U.S. GEOLOGICAL SURVEY CIRCULAR 1076 

The Alaska Mineral Resource Assessment 

Program: Background Information to 

Accompany Geologic and Mineral-Resource 

Maps of the Cordova and Middleton Island 

Quadrangles, Southern Alaska 
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The Alaska Mineral Resource Assessment 

Program: Background Information to 

Accompany Geologic and Mineral-Resource 

Maps of the Cordova and Middleton Island 

Quadrangles, Southern Alaska 

By G.R. WINKLER, GEORGE PLAFKER, R.J. GOLDFARB, and 

J.E. CASE 

U.S. GEOLOGICAL SURVEY CIRCULAR 1076 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

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

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

UNITED STATES GOVERNMENT PRINTING OFFICE: 1992 

For sale by the 

Books and Open-File Reports Section 

U.S. Geological Survey 

Federal Center 

Box 25425 

Denver, CO 80225 

Library of Congress Cataloging-in-Publication Data 

The Alaska Mineral Resource Assessment Program :background information to 

accompany geologic and mineral-resource maps of the Cordova and Middleton 

Island quadrangles, southern Alaska I by G.R. Winkler ... [et al.]. 

p. cm.-(U.S. Geological Survey circular; 1076) 

Includes bibliographical references. 

1. Geology-Alaska-Prince William Sound Region. 2. Mines and mineral 

resources-Alaska-Prince William Sound Region. 3. Alaska Mineral Resource 

Assessment Program. I. Winkler, Gary R. II. Series. 

QE84.P7A53 1992 91-38969 

557.98'3-dc20 CIP 
CONTENTS 

Abstract 1 

Introduction 1 

Putpose and scope 1 

Geography and access 1 

Acknowledgments 4 

Summary of mineral and energy production and exploration 4 

Copper 4 

Gold 5 

Manganese 7 

Uranium 8 

Coal 8 

Petroleum 8 

Geologic investigations 9 

Geologic and tectonic summary 11 

Geochemical investigations 13 

Geophysical investigations 14 

References cited 15 

FIGURES 

1. Location map of the Cordova and Middleton Island quadrangles 3 

2. Generalized geologic map of the Cordova and Middleton Island quadrangles 6 

3. Geologic terrane map of the northern Gulf of Alaska region, showing selected 

faults and boundaries of 1 °X3° quadrangles 10 

TABLE 

1. List of geologic, geochemical, geophysical, and mineral-resource maps of the 

Cordova and Middleton Island quadrangles 2 

Contents Ill 

The Alaska Mineral Resource Assessment Program: 

Background Information to Accompany Geologic and 

Mineral-Resource Maps of the Cordova and 

Middleton Island Quadrangles, Southern Alaska 

By G.R. Winkler, George Plafker, R.J. Goldfarb, and J.E. Case 

Abstract 

This report summarizes rec;ent results of integrated 

geological, geochemical, and geophysical field and laboratory 

studies conducted by the U.S. Geological Survey in the 

Cordova and Middleton Island 1 °X3° quadrangles of coastal 

southern Alaska. Published open-file reports and maps accompanied by descriptive and interpretative texts, tables, diagrams, 

and pertinent references provide background information for a 

mineral-resource assessment of the two quadrangles. 

Mines in the Cordova and Middleton Island quadrangles 

produced copper and byproduct gold and silver in the first 

three decades of the 20th century. The quadrangles may 

contain potentially significant undiscovered resources of precious and base metals (gold, silver, copper, zinc, and lead) in 

veins and massive sulfide deposits hosted by Cretaceous and 

Paleogene sedimentary and volcanic rocks. Resources of 

manganese also may be present in the Paleogene rocks; 

uranium resources may be present in Eocene granitic rocks; 

and placer gold may be present in beach sands near the mouth 

of the Copper River, in alluvial sands within the canyons of the 

Copper River, and in smaller alluvial deposits underlain by 

rocks of the Valdez Group. Significant coal resources are 

present in the Bering River area, but difficult access and 

structural complexities have discouraged development. Investigation of numerous oil and gas seeps near Katalla in the 

eastern part of the area led to the discovery of a small, shallow 

field from which oil was produced between 1902 and 1933. 

The field has been inactive since, and subsequent exploration 

and drilling onshore near Katalla in the 1960's and offshore 

near Middleton Island on the outer continental shelf in the 

1970's and 1980's was not successful. 

Manuscript approved for publication September 6, 1991. 

INTRODUCTION 

Purpose and Scope 

This report integrates and summarizes results of 

recent U.S. Geological Survey field and laboratory studies 

of the geologic setting of mineral and energy deposits in the 

Cordova and Middleton Island 1 °x3° quadrangles in coastal 

southern Alaska. Geologic, geochemical, and geophysical 

investigations were conducted as part of the Alaska Mineral 

Resource Assessment Program (AMRAP) and the Mineral 

Resources of Public Lands (MRPL) investigations of the 

Chugach National Forest, which includes more than 90 

percent of the land area of the two quadrangles. These 

multidisciplinary investigations were completed in 1988; 

however, they incorporate much fundamental geologic 

information that was obtained during the 1950's, 1960's, 

and 1970's during studies of the Gulf of Alaska Tertiary 

province and the epicentral region of the 1964 Alaska 

earthquake. A list of maps and reports that refer specifically 

to the two quadrangles is in table 1. Other sources of 

information on the geology and mineral deposits of the 

quadrangles are cited in the text and listed in the 

accompanying references. 

Geography and Access 

The Cordova and Middleton Island quadrangles 

include about 35,000 km2 (square kilometers) of southern 

Alaska along the continental margin (fig. 1). The quadrangles are bounded by the 59° and 61° parallels and by the 

144° and 147° meridians. The quadrangles include, from 

north to south, the rugged, glacier-clad, fiord-indented 

Chugach Mountains, part of the Pacific Border Ranges 

Introduction 1 
Table 1. List of geologic, geochemical, geophysical, and mineral-resource maps of the Cordova and Middleton Island 

quadrangles, Alaska 

Authors Subject 

U.S. Geological Survey (1979, 1988) Aeromagnetic surveys. 

Winkler and Plafker (1981, 1991) ........ . Geology. 

Sutley and others (1986) ............... . Geochemical survey: analytical results and sample-locality maps. 

Goldfarb and others (1989) ............. . Geochemical survey: maps and tabulations of areas with geochemical 

anomalies, particularly for gold and base metals. 

Case and others (written commun., 1992) ... Aeromagnetic map and interpretation. 

Goldfarb and others (in press) .......... . Mineral-resource assessment: tabulations of deposits and occurrences 

and maps of areas with potential for undiscovered resources of 

precious, base, and ferrous metals; uranium; coal; and petroleum. 

physiographic province (W ahrhaftig, 1965); the more 

subdued ridges, plains, and islands of the ,Gulf of Alaska 

coastal province; the continental shelf with emergent areas 

at Seal Rocks, Wessels Reef, and Middleton Island; and, 

along the southern part of the Middleton Island quadrangle, 

the continental slope, which descends into the northeastern 

end of the Aleutian Trench, where water depths exceed 

4,500 m. 

The Copper River (fig. 1), Alaska's third largest 

drainage, flows southward from the Copper River Basin 

across the Chugach Mountains through a series of deep 

canyons to emerge in the eastern part of the Cordova 

quadrangle, where its sediment load has been deposited as a 

large delta fringed by offshore sandbars. Several other 

major rivers, such as the Bering and Martin Rivers, 

originate in piedmont glaciers near the coast. All of these 

rivers have large seasonal flows and carry enormous loads 

of sediment, which have been deposited as broad alluvial 

plains to form coastal forelands. Other large rivers originate 

in valley glaciers in the coastal mountains. The Rude and 

Gravina Rivers, among others, have partly filled deepwater 

fiords and created steep delta fronts where they meet 

tidewater in arms of Prince William Sound. 

Topographic relief in the quadrangles exceeds 

2,350 m (meters). Most ridges on the mainland are very 

steep sided, having been quarried by and submerged 

beneath glaciers until recently. During the seismic shaking 

of the 1964 Alaska Good Friday earthquake, many such 

oversteepened slopes failed and slid into tidewater, valley 

bottoms, or onto glaciers. Moving ice, water, and wind also 

are dynamic erosive processes throughout the quadrangles. 

The coastline from Montague Island to Controller 

Bay (fig. 1) faces the tempestuous open waters of the Gulf 

of Alaska. Lighthouses at Cape Hinchinbrook and Cape St. 

Elias, which were manned stations until recently, are the 

2 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

only facilities along this stretch of exposed coastline. The 

prominent pinnacles that make up Cape S~. Elias were the 

first Alaskan landfall for the Russian-contracted Danish 

explorer Vitus Bering in 1741. Soon thereafter the abundance of fur-bearing marine mammals attracted Russian 

hunters and traders to the rich waters of Alaska. As animals 

were depleted first in the Aleutian Islands and then around 

Kodiak Island, the Russians migrated to Prince William 

Sound. The Russian S.K. Zaikof entered Prince William 

Sound in a trading vessel in 1783, and Fort Konstantine was 

established at Nuchek on the west end of Hinchinbrook 

Island to guard one entrance to the fur-harvesting grounds. 

Nuchek was a Russian trading post from 1793 to 1848 and 

continued as a native settlement until the winter of 1929-30 

(de Laguna, 1956). The early Russian name for Prince 

William Sound, Chugatskay Zaliv (Chugach Gulf), has been 

retained only in the name of the surrounding mountains, and 

few other Russian names have survived from this era. 

Waves of competitive exploration by English (Cook, 

Meares, Dixon, Portlock, Whidbey, and Vancouver) and 

Spanish (Arteaga, Martinez, and Fidalgo) mariners resulted 

in replacement with the names used on modem maps. 

Eastern Prince William Sound is somewhat protected from 

the full brunt of storms born in the Gulf of Alaska by the 

elevated ridges of Montague, Hinchinbrook, and Hawkins 

Islands (fig. 1), which nearly enclose the sound on the south. 

Hinchinbrook Entrance between Montague and Hinchinbrook Islands provides the eastern access for deep-draft 

vessels to the sound; it is the route used by oil tankers to and 

from the marine facility at the southern end of the transAlaska pipeline near the head of Port Valdez. 

Only two communities are in the quadrangles: Cordova (and several nearby fish canneries) (fig. 1), with 2,053 

permanent residents in 1990, and the native village of 

Tatitlek (population 108). Both can be reached only by sea 
QUADRANGLE LOCATION 

Wessels Reef X 

Middleton lslan~ 

0 

I 

I 

0 

CONTINENTAL 

GULF OF ALASKA 

I 

20 

20 

I 

I 

40 

SHELF 

I 

40 MILES 

I 

60 KILOMETERS 

Cape St. Elias 

Figure 1. Location map of the Cordova and Middleton Island quadrangles, Alaska. Submarine contours are in meters. 

Introduction 3 
or air transportation. Cordova has the only year-round 

harbor facilities in the map area. It is a port-of-call for 

ferries on the Alaska Marine Highway system and is the 

base for a U.S. Coast Guard cutter and a large fleet of 

fishing vessels. Cordova is served by an all-weather airport 

with daily jet service. Between 1911 and 1938, the city was 

the terminus of the Copper River and Northwestern 

Railroad, which extended inland up the Copper River 

canyons 316 km to the bonanza copper mines at Kennicott 

in the southern Wrangell Mountains. More than 1.2 billion 

pounds of copper and 9 million troy ounces of silver from 

the Kennicott mines (Douglass, in MacKevett and others, 

1977) were carried by the railroad to the Cordova shipping 

docks during 27 years of production. Most of the rails were 

salvaged for scrap metal during World War IT, and the 

roadbed was graded and maintained for passenger vehicles 

as far as Allen Glacier. However, during the 1964 Alaska 

earthquake, one end of the northern span of the steel 

"Million-dollar Bridge" at the outlet of Miles Lake was 

jarred from its foundations and fell into the Copper River. 

