GEOLOGICAL SURVEY CIRCULAR 775

The Alaskan Mineral Resource Assessment Program: 

Background Information to Accompany Folio of 

Geologic and Mineral Resource Maps of the 

Talkeetna Quadrangle, Alaska
The Alaskan Mineral Resource Assessment Program: 

Background Information to Accompany Folio of 

Geologic and Mineral Resource Maps of the 

Talkeetna Quadrangle, Alaska

By Bruce L. Reed, Gary C. Curtin, Andrew Griscom,

Steven W. Nelson, Donald A. Singer, and Wm. Clinton Steele

GEOLOGICAL SURVEY CIRCULAR 775

1979
United States Department of the Interior 

CECIL D. ANDRUS, Secretary

Geological Survey

H. William Menard, Director

Library of Congress Cataloging in Publication Data

United States. Geological Survey.

The Alaskan mineral resource assessment program.

(Geological Survey Circular 775) 

Bibliography: p. 13-17.

1. Mines and mineral resources-Alaska. 2. Geology-Alaska. I. Reed, Bruce L., 1934-

II. Title. III. Series: United States. Geological Survey. Circular 775. 

QE75.C5 no. 775 [TN24.A4] 557.3'08s [553'.09798'3] IB-21122

Free on application to Branch of Distribution, U.S. Geological Survey, 1200 South Eads Street, AHington, VA 22202
CONTENTS

Abstract 1 

Introduction 1

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ILLUSTRATIONS

FIGURE 1. Index map of Alaska showing location of Talkeetna quadrangle 3

2. Map showing Talkeetna quadrangle and the Alaska Range in south-central Alaska 4

3. Map showing geologic terranes in the Talkeetna quadrangle, Alaska 7

4. Map of Talkeetna quadrangle indexing the 24 larger scale (1:63,360) quadrangles and the classification

and boundaries of proposed and existing categories of land in the quadrangle - 12

TABLE

Page

TABLE 1. Component maps of the Talkeetna quadrangle mineral resource assessment 1

III
The Alaskan Mineral Resource Assessment

Program: Background Information to Accompany

Folio of Geologic and Mineral Resource Maps

of the Talkeetna Quadrangle, Alaska

By Bruce L. Reed, Gary C. Curtin, Andrew Griscom, 

Steven W. Nelson, Donald A. Singer, and Wm. Clinton Steele

ABSTRACT

The Talkeetna 1° by 3° quadrangle, which consists of about 

17,155 km2 in south-central Alaska, was investigated by integrated field and laboratory studies in the disciplines of geology, 

geochemistry, geophysics, and Landsat data interpretation for 

the purpose of assessing its mineral resource potential. Past 

mineral production has been limited to gold from the Yentna 

district, but the quadrangle contains potentially significant resources of tin and silver and possibly a few other commodities 

including chromite and copper. The results of the mineral resource assessment are given in a folio of maps which are accompanied by descriptive texts, diagrams, tables, and pertinent references. This Circular provides background information on these 

investigations and integrates the component maps. A bibliography cites both specific and general references to the geology and 

mineral deposits of the quadrangle.

INTRODUCTION 

PURPOSE AND SCOPE

This Circular and a separately available folio of 

maps are part of a series of U.S. Geological Survey 

reports prepared to furnish information on the mineral resources and mineral resource potential of 

Alaska. This work is being done under the Alaska 

Mineral Resource Assessment Program (AMRAP) 

and is intended to provide information both for 

long-range national minerals policy and for State, 

Federal, and industry decisions concerning the future use of Alaskan lands and its resources. In addition, it is the intent of this folio of maps to increase 

the geologic knowledge of the region and to provide 

guidance for minerals exploration.

Most of the basic data for these map reports (table 1) were collected between 1974 and 1976 when

an interdisciplinary team of earth scientists carried 

out field and laboratory investigations necessary 

for a mineral resource appraisal. The reports and 

this Circular supply information on the geology, and 

land status of the quadrangle. A bibliography of 

geologic literature pertinent to the Talkeetna quadrangle is included.

TABLE I. Component maps of the Talkeetna quadrangle mineral resource assessment

U.S. Geological Survey

Miscellaneous Field

Studies Map Subject

MF-870-A (Reed and

Nelson, 1977) 

MF-870-B (Griscom, 1978)

MF-870-C (Steele and

Albert, 1978) 

MF-870-D (Reed and

others, 1978) 

MF-870-E (Curtin and

others, 1978c) 

MF-870-F (Curtin and

others, 1978e)

MF-870-G (Curtin and

others, 1978d)

MF-870-H (Curtin and 

others, 1978f)

MF-870-I (Tripp and others,

1978) 

MF-870-J (Nelson and Reed,

1978)

Geology.

Aeromagnetic map and interpretation.

Interpretation of Landsat 

imagery.

Mineral resources.

Geochemical distribution and 

abundance of gold and silver.

Geochemicah distribution and 

abundance of tin, tungsten, 

and beryllium.

Geochemical distribution and 

abundance of copper, lead, 

zinc, and molybdenum.

Geochemical distribution and 

abundance of chromium and 

nickel.

Mineralogical data for heavymineral concentrates.

Surficial deposits.
GEOGRAPHY AND ACCESS

The Talkeetna quadrangle covers about 17,155 

km2 in south-central Alaska (figs. 1 and 2) between 

lat 62° and 63° N. and long 150° and 153° W. Parts 

of three physiographic provinces are present in the 

quadrangle; from northwest to southeast they are 

the Tanana-Kuskokwim Lowland, Central Alaska 

Range, and Cook Inlet-Susitna Lowland (Wahrhaftig, 1965). The topography is dominated by the 

high, spectacularly glaciated Alaska Range which 

forms a northeast-trending arc of mountains in this 

part of Alaska (fig. 2). Mount Foraker, the third 

highest peak in North America, with an altitude of 

5,304 m, lies in the north-central part of the quadrangle (fig. 2). North America's highest mountain, 

Mount McKinley, is 23 km northeast of Mount 

Foraker in the adjacent Mount McKinley quadrangle.

Topographic releif within the Alaska Range is 

high, the altitude ranging from 3,475 m to 600 m. 

This contrasts sharply with the essentially flat 

Tanana-Kuskokwim and Cook Inlet-Susitna lowlands which, within the quadrangle, have an average altitude of 550 m and 215 m respectively.

Owing to the physiographic barrier created by 

the Alaska Range, precipitation is relatively heavy 

on its southern side. In the high core of the mountains is a nearly continuous network of large alpine 

glaciers, which meander between the snow- and 

ice-covered mountains that tower above them. The 

largest glaciers, the Ruth, Kahiltna, Yentna, and 

Tokositna, are 40-72 km long and descend to altitudes of less than 300 m. The lowest few kilometers of their lengths is mantled by rock debris and, 

locally, by vegetation.

The Susitna River is the master drainage artery 

for most of the quadrangle. It flows south along the 

easternmost part of the quadrangle, is joined by the 

second largest drainage, the Chulitna River, at 

Talkeetna, and discharges to upper Cook Inlet 

about 40 km west of Anchorage. Other major rivers 

include the Yentna and the Kahiltna, which join 

south of the quadrangle and then flow into the 

Susitna River. North of the Alaska Range, in the 

northwestern part of the quadrangle, the major 

drainage is the Tonzona River, which flows to the 

northwest, and joins the Kuskokwim River east of 

McGrath. Most of the larger rivers in the quadrangle are nourished by alpine glaciers. In summer 

months they are turbid from a continuous supply of 

glacier-derived material.

