss, L. L., and Laird, W. M., 1945, Mississippian and 

Devonian stratigraphy of northwestern 

Montana: U.S. Geological Survey Oil and Gas 

Investigations Preliminary Chart 15. 

1946, Devonian stratigraphy of central and north-

-- western Montana: U.S. Geological Survey Oil 

and Gas Investigations Preliminary Chart 25. 

194 7, Devonian system in central and 

-- northwestern Montana: American Association of 

Petroleum Geologists Bulletin, v. 34, no. 8, p. 

1404-1430. 

Smith, A. G., and Barnes, W. C., 1966, Correlation of 

and facies changes in the carbonaceous, calcareous, and dolomite formations of the 

Precambrian Belt-Purcell Supergroup: 

Geological Society of America Bulletin, v. 77, no. 12, p. 1399-1426. 
Smith, R. B. 1970, Regional gravity survey of western 

and central Montana: American Association of 

Petroleum Geologists Bulletin, v. 54, no. 7, 

p. 1171-1183. 

Sommers, D. A., 1966, Stratigraphy and structure of a 

portion of the Bob Marshall Wilderness area, 

northwestern Montana: Massachusetts University Ph. D. thesis, 234 p. 

Stebinger, Eugene, 1915, The Montana group of northwestern Montana: U.S. Geological Survey 

Professional Paper 90-G, p. 61-68. 

__ 1919, Oil and gas geology of the Birch Creek-Sun 

River area, northwestern Montana: U.S. Geological Survey Bulletin 691-E, p. 149-184. 

Trammell, J. W., 1975, Strata-bound copper mineralization in the Empire Formation and Ravalli 

Group, Belt Supergroup, northwest Montana: 

Seattle, University of Washington, Ph. D. thesis. 

U.S. Geological Survey, 1969, Aeromagnetic map of 

the Cut Bank-Hungry Horse Reservoir Area, 

northwest Montana: U.S. Geological Survey 

Open-File Report. 

__ 1971, Montana Disturbed Belt-Dating the 

Eldorado thrust in Geological Survey Research 

1971: U.S. Geological Survey Professional Paper 

750-A, p. A37. 

__ 1979, Aeromagnetic map of the Wallace-Flathead 

area, Montana: U.S. Geological Survey OpenFile Report 79-713. 

__ 1980a, Aeromagnetic map of the Rodgers Pass 

area, Montana: U.S. Geological Survey OpenFile Report 80-244, scale 1:62,500. 

__ 1980b, Aeromagnetic map of the southwest part 

of the Flathead National Forest, Montana: U.S. 

Geological Survey Open-File Report 80-1127, 

scale 1:50,000. 

8 

Viele, G. W., 1960, The geology of the Flat Creek area, 

Lewis and Clark County, Montana: Utah University Ph. D. thesis, 213 p. 

Viele, G. W ., and Harris, F. G., 3d, 1965, Montana 

group stratigraphy, Lewis and Clark County, 

Montana: American Association of Peteroleum 

Geologists Bulletin, v. 49, no. 4, p. 379-417. 

Walcott, C. D., 1899, Pre-Cambrian fossiliferous formations: Geological Society of America 

Bulletin, v. 10, p. 199-244. 

1906, Algonkian formations of northwestern 

--Montana: Geological Society of America 

Bulletin, v. 17, p. 1-28. 

1908, Cambrian sections of the Cordilleran area: 

--Smithsonian Miscellaneous Collection, v. 53, p. 

167-230. 

1915, The Cambrian and its problems in the 

Cordilleran region, in Problems of American 

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Weimer, R. J., 1955, Geology of the Two MedicineBadger Creek area, Glacier and Pondera 

Counties, Montana: Billings Geological Society 

6th Annual Field Conference Guidebook, p. 143-

149. 

*Whipple, J. W., 1979, Preliminary geologic map of the 

Rodgers Pass area, Lewis and Clark County, 

Montana: U.S. Geological Survey Open-File 

Report 79-719, scale 1:250,000. 

Wilson, J. L., 1955, Devonian correlations in northwestern Montana: Billings Geological Society 

6th Annual Field Conference Guidebook, p. 70-

77. 

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Montana: U.S. Bureau of Mines Report of Investigations 3981, 12 p. 
Table 1.-Maps of the Choteau 1 °x 2° quadrangle folio 

[MF, U.S. Geological Survey Miscellaneous Field Studies Map; OF, Open-File Report] 

Series No. Author 

MF-858A Earhart, Mudge, Whipple,and Connor (1980) ... 

MF-8588 Grimes and Leinz (1980a) ..............•.••• 

MF-858C Grimes and Leinz (1980b) .....•............. 

OF 80-1258 Grimes, Leinz, and Hopkins (1980) ..•.•....•. 

MF-858D Leinz and Grimes (1980a) ...............••.• 

MF-858E Leinz and Grimes (1980b) .•....•........•••• 

MF-858F Leinz and Grimes (1980c) •........••.....••. 

MF-858G Kleinkopf (1980) ••....•.•..••........•••.• 

OF 80-24 Mudge, Clayton, and McNichols (1980) ......•. 

OF 79-280 Mudge, Earhart, Whipple, and .....••••...... 

Harrison (1979a)1 

OF 79-863 Mudge, Earhart, Whipple, and .......••...... 

Harrison (1979b)1 

OF 79-719 Whipple (1979) ..•.•••..••...•.........•... 

Subject 

Mineral resources. 

Geochemical distribution and 

abundance of copper. 

Geochemical distribution and 

abundance of silver. 

Spectrographic and chemical 

analyses, and sample-location 

maps. 

Geochern ical distribution and 

abundance of lead. 

Geochern ical distribution and 

abundance of zinc. 

Geochemical distribution and 

abundance of mercury, arsenic, 

and molybdenum. 

Aeromagnetic map and 

interpretation. · 

Hydrocarbons. 

Geology. 

Structure. 

Geologic map of southwestern 

part of quadrangle. 

1u.s. Geological Survey Open-File Reports are preliminary and printed in black and white; a final 

version will be published in color in the Miscellaneous Investigations series (Mudge, Earhart, Whipple, 

and Harrison, in press). 

1-r U.S. GOVERNMENT PRINTING OFFICE: 1981- 3-41-614 1157