The span has not been reset, and today it is possible to drive 

only to the south shore of the lake about 68 km northeast of 

Cordova. Other road access in the quadrangles is limited to 

a few kilometers of graded side roads around Cordova and 

from the airport to a campground and a view point near 

Sheridan Glacier. 

The only other facilities in the quadrangles are U.S. 

Government communications facilities on Hinchinbrook 

and Middleton Islands, several private fishing and hunting 

cottages, and U.S. Forest Service public-use cabins on 

outlying islands in Prince William Sound and on the 

mainland east of Ragged Mountain. These facilities are 

accessible by boat or small plane only. 

Acknowledgments 

Many U.S. Geological Survey colleagues participated 

in the earth-science investigations of the Cordova and 

Middleton Island quadrangles that are summarized in this 

circular. We gratefully acknowledge their important scientific contributions, many of which are cited in the accompanying list of references. We are indebted particularly to 

D.F. Barnes, J.A. Dumoulin, Andrew Griscom, T.L. 

Hudson, J.S. Lull, M.L. Miller, R.L. Morin, S.W. Nelson, 

W.J. Nokleberg, R.M. O'Leary, W.J. Pickthorn, S.M. 

Roeske, S.C. Smith, S.J. Sutley, R.B. Tripp, and R.G. 

Tysdal, who participated in geologic, geochemical, and 

geophysical studies in the quadrangles. The detailed geologic mapping and stratigraphic studies of D.J. Miller in the 

Katalla area provided an inspiration and a framework for 

our later studies. Miller's contributions are recognized by a 

range of hills on the north side of Controller Bay that is 

named in his honor. In addition, the Research Vessels Don 

J. Miller and Don J. Miller II, under the command of 

4 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

Captains R.J. Stacey and A.C. Frothingham and Chief 

Engineer Ed Magalhaes, provided reliable and cheerful 

havens during many of our studies in Prince William Sound. 

Hollis and Shirley Henrichs (deceased), long-time 

residents of Cordova, always provided warm hospitality and 

insightful views of the region's history and continuing 

development. U.S. Forest Service personnel of the Cordova 

Ranger District and U.S. Federal Aviation Administration 

personnel of the Cordova flight station provided frequent 

advice, logistical support, and use of remote facilities on 

Hinchinbrook and Middleton Islands. The pilots of Cordova 

Airlines, Chitina Air Service, and Parkair in Cordova 

provided competent and timely fixed-wing air support, 

many times under demanding conditions. 

SUMMARY OF MINERAL AND ENERGY 

PRODUCTION AND EXPLORATION 

Identified mineral and energy resources in the Cordova and Middleton Island quadrangles include deposits of 

copper (with or without zinc or silver), gold, manganese, 

coal, and petroleum. Approximately 22 million pounds of 

copper, 199,000 oz of silver, and 51,450 oz of gold were 

produced between 1900 and 1930 from mines in the Ellamar 

district in the northwest part of the Cordova quadrangle; 

recorded production from the Ellamar mine alone exceeded 

15.7 million pounds of copper, 51,300 oz of gold, and 

191,600 oz of silver (Jansons and others, 1984). Zinc, minor 

lead, and anomalous cobalt values also were noted in the ore 

(Capps and Johnson, 1915), but no production was 

recorded. Sixteen ounces of gold reportedly were produced 

sometime before 1912 from the McKinley Lake district 

(Jansons and others, 1984). Eighteen thousand to 20,000 

tons of coal were shipped from the Bering River field 

between 1910 and 1920 (Janson, 1979). Approximately 

154,000 barrels of oil were produced between 1902 

and 1933 from a small abandoned field at Katalla (Miller, 

1975; see fig. 1 for locations). No other mineral or energy 

commodities are known to have been produced from the 

quadrangles. 

Copper 

Large abandoned surface facilities near Ellamar, 

Landlocked Bay, and Port Fidalgo (fig. 1) attest to the 

importance of former copper mining in the Ellamar district. 

Numerous workings were developed along stratabound, 

massive iron-copper-zinc sulfide deposits hosted by rocks 

of the lower Tertiary Orca Group (Capps and Johnson, 

1915; Wiltse, 1973; Winkler and others, 1977). The most 

productive deposits, such as those at the Ellamar mine and 

the Schlosser mine south of Port Fidalgo (fig. 2), were 
hosted by fine-grained sedimentary rocks. Pyrite, pyrrhotite, 

chalcopyrite, and sphalerite formed tabular masses, lenses, 

and stringers in nested layers that were conformable to 

bedding; arsenopyrite and tetrahedrite were present in minor 

or trace amounts. The Ellamar deposit was overlain by a 

pyritic cap 8-10 m thick. In a few locations, mafic volcanic 

rocks were intercalated with the mineralized shale and 

siltstone. Deposits that were hosted by volcanic rocks, such 

as deposits in Boulder and Landlocked Bays southeast of 

Ellamar, generally were much smaller than those hosted by 

sedimentary rocks, but some were higher grade. These 

deposits contained nested pyrite-chalcopyrite-pyrrhotitesphalerite layers within pillow breccia or aquagene tuff and 

lenses of sulfide minerals enclosed between flows and tuff 

or sediment. Cubanite and galena were found locally as 

late-stage sulfide mineral phases in volcanic rock-hosted 

deposits. Some deposits are underlain by heavily oxidized 

or silicified boxwork zones (S.W. Nelson, U.S. Geological Survey, written commun., 1990). Apparently, most 

deposits were syngenetic and formed in areas fringing local 

centers of mafic submarine volcanism. However, in many 

places, the sulfide minerals were remobilized along crosscutting faults, probably during regional deformation and 

metamorphism. 

Copper production ceased about 1930, but significant 

resources remain in and adjacent to mined properties in the 

Ellamar district, and a caretaker still lives at the Ellamar 

mine townsite. Jansons and others (1984) inferred approximately 2 million tons of reserves with grades between 0.3 

and 7.9 percent copper in deposits hosted by volcanic rocks 

in the Ellamar district, and approximately 750,000 tons with 

grades between 0.6 and 3.2 percent in deposits hosted by 

sedimentary rocks. However, active exploration and evaluation programs for massive sulfide deposits by several 

companies in the late 1970's failed to locate economically 

viable deposits, and there has been little subsequent interest. 

Metavolcanic and metasedimentary rocks of the 

Cretaceous Valdez Group (fig. 2) are hosts to stratabound 

iron-copper-zinc sulfide mineral deposits in adjacent parts 

of the Valdez quadrangle to the north, such as at Solomon 

and Sulphide Gulches (Johnson, 1919; Moffit and Fellows, 

1950; Winkler, Miller, and others, 1981; Nelson and Koski, 

1987). The Midas mine in Solomon Gulch produced approximately 3.4 million pounds of copper between 1912 and 

1930 from a tabular layer of nearly massive pyrite, chalcopyrite, and sphalerite 4--10 m thick. This layer was not 

mined out completely but is exposed in underground 

workings with a minimum strike length of about 225 m and 

a downdip extension of at least 120m (S.W. Nelson, written 

commun., 1990 ). Disseminated sulfide minerals are present 

in rocks of the Valdez Group in many places in the Cordova 

quadrangle, particularly in and near diabase dikes associated with pillowed greenstone. Oxidation of the sulfide 

minerals, especially pyrite, causes these rocks to weather 

rusty brown. Despite extensive exploration during the more 

than two decades that copper mines in the area were 

producing, no deposits comparable to those at the Midas 

mine were discovered. 

Geologic environments favorable for formation of 

volcanogenic massive sulfide deposits are widespread in the 

Cordova quadrangle, and the likelihood is high that undiscovered resources of copper (and associated zinc, lead, 

silver, and gold) exist in rocks of the Orca and Valdez 

Groups (Nelson and others, 1984; Bliss, 1989; Goldfarb and 

others, in press). Using grade-tonnage models for Cyprus 

(volcanic rock-hosted) and Besshi (sedimentary rockhosted) massive-sulfide deposit types, Bliss (1989) prepared 

a probabilistic quantitative assessment of contained metal 

values for favorable tracts in the Chugach National Forest. 

The tracts include approximately one-third of the onshore 

area of the Cordova quadrangle. 

Gold 

In the McKinley Lake district, 32 km southeast of 

Cordova, sedimentary rocks of the Orca Group host quartz 

veins that bear minor gold, pyrite, and arsenopyrite (Chapin, 

1913). Prospecting and development occurred mainly 

before 1920, but sporadic work continued until World War 

II (Haney and Jansons, 1987). The principal mineralized 

veins form networks approximately parallel to bedding in 

the enclosing rocks, and they generally are at contacts 

between sandstone and shale where the sandstone has been 

brecciated extensively. Discordant quartz veins also have 

minor gold values, even where free gold is not visible. 

Eocene intrusive rocks near the prospects are virtually 

unmineralized (Haney and J ansons, 1987). Several adits 

totaling at least 775 m in length were excavated, but 

reported gold production was virtually nil; lode claims 

active in the area in 1983 revealed no zones with economic 

grades (Haney and Jansons, 1987). 

In sedimentary rocks of the Orca Group north of Port 

Fidalgo (fig. 1), stockworks of gold-bearing quartz veins 

were worked at Graveyard Point on the north side of Port 

Fidalgo and at two places on Bligh Island in the early 

1900's (Capps and Johnson, 1915). No production was 

reported. The U.S. Bureau of Mines (1973) reported a 

lode-gold prospect in mafic volcanic rocks of the Orca 

Group at the north end of Wingham Island. No other 

lode-gold occurrences are known in rocks of the Orca 

Group in the Cordova and Middleton Island quadrangles. 

However, quartz veins are scattered through much of the 

Orca Group, particularly near granitic stocks that may have 

provided heat or fluids during the formation of quartz veins. 

Goldfarb and others (1989) reported anomalous gold and 

silver values and microscopically visible gold grains from 

heavy-mineral concentrate samples collected in areas 

underlain by the Orca Group near the headwaters of the 

Rude River. 

Summary of Mineral and Energy Production and Exploration 5 
Middleton Island /) 

Ts---tf~ 

Middleton Island 

State No.1 

0 

I 

I 

0 

GULF OF ALASKA 

I 

20 

20 

I I 

40 

40 MILES 

I 

I 

60 KILOMETERS 

Figure 2 (above and facing page). Generalized geologic map of the Cordova and Middleton Island quadrangles, Alaska 

(modified from Plafker and others, 1982). 

6 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 
Oal 

Ts 

Tg 

Tl 

Tv 

Kms 

Kmv 

EXPLANATION 

Quaternary alluvial deposits 

Upper and middle Tertiary sedimentary and volcanic rocksAs mapped, includes Pleistocene deposits on Middleton Island 

Tertiary granitic rocks 

Lower Tertiary sedimentary rocks 

Lower Tertiary volcanic rocks 

Cretaceous metasedimentary rocks-Valdez Group (part) 

Cretaceous metavolcanic rocks-Valdez Group (part) 

----Contact-Dashed where concealed 

---- Steep fault-Dotted where concealed 

.......... ...._ Thrust fault-Dashed or dotted where concealed 

-<:>- Drill hole 

Quartz veins bearing anomalous amounts of gold, 

lead, zinc, silver, antimony, and arsenic are localized in 

slate, argillite, and graywacke of the Valdez Group in the 

Port Valdez area, 20 km north of the map area. In the 

heavily glaciated northern part of the Cordova quadrangle 

west of Copper River, quartz veins and stringers are widely 

dispersed within metasedimentary rocks of the Valdez 

Group, but they have not been explored extensively. Quartz 

stringers and veins, generally less than 1 m thick, have been 

prospected in the Jack Bay area near the northwest edge of 

the Cordova quadrangle (Johnson, 1919). No records of 

metal production exist for this area, and assays of recently 

collected samples showed no significant gold values (Jansons and others, 1984). 