Population in the quadrangle is sparse and centered at Talkeetna, which had a population of 182 in 

1970; this, however, has undoubtedly increased 

over the last 8 years. Other permanent residents 

have built houses or places of business along the 

newly completed Parks Highway; they operate 

transportation facilities or live on homesteads. The 

larger guiding camps in the area are maintained by 

year-round caretakers. Population increases markedly during the summer months owing to an influx 

of tourists, mountain climbers, placer miners in the 

Peters Hills-Dutch Hills area, fishermen, hunters, 

guiding camp personnel, summer residents, nature 

enthusiasts, and persons involved in mineral exploration. The main guiding establishments are at 

Rainy Pass Lodge, at Amos Lake, and near Boulder Creek on the north side of the Alaska Range. A 

fly-in tourist and fishing lodge is maintained at 

Chelatna Lake, and fishing camps are present at 

numerous smaller lakes in the southeastern part of 

the quadrangle.

The Parks Highway, an all-weather paved road, 

and the Alaska Railroad follow the Susitna and 

Chulitna Rivers in the easternmost part of the 

quadrangle. A gravel road, constructed for and 

presently used primarily for access to the Peters 

Hills gold placer operations, receives moderate use 

during the summer months. The road is about 65 

km long and extends from near Talkeetna to Cache 

Creek in the Peters Hills. A few short roads used in 

connection with mineral exploration and which require four-wheel-drive vehicles are used intermittently in the Boulder Creek area. Access to Boulder 

Creek is by air, where one airstrip can accommodate C-46-type aircraft. Travel to and within the 

quadrangle is chiefly by small fixed-wing aircraft 

equipped with skis, wheels, or floats. Larger drainages provide numerous gravel bars from which 

small aircraft can operate, and airstrips have been 

constructed at several gold placer operations from 

Fairview Mountain northeast to the Dutch and 

Peters Hills. Small ski-equipped aircraft can land 

on some glaciers in the Alaska Range and provide 

access for an increasing number of mountain climbers during the summer months.

ACKNOWLEDGMENTS

This folio of maps results from the participation 

of many earth scientists, whose many contributions 

are gratefully acknowledged. Many of these persons were visiting scientists and laboratory
174° 171" 168° 165° 162° 159° 153° ISO" 147° 144" 141°

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134° 132° 130° 170" 168" 166° 164° 162° 160° 158° 156° 154°

FIGURE 1. Index map of Alaska showing location of Talkeetna quadrangle. Places mentioned in the text of this report can be found on the individual folio maps.
148°

630

610

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50 

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100 MILES 

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50

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100 200 KILOMETERS

FIGURE 2. Map showing Talkeetna quadrangle (shaded) and the Alaska Range (dotted) in south-central Alaska, (1) Glenn

Highway; (3) Parks Highway.

specialists who have been cited for their work on 

the specific maps in the folio. It does, however, 

seem appropriate to mention specifically a few colleagues who made noteworthy contributions. These 

include geologists R. L. Detterman, J. C. Ratte, 

and D. H. Richter, whose exceptional fieldmapping capabilities provided a better understanding of the complex geology and stratigraphy in the 

areas of Shellabarger Pass and north of the Denali 

fault, and D. L. Jones, whose expertise in regional 

tectonics and paleontology was a prime factor in the 

interpretation of the complex geologic terranes in 

the quadrangle. Tribute is also due to several

paleontologists without whose interest and effort 

the knowledge of the stratigraphic sequence of the 

many geologic terranes would be woefully short. 

Among those who made significant contributions 

are A. K. Armstrong, Claire Carter, J. T. Dutro, 

Jr., Anita Harris, W. A. Oliver, Jr., N. J. Silberling, and J. A. Wolfe. M. A. Lanphere, whose understanding of granite tectonics and willingness to 

provide data on the age of the many plutonic rocks 

in the quadrangle, provided the factual information 

on periods of granitic emplacement for this part of 

Alaska.

The cooperation of, and subsequent discussions
with, geologists engaged in oil and mineral exploration, is gratefully acknowledged; particularly helpful were H. E. Mann, C. A. Arbens, Tak Matsumoto, and C. C. Hawley. Special thanks are also 

due to J. J. McDougall, who, over a period of years, 

has provided samples and information relative to 

the geology and minerals exploration in the region. 

The geologic investigations in this remote area 

were especially facilitated by the cooperation and 

assistance of several local people. David and Angie 

Purkey provided logistic assistance, geologic knowledge of the area, and drill-hole information on tinsilver prospects. Mike Branham, Ann Budzynski, 

and Forest Charlton also were helpful in many 

ways.

The able and cheerful field and laboratory assistance of D. B. Clemens and D. K. Cohen is much 

appreciated. H. C. Berg, manager of AMRAP, 

coordinated various parts of this project.

GEOLOGIC INVESTIGATIONS

PREVIOUS INVESTIGATIONS

The earliest geologic data from the quadrangle 

were recorded in 1898 by a U.S. Geological Survey 

exploration team under the direction of J. E. Spurr 

(1900). This remarkable journey included the difficult task of lining canoes up the Squentna 

(Skwentna) River, portaging them across the 

Alaska Range at Portage Creek (5 km south of the 

southwestern corner of the quadrangle), and then 

descending the Kuskokwim River to its mouth. 

This same year G. H. Eldridge (1900) made a 

reconnaissance of the Sushitna (Susitna) River.

A second monumental expedition across this part 

of the Alaska Range was made four years later, in 

1902, when A. H. Brooks (1911a) led a survey team 

supported by packhorses across the Alaska Range. 

His route followed the Kichatna River, across 

Rainy Pass to the South Fork of the Kuskokwim, 

then northeast along the north flank of the Alaska 

Range to the Nenana River. Discovery of placer 

gold on Cache Creek in 1905 led to a series of 

studies by various workers of the U.S. Geological 

Survey. Beginning with the early work of S. R. 

Capps (1913), several investigations of the district 

have been made, and these reports are cited in the 

bibliography. In 1925 Capps (1927) conducted a reconnaissance survey along the north flank of the 

Alaska Range from the Mount McKinley Park railroad station west to the Tonzona River. This survey, in part, followed the earlier traverse by

Brooks. In a comprehensive study of the geology 

along the Alaska Railroad, Capps (1940) compiled a 

map which included part of the Alaska Range in the 

northeastern part of the quadrangle. All the earlier 

investigations mentioned above were directed toward geography, regional geology, or studies of 

mining districts. For the most part, little was 

known about the geology and mineral resources of 

the high rugged mountains of the Alaska Range.

RECENT INVESTIGATIONS AND PRESENT STUDY

Geologic studies in the quadrangle after World 

War II consisted chiefly of radioactivity investigations and were concentrated primarily in the 

Yentna gold-placer district. It was not until 1967, 

when the U.S. Geological Survey initiated the 

helicopter-supported heavy-metals program, that 

significant progress was made toward understanding the geology in this part of the Alaska Range. 

Hawley and Clark (1973, 1974) added considerably 

to knowledge of the geology and mineral deposits of 

the Chulitna-Yentna mineral belt, and Reed and Elliott (1968) completed a geochemical survey in the 

northwestern part of the quadrangle. The latter 

work led to the discovery of the massive sulfide 

deposits at Shellabarger Pass (Reed and Eberlein, 

1972). While undertaking reconnaissance topical 

studies on the Alaska-Aleutian batholith in 1970- 

72, Reed and Lanphere mapped and age-dated by 

potassium-argon methods the larger plutonic 

bodies in the quadrangle. These results were published in a series of papers (Reed and Lanphere, 

1972, 1973a, 1973b, 1974).