Fluid-inclusion and stable-isotope data from precious 

metal-bearing quartz veins throughout the Valdez Group 

indicate that they formed from low-salinity fluids at temperatures and pressures exceeding 210 °C and 1 kilobar, 

respectively (Goldfarb and others, 1986). The isotopic data 

indicate ore-fluid genesis by devolatilization reactions 

during regional metamorphism, which affected much of the 

northern part of the Cordova quadrangle. Thus, favorable 

geologic conditions are widespread, and the likelihood is 

high that undiscovered resources of gold (and byproduct 

silver) exist, particularly in small, high-grade lodes in rocks 

of the Valdez Group (Nelson and others, 1984; Bliss, 1989; 

Goldfarb and others, in press). Based on production data 

from known deposits in the Chugach National Forest, Bliss 

(1989) developed a grade-tonnage model for precious 

metal-bearing metamorphic quartz veins and prepared a 

probabilistic quantitative assessment of contained gold and 

silver values for favorable tracts. The tracts include approximately one-fifth of the onshore area of the Cordova 

quadrangle. 

No gold is known to have been recovered from placer 

sources in the northern Cordova quadrangle, even though 

the area is underlain by rocks of the Valdez Group containing abundant metamorphic quartz veins. Much of this 

region has steep topography and active alpine glaciers. 

Although anomalous gold was detected in many panned 

concentrates from this area (Goldfarb and others, 1989), 

most samples were derived from fluvioglacial material. 

Inasmuch as glaciation generally either destroys preexisting placers or dilutes them below economic grade, the 

potential for resources of gold in placers is thought to be 

low (Goldfarb and others, in press). 

Concentrations of heavy minerals, including gold, 

were found in sands sampled from offshore beach bars of 

the Copper River Delta (Reimnitz and Plafker, 1976) . 

Although gold concentrations were only 0.25 ppm (parts per 

million) in the highest grade samples, the large volume of 

easily accessible sand in the Copper River barrier beaches 

may warrant additional evaluation of gold values. 

Jansons and others (1984) noted trace amounts of 

gold (0.004-0.005 ounces per cubic yard) in alluvial sand at 

numerous sites along the Copper River. Aeromagnetic highs 

along the Copper River have been attributed to areas of 

probable black-sand accumulations that also are likely to 

contain placer gold (Case and others, written commun., 

1992). The large volume of accessible material constitutes a 

potential resource that should be evaluated further. 

Beach sand collected by Eyles (1990) between Icy 

Bay and Cape Yakataga, 150 km east of the Cordova and 

Middleton Island quadrangles, contained as much as 37 

ppm Au. Eyles suggested that the placer gold was derived 

from the lower part of the Yakataga Formation. However, 

beach-sand samples collected in the Cordova and Middleton 

Island quadrangles from areas underlain by the lower part of 

the Yakataga Formation contained only background values 

of 10-20 ppb (parts per billion) or less Au (Reimnitz and 

Plafker, 1976; Goldfarb and others, 1984; Sutley and others, 

1986). 

Manganese 

Goodfellow and others (1984) described a newly 

discovered deposit of nodular manganese that occurs in 

iron-stained mudstone intercalated with volcanic rocks of 

the Orca Group on Hinchinbrook Island. Rocks of the Orca 

Group host another small deposit in the Seward quadrangle 

in western Prince William Sound (Kurtak, 1982). These are 

the only occurrences that are known in the region, although 

potentially favorable intercalated pelitic and volcanic host 

rocks are widespread in both the Valdez and Orca Groups in 

the Cordova quadrangle. Sediment and heavy-mineralconcentrate samples throughout the Gravina River 

watershed are strongly anomalous in manganese (Goldfarb 

and others, 1989); the area is mainly underlain by 

Summary of Mineral and Energy Production and Exploration 7 
metasedimentary rocks of the Valdez Group, but the source 

of the extensive anomalies is presently unknown. At the 

occurrence on Hinchinbrook Island, grab samples from an 

area of rubbly outcrop about 10 by 30 m in extent averaged 

about 30 percent Mn. Although no volcanogenic sulfide 

deposits are known to crop out in the vicinity of this deposit, 

Goodfellow and others ( 1984) believed that the mineralogy 

of the occurrence indicated submarine volcanogenic hot 

springs as a likely source. By assuming that the occurrences 

are analogous to small-volume, low-tonnage volcanogenic 

manganese deposits of the Olympic Peninsula in 

Washington, Bliss (1989) prepared a quantitative assessment of potential undiscovered resources of manganese in 

the Chugach National Forest, including areas of low 

potential on Hinchinbrook and Hawkins Islands and east of 

Cordova. 

Uranium 

A National Uranium Resource Evaluation (NURE) 

reconnaissance airborne gamma-ray survey of the Cordova 

quadrangle indicated that a uranium anomaly existed just 

north of Sheep Bay (U.S. Department of Energy, 1978) 

where a large granodioritic pluton intrudes sedimentary and 

volcanic rocks of the Orca Group. Dickinson and Morrone 

(1982) evaluated several anomalies in the NURE data for 

the quadrangle, and they found that they resulted from 

radiometric contrasts between mafic volcanic, sedimentary, 

and plutonic rocks, and icefields. NURE sediment samples 

from streams draining the Sheep Bay pluton contained 6-

35 ppm U, and some had uranium-thorium ratios greater 

than 1 (D'Andrea, 1981). U.S. Geological Survey heavymineral-concentrate samples collected from around the 

pluton contained monazite and thorite and were strongly 

anomalous in bismuth, lanthanum, niobium, tin, tungsten, 

yttrium, and thorium, anomalies that indicate a high degree 

of differentiation of the pluton (Goldfarb and others, 1989). 

Scintillometer readings as high as 375 counts per second 

were taken over some outcrops of the pluton, and samples of 

the more radioactive outcrops assayed as high as 8 ppm U. 

The anomalous uranium content of the Sheep Bay pluton 

indicates a low potential for resources of uranium (Goldfarb 

and others, in press). 

Coal 

The Bering River coal field (fig. 1) was discovered in 

1896, and practically the entire 180-kril2 field northeast of 

Bering Lake was covered by coal claims by 1905 (Barnes, 

1951 ). The first extensive study of the area was by Martin 

( 1908), who prepared a geologic map and measured and 

sampled many of the coal beds. The numerous coal beds, 

which are contained entirely in the Kulthieth Formation, 

8 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

range from low-volatile bituminous to anthracite in rank and 

include some coal of coking quality (Martin, 1908; Barnes, 

1951, 1967). Evaluations prior to 1920 focused on potential 

use as fuel in steamships, and there may have been minor 

shipments during this time (Janson, 1979). These early 

investigations were hindered by outcrops that were isolated 

by heavy soil and vegetation; nonetheless, the studies were 

adequate to indicate that the coal beds change markedly in 

thickness within short distances and have measured thicknesses ranging from several centimeters to 19 m. The coal 

is strongly crushed and sheared, and the thicker beds have 

podlike shapes due to extreme structural deformation. 

Hypothetical resources of 3.6 billion tons have been 

estimated for the field (Sanders, 1975), which includes the 

Carbon Mountain area just east of the Cordova quadrangle. 

An extensive drilling program conducted by an industrynative corporation partnership in the early 1980's tested the 

economic potential of the coal in the Carbon Mountain area 

(Nelson and others, 1984). No production has ensued. The 

major obstacles to development in the Bering Lake area 

include complex structure of the coal-bearing strata, the 

presence of gas and abundant water underground, the lack 

of a deep-water port, and the difficulties in developing coal 

mines and shipping facilities in a remote and environmentally sensitive area. 

Petroleum 

Oil and gas seeps were discovered east of Katalla 

about 1896, and active onshore exploration for petroleum 

began soon thereafter in Tertiary rocks of the northern Gulf 

of Alaska region (Martin, 1908, 1921; Plafker, 1967, 1971, 

1987; Plafker and others, 1975). A small field was 

developed near the seeps. From 1902 through 1933, the 

Katalla field (fig. 1) produced about 153,992 barrels of 

paraffin-base crude oil from 18 shallow wells that tapped 

fracture porosity in the Poul Creek Formation (Miller, 

1975). Numerous oil seeps have been noted in the Don 

Miller Hills, east of the Bering River, and west of Ragged 

Mountain (fig. 1 ); several gas seeps have been located along 

the south edge of Bering Lake (Miller, 1961, 1975; Tysdal 

and others, 1976a). In addition to the petroleum seepages on 

the mainland, one seep of live light, low-sulfur, paraffinbase oil occurs in the Tokun Formation at the south end of 

Wingham Island (Plafker, 1987). Probably much or all of 

the petroleum was generated in deeply buried Eocene strata 

(Plafker and Claypool, 1979; Plafker, 1987). Twenty-five 

wells and core holes were drilled and abandoned onshore 

between 1954 and 1963, including two in the Katalla area. 

The Richfield Oil Corporation Bering River No. 1 well at 

Bering Lake (fig. 2) penetrated 1,882 m of the Tokun 

Formation and Kulthieth(?) Formation; the Bering River 

No. 2 well at Bering River was drilled to 1,835 m in the 

Poul Creek Formation and Tokun(?) Formation (Rau and 
others, 1983). One offshore well was drilled and abandoned 

in 1969 on state lands near Middleton Island. The Tenneco 

Middleton Island State No. 1 well, which penetrated 3,658 

m of strata correlative with the Yakataga, Poul Creek, and 

Tokun Formations, bottomed in strata of Eocene age (Rau 

and others, 1983; A.D. Warren, ARCO Alaska, Inc., written 

commun., 1990). During 1975-78, 1 stratigraphic test and 

10 wildcat wells that penetrated correlative rocks in tracts in 

Outer Continental Shelf Lease Sale No. 39 east of the 

Cordova and Middleton Island quadrangles were drilled and 

abandoned. The onshore and offshore wells did not discover 

economically recoverable petroleum due to a general lack of 

permeable reservoir rocks and, in the area of the Katalla 

wells, to structural complexity at depth. The Tertiary 

sequence on the Middleton Island shelf (west of the 

Chugach-Ragged Mountain-Wingham fault system, fig. 2) 

also apparently lacks suitable source rocks. To the east of 

this fault system, potential source and sandstone reservoir 

beds are found in thermally mature Eocene strata, which 

generally occur at depths exceeding 4,500 m (Plafker, 

1987). The major exploration problem is to find, in this 

structurally complex part of the Tertiary basin, suitable traps 

that have the Eocene section at economically producible 

depths. 

GEOLOGIC INVESTIGATIONS 

Field studies by U.S. Geological Survey personnel 

have been carried out intermittently in the Cordova and 

Middleton Island quadrangles from 1898 to the present 

time. The earliest geologic reconnaissance in eastern Prince 

William Sound was carried out by Schrader (1900), who 

distinguished two major rock units of regional extent, the 

Valdez and Orca Groups, and visited the copper prospects at 

Landlocked Bay and Ellamar (fig. 1). The first decade of 

geologic investigations throughout the sound was summarized by Grant and Higgins (1910). During the same 

period, the geology and mineral resources of the Controller 

Bay region were investigated by Martin (1908), who was 

the first to evaluate petroleum and coal occurrences in 

coastal southern Alaska. As copper mining was underway in 

northeastern Prince William Sound, detailed studies of the 

geologic settings for the deposits were conducted by Capps 

and Johnson (1913) in the Ellamar district and by Johnson 

(1919) in the Jack Bay area, a detailed geologic map of the 

Ellamar area was published (Capps and Johnson, 1915), and 

annual updates on mining in Prince William Sound were 

prepared by Johnson from 1913 to 1917. Additional 

investigations by Johnson and F.H. Moffit from 1923 to 

1925 and by Moffit and R.E. Fellows in 1943 were 

summarized in Moffit and Fellows (1950) and Moffit 

(1954), which added substantial new information about the 

mines and prospects and the areal geology, respectively, 

throughout Prince William Sound. Continuing stratigraphic 

studies in the coastal Tertiary sequences were conducted 

during these years (Taliaferro, 1932), but there was a 

general lull in geologic investigations in the region as the 

focus of Alaskan investigations shifted elsewhere. 

U.S. Geological Survey investigations were renewed 

in the Cordova and Middleton Island quadrangles in the late 

1950's with the beginning of a regional study of the Gulf of 

Alaska Tertiary province. Detailed studies in the southern 

Katalla area (Miller, 1961, 1975; Kachadoorian, 1960), and 

on Kayak and Wingham Islands (Plafker, 1974) provided 

part of the foundation for subsequent regional syntheses 

(Plafker, 1967, 1971, 1987). 