The present study began in 1974 when fieldwork 

was initiated under one of four Prototype Alaskan 

Minerals Resource Assessment Programs (PAMRAP). The Talkeetna project differed from the 

other PAMRAP quadrangles (Nabesna, Tanacross, 

McCarthy) in that only a minimum amount of 

geologic information was available before the start 

of fieldwork. In 1974, helicopter-supported 

fieldwork was done north of the crest of the Alaska 

Range. In 1975 geologic investigations were completed in the western half of the quadrangle, and a 

geochemical and gravity reconnaissance was initiated in the northwestern part of the quadrangle. 

Geologic, geochemical, and geophysical field investigations were completed for the entire quadrangle 

in 1976. Most of the above fieldwork was concentrated in the Alaska Range. Data on the surficial 

geology are chiefly from interpretation of aerial 

photographs.
The primary purpose of the project was to (1) produce a modern geologic map, (2) provide reliable 

geologic and geochemical data on the mineral deposits and mineral resources, and (3) obtain structural and stratigraphic data which will allow for a 

better understanding of the tectonic history of this 

part of Alaska. In large part, these goals have been 

accomplished, and their results are included in the 

folio of maps and in this Circurlar. As with any 

scientific investigation, the gathering of new data 

opens doors to other problems. Much work remains 

to be done, and although this work has greatly increased our knowledge of the geology and mineral 

resource potential of the quadrangle, it is only the 

start of a thorough understanding of the geologic 

history and complex processes that produced the 

various mineral deposits in the quadrangle.

MINERAL PRODUCTION

Placer gold production in the Yentna district, 

which inludes the Peters and Cache Creek drainages and the area near Fairview Mountain, totaled 

about 204,000 troy ounces through 1960 (Clark and 

Hawley, 1968). Recorded gold production through 

1975 was slightly more than 211,000 ounces, although actual production may be closer to 300,000 

ounces. For example, although there were 27 operations in the Cache Creek area in 1975, there was 

no recorded production (R. G. Bottge, 1977, written commun.). The recent rise in the price of gold 

has brought many of the placer mines back into 

operation, and this trend of increased activity will 

probably continue if environmental restrictions can 

be met economically.

Sand and gravel deposits along the Chulitna and 

Susitna Rivers were utilized for the construction of 

the Parks Highway, and granite along the highway 

has locally been quarried to provide material for 

bridge construction and erosion control.

DESCRIPTION OF COMPONENT MAPS OF 

THE TALKEETNA QUADRANGLE FOLIO

GEOLOGY

(map MF-870-A)

The Talkeetna quadrangle comprises five distinctive, generally fault-bounded, geologic terranes. 

The northernmost terrane (terrane A, fig. 3) is 

truncated on the south by the McKinley segment of 

the Denali fault system. Sedimentary and volcanic 

rocks in this terrane consist, from oldest to

youngest, of (1) a multiply folded, regionally 

metamorphosed quartzite, quartz semischist, 

quartz grit, metavolcanic rocks, and minor conglomerate, limestone, and phyllite; (2) an overlying 

allochthonous sequence of black, sooty, carbonaceous and calcareous shale and limestone that contains numerous dikes and sills of gabbro and quartz 

diorite; (3) a thick unit of Jurassic(?) and Lower 

Cretaceous argillite, siltstone, chert, graywacke, 

and pillow basalt; and (4) early and middle Tertiary 

continental sedimentary rocks. Within the quadrangle these four units are fault bounded, and their 

bases are not exposed. Serpentinite is locally developed along some faults, and the terrane is cut by 

McKinley sequence (55 m.y. old) granite. Schistosity and metamorphic grade of the quartzite and 

quartz semischist unit increase to the northeast. 

This unit is inferred to correlate with the Birch 

Creek Schist of former usage in the Kantishna Hills 

and is considered to be early Paleozoic or possibly 

late Precambrian. The age of the carbonaceous 

shale and limestone is unknown, but the unit may 

be equivalent to shale containing Ordovician graptolites 65 km to the southwest. The lower Tertiary 

continental rocks are thought to be remnants of an 

extensive continental sequence deposited in this 

part of the Alaska Range and now preserved in 

fault slivers chiefly along the Denali fault zone. 

They are believed to be equivalent to the Cantwell 

Formation of Paleocene age. Middle Tertiary coalbearing rocks are in fault contact with the other 

sedimentary rocks in the northwestern part of the 

quadrangle and probably underlie the lowlands to 

the north.

In this part of the Alaska Range, the McKinley 

segment of the Denali fault system has undergone 

right-lateral displacement of about 38 km in the last 

38 m.y. Furthermore, the straight north-facing 

scarp along this part of the range indicates that as 

much as 3 km of south-side-up vertical component 

of movement may have occurred since middle Tertiary time. Before this investigation, it was thought 

that the Denali fault system in this part of the 

Alaska Range separated the central Alaska Range 

into a northern sedimentary terrane of middle 

Paleozoic and older age and a southern sedimentary 

terrane chiefly of Mesozoic age. It is now known 

that the terrane adjacent to and south of the Denali 

fault in the quadrangle (terrane B, fig. 3) consists of 

a middle and upper Paleozoic (Devonian to 

Pennsylvanian) allochthonous sequence composed 

of marine flyschoid sedimentary rocks which in-
150°

62°

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5 10 15 20 25 MILES 

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FIGURE 3. Geologic terranes in the Talkeetna quadrangle, Alaska. A, sedimentary, metamorphic, and volcanic rocks that range in 

age from early Paleozoic through middle Tertiary; B, middle and late Paleozoic trench, slope, and terrestrial assemblages; C 

lower Paleozoic sedimentary rocks of the Dillinger River; D, Jurassic and Cretaceous lithic graywacke, phyllite, and shale; E, 

Chulitna sequence of late Paleozoic, Triassic, and early Jurassic age.

elude (1) trench assemblages (and possibly intraoceanic arc deposits) characterized by terrigenous turbidites, cherty pelagites, and pillow basalt 

(all of which underwent complex undersea sliding 

and later multiple thrusting and folding); (2) slope 

and shelf assemblages which include chert, shale, 

reefoid limestone, and, locally, terrestrial conglomerate and redbeds. A third part of the sequence is a 

thick, locally terrestrial conglomerate and 

sandstone assemblage. This assemblage is typified 

by the Middle Pennsylvanian conglomerate of 

Mount Ball, a limestone-chert conglomerate, 

sandstone, and siltstone unit at least 1,500 m thick 

that is gradational downward into the flyschoid 

sedimentary rocks. These three dissimilar depositional sequences, which largely form disrupted 

nappes, are nearly everywhere justaposed by

thrust faults on all scales. Structural features generally show a westerly vergence. Terrane B is 

thrust over, and allochthonous with respect to, terrane C (fig. 3), intruded by dunite and associated 

ultramafic rocks along its southern margin, and cut 

by a sequence of Upper Cretaceous and lower Tertiary plutons of varying compositions and by the 

middle Tertiary Foraker pluton. A 65-m.y.-old 

stock which cuts the southern fault boundary of the 

terrane gives a minimum age for this terrane's 

emplacement. A maximum age is suggested by 

Early Cretaceous fossils in terrane D.