In response to the 1964 Alaska earthquake, earthscience studies in southern Alaska, particularly in the 

epicentral region of Prince William Sound, were accelerated 

greatly. Evaluations of the aftereffects of such an extreme 

tectonic event included numerous detailed studies in the 

Cordova and Middleton Island quadrangles, most notably in 

the Sheridan Glacier area (Plafker, 1968), as well as 

regional syntheses (for example, Case and others, 1966; 

Plafker, 1969). The potential earthquake hazards posed by 

activity on major faults in the region soon became a focus 

and led to detailed studies of the Hinchinbrook Island 

(Winkler, 1973) and Ragged Mountain areas in the quadrangles (Tysdal and others, 1976a, 1976b), as well as 

regional studies of major fault systems (for example, Plafker 

and others, 1977, 1986). Paleoseismologic studies were 

carried out in coastal areas, most notably at Middleton 

Island and the Copper River Delta, to determine the 

recurrence times for previous great earthquakes comparable 

to the 1964 earthquake (Plafker, 1969; Plafker and Rubin, 

1978; Plafker and others, 1991). 

In the early 1970's, the U.S. Geological Survey 

initiated studies of submarine geology and hazards related 

to petroleum exploration on the outer continental shelf in 

the eastern Gulf of Alaska. These studies, which supported 

Federal preparations for leasing tracts in the offshore region, 

yielded abundant new data in areas for which little 

information had been published previously. During marine 

geophysical and dredging cruises (Plafker and others, 1975; 

Bayer and others, 1978; Plafker and others, 1979, 1980), the 

stratigraphic sequences and structure of the submerged 

continental margin were confirmed to differ dramatically 

west and east of Kayak Island. Two features are most 

significant for inferences of petroleum potential: ( 1) the 

presence of thousands of meters of Neogene strata deformed 

by growth anticlines above the prospective sequences, and 

(2) structural segmentation of an accreting continental 

fragment (the Yakutat terrane) by oblique underthrusting at 

the continental margin (Plafker and others, 1978; Bruns, 

1979, 1985; Bruns and Plafker, 1982; Plafker, 1987). 

During the middle and late 1970's, the U.S. 

Geological Survey conducted interdisciplinary mineralresource assessments of adjacent 1 °X3° quadrangles-the 

Seward and Blying Sound quadrangles on the west (Tysdal, 

Geologic Investigations 9 
PACIFIC PLATE 

-==-~~ 50~ .alOOMILES 

0 50 100 150KILOMETERS 

Su bmonne contours in meters 

EXPLANATION 

Fault-Dashed where approximately located, dotted where concealed, queried where inferred 

Cenozoic volcanic rocks-Star 

shows andesitic volcanoes 

Terranes ••••• Thrust-Sawteeth on upper plate 

}@/.U·X Yakutat . ·~ 

Strike slip-Arrows indicate relative horizontal motion 

Oblique thrust-Sawteeth on upper plate, arrows indicate 

;~~:~;:: Ji~E· Prince William 

Chugach 

Peninsular/Wrangellia 

Alexander 

Ghost Rocks 

Undifferentiated 

BRFS 

CFS 

relative horizontal motion 

Border Ranges fault system 

Contact fault system 

AM Aleutian megathrust 

CSFS 

RMF 

WF 

KIZ 

PZ 

Chugach-St.Elias fault system 

Ragged Mountain fault 

Wingham fault 

Kayak Island zone 

Pamplona zone 

Figure 3. Geologic terranes of the northern Gulf of Alaska region, showing selected faults and boundaries of 1 °X3° quadrangles 

(modified from Plafker, 1987). Names of quadrangles are: A, Anchorage; BG, Bering Glacier; BS, Blying Sound; C, Cordova; IB, Icy 

Bay; M, McCarthy; Ml, Middleton Island; S, Seward; V, Valdez. 

1978; Tysdal and Case, 1979, 1982), and the Valdez 

quadrangle (Winkler, Miller, and others, 1981; Winkler, 

Silberman, and others, 1981) on the north (fig. 3). These 

investigations provided detailed information on the geology 

and mineral resources of the Chugach and Prince William 

terranes, which extend directly into the Cordova and Middleton Island quadrangles. 

1 0 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

In the early 1980's, a regional study of the potential 

for undiscovered mineral resources in the Chugach National 

Forest was completed (Nelson and others, 1984). Parts of an 

existing preliminary geologic map of the Cordova and 

Middleton Island quadrangles (Winkler and Plafker, 1981) 

were revised significantly during the regional study and 

were incorporated in a new map of the entire national forest 
(Nelson ·and others, 1985). A geochemical survey of the 

forest was completed (Goldfarb and others, 1984), and maps 

were produced that showed distribution of suites of anomalous elements (Goldfarb and Smith, 1987) and selected 

metallic minerals (Tripp and others, 1985; Goldfarb and 

Tripp, 1985; Goldfarb and others, 1985). Additional gravity 

data were collected in many places in the forest, and a 

summary gravity contour map and interpretation of the data 

were prepared (Barnes and Morin, 1990). During this field 

work, a small manganese deposit was discovered on 

Hinchinbrook Island (Goodfellow and others, 1984). Subsequently, a quantitative assessment of potential endowment of precious, base, and ferrous metals for selected 

mineral-deposit types throughout the forest was prepared 

(Bliss, 1989). 

For the recent Alaska Mineral Resource Assessment 

Program (AMRAP) investigations, a revised geologic map 

of the Cordova and Middleton Island quadrangles was 

prepared (Winkler and Plafker, in press); a geochemical 

survey was completed (Sutley and others, 1986), and areas 

geochemically favorable for metallic mineral resources 

were delineated (Goldfarb and others, 1989); an interpretation of aeromagnetic data for the quadrangles was 

completed (Case and others, written commun., 1992); and 

summary maps were prepared that define areas, based on 

geological, geochemical, and geophysical characteristics 

and mineral-deposit models, that are favorable for the 

occurrence of specific types of mineral resources (Goldfarb 

and others, in press). 

In the mid-1980's, multidisciplinary geophysical 

investigations of the deep crustal structure of southern 

Alaska were conducted along the southern part of the 

Trans-Alaska Crustal Transect (TACT). Detailed surface 

geologic studies were carried out in support of the geophysical studies, including mapping of six 15-minute quadrangles in the Cordova 1 °X3° quadrangle (George Plafker, 

and J.S. Lull, U.S. Geological Survey, written commun., 

1990) and a variety of detailed structural, geochemical, and 

isotopic studies near the transect. Geological and structural 

interpretations of terranes that extend into the quadrangles 

have been reported by Plafker and others (1989) and 

Nokleberg and others (1989). Within and near the Cordova 

and Middleton Island quadrangles, recent TACT reports 

include: (1) paleomagnetic studies of volcanic sequences at 

Galena Bay just north of the Cordova quadrangle (Plumley 

and Plafker, 1985) and near Wingham Island (P.W. Plumley, written commun., 1990), and (2) a study of the Contact 

fault system that separates the Chugach and Prince William 

terranes (Plafker and others, 1986). Additional reports are 

being prepared on anatectic granites in the Cordova 

quadrangle west of the Copper River (Fred Barker, U.S. 

Geological Survey, written commun., 1990) and on geochemical and isotopic evidence for the provenance of the 

Orca and Valdez Groups (G.L. Farmer, University of 

Colorado, written commun., 1990). 

GEOLOGIC AND TECTONIC SUMMARY 

The Cordova-Middleton Island region (Winkler and 

Plafker, in press) consists of three distinctive fault-bounded 

terranes (figs. 2, 3), the Chugach, Prince William, and 

Yakutat terranes (Jones and others, 1987). From north to 

south, these terranes become progressively younger and less 

severely deformed and metamorphosed (Plafker, 1969, 

1971, 1987). 

The oldest (Chugach) terrane, in the northern part of 

the Cordova quadrangle, is underlain by the Upper 

Cretaceous Valdez Group and is considered to be part of the 

Chugach terrane as defined by Berg and others (1972). The 

Valdez Group (units Kms and Kmv, fig. 2) consists chiefly 

of fault-bounded wedges of volcanogenic flysch and subordinate tholeiitic basalt; one occurrence of ultramafic rocks 

is known near the head of Port Fidalgo (Nelson and others, 

1985). The Valdez Group is regionally metamorphosed to 

lower greenschist facies. The rocks are foliated, tightly 

folded, and commonly overturned toward the south, and are 

imbricated along numerous steeply dipping faults. 

The metamorphic grade of the Valdez Group 

increases to the east, where the rocks grade into a belt of 

schist, gneiss, and migmatite that extends eastward across 

the adjacent Bering Glacier quadrangle to the Canadian 

border. Typical granoblastic textures and the superimposition of progressive metamorphism across regional structural trends indicate that much of the amphibolite-facies 

metamorphism of the Valdez Group occurred after it was 

deformed against and accreted to the continental margin 

(Hudson and Plafker, 1982). These high-grade metamorphic 

rocks represent deeply buried parts of the accretionary 

prism, and their development is believed to be spatially and 

genetically related to emplacement of early Eocene anatectic granitic plutons (Hudson and others, 1979). 

No valid paleomagnetic data exist for the Chugach 

terrane. Although variable amounts of northward translation 

have been proposed for the Chugach terrane (Gromme and 

Hillhouse, 1981; Stone and Packer, 1979; Stone and others, 

1982), all previous determinations of paleolatitudes may be 

challenged on the basis of unresolved structural problems. 

Three characteristics of the Chugach terrane make longdistance translation improbable; instead, they indicate a 

probable linkage with the adjacent continental margin of 

southern and southeastern Alaska and British Columbia. 

First, the volume and provenance of flysch that makes up 

the bulk of the Chugach terrane suggest derivation from an 

active westward-facing Andean-type magmatic arc that 

Plafker and others (1989) have informally named the 

Kluane arc. Second, the lateral extent of the flysch in the 

region aligns approximately with this discontinuously 

exposed landward belt of coeval inferred magmatic arc 

rocks that extends from the central Alaska Range 

southeastward through the Coast crystalline complex into 

British Columbia (Monger and others, 1982). Third, 

Geologic and Tectonic Summary 11 
sedimentologic and isotopic data indicate that a major part 

of the Chugach flysch came from the region of southeastern 

Alaska and British Columbia and was transported northwestward along the continental margin (Hollister, 1979; 

Zuffa and others, 1980; Dumoulin, 1987). Although alternative sediment sources for the Chugach flysch are possible, 

they require improbably large and rapid strike-slip movement of the terrane from these sources; this movement 

would have imposed tectonic effects and histories on the 

southern Alaska margin that have not been observed. 

A major change in plate motions in the Eocene 

resulted in northwestward movement of the Pacific oceanic 

crust relative to the Alaska continental margin. Also about 

this time, counterclockwise oroclinal bending of western 

Alaska occurred along a main axis in the eastern part of 

Prince William Sound (Carey, 1958; Plafker, 1969). As a 

result of these relative plate movements, ensimatic deep-sea 

fan deposits and intercalated tholeiitic basalt of late Paleocene and Eocene age, which make up the Orca Group of the 

Prince William terrane, were accreted, principally along the 

western limb of the oroclinal bend where they form a belt 

that is more than 110 km wide from southeast of Minchinbrook Island to northwest of Valdez Arm. The combination 

of northwest-southeast compression during accretion and 

east-west compression due to virtually simultaneous oroclinal bending resulted in the complex deformation of the 

Orca Group, particularly in the eastern part of the Cordova 

quadrangle. An analysis of the variable deformational styles 

in the Orca Group is presented by Winkler and Plafker (in 

press). 

In the Cordova and Middleton Island quadrangles, 

Orca sedimentary rocks apparently do not retain magnetization of syndepositional origin, which has made the 

determination of original paleolatitudes difficult (Hillhouse 

and Gromme, 1985). However, preliminary paleolatitudes 

from 13°-18°±12°-20° N have been determined from 

pillow-basalt sequences at Galena Bay and near Wingham 

and Whale Islands (Plumley and Plafker, 1985; P.W. 

Plumley, written commun., 1990); these determinations 

indicate possible large northward movement of at least these 

parts of the Orca Group relative to cratonic North America. 

The Contact fault system (fig. 3) separates the Chugach terrane from the Prince William terrane (Plafker and 

others, 1977; Plafker and others, 1986). The system is a 

major early Tertiary terrane boundary that extends from 

near Mount Saint Elias, 170 km east of the Cordova and 

Middleton Island quadrangles, to Kodiak Island. In the 

Cordova quadrangle (fig. 2), the Contact fault system 

consists of northward-dipping reverse faults-the Bagley, 

Gravina, and Landlock segments. Each of these fault 

segments has distinctive characteristics that may reflect 

some post-Orca oroclinal bending of an initially more linear 

structure (Winkler and Plafker, in press). The various 

12 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

segments were discussed in more detail by Plafker and 

Lanphere (1974), Winkler and Plafker (1975), Winkler and 

others (1981), and Plafker and others (1986). Accretion of 

the Orca Group south of the Contact fault system was 

accompanied by intense folding and faulting in both Valdez 

and Orca rocks, resulting in parallel structures in both 

groups adjacent to parts of the fault system. Along the 

TACT corridor, the Contact fault marks an abrupt change in 

deep crustal structure (Fuis and Plafker, 1991). 

Successive accretionary wedges within the Orca 

Group may be bounded by major northeast-trending splays 

from the Contact fault system, including the Martin, Rude 

River, Cordova, and Etches faults (fig. 2). Tysdal and Case 

(1979) and Helwig and Emmet (1981) described comparable fault-bounded belts within the Orca Group in 

western Prince William Sound. 

Anatectic granitic plutons of early Eocene age were 

emplaced within both the Orca and Valdez rocks shortly 

after the major phase of early Tertiary accretion, deformation, and metamorphism (Hudson and others, 1979). 

Tectonic and isotopic models attribute the heat for melting 

the accretionary prism to subduction of a magmatically 

active Kula oceanic plate beneath the continental margin. 

Plausible alternative explanations for specific sources of 

heat include oceanic islands or seamounts (Winkler, 1976), 

a triple junction (Marshak and Karig (1977), a leaky 

transform (Tysdal and others, 1977), thermal surge with 

change in subduction regime (Hudson and others, 1979), 

opening of a mantle window during ridge subduction 

(Plafker and others, 1989), or subduction of a very young, 

still-hot oceanic slab (Sisson and others, 1989). Inasmuch as 

at least three types of basalt occur in the accretionary prism 

(Lull and Plafker, 1990; S.W. Nelson, U.S. Geological 

Survey, written commun., 1990), a combination ofmagmatically active settings may be responsible. 

The Orca Group is bounded on the south and east by 

the Chugach, Ragged Mountain, and Wingham faults (figs. 

2, 3), which delineate the west margin of the Yakutat 

terrane. The faults juxtapose an upper plate of older, more 

competent, prehnite-pumpellyite facies metamorphic rocks 

of the Orca Group and a lower plate of unmetamorphosed 

bedded Tertiary rocks of the Yakutat terrane (fig. 3). 

The Yakutat terrane is allochthonous with respect to 

the Orca Group (Plafker and others, 1975; Lahr and Plafker, 

1980; Bruns and Plafker, 1982; Plafker, 1987). West of the 

Chugach-Ragged Mountain-Wingham fault system, the basement is composed largely, if not entirely, of the Orca Group 

and associated plutonic rocks (Plafker and others, 1982), 

whereas to the east, the basement is probably oceanic crust 

(Bayer and others, 1978). To the west, pre-Miocene bedded 

rocks above the Orca are exposed only on Wessels Reef 

and were penetrated in the Middleton Island State 

No. 1 well near Middleton Island. The Paleogene rocks have 

not been studied thoroughly, but they differ lithologically 

and paleontologically from coeval sequences east of the 
fault system (Rau and others, 1983; Plafker, 1987; A.D. 

Warren, ARCO Alaska, Inc., written commun., 1990). To 

the east, the pre-Miocene sequences are well known (Miller, 

1961, 1971, 1975; Plafker, 1971, 1974, 1987), and they 

were deposited at or near a continental margin. The Stillwater, Kulthieth, and lower part of the Tokun Formations, 

of (overall) middle to late Eocene age, are a regressive 

sequence consisting of thick, interfingering, coal-bearing 

lagoon, barrier-beach, and delta complexes. Their sandstone 

beds predominantly are arkosic (Winkler and others, 1976) 

and reflect derivation from a predominantly granitic and 

metamorphic source terrane. During Oligocene and presumably early Miocene time, predominantly shaly sediment, in part rich in organic material and intercalated with 

water-laid alkalic basaltic tuff, breccia, and pillow lava, 

accumulated to form the Poul Creek Formation and perhaps 

the lower part of the sandy and conglomeratic Redwood 

Formation. Transgression is indicated by neritic and bathyal 

fauna in these units (Rau and others, 1983). 

The Cenozoic sequence of post-Orca age in the 

Katalla area and on Kayak, Wingham, and Middleton 

Islands does not include major unconformities. It appears to 

have been deformed essentially as a unit, beginning in 

post-middle Miocene time. The structural style and timing 

of this deformation were discussed in detail by Plafker 

( 1987) and Winkler and Plafker (in press). 

The present sedimentary and tectonic regime results 

from northwestward movement of the Pacific plate and 

Yakutat terrane relative to the Alaskan continental margin 

since the Miocene and the resulting accretion of the Yakutat 

terrane to southern Alaska, a process that continues to the 

present (Plafker, 1987). Large topographic relief, intense 

seismicity, recent faulting, and regional warping that 

characterize this part of the Gulf of Alaska region (Plafker, 

1969) result from the Pacific plate colliding with and 

underthrusting the North American plate. From about the 

middle Miocene to the present, an enormous thickness of 

clastic sedimentary rocks comprising the Yakataga Formation and part of the Redwood Formation and including 

much glacially derived material from the Chugach and Saint 

Elias Mountains (north and east of the Cordova and Middleton Island quadrangles) was deposited in a predominantly shelf environment (Miller, 1953; Plafker and 

Addicott, 1976). Structures in the Neogene sequence tend to 

parallel trends of older structures; locally divergent trends in 

the Katalla area may reflect local deformation of the 

younger rocks against the more competent backstop of the 

Orca Group during relative westward underthrusting along 

the Chugach-Ragged Mountain-Wingham fault system 

(Tysdal and others, 1976b). 

GEOCHEMICAL INVESTIGATIONS 

A reconnaissance geochemical survey of the Cordova 

and Middleton Island quadrangles was conducted by the 

U.S. Geological Survey from 1979 through 1984. A total of 

844 sediment samples and 749 nonmagnetic heavy-mineralconcentrate samples was collected from streams and 

moraines; they were analyzed by semiquantitative emission 

spectrography, and selected elements in the sediments were 

determined by atomic-absorption spectrophotometry. The 

data were tabulated by Sutley and others (1986) and were 

evaluated by Goldfarb and others ( 1989), who included an 

extensive R-mode factor analysis of geochemical associations for stream-sediment and concentrate samples and 

described geochemical anomalies in detail. Goldfarb and 

others (1989) also evaluated data from 499 stream-sediment 

samples collected in the quadrangles during the NURE 

program of the U.S. Department of Energy (D'Andrea and 

others, 1981 ). 

Concentrate samples with gold values of 20 ppm or 

more were collected from much of the northern quarter of 

the Cordova quadrangle from streams that drain areas where 

the Valdez Group crops out. Silver values of 1 ppm or more 

are associated with virtually all the anomalous gold values; 

the gold and silver values identify drainage basins likely to 

contain precious-metal-bearing quartz veins. Arsenopyrite, 

and to a lesser extent galena, sphalerite, and chalcopyrite, 

are found with pyrite in many of the precious-metal-bearing 

quartz veins in the Valdez Group (Goldfarb and Tripp, 

1985; Goldfarb and others, 1985). Despite the presence of 

gold values in many concentrates, placer-gold resources are 

not likely to be present in the northern Cordova quadrangle. 

Most unconsolidated material in the area is fluvioglacial; 

thus, any placers that may have existed prior to glaciation 

are likely to have been either destroyed or diluted below 

economic grade (Goldfarb and others, in press). 

Concentrate samples with anomalous gold values also 

were collected in scattered places from streams that drain 

the Orca Group (Goldfarb and others, 1989). Bedrock 

upstream from sample sites generally included quartz 

stringers and veins in Orca sedimentary rocks. Nearby 

stocks or sills were inferred to have provided heat and fluids 

during formation of the veins. 

Reimnitz and Plafker (1976) noted concentrations of 

heavy minerals with gold values as high as 0.25 ppm in 

sands sampled from offshore beach bars of the Copper 

River Delta. Beach-sand samples collected elsewhere in the 

Cordova and Middleton Island quadrangles, however, 

contained only background values of 10--20 ppb or less Au 

(Reimnitz and Plafker, 1976; Goldfarb and others, 1984; 

Sutley and others, 1986). Jansons and others (1984) noted 

trace amounts of gold (0.004-0.005 ounce per cubic yard) in 

alluvial sand at numerous sites along the Copper River. 

Although the sources for the gold placers in the Copper 

River barrier beaches and alluvial deposits are unknown, the 

large volume of easily accessible sand may warrant 

additional evaluation. 

Concentrate samples with anomalous tungsten ( 100 

ppm or more) are widespread in the Cordova. quadrangle 

Geochemical Investigations 13 
and correlate with the presence of microscopically visible 

scheelite (Goldfarb and others, 1989). The spatial 

distribution of scheelite, and to a lesser extent anomalous 

tungsten, roughly correlates with the distribution of rocks of 

the Valdez Group or with areas where the Orca Group has 

been metamorphosed thermally by intrusion of Eocene 

granodioritic rocks. The source of the scheelite has not been 

demonstrated conclusively but likely is the ubiquitous 

metamorphic quartz veins (Goldfarb and others, 1989). 

Concentrate samples enriched in iron, cobalt, copper, 

and nickel, and less consistently in silver, arsenic, and lead, 

delineate a widespread belt in the higher elevations of the 

Cordova quadrangle west of the Copper River, the central 

sulfide belt of Goldfarb and others (1989). Pyrite and 

chalcopyrite are abundant in most concentrate samples, and 

galena and sphalerite are present in many (Goldfarb and 

Tripp, 1985; Goldfarb and others, 1985). This area of 

base-metal-sulfide geochemical associations is underlain by 

rocks of both the Valdez and Orca Groups, and is likely to 

include occurrences of massive or disseminated sulfide 

deposits and base-metal-bearing quartz veins. Areas near 

Ellamar, south of Port Fidalgo, central Hawkins Island, and 

between Cordova and the Copper River contain anomalous 

zinc in stream-sediment samples. Goldfarb and others 

(1989) interpreted the presence of clusters of elevated zinc 

values in these areas underlain by the Orca Group to 

indicate the most favorable ground for volcanogenic 

massive-sulfide occurrences. 

· · Concentrate samples that contain anomalous barium 

(3,000 to more than 10,000 ppm) define a distinct belt from 

Hinchinbrook Island to the mainland east of Cordova 

(Goldfarb and others, 1989). The belt of elevated barium 

concentrations generally coincides with outcrops of sedimentary rocks in the Orca Group and most likely reflects 

abundant detrital barite, which is microscopically visible in 

many samples (Goldfarb and others, 1985). 

Highly anomalous values for manganese in stream 

sediments and concentrates from the Gravina River area, 

which is underlain by metasedimentary rocks of the Valdez 

Group, may indicate an additional region of rocks that are 

enriched in base metals or manganese. 

In the southeastern part of the Cordova quadrangle 

and adjacent parts of the Middleton Island quadrangle, 

barium and zinc values in stream-sediment concentrates are 

consistently highly anomalous. This area includes virtually 

all of Kayak Island and may contain bedded or disseminated 

accumulations of these metals in the younger Tertiary 

sedimentary rocks of the Yakutat terrane from which the 

sediments were derived. 