The oldest terrane (terrane C) south of Denali 

fault is composed of sedimentary rocks of the Dillinger River area. These rocks are multiply folded, 

at least 3,000 m thick, and continue to the west at 

least as far as the South Fork of the Kuskokwim
River (McGrath quadrangle). They contain abundant carbonate rocks and consist chiefly of wellbedded lime mudstone and shale, interbedded 

sandstone, shale and limestone, and deep-water 

lime mudstone. The base of the unit is not exposed. 

Rare graptolites, pelecypods, and conodonts from 

different horizons are of Middle and Late Silurian 

age, and Ordovician graptolites are present in rocks 

tentatively assigned to this terrane.

The southern terrane (D, fig. 3), composed of a 

thick sequence of lithic graywacke, phyllite, and 

shale of Jurassic and Cretaceous age, is in fault 

contact with terrane B. It overlies the sedimentary 

rocks of the Dillinger River (terrane C) with angular unconformity, although this contact, in most 

places, has subsequently been faulted. Along the 

southern foothills of the Alaska Range, terrane D is 

unconformably overlain by fluvial sedimentary 

rocks correlative with estuarine and nonmarine 

clastic sedimentary Tertiary formations assigned to 

the Kenai Group (Calderwood and Fackler, 1972) in 

the Cook Inlet basin. Tertiary volcanic rocks locally 

overlie terrane D in the southwest part of the quadrangle.

The informal term "Chulitna sequence" (terrane 

E, fig. 3) refers to an allochthonous sequence of 

upper Paleozoic limestone, tuff, and argillite, 

Lower and Upper Triassic limestone, basalt, and 

volcanic redbeds, and Upper Triassic and Lower 

Jurassic marine sandstone and argillite that crops 

out on the south flank of the Alaska Range along 

the Chulitna valley northeast of the Talkeetna 

quadrangle (Jones and others, 1976; Hawley and 

Clark, 1974; Clark and others, 1972). In the 

Chulitna area these rocks include a dismembered 

ophiolite (oceanic crust) sequence of Late Devonian 

age which has not been observed in the Talkeetna 

quadrangle. Within the Talkeetna quadrangle the 

Chulitna sequence consists of Upper Triassic limestone and basalt, Upper TViassic volcaniclastic and 

clastic sedimentary rocks, and Upper Triassic(?) 

and Lower Jurassic massive to well-bedded siliceous argillite, chert, and minor pillow basalt. 

These rocks structurally overlie Jurassic (?) and 

Cretaceous graywacke, shale, and phyllite (terrane 

D) and are locally cut by granitic rocks of early 

Tertiary age.

Plutonic rocks of various compositions were 

emplaced in Late Cretaceous to early Tertiary (55 

to 67 m.y.) and in middle Tertiary (38 m.y.) time 

(Reed and Lanphere, 1973b). The larger and better 

exposed plutons of biotite or biotite and muscovite 

granite belong to the McKinley sequence (55 m.y).

South of the Denali fault, these plutonic rocks intrude Jurassic and Cretaceous sedimentary rocks 

and are not present in terrane B. A series of nine 

relatively small plutonic bodies forms a 65-km-long 

curvilinear belt in the southwestern part of the 

quadrangle. The average composition of these plutons is quartz monzonite, but the larger, wellexposed plutons are composite in nature and appear 

to range in composition from peridotite to granite. 

Two potassium-argon age dates indicate that this 

composite belt of rocks was emplaced about 65 m.y. 

ago (Reed and Lanphere, 1973b). Also present in 

the western part of the quadrangle, but lying 

southeast of the composite plutons, are scattered 

small granodiorite bodies referred to as the 

Kichatna plutons. A single potassium-argon age on 

biotite from one of these plutons is 67 m.y. (Reed 

and Lanphere, 1973b). The youngest plutonic event 

in the quadrangle occurred about 38 m.y. ago and is 

represented by the Foraker pluton. This granodiorite pluton has mineralogy and chemistry nearly 

identical to the McGonagall pluton in the Mount 

McKinley quadrangle, and both plutons are considered to be parts of a single igneous mass that has 

undergone about 38 km of right-lateral displacement along the McKinley segment of the Denali 

fault system.

The modern landscape of the region is chiefly a 

product of glaciation and glacier-related processes. 

Surficial deposits that cover the lowlands in the 

northwest and southeast parts of the quadrangle 

are described in map MF-870-J.

GEOPHYSICS

(map MF-870-B)

The aeromagnetic map (sheet 1) of the Talkeetna 

quadrangle was made in 1973 and released by the 

State of Alaska as an open-file map (Alaska Div. 

Geol. Geophys. Surveys, 1973). The variations in 

the magnetic field on maps such as this provide 

valuable information concerning the lateral and 

vertical extent of rock units containing various percentages of magnetic minerals, usually magnetite. 

Aeromagnetic maps thus are a most useful support 

for a geologic mapping program as well as for mineral resource assessment. An interpretive map 

(sheet 2) identifies various rock units in the Talkeetna quadrangle that possess characteristic 

magnetic anomalies and enables the interpreter to 

extrapolate geologic information from known areas 

into covered or inaccessible regions. In particular 

this aeromagnetic map makes it possible to locate 

the contact-metamorphosed rocks bordering many
plutons, some of which are concealed. In addition 

the map indicates two possible belts of ultramafic 

and volcanic rocks.

INTERPRETATION OF LANDSAT IMAGERY

(map MF-870-C)

Interpretations of Landsat data were made on 

(1) a black-and-white Landsat mosaic (band 7) of 

the State of Alaska compiled by the U.S. Department of Agriculture and (2) computer-enhanced 

black-and-white and color Landsat imagery processed by the U.S. Geological Survey in Flagstaff, 

Ariz. Landsat scenes selected for computer enhancement are: 1428-20554, taken September 24, 

1973; 1734-20485, taken July 27, 1974; and 1772- 

20580, taken September 3, 1974.

The black-and-white computer-enhanced product is a horizontal first derivative image. Color 

computer-enhanced Landsat products include a 

linearly "stretched" standard fale-color image, two 

sinusoidally "stretched" false-color images, and a 

simulated natural color image.

As a geologic mapping tool, Landsat imagery is 

probably most effective for reconnaissance studies, 

contributing remotely sensed information about 

geomorphology, structural features, and variations 

in spectral response of surficial materials, which 

can be used to plan and direct geologic mapping 

and geochemical sampling. However, in the Talkeetna quadrangle, where reconnaissance geologic 

mapping and geochemical sampling were completed before the Landsat study, the Landsat interpretation augmented geological and geophysical 

observations by: (1) identifying the possible extensions of mapped faults; (2) providing additional 

evidence for the presence and location of possible 

faults not clearly evident on the ground or on aerial photographs; (3) identifying numerous lineaments that have been previously unnoticed; (4) 

analyzing joint and fracture patterns on a 

quadrangle-wide basis; (5) identifying circular features; and (6) identifying arcuate features.

Many of the methods used to apply Landsat imagery to mineral resource assessment in the Talkeetna quadrangle are relatively new and their potential to solve geologic problems has yet to be 

fully explored. The various computer enhancement 

techniques used to generate Landsat imagery for 

this study are in the development stage. In addition, a large number of lineaments and circular 

features observed on this imagery do not correspond to geologically known or geophysically inferred features and may indicate poorly understood, or perhaps unknown, tectonic processes. 