GEOPHYSICAL INVESTIGATIONS 

Following the Alaska earthquake of March 27, 1964, 

the U.S. Geological Survey intensively investigated the 

effects of the earthquake in the Prince William Sound 

14 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

region, including studies to establish the geologic and 

tectonic setting of the earthquake. A regional gravity survey 

was completed that included approximately 120 stations in 

the Cordova quadrangle (Case and others, 1966). A pronounced gravity high with an amplitude of about 25 mGal 

(milligals) near Ellamar was found to correspond to areas of 

dense mafic volcanic rocks within the Orca Group. A broad 

gravity low with an amplitude of more than 10 mGal 

centered on Port Gravina was related to the relatively low 

density granitic rocks of the Sheep Bay pluton, which were 

presumed to be more extensive at depth. Additional gra~ity 

data were acquired intermittently over the followmg 

decades, most recently during mineral-resource studies of 

the Chugach National Forest. Barnes and Morin (1990) 

incorporated all the gravity data into an anomaly map of the 

national forest. The map includes most of the Cordova and 

Middleton Island quadrangles but does not extend onto the 

outer continental shelf. Gravity values become increasingly 

negative northwest across the quadrangles, consistent with 

increase in crustal thickness (Barnes and Morin, 1990). In 

the northeast part of the Cordova quadrangle, a gravity high 

with an amplitude in excess of 50 mGal occurs in areas of 

mafic metavolcanic rocks in the Valdez Group and extends 

eastward with diminishing amplitude at least as far as the 

Copper River. Its source is probably within the upper crust. 

The work of Barnes and Morin (1990) reconfirmed the 

gravity low in the Port Gravina area and indicates that it is 

one of a series of disconnected lows with amplitudes as 

much as 25 mGal that extend eastward across the entire 

Cordova quadrangle along the lineament defined by 

drainages of the Rude River, Childs Glacier, and Miles 

Glacier. Scattered outcrops of Eocene granitic plutons along 

this entire trend (Winkler and Plafker, in press) support the 

inference that intrusive rocks are widespread at depth. The 

plutonic rocks are slightly less dense than surrounding 

metasedimentary rocks of the Orca and Valdez Groups and 

may be responsible for these negative gravity-anomaly 

features. 

Marine and airborne magnetic surveys were conducted in the Cordova and Middleton Island quadrangles 

and southward into the Gulf of Alaska in the early and 

middle 1970's (Naugler and Wageman, 1973; Taylor and 

O'Neill, 1974; U.S. Geological Survey, 1979; Schwab and 

Bruns, 1979). In the late 1980's, additional detailed aeromagnetic data were acquired over the offshore continental 

margin and deep ocean floor (U.S. Geological Survey, 

1988). Using the new data, Griscom and Sauer (1990) 

modeled the depth and geometry of the so-called "Slope" 

magnetic anomaly. This anomaly extends 500 km from near 

Cross Sound westward along the continental slope to near 

Kayak Island (Schwab and others, 1980) and apparently is 

caused by the truncated edge of a tabular, undulating slab of 

highly magnetic Paleogene oceanic crust that composes the 

basement of the Yakutat terrane (Plafker, 1987). From the 

Kayak Island structural zone (the landward extension of the 
Aleutian· subduction zone, fig. 3), the slope anomaly 

extends westward beneath the continental margin, and its 

magnetic signature can be detected beneath the overriding 

plate for at least another 200 km to the west (Griscom and 

Sauer, 1990). 

In the Cordova and Middleton Island quadrangles, 

Case and others (written commun., 1992) have combined 

the new data on the continental shelf with earlier data from 

over the islands and mainland for a detailed interpretation of 

magnetic anomalies of shallow source. Many highamplitude positive magnetic anomalies that correspond 

closely with mapped outcrops of volcanic rocks of the 

Paleocene and Eocene Orca Group extend onto the shelf 

where they form aligned discontinuous belts. In addition, 

high-amplitude positive anomalies on the mainland in the 

northern Cordova quadrangle are associated with mafic 

volcanic and ultramafic rocks in the Cretaceous Valdez 

Group. However, in detail the magnetic expression of the 

volcanic and metavolcanic sequences is quite variable and 

depends not only on original magnetite content and 

thickness of units, but also on subsequent alteration and 

metamorphism. The character of the pronounced positive 

anomalies constrains interpreted location and dip of both 

sequences of volcanic rocks in the subsurface, even through 

considerable thickness of water, glaciers, or unconsolidated 

deposits. However, the variability of magnetic expression 

influences the reliability of depth estimates based on 

horizontal extents of steepest gradients. Moreover, the 

bottoms of volcanic sequences are not defined by the 

magnetic data. Some magnetic highs in the canyon of the 

Copper River and the Copper River delta may be produced 

by concentrations of magnetite in alluvial or glacial deposits 

rather than by concealed volcanic rocks. These areas of 

probable black-sand accumulations also are likely to contain 

placer gold (Case and others, written commun., 1992 ). The 

large volume of accessible material constitutes a potential 

resource that should be evaluated further. 

In the mid-1980's, geophysical investigations of the 

deep crustal structure of southern Alaska were conducted 

onshore along the southern part of the Trans-Alaska Crustal 

Transect. The deep crustal structure of offshore parts of the 

region was investigated in 1988 by a shipborne survey using 

a large airgun array (Brocher and others, 1991 ). Onshore 

studies of seismic reflection (Fisher and others, 1989) and 

refraction (Puis and others, 1991; Wolf and others, 1991) 

yielded abundant data on the deep crust and compare well 

with offshore seismic reflection and refraction data in and 

near Prince William Sound (Fisher and others, 1987; 

Brocher and others, 1991). Depth to the Moho discontinuity 

is about 13 km below sea level in the Pacific plate south of 

Middleton Island (Brocher and others, 1991) and increases 

in depth northward to about 25-40 km under the Prince 

William and Chugach terranes (Fuis and Plafker, 1991; Fuis 

and others, 1991). The crustal velocity structures of the 

Chugach and Prince William terranes are distinct to at least 

1 0-km depth (Wolf and others, 1991 ), which indicates that 

the contact fault is a fundamental crustal boundary. P-wave 

velocities are about 5.9-7.4 km/s (kilometers per second) in 

the lower crust of these terranes and about 7.8 km/s in the 

upper mantle. Subparallel, north-dipping, strong seismic 

reflectors between about 8 and 24 km depth in the Chugach 

Mountains north of the Cordova quadrangle have been 

interpreted (Puis and Plafker, 1991) as underplated oceanic 

crust and possibly upper mantle. Ultramafic rocks that are 

exposed in one small area north of Port Fidalgo (Nelson and 

others, 1985) may be a fragment of these rocks at the 

surface. Fuis and Plafker (1991) inferred that undulating 

reflectors at depths between about 6 and 10 km in the upper 

crust are tonalitic plutons, which fed swarms of dikes that 

are exposed at the surface directly above. Studies of 

earthquake seismicity (Page and others, 1989) have led to 

inferences that the subducted oceanic crust is buckled 

around a north-trending axis beneath northeastern Prince 

William Sound, which is approximately the axis of the 

southern Alaska orocline. 

REFERENCES CITED 

Barnes, D.F., and Morin, R.L., 1990, Gravity contour map and 

interpretation of gravity data for the Chugach National 

Forest, Alaska: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1645-F, 5 p., 1 sheet, scale 1:250,000. 

Barnes, F.F., 1951, A review of the geology and coal resources of 

the Bering River coal field, Alaska: U.S. Geological Survey 

Circular 146, 11 p. 

__ 1967, Coal resources of Alaska: U.S. Geological Survey 

Bulletin 1242-B, p. B1-B36. 

Bayer, K.C., Mattick, R.E., Plafker, George, and Bruns, T.R., 

1978, Refraction studies between Icy Bay and Kayak Island, 

eastern Gulf of Alaska: U.S. Geological Survey Journal of 

Research, v. 6, no. 5, p. 625-636. 

Berg, H.C., Jones, D.L., and Richter, D.H., 1972, GravinaNutzotin belt-tectonic significance of an upper Mesozoic 

sedimentary and volcanic sequence in southern and southeastern Alaska, in Geological Survey research 1972: U.S. 

Geological Survey Professional Paper 800-D, p. D1-

D24. 

Bliss, J.D., 1989, Quantitative mineral resource assessment of 

undiscovered mineral deposits for selected mineral deposit 

types in the Chugach National Forest, Alaska: U.S. 

Geological Survey Open-File Report 89-345, 25 p. 

Brocher, T.M., Fisher, M.A., Stephens, C.D., Moses, M.J., and 

Geist, E.L., 1991, Structure and tectonics of the northern 

Gulf of Alaska [abs.]: Geological Society of America 

Abstracts with Programs, v. 23, no. 2, p. 8. 

Bruns, T.R., 1979, Late Cenozoic structure of the continental 

· margin, northern Gulf of Alaska, in Sisson, A., ed., The 

relationship of plate tectonics to Alaskan geology and 

resources: Anchorage, Alaska Geological Society, Sixth 

Symposium Proceedings, p. 11-130. 

__ 1985, Tectonics of the Yakutat block, an allochthonous 

terrane in the northern Gulf of Alaska: U.S. Geological 

Survey Open-File Report 85-13, 112 p. 

References Cited 15 
Bruns, T.R., and Plafker, George, 1982, Geology, structure, and 

petroleum potential of the southeastern Alaska and northern 

Gulf of Alaska continental margins, in Bruns, T.R., ed., 

Hydrocarbon resource potential for proposed OCS lease 

sale 88-Southeastern Alaska, northern Gulf of Alaska, 

Cook Inlet, and Shelikof Strait, Alaska: U.S. Geological 

Survey Open-File Report 82-928, p. 11-52. 

Capps, S.R., and Johnson, B.L., 1913, Mineral deposits of the 

Ellamar district, in Mineral resources of Alaska, 1912: U.S. 

Geological Survey Bulletin 542, p. 86-124. 

_1915, The Ellamar district, Alaska: U.S. Geological 

Survey Bulletin 605, 125 p. 

Carey, S.W., 1958, The tectonic approach to continental drift, in 

Carey, S.W., convenor, Continental drift symposium, 

present status of the continental drift hypothesis (March 

1956): Hobart, Australia, University of Tasmania, Geology 

Department, p. 177-355. 

Case, J.E., Barnes, D.F., Plafker, Geroge,a nd Robbins, S.L., 1966, 

Gravity survey and regional geology of the Prince William 

Sound epicentral region, in The Alaska earthquake, 

March 27, 1964-Regional effects: U.S. Geological Survey 

Professional Paper 543-C, p. C1-C12. 

Chapin, Theodore, 1913, The McKinley Lake district, in Mineral 

resources of Alaska, 1912: U.S. Geological Survey Bulletin 

542-C, p. 78-80. 

D'Andrea, R.F., Jr., and others, 1981, Uranium hydrogeochemical 

and stream sediment reconnaissance of the Cordova NTMS 

quadrangle, Alaska: U.S. Department of Energy Open-File 

Report GJBX-185(81), 67 p. Available from Books and 

Open-File Services Section, U.S. Geological Survey, 

Federal Center, Box 25046, Denver, CO 80225. 

de Laguna, Frederica, 1956, Chugach prehistory-The archaeology of Prince William Sound, Alaska: Seattle, University 

of Washington Press, 289 p. 

Dickinson, K.A., and Morrone, J.F., 1982, Distribution of uranium 

and thorium in the lower Tertiary Orca Group and related 

rocks in part of the Cordova quadrangle, southern Alaska: 

U.S. Geological Survey Open-File Report 82-1032, 10 p. 

Dumoulin, J.A., 1987, Sandstone composition of the Valdez and 

Orca Groups, Prince William Sound, Alaska: U.S. 

Geological Survey Bulletin 1774, 37 p. 

Eyles, Nicholas, 1990, Glacially derived, shallow-marine gold 

placers of the Cape Yakataga district, Gulf of Alaska: 

Sedimentary Geology, v. 68, p. 171-185. 

Fisher, M.A., Brocher, T.M., Nokleberg, W.J., Plafker, George, 

and Smith, G.L., 1989, Seismic reflection images of the 

crust of the northern part of the Chugach terrane, 

Alaska-Results of a survey for the Trans-Alaska Crustal 

Transect: Journal of Geophysical Research, v. 94, no. B4, 

p. 4424-4440. 

Fisher, M.A., von Huene, Roland, and Smith, G.L., 1987, 

Reflections from midcrustal rocks within the Mesozoic 

subduction complex near the eastern Aleutian trench: 

Journal of Geophysical Research, v. 92, no. B4, p. 7907-

7915. 

Puis, G.S., Ambos, E.L., Mooney, W.D., Christensen, N.I., and 

Geist, Eric, 1991, Crustal structure of accreted terranes in 

southern Alaska, Chugach Mountains, and Copper River 

basin from seismic refraction results: Journal of Geophysical Research, v. 96, no. B3, p. 4187-4227. 

16 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

Puis, G.S., and Plafker, George, 1991, Evolution of deep structure 

along the Trans-Alaska Crustal Transect, Chugach Mountains and Copper River Basin, southern Alaska: Journal of 

Geophysical Research, v. 96, no. B3, p. 4229-4253. 

Goldfarb, R.J., Case, J.E., Plafker, George, and Winkler, G.R., in 

press, Map showing areas of potential for mineral resources 

in the Cordova and northern Middleton Island 1 °x2° 

quadrangles, southern Alaska: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-2190, 1 sheet, scale 

1:250,000. 

Goldfarb, R.J., Leach, D.L., Miller, M.L., and Pickthorn, W.J., 

1986, Geology, metamorphic setting, and genetic constraints of epigenetic lode-gold mineralization within the 

Cretaceous Valdez Group, south-central Alaska, in Keppie, 

J.D., Boyle, R.W., and Haynes, S.J., eds., Turbidite-hosted 

gold deposits: Geological Association of Canada Special 

Paper 32, p. 87-105. 

Goldfarb, R.J., Nelson, S.W., Dumoulin, J.A., and Miller, M.L., 

1984, Data report and statistical summary for samples of 

moraine and stream-sediment, nonmagnetic heavy-mineralconcentrate, and rock samples from the Chugach National 

Forest, Alaska: U.S. Geological Survey Open-File Report 

84-355, 466 p. 

Goldfarb, R.J., O'Leary, R.M., Sutley, S.J., and Tripp, R.B., 1989, 

Geochemical survey of the Cordova and Middleton Island 

1 °x3° quadrangles, south-central Alaska: U.S. Geological 

Survey Bulletin 1865, 32 p., 3 sheets, scales 1:250,000 and 

1:125,000. 

Goldfarb, R.J., and Smith, S.C., 1987, Geochemical map showing 

distribution of anomalous element suites in nonmagnetic 

heavy-mineral concentrates from the Chugach National 

Forest, Alaska: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1645-F, 1 sheet, scale 1:250,000. 

Goldfarb, R.J., and Tripp, R.B., 1985, Geochemical map showing 

distribution of chalcopyrite within the Chugach National 

Forest, Alaska: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1645-E, 1 sheet, scale 1:250,000. 

Goldfarb, R.J., Tripp, R.B., and Smaglik, S.M., 1985, Geochemical map showing distribution of barite, galena, and 

sphalerite within the Chugach National Forest, Alaska: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF-1645-C, 1 sheet, scale 1:250,000. 

Goodfellow, Robert, Nelson, S.W., Bouse, R.M., and Koski, R.A., 

1984, The geologic setting and composition of a newly 

discovered manganese deposit on Hinchinbrook Island, 

Alaska: U.S. Geological Survey Open-File Report 84-671, 

9 p. 

Grant, U.S., and Higgins, D.F., 1910, Reconnaissance of the 

geology and mineral resources of Prince William Sound, 

Alaska: U.S. Geological Survey Bulletin 443, 89 p. 

Griscom, Andrew, and Sauer, P.E., 1990, Interpretation of magnetic maps of the northern Gulf of Alaska, with emphasis on 

the source of the Slope anomaly: U.S. Geological Survey 

Open-File Report 90-348, 18 p. 

Gramme, S., and Hillhouse, J.W., 1981, Paleomagnetic evidence 

for northward movement of the Chugach terrane, southern 

and southeastern Alaska, in Albert, Nairn, and Hudson, 

Travis, eds., The United States Geological Survey in 

Alaska-Accomplishments during 1979: U.S. Geological 

Survey Circular 823-B, p. B161-164. 
Haney, J.M., and Jansons, Uldis, 1987, Geology of the McKinley 

Lake gold area, Chugach National Forest, southcentral 

Alaska: U.S. Bureau of Mines Open-File Report OFR 

32-87, 40 p., 1 sheet, scale 1:15,840. 

Helwig, James, and Emmet, Peter, 1981, Structure of the early 

Tertiary Orca Group in Prince William Sound and some 

implications for the plate tectonic history of southern 

Alaska: Alaska Geological Society Journal, v. 1, no. 1, 

p. 12-35. 

Hillhouse, J.W., and Gromme, S., 1985, Paleomagnetism of 

sedimentary rocks in the Prince William and Yakutat 

terranes, in Bartsch-Winkler, Susan, ed., The United States 

Geological Survey in Alaska-Accomplishments during 

1984: U.S. Geological Survey Circular 967, p. 60-62. 

Hollister, L.S., 1979, Metamorphism and crustal displacements-New insights: Episodes, v. 1979, no. 3, p. 3-8. 

Hudson, Travis, and Plafker, George, 1982, Paleogene metamorphism of an accretionary flysch terrane, eastern Gulf of 

Alaska: Geological Society of America Bulletin, v. 93, 

no. 12,p. 1280-1290. 

Hudson, Travis, Plafker, George, and Peterman, Z.E., 1979, 

Paleogene anatexis along the Gulf of Alaska margin: 

Geology, v. 7, no. 12, p. 573-577. 

Janson, L.E., 1979, The copper spike: Anchorage, Alaska 

Northwest Publishing Co., 175 p. 

Jansons, Uldis, Hoekzema, R.B., Kurtak, J.M., and Fechner, S.A., 

1984, Mineral occurrences in the Chugach National Forest, 

southcentral Alaska: U.S. Bureau of Mines Open-File 

Report MLA 5-84, 218 p., 2 maps, scale 1:250,000. 

Johnson, B.L., 1919, Mineral resources of Jack Bay district and 

vicinity, Prince William Sound: U.S. Geological Survey 

Bulletin 692, p. 153-173. 

Jones, D.L., Silberling, N.J., Coney, P.J., and Plafker, George, 

1987, Lithotectonic terrane map of Alaska (west of the 41st 

meridian): U.S. Geological Survey Miscellaneous Field 

Studies Map MF-1874-A, 1 sheet, scale 1:2,500,000. 

Kachadoorian, Reuben, ~ 960, Engineering geology of the Katalla 

area, Alaska: U.S. Geological Survey Miscellaneous 

Geologic Investigations Map I-308, 1 sheet, scale 1 :63,360. 

Kurtak, J .M., 1982, A manganese occurrence on Chenega Island, 

Prince William Sound, Alaska: U.S. Bureau of Mines 

Open-File Report MLA 124-82, 9 p. 

Lahr, J.C., and Plafker, George, 1980, Holocene Pacific-North 

American plate interaction in southern Alaska-Implications for the Yakataga seismic gap: Geology, v. 8, no. 10, 

p. 483-486. 

Lull, J .S., and Plafker, George, 1990, Geochemistry and paleotectonic implications of metabasaltic rocks in the Valdez 

Group, southern Alaska, in Dover, J.H., and Galloway, J.P., 

eds., Geologic studies in Alaska by the U.S. Geological 

Survey, 1989: U.S. Geological Survey Bulletin 1946, 

p. 29-38. 

MacKevett, E.M., Jr., Albert, N.R.D., Barnes, D.F., Case, J.E., 

Robinson, Keith, and Singer, D.A., 1977, The Alaskan 

mineral resource assessment program-Background information to accompany folio of geologic and mineral resource 

maps of the McCarthy quadrangle, Alaska: U.S. Geological 

Survey Circular 739, 23 p. 

Marshak, R.S., and Karig, D.E., 1977, Triple junctions as a cause 

for anomalously near-trench igneous activity between the 

trench and volcanic arc: Geology, v. 5, no. 4, p. 233-236. 

Martin, G.C., 1908, Geology and mineral resources of the 

Controller Bay region, Alaska: U.S. Geological Survey 

Bulletin 335, 141 p. 

__ 1921, Preliminary report on petroleum in Alaska: U.S. 

Geological Survey Bulletin 719, 83 p. 

Miller, D.J., 1953, Late Cenozoic marine glacial sediments and 

marine terraces of Middleton Island, Alaska: Journal of 

Geology, v. 61, no. 1, p. 17-40. 

__ 1961, Geology of the Katalla district, Gulf of Alaska 

Tertiary province, Alaska: U.S. Geological Survey OpenFile Report 61-99, 2 sheets, scale 1 :96,000. 

__ 1971, Geologic map of the Yakataga district, Gulf of 

Alaska Tertiary province, Alaska: U.S. Geological Survey 

Miscellaneous Geologic Investigations Map I~ 10, 1 sheet, 

scale 1 :40,000. 

__ 1975, Geologic map and sections of the central part of the 

Katalla district, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-722, 2 sheets, scale 

1:40,000. 

Moffit, F.H., 1954, Geology of the Prince William Sound region, 

Alaska, in Mineral resources of Alaska, 1951-1953: U.S. 

Geological Survey Bulletin 989-E, p. 225-310. 

Moffit, F.H., and Fellows, R.E., 1950, Copper deposits of the 

Prince William Sound district, Alaska: U.S. Geological 

Survey Bulletin 963-B, p. 47-79. 

Monger, J.W.H., Price, R.A., and Templeman-Kluit, D.J., 1982, 

Tectonic accretion and the origin of the two major metamorphic and plutonic welts in the Canadian Cordillera: 

Geology, v. 10, no. 2, p. 70-75. 

Naugler, F.P., and Wageman, J.M., 1973, Gulf of AlaskaMagnetic anomalies, fracture zones, and plate interactions: 

Geological Society of America Bulletin, v. 84, no. 5, 

p. 1575-1584. 

Nelson, S.W., Dumoulin, J.A., and Miller, M.L., 1985, Geologic 

map of the Chugach National Forest, south-central Alaska: 

U.S. Geological Survey Miscellaneous Field Studies Map 

MF-1645-B, 16 p., 1 sheet, scale 1:250,000. 

Nelson, S.W., and Koski, R.A., 1987, The Midas mine-A 

stratiform Fe-Cu-Zn-Pb sulfide deposit in late Cretaceous 

turbidite near Valdez, Alaska [abs.]: Geological Society of 

America Abstracts with Programs, v. 19, no. 6, p. 436. 

Nelson, S.W., Miller, M.L., Barnes, D.F., Dumoulin, J.A., 

Goldfarb, R.J., Koski, R.A., Mull, G.C., Pickthorn, W.J., 

Jansons, Uldis, Hoekzema, R.B., Kurtak, J.M., and Fechner, 

S.A., 1984, Mineral resource potential of the Chugach 

National Forest, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1645-A, 24 p., 1 sheet, 

scale 1 :250,000. 

Nokleberg, W.J., Plafker, George, Lull, J.S., Wallace, W.K., and 

Winkler, G.R., 1989, Structural analysis of the southern 

Peninsular, southern Wrangellia, and northern Chugach 

terranes along the Trans-Alaska Crustal Transect, northern 

Chugach Mountains, Alaska: Journal of Geophysical 

Research, v. 94, no. B4, p. 4297-4320. 