The role of these phenomena and their relation to 

mineralization in the Talkeetna quadrangle are 

rather vague at present, but with further study 

their full implications may be understood.

MINERAL RESOURCES

(map MF-870-D)

The potentially favorable mineral resource areas 

of the Talkeetna quadrangle and the locations and 

brief descriptions of the known prospects, mineral 

and coal occurrences, and active and inactive 

placer mines are shown on the minerals resources 

map (Reed and others, 1978).

Eighty-nine mineral deposits and principal occurrences are categorized into active or inactive 

prospects, noteworthy occurrences, and active or 

inactive mines. Of these 89 locations, 14 are occurrences of coal, 33 are placer gold deposits or 

prospects, and the rest are lode mineral deposits 

or occurrences. The mineral deposits are classified 

by type and by economic commodities. A 

supplementary table on the map sheet gives brief 

descriptions of all the mineral deposits and, if 

available, references for additional information.

In addition to the locations of known mineral occurrences, the mineral resources map outlines 

favorable areas for mineral resources. This assessment is based on the known deposits, the 

presence of geologic conditions favorable for 

undiscovered deposits of similar type, and the interpretation of the geochemical, geophysical, and 

Landsat information given in the folio of maps. 

Tables list and briefly describe the criteria that led 

to the selection and boundaries of each favorable 

mineral resource area on the map. An accompanying text discusses the principal mineral commodities and presents information on their 

geologic setting, mineralogy, controls, grade, and 

genesis of the deposits.

The known and potential mineral resources of 

the quadrangle include gold, silver, tin, chrome, 

copper, molybdenum, nickel, coal, and possibly a 

few other commodities, including beryllium, 

tungsten, and natural gas. Gold has been the principal mineral product of the quadrangle. It occurs 

primarily in placer deposits in the Yentna district 

(Peters and Cache Creeks and Fairview Mountain 

area). Although additional detailed studies, including geochemical and drilling data, are required, 

areas are delineated as potentially favorable for
placer or lode gold resources. Among these are 

areas between the East and West Forks of the 

Yentna River, Kichatna River drainage, and upper 

Sunflower Creek.

Tin metallization is known to be closely associated with the biotite and muscovite granite of 

the McKinley sequence. A cassiterite-sulfide 

stockwork deposit in metasedimentary rocks 

above a granite cusp at Boulder Creek has high 

concentrations of tin; elsewhere within and adjacent to the quadrangle, granite of the McKinley 

sequence contains fluoritized or tourmalinized 

greisen zones. Pan-concentrate samples from several areas adjacent to or within the granite contain 

abundant cassiterite. The nonmagnetic fractions of 

these concentrates commonly contain in excess of 

1,000 ppm tin. This, in itself, suggests a terrane 

favorable for tin metallization. Although detailed 

work has not been done in most of the areas delineated for tin deposits and there is no guarantee 

that workable tin lodes will be found in or near 

these areas, the possibility exists that tin associated with the granite is a significant resource.

Podiform chromite was discovered in alpine-type 

ultramafic rocks exposed along the Yentna and 

Lacuna Glaciers. The chromite is of metallurgical 

grade and occurs in discontinuous sills and irregular bodies of dunite which crop out for a distance of 

about 25 km. Chromite occurs as disseminations, 

streaks, and lenses, as disrupted and irregular 

pods up to 20 m in maximum dimension, and as 

lenses up to 2 m thick. None of the dunite bodies 

was investigated in detail, and although the observed chromite occurrences are relatively small, 

additional exploration for minable deposits is warranted.

The Foraker pluton contains many alteration 

zones. Some of these have associated geochemical 

anomalies, and altered cobbles of granodiorite 

found in glacial moraines have fractures healed 

with molybdenite, pyrite, and chalcopyrite. 

Molybdenite-bearing quartz veins are also associated with the pluton. Taken collectively, the 

above evidence suggests that the Foraker pluton 

is potentially favorable for molybdenum and copper deposits of the porphyry or stockwork type.

Numerous lode occurrences of copper suggest 

that it may be a significant resource in the quadrangle. It occurs in a variety of deposit types 

volcanogenic, contact-metamorphic, and possibly 

as stockwork and porphyry deposits. The volcanogenic and contact-metamorphic deposits appear to be the most promising because of possible 

precious-metal content and base-metal grade. Although the indicated tonnage of the known 

copper-bearing massive sulfide deposits at Shellabarger Pass (Reed and Eberlein, 1972) is only on 

the order of 50,000 tons, the probability of additional massive sulfide bodies occurring in this assemblage of eugeosynclinal rocks is considered 

very high.

Estimated resources of known coal occurrences 

in the quadrangle are about 87 million tons. Owing 

to lack of road transportation, use of coal has been 

restricted to local consumption. The economic potential of coal within the quadrangle depends on its 

proximity to urban population centers or electric 

generators; it is currently low. Future use of the 

coal as an energy source must, however, be considered economically significant.

Two gravity lows in the upper part of the Cook 

Inlet basin probably represent thick sequences of 

Tertiary sedimentary rocks which crop out along 

the margin of the basin have adequate petroleum 

reservoir-quality rocks. The potential for oil accumulation in these basins is, however, considered 

minimal, although there might be accumulations of 

dry gas.

GEOCHEMISTRY

(maps MF-870-E-I)

Geochemical studies were made in the Talkeetna 

quadrangle to identify areas of anomalous concentrations of metallic elements. The data delineate 

areas of known mineral occurrences and additional 

areas possibly containing undiscovered potentially 

economic mineral resources.

During the summers of 1975 and 1976, sediment 

samples were collected at 835 sites in streams 

whose drainage areas range from approximately 7 

to 13 km2 . Glacial debris was sampled at 108 sites 

on glaciers within basins with drainage areas similar to those of the streams. The minus-80-mesh 

fraction of these samples was analyzed for 30 elements by a semiquantitative emission spectrographic method (Grimes and Marranzino, 1968) and 

for copper, lead, zinc, and gold by atomic absorption (Ward and others, 1969). Heavy-mineral concentrates of stream sediment were made for 812 of 

the stream sites. The nonmagnetic fraction of these 

samples was also analyzed for 30 elements by the 

spectrographic method. In addition, bulk fractions 

(with only the magnetite removed) of 387 heavymineral concentrate samples from the south flank of

10
the Alaska Range were similarly analyzed for 30 

elements and for gold. These results and analytical 

data from earlier reports (Clark and Hawley, 1968; 

Reed and Elliott, 1970) were used in compiling the 

geochemical maps in this folio. Other analytical 

data for stream sediments, glacial debris, and 

heavy-mineral concentrates are available in openfile reports (O'Leary and others, 1978; Curtin and 

others, 1978a).

The distribution and abundance of gold, silver, 

tin, beryllium, tungsten, copper, lead, zinc, molybdenum, chromium, and nickel in heavy-mineral 

concentrates, stream sediments, and glacial debris 

are described in this folio. Geochemical plots of 

these and a number of other elements are also 

available in open-file reports (Curtin and others, 

1978b).

These geochemical data show that some of the 

areas of known mineral occurrences are well defined by the distribution of anomalous amounts of 

metals in heavy-mineral concentrates. In this quadrangle, pan concentrates have proved to be a better 

reconnaissance tool than stream sediment or glacial 

debris samples. Mechanical weathering is the primary destructive process in the central Alaska 

Range; relatively fresh fragments of sulfide minerals and other ore minerals are released from zones 

of mineralized bedrock and deposited in the nearby 

streams along with comparatively light minerals 

such as quartz and feldspar. The dilution effect of 

the light minerals which can compose the bulk of 

the stream sediment may mask the presence of 

ore-related minerals. The effect of dilution is eliminated by preparing heavy-mineral concentrate 

samples free of light minerals.