References Cited 17 
Page, R.A., Stephens, C.D., and Lahr, J.C., 1989, Seismicity of the 

Wrangell and Aleutian Wadati-Benioff zones and the North 

American plate along the Trans-Alaska Crustal Transect, 

Chugach Mountains and Copper River basin, southern 

Alaska: Journal of Geophysical Research, v. 94, no. B 11, 

p. 16,059--16,082. 

Plafker, George, 1967, Geologic map of the Gulf of Alaska 

Tertiary province: U.S. Geological Survey Miscellaneous 

Geologic Investigations Map 1-484, 1 sheet, scale 

1:500,000. 

___ 1968, Source areas of the Shattered Peak and Pyramid 

Peak landrlides at Sherman Glacier, in The great Alaskan 

earthquake of 1964--Hydrology: National Academy of 

Sciences Publication 1603, p. 374-382. 

___ 1969, Tectonics of the March 27, 1964, Alaska 

earthquake, in The Alaska earthquake, March 27, 1964--

Regional effects: U.S. Geological Survey Professional 

Paper 543-1, p. 11-174. 

___ 1971, Possible future petroleum resources of Pacificmargin Tertiary basin, Alaska, in Future petroleum 

provinces of North America: American Association of 

Petroleum Geologists Memoir 15, p. 120-,135. 

___ 1974, Preliminary geologic map of Kayak and Wingham 

Islands, Alaska: U.S. Geological Survey Open-File Report 

74-82, 1 sheet, scale 1:31,680. 

__ 1987, Regional geology and petroleum potential of the 

northern Gulf of Alaska continental margin, in Scholl, 

D.W., Grantz, Arthur, and Vedder, J.W., eds., Geology and 

resource potential of the continental margin of western 

North America and adjacent ocean basins: American 

Association of Petroleum Geologists, Circum-Pacific Earth 

Science Series, v. 6, p. 229-268. 

Plafker, George, and Addicott, W.O., 1976, Glaciomarine deposits 

of Miocene through Holocene age along the Gulf of Alaska 

margin, Alaska: U.S. Geological Survey Open-File Report 

76-84,36 p. 

Plafker, George, Bruns, T.R., Carlson, P.R., Molnia, B.F., Scott, 

E.W., Kahler, Rodger, and Wilson, Charles, 1978, 

Petroleum potential, geologic hazards, and technology for 

exploration in the outer continental shelf of the Gulf of 

Alaska Tertiary province: U.S. Geological Survey OpenFile Report 78-490, 50 p. 

Plafker, George, Bruns, T.R., and Page, R.A., 1975, Interim report 

on petroleum resource potential and geologic hazards in the 

outer continental shelf of the Gulf of Alaska Tertiary 

province: U.S. Geological Survey Open-File Report 

75-592, 74 p. 

Plafker, George, Bruns, T.R., Winkler, G.R., and Tysdal, R.G., 

1982, Cross section of the eastern Aleutian arc from Mount 

Spurr to the Aleutian trench near Middleton Island, Alaska: 

Geological Society of America Map and Chart Series 

MC-28P, 1 sheet, scale 1:1,000,000. 

Plafker, George, Carlson, P.R., Coonrad, W.L., Hunt, S.J., and 

Quinterno, Paula, 1979, Geologic implications of 1978 

outcrop sample data from the continental slope in the 

eastern Gulf of Alaska: U.S. Geological Survey Circular 

804-B, p. B 143-B 146. 

18 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

Plafker, George, and Claypool, George, 1979, Petroleum source 

rock potential of rocks dredged from the continental slope in 

the eastern Gulf of Alaska: U.S. Geological Survey OpenFile Report 79--295, 24 p. 

Plafker, George, Jones, D.L., and Pessagno, E.A., Jr., 1977, A 

Cretaceous accretionary flysch and melange terrane along 

the Gulf of Alaska margin, in Blean, K.M., ed., The United 

States Geological Survey in Alaska-Accomplishments 

during 1976: U.S. Geological Survey Circular 751-B, 

p. B41-B43. 

Plafker, George, LaJoie, K.R., and Rubin, Meyer, 1991, New data 

on the recurrence interval and seismic cycle for great 

1964-type earthquakes in the Copper River Delta, Alaska 

[abs.]: Seismological Research Letters, v. 62, no. 1, p. 38. 

Plafker, George, and Lanphere, M.A., 1974, Age of the Bagley 

fault, in Carter, Claire, ed., United States Geological Survey 

Alaska program, 1974: U.S. Geological Survey Circular 

700, p. 52. 

Plafker, George, Nokleberg, W.J., and Lull, J.S., 1989, Bedrock 

geology and tectonic evolution of the Wrangellia, 

Peninsular, and Chugach terranes along the Trans-Alaska 

Crustal Transect in the northern Chugach Mountains and 

southern Copper River basin, Alaska: Journal of Geophysical Research, v. 94, no. B4, p. 4255-4295. 

Plafker, George, Nokleberg, W.J., Lull, J.S., Roeske, S.M., and 

Winkler, G.R., 1986, Nature and timing of deformation 

along the Contact fault system in the Cordova, Bering 

Glacier, and Valdez quadrangles, in Bartsch-Winkler, 

Susan, and Reed, K.M., eds., Geologic studies in Alaska by 

the U.S. Geological Survey during 1985: U.S. Geological 

Survey Circular 978, p. 74-77. 

Plafker, George, and Rubin, Meyer, 1978, Uplift history and 

earthquake recurrence as deduced from marine terraces on 

Middleton Island, Alaska, in Proceedings of Conference VI, 

Methodology for identifying seismic gaps and soon-tobreak gaps: U.S. Geological Survey Open-File Report 

78-943,p. 687-721. 

Plafker, George, Winkler, G.R., Coonrad, W.L., and Claypool, 

George, 1980, Preliminary geology of the continental slope 

adjacent to OCS lease sale 55, eastern Gulf of AlaskaPetroleum resource implications: U.S. Geological Survey 

Open-File Report 80-1089, 72 p. 

Plumley, P.W., and Plafker, George, 1985, Additional estimate of 

paleolatitude for the Paleocene/Eocene(?) Prince William 

terrane-Orca volcanics [abs.]: Geological Society of 

America Abstracts with Programs, v. 17, no. 6, p. 401. 

Rau, W.W., Plafker, George, and Winkler, G.R., 1983, Foraminiferal biostratigraphy and correlations in the Gulf of Alaska 

Tertiary province: U.S. Geological Survey Oil and Gas 

Investigations Chart OC-120, 11 p., 3 sheets. 

Reimnitz, Erk, and Plafker, George, 1976, Marine gold placers 

along the Gulf of Alaska margin: U.S. Geological Survey 

Bulletin 1415, 16 p. 

Sanders, R.B., 1975, Geology and coal resource of the Bering 

River coal field, in Rao, P.D., and Wolff, R.D., eds., Focus 

on Alaska's coal, '75: Fairbanks, University of Alaska 

Minerals. Industry Research Laboratory Report 37, p. 21-32, 

54-58. 
Schrader, F.C., 1900, A reconnaissance of a part of Prince William 

Sound and the Copper River district, Alaska, in 1898: U.S. 

Geological Survey 20th Annual Report, pt. 7, p. 342-423. 

Schwab, W.C., and Bruns, T.R., 1979, Preliminary residual 

magnetic map of the northern Gulf of Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1 054, 

1 sheet, scale 1 :500,000. 

Schwab, W.C., Bruns, T.R., and von Huene, Roland, 1980, Maps 

showing structural interpretation of magnetic lineaments in 

the northern Gulf of Alaska: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1245, 2 sheets, scale 

1:500,000. 

Sisson, V.B., Hollister, L.S., and Onstott, T.C., 1989, Petrologic 

and age constraints on the origin of a low-pressure/hightemperature metamorphic complex, southern Alaska: Journal of Geophysical Research, v. 94, no. B4, p. 4392-4410. 

Stone, D.B., and Packer, D.R., 1979, Paleomagnetic data from the 

Alaska Peninsula: Geological Society of America Bulletin, 

v. 90, p. 545--560. 

Stone, D.B., Panuska, B.C., and Packer, D.R., 1982, Paleolatitudes 

versus time for southern Alaska: Journal of Geophysical 

Research, v. 87, p. 3697-3707. 

Sutley, S.J., O'Leary, R.M., and Goldfarb, R.J., 1986, Analytical 

results and sample locality map of moraine-sediment, 

stream-sediment, and heavy-mineral-concentrate samples 

from the Cordova and Middleton Island 1 °X3° quadrangles, 

Alaska: U.S. Geological Survey Open-File Report 86-381, 

115 p. 

Taliaferro, N.L., 1932, Geology of the Yakataga, Katalla, and 

Nichawak districts, Alaska: Geological Society of America 

Bulletin, v. 43, p. 749-782. 

Taylor, P.T., and O'Neill, N.J., 1974, Results of an aeromagnetic 

survey in the Gulf of Alaska: Journal of Geophysical 

Research, v. 79, no. 5, p. 719-723. 

Tripp, R.B., Goldfarb, R.J., and Pickthorn, W.J., 1985, Geochemical map showing distribution of gold within the 

Chugach National Forest, Alaska: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1645-D, 1 sheet, 

scale 1 :250,000. 

Tysdal, R.G., 1978, Mines, prospects, and occurrences map of the 

Seward and Blying Sound quadrangles, Alaska: U.S. 

Geological Survey Miscellaneous Field Studies Map 

MF-880-A, 1 sheet, scale 1 :250,000. 

Tysdal, R.G., and Case, J.E., 1979, Geologic map of the Seward 

and Blying Sound quadrangles, Alaska: U.S. Geological 

Survey Miscellaneous Investigations Series Map 1-1150, 

12 p., 1 sheet, scale 1 :250,000. 

___ 1982, Metalliferous mineral resource potential of the 

Seward and Blying Sound quadrangles, southern Alaska: 

U.S. Geological Survey Miscellaneous Field Studies Map 

MF-880-H, 1 sheet, scale 1 :250,000. 

Tysdal, R.G., Case, J.E., Winkler, G.R., and Clark, S.H.B., 1977, 

Sheeted dikes, gabbro, and pillow basalt in flysch of coastal 

southern Alaska: Geology, v. 5, no. 6, p. 377-383. 

Tysdal, R.G., Hudson, Travis, and Plafker, George, 1976a, 

Geologic map of the Cordova B-2 quadrangle and northern 

part of the Cordova A-2 quadrangle, south-central Alaska: 

U.S. Geological Survey Miscellaneous Field Studies Map 

MF-783, 1 sheet, scale 1:63,360. 

___ 1976b, Surface features and recent movement along the 

Ragged Mountain fault, south-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-782, 

1 sheet, scale 1:63,360. 

U.S. Bureau of Mines, 1973, Alaska 1:250,000-scale quadrangle 

map overlays showing mineral deposit locations, principal 

minerals, and number and type of claims: U.S. Bureau 

of Mines Open-File Report 20-73, 106 overlays, scale 

1:250,000. 

U.S. Department of Energy, 1978, NURE aerial gamma-ray and 

magnetic reconnaissance survey, Chugach-Yakutat area, 

Alaska-Bering Glacier, Icy Bay, Valdez, Cordova, Mt. 

Saint Elias, and Yakutat NTMS quadrangles, v. 1-

Narrative report: U.S. Department of Energy Open-File 

Report GJBX-127(78). Available from Books and OpenFile Services Section, U.S. Geological Survey, Federal 

Center, Box 25046, Denver, CO 80225. 

U.S. Geological Survey, 1979, Aeromagnetic map of part of the 

Cordova and Middleton Island 1 °X3° quadrangles, Alaska: 

U.S. Geological Survey Open-File Report 79-223, 1 sheet, 

scale 1 :250,000. 

___ 1988, Aeromagnetic map of part of the Middleton Island 

quadrangle and vicinity, Alaska: U.S. Geological Survey 

Open-File Report 88-505, 1 sheet, scale 1 :250,000. 

Wahrhaftig, Clyde, 1965, Physiographic divisions of Alaska: U.S. 

Geological Survey Professional Paper 482, 52 p. 

Wiltse, M.A., 1973, Fe-Cu massive sulfide deposits in ancient 

outer-