Two notable geochemical features within the 

quadrangle are (1) the tin, beryllium, and tungsten 

anomalies in nonmagnetic heavy-mineral concentrates collected within and adjacent to granitic plutons of the McKinley sequence (Curtin and others, 

1978e) and (2) anomalous gold and silver values in 

heavy-mineral concentrates, stream sediment, and 

glacial debris which are, with few exceptions, from 

Jurassic and Cretaceous marine sediments and associated intrusive bodies on the south flank of the 

Alaska Range (Curtin and others, 1978c). The 

anomalous tin, beryllium, and tungsten values may 

be derived from small greisen zones in granitic 

rocks similar to an occurrence described by Reed 

and others (1978, No. 42, table 1). Plots of anomalous gold and silver values form clusters where 

granitic plutons of the McKinley sequence and

granodiorite and quartz diorite plutons intrude the 

Jurassic and Cretaceous rocks and probably reflect 

mineralization associated with the intrusions.

Known and possible occurrences of other base 

metals are outlined by anomalous copper, lead, 

zinc, and molybdenum values in heavy-mineral concentrates and in stream sediment and glacial debris.

SURFICIAL DEPOSITS

(map MF-870-J)

Surficial deposits of late Pleistocene and 

Holocene age cover about 65 percent of the Talkeetna quadrangle. The deposits are primarily the 

result of glaciation and have subsequently been 

modified by alluvial, glaciofluvial, lacustrine, and 

mass-wasting processes. The glacial and glacialrelated deposits are most extensive south of the 

Alaska Range because precipitation is heavier in 

this area. In contrast, the region north of the 

Alaska Range was much drier, and glacial deposits 

extend only short distances beyond the mountain 

front. Within the Alaska Range there remain 

numerous glaciers, although unconsolidated mass 

wasting and glacial deposits occur locally.

Subdued lateral(?) and ground moraines of preIllinoian age on the north side of the Alaska Range 

and glacial erratics on top of the Yenlo Hills south of 

the range represent the oldest surficial deposits in 

the quadrangle. These deposits are correlative with 

the Mount Susitna Glaciation in the Cook Inlet 

area.

Glacial deposits of Illinoian age are represented 

by drift of the Eklutna Glaciation. These deposits 

are greatly modified and include lateral and ground 

moraines that are largely covered by younger deposits on the south side of the Alaska Range. End 

and lateral moraines and knob-and-kettle topography of Eklutna age on the north side of the 

Alaska Range are moderately well preserved. 

Karlstrom (1960) estimated that this glaciation 

reached its maximum extent 90,000-110,000 years 

ago.

Drift of the Knik Glaciation, of early Wisconsin 

age, is exposed only in the northwestern part of the 

quadrangle. These deposits correlate with the 

Farewell I glacial deposits in the upper Kuskokwim 

region (Karlstrom and others, 1964). On the south 

side of the Alaska Range, the deposits of the Knik 

Glaciation were very extensive but are now covered by the deposits of the younger Naptowne 

Glaciation.

Most of the surficial materials, as well as much of

11
63

153° T A

N A

lllliil

150°

C6

O B4

AS

8

62°

10 15 20 

J_

25 MILES

1 I' I 1 I

10 15 20 25 30 KILOMETERS

r^S?af^^

eligibility for land selection not finally determined.

the present topography of the quadrangle, resulted 

from four advances of the late Wisconsin Naptowne 

Glaciation. During early Naptowne time large valley glaciers filled the present-day valleys of the 

Yentna, Kahiltna, Tokositna, Chulitna, and Susitna 

Rivers and coalesced in the lowland areas, forming 

a broad glacial front extending 40 km into the 

northeastern half of the Tyonek quadrangle.

Fluviolacustrine deposits of glacial origin occur 

primarily in the Cache Creek basin. The formation 

of these deposits is significant to the development 

of the placer gold deposits found in this area. During the late Miocene and Pliocene, placer gold was 

locally concentrated in lower clastic beds of the 

Kenai Group. During early Wisconsin time, glaciers

covered most of the Dutch and Peters Hills, and 

partly scoured the Cache Creek basin. In the early 

part of the late Wisconsin (early Naptowne Glaciation), a large glacier occupied the Kahiltna valley, 

and valley glaciers in the Dutch and Peters Hills 

again scoured and partially filled the valley of 

Cache Creek, although they apparently did not 

coalesce with the Kahiltna Glacier. After the retreat of these valley glaciers, the morainal debris 

was modified by meltwater both from the valley 

glaciers and the high-standing Kahiltna Glacier. 

During this fluvial episode, gold derived from the 

underlying Cretaceous and Tertiary formations was 

reworked and deposited in the basal part of the 

early Naptowne outwash deposit. The Kahiltna

12
Glacier dammed the Cache Creek valley and 

changed the dominantly fluvial environment to a 

lacustrine environment. During the lacustrine 

episode, a sequence of glacially derived bluish-gray 

mud accumulated in small ponds and lakes on top of 

the fluvial deposits.

The two advances of the Alaskan Glaciation, of 

Holocene age, have been correlated with the Tustumena and Tunnel advances recognized by 

Karlstrom (1957) on the Kenai Peninsula. These 

deposits were formed by alpine-valley glaciers occurring at higher altitudes in the Alaska Range. 

End moraines of the Tustumena Stade extend an 

average of 1.6 km from present-day ice fronts, and 

end moraines from the younger Tunnel Stade extend, on the average, about 0.8 km. The existing 

glaciers in the quadrangle are all recessional remnants of the Alaskan Glaciation.

LAND STATUS

The land status map (fig. 4) shows the classifications and boundaries of proposed and existing 

categories of land in the Talkeetna quadrangle. The 

map was compiled from a smaller scale map prepared by the Bureau of Land Management in 1974. 

Although subsequent changes have occurred 

primarily because of land selections included under 

terms of the Alaska Native Claims Settlement Act 

of 1971, the map is useful as a general guide until 

new maps are prepared.

BIBLIOGRAPHY

(The asterisks (*) denote references cited in this Circular and the folio of maps. 

References without asterisks are general, regional, or topical in scope but ccntain 

material relevant to the Talkeetna quadrangle.]

*Alaska Department of Mines, 1954, Report to the Commissioner of Mines, biennium ended Dec. 31, 1954:110 p.

Alaska Division of Geological and Geophysical Surveys, 1972a, 

Aeromagnetic survey, east Alaska Range, Talkeetna, 

Alaska: Alaska Div. Geol. and Geophys. Surveys 

aeromagnetic series, 22 sheets, scale 1:63,360.

 1972b, Aeromagnetic map, Talkeetna quadrangle, 

Alaska: Alaska Div. Geol. and Geophys. Surveys open-file 

map, scale 1:250,000.

-1973, Aeromagnetic survey east Alaska Range, Talkeetna quadrangle, Alaska: Alaska Div. Geol. and Geophys. 

Surveys open-file rept. 19, 1 sheet, scale 1:250,000.

Alaska Geology Branch, U.S. Geological Survey, 1972, The 

status of mineral resource information on the major land 

withdrawals of the Alaska Native Claims Settlement Act of 

1971: U.S. Geol. Survey open-file rept., 164 p.

 Albert, N. R. D., 1975, Interpretation of Earth Resources 

Technology Satellite imagery of the Nabesna quadrangle, 

Alaska: U.S. Geol. Survey Misc. Field Studies Map MF655-J, 2 sheets, scale 1:250,000.

*Albert, N. R. D., and Steele, W. C., 1976a, Interpretation of 

Landsat imagery of the Tanacross quadrangle, Alaska: U.S. 

Geol. Survey Misc. Field Studies Map MF-767-C, 3 

sheets, scale 1:250,000 [supersedes Open-File Rept. 76- 

850].

* 1976b, Interpretation of Landsat imagery of the McCarthy quadrangle, Alaska: U.S. Geol. Survey Misc. Field 

Studies Map MF-773-N, 3 sheets, scale 1:250,000.

*Armstrong, A. K., Reed, B. L., and Carter, C., 1977, Paleozoic 

sediments in the northwest part of the Talkeetna quadrangle, Alaska Range, Alaska: U.S. Geol. Survey Circ. 

751-B, p. B61.

Barnes, D. F., 1976, Bouger gravity map of Alaska: U.S. Geol. 

Survey Open-File Map 76-70, scale 1:2,500,000.

*1977, Gravity map of the eastern part of southern Alaska: 

U.S. Geol. Survey Open-File Rept. 77-169-C.

*Barnes, F. F. 1966, Geology and coal resources of the BelugaYentna region, Alaska: U.S. Geol. Survey Bull. 1202-C, 

54 p.

*Bates, R. G., and Wedow, Helmuth, Jr., 1953, Preliminary 

summary review of thorium-bearing mineral occurrences in 

Alaska: U.S. Geol. Survey Circ. 202, 13 p.

*Beikman, H. M., 1974a, Preliminary geologic map of the southeast quadrant of Alaska: U.S. Geol Survey Misc Field 

Studies Map MF-612, 2 sheets, scale 1:1,000,000.

* 1974b, Preliminary geologic map of the southwest quadrant of Alaska: U.S. Geol. Survey Misc. Field Studies Map 

MF-611, 2 sheets, scale 1:1,000,000.

* 1975a, Preliminary geologic map of southeastern Alaska: 

U.S. Geol. Survey Misc. Field Studies Map MF-673, 2 

sheets, scale 1:1,000,000.

-1975b, Preliminary geologic map of the Alaska Peninsula

and Aleutian Islands: U.S. Geol. Survey Misc. Field Studies 

Map MF-674, 2 sheets, scale 1:1,000,000.

*Beikman, H. M., Holloway, C. D., and MacKevett, E. M., Jr., 

1977, Generalized geologic map of the eastern part of southern Alaska: U.S. Geol. Survey Open-File Rept. 77-169-B.

*Beikman, H.M., and Lathram, E. H., 1976, Preliminary 

geologic map of northern Alaska: U.S. Geol. Survey Misc. 

Field Studies Map MF-789, 2 sheets, scale 1:1,000,000.

*Berg, H. C., and Cobb, E. H., 1967, Metalligerous lode deposits of Alaska: U.S. Geol. Survey Bull. 1246, 254 p.

Bottge, R. G., 1974, Potential mineral resources in selected D-2 

lands: U.S. Bur. Mines open-file rept. 9-74, 55 p.

Brooks, A. H., 1906, The mining industry in 1905: U.S. Geol. 

Survey Bull. 284, p. 4-9.

 1908, The mining industry in 1907: U.S. Geol. Survey 

Bull. 345, p. 30-53.

 1910, The mining industry in 1909: U.S. Geol. Survey 

Bull. 442, p 20-46.

* 1911a, The Mount McKinley region, Alaska, with descriptions of the igneous rocks and of the Bonnifield and 

Kantishna districts, by L. M. Prindle: U.S. Geol. Survey 

Prof. Paper 70, 234 p.

* 1911b, The mining industry in 1910: U.S. Geol. Survey 

Bull. 480, p. 21-42.

 1913, The mining industry in 1912, U.S. Geol. Survey 

Bull. 542, p. 18-51.

 1914, The Alaskan mining industry in 1913: U.S. Geol. 

Survey Bull. 592, p. 45-74.

 1915, The Alaskan mining industry in 1914: U.S. Geol.

Survey Bull. 622, p. 15-68.

13
 1918, The Alaskan mining industry in 1916; U.S. Geol. 

Survey Bull. 662, p. 11-62.

 1919, Alaska's mineral supplies, in McCaskey, H. D., and 

Burchard, E. F., Our mineral supplies: U.S. Geol. Survey 

Bull. 666, p. 89-102.

 1921, The future of Alaska mining: U.S. Geol. Survey 

Bull. 714, p. 5-57.

 1922, The Alaskan mining industry in 1920: U.S. Geol. 

Survey Bull. 722, p. 7-74.

 1923, The Alaskan mining industry in 1921: U.S. Geol. 

Survey Bull. 739, p. 1-50. 

-1925, Alaska's mineral resources and production, 1923:

U.S. Geol. Survey Bull. 773, p. 3-52.

Brooks, A. H., and Capps, S. R., 1924, The Alaskan mining 

industry in 1922: U.S. Geol. Survey Bull. 755, p. 3-56.

Brooks, A. H., and Martin, G. C., 1921, The Alaskan mining 

industry in 1919: U.S. Geol. Survey Bull. 714, p. 59-95.

Bultman, T. R., 1973, Denali fault (Hines Creek strand) near the 

Nenana River, Alaska: Geol. Soc. America Abs. with Programs (North-Central Sec.), v. 5, n°. 4, p. 304.

*Bundtzen, T. K., Smith, T. E., and Tosday, R. M., 1975, Progress report: Geology and mineral deposits of the Kantishna 

Hills, Alaska: Alaska Div. Geol. and Geophys. Surveys 

open-file rept. 98, 80 p.

*Calderwood, K. W., and Fackler, W. C., 1972, Proposed 

stratigraphic nomenclature for Kenai Group, Cook Inlet basin, Alaska: Am. Assoc. Petroleum Geologists Bull., v. 56, 

no. 4, p. 739-754.

Campbell, D. D., 1972, Regional faults and Ridge River gold 

deposits [abs.], in Program and abstracts, Symposium on 

faults, fractures and lineaments and related mineralization 

in the Canadian Cordillera, Vancouver, B. C., Feb., 1972: 

Geol. Assoc. Canada, Cordilleran Sec., p. 16.

Capps, S. R., 1912, Gold placers of the Yentna district: U.S. 

Geol. Survey Bull. 520, p. 174-200.

* 1913, The Yentna district, Alaska: U.S. Geol. Survey 

Bull. 534, 75 p.

*1924, Geology and mineral resources of the region 

traversed by the Alaska Railroad: U.S. Geol. Survey Bull. 

755, p. 73-150.

* 1925, An early Tertiary placer deposit in the Yentna 

district: U.S. Geol. Survey Bull. 773, p. 53-61.

* 1927, The Toklat-Tonzona River region: U.S. Geol. Survey Bull. 792, p. 73-110.

*1933, Geology of the eastern portion of Mount McKinley 

National Park: U.S. Geol. Survey Bull. 836-D, p. 219-300. 

-1940, Geology of the Alaska Railroad region: U.S. Geol.

Survey Bull. 907, 201 p.

Carnes, D. R., 1976, Active Alaskan placer operations 1975: 

U.S. Bur. Mines open-file rept. 98-76, 90 p.

Churkin, Michael, Jr., 1973, Paleozoic and Precambrian rocks of 

Alaska and their role in its structural evolution: U.S. Geol. 

Survey Prof. Paper 740, 64 p.

"Churkin, Michael, Jr., Reed, B. L., Carter, Claire, and Winkler, G., 1977, Lower Paleozoic graptolitic section from the 

Terra Cotta Mountains, southern Alaska Range: U.S. Geol. 

Survey Circ. 751-B, p. B37.

Clark, A. H., and Cobb, E. H., 1972, Metallic mineral resources 

map of the Talkeetna quadrangle, Alaska: U.S. Geol. Survey Misc. Field Studies Map MF-369, scale 1:250,000.

*Clark, A. L., Clark, S. H. B., and Hawley, C. C. 1972, Significance of upper Paleozoic oceanic crust in the Upper Chulitna 

district, west-central Alaska Range, in Geological Survey

Research 1972: U.S. Geol. Survey Prof. Paper 800-C, 

p. C95-C101.

*Clark, A. L., and Hawley, C. C., 1968, Reconnaissance geology, mineral occurrences, and geochemical anomalies of the 

Yentna district, Alaska: U.S. Geol. Survey open-file rept., 

64 p.

*Cobb, E. H., 1973, Placer deposits of Alaska: U.S. Geol. Survey Bull. 1374, 213 p.

*1974, Index of metallic mineral deposits of Alaska compiled from published reports of Federal and State agencies 

through 1972: U.S. Geol. Survey, 590 p. Available from 

Natl. Tech. Inf. Service, U.S. Dept. Commerce, 

Springfield, Va., no. PB-233 217/AS.

Cobb, E. H., Bacon, C. D., MacKevett, E. M., Jr., and Berg, H. 

C., 1977, Map showing distribution of mineral deposits 

(other than organic fuels and construction materials) in 

Alaska: U.S. Geol. Survey Open-File Rept. 77-496, scale 

1:2,500,000.

*Conwell, C. N., 1973, Gran view Exploration Company tin and 

silver prospects, Talkeetna D-5 quadrangle, Alaska: Alaska 

and Div. Geol. Geophys. Surveys, Prospect Examination 

75-4, 39 p.

Coulter, H. W., Hopkins, D. M., Karlstrom, T. N. V., Pewe, T. 

L., Wahrhaftig, Clyde, and Williams, J. R., 1965, Extent of 

glaciations in Alaska: U.S. Geol. Survey Misc. Geol. Inv. 

Map 1-415, scale 1:2,500,000.

*Crick, R. W., 1971, Potential petroleum reserves, Cook Inlet, 

Alaska, in Future petroleum provinces of the United 

States; Their geology and potential: Am. Assoc. Petroleum 

Geologist Mem. 15, v. 1, p. 109-119.

*Curtin, G. C., Cooley, E. F., O'Leary, R. M., and McDanal, S. 

K., 1978a, Spectrograp ic and chemical analysis of bulk 

heavy-mineral concentrate samples from the Talkeetna 

quadrangle, Alaska: U.S. Geol. Survey Open-File Rept. 

78-146, 26 p., Ipl.

*Curtin, G. C., Karlson, R. C., Day, G. W., O'Leary, R. M., and 

Tripp, R. B., 1978b, Geochemical maps showing distribution and abundance of selected elements in the Talkeetna 

quadrangle, Alaska: U.S. Geol. Survey Open-File Rept. 

78-301, 15 sheets, scale 1:250,000.

*Curtin, G. C., Karlson, R. C., O'Leary, R. M., Day, G. W., and 

McDanal, S. K., 1978c, Geochemical maps showing the distribution and abundance of gold and silver in the Talkeetna 

quadrangle, Alaska: U.S. Geol. Survey Misc. Field Studies 

Map MF-870-E, 2 sheets, scale 1:250,000.

*Curtin, G. C., Karlson, R. C., O'Leary, R. M., Day, G. W., and 

Me Dougal, C. M., 1978d, Geochemical maps showing the 

distribution and abundance of copper, lead, zinc and molybdenum in the Talkeetna quadrangle, Alaska: U.S. Geol. 

Survey Misc. Field Studies Map MF-870-G, 4 sheets, 

scale 1:250,000.

*Curtin, G. C., Karlson, R. C., Tripp, R. B., and Day, G. W., 

1978e, Geochemical map showing the distribution and abundance of tin, tungsten and beryllium in the Talkeetna quadrangle, Alaska: U.S. Geol. Survey Bull.U.S. Geol. Survey 

Bull. Misc. Field Studies Map MF-870-F, 3 sheets, scale 

1:250,000.

*Curtin, G. C., Karlson, R. C., Tripp, R. B., Day, G. W., 

Cooley, E. F., and McDougal, C. M., 1978f, Geochemical 

maps showing the distribution and abundance of chromium 

and nickel in the Talkeetna quadrangle, Alaska:U.S. Geol. 

Survey Misc. Field Studies Map MF-870-H, 2 sheets, 

scale 1:250,000.

14
*Decker, John, and Karl, Susan, 1977a, Preliminary aeromagnetic map of central Alaska: U.S. Geol. Survey Open-File 

Kept. 77-168-E, scale 1:1,000,000.

* 1977b, Preliminary aeromagnetic map of eastern part of 

southern Alaska: U.S. Geol. Survey Open-File Kept. 77- 

169-E, scale 1:1,000,000.

* 1977c, Preliminary aeromagnetic map of the Brooks 

Range and Arctic Slope, Alaska: U.S. Geol. Survey OpenFile Kept. 77-166-E, scale 1:1,000,000.

-1977d, Preliminary aeromagnetic map of western part of

southern Alaska: U.S. Geol. Survey Open-File Kept. 77- 

169-J, scale 1:1,000,000.

*De Young, J. H., Jr., 1978, Mineral resources map of the Chandalar quadrangle, Alaska: U.S. Geol. Survey Misc. Field 

Studies Map MF-878-B, 1 sheet, scale 1:250,000 (in press).

*Douglas, R. J. W., ed., 1970, Geology and economic minerals of 

Canada: Geol. Survey of Canada, 838 p.

*Drummond, A. D., and Godwin, C. I., 1976, Hypogene 

mineralization; an empirical evaluation of alteration zoning, 

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15
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* 1970, Reconnaissance geologic map, analyses of bedrock 

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* 1939a, Mineral industry of Alaska in 1937: U.S. Geol. 

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*1941, Mineral industry of Alaska in 1939: U.S. Geol. 

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16
"Tripp, R. B., Karlson, R. C., and Curtin, G. C., 1978, Maps 

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"U.S. Bureau of Mines, 1973, Alaska 1:250,000 scale quadrangle map overlays showing mineral deposit locations, 

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Wahrhaftig, Clyde, 1958, Quaternary geology of the Nenana 

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*Ward, F. N., Nakagawa, H. M., Harms, T. F., and Van 

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Wegner, W. W., 1973, The Denali fault (Hines Creek strand) in 

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Wilson, F. H., and Turner, D. L., 1975, Radiometric age map 

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Wolfe, J. A., Hopkins, D. M., and Leopold, E. B., 1966, Tertiary stratigraphy and paleobotany of the Cook Inlet region, Alaska: U.S. Geol. Survey Prof. Paper 398-A, 29 p.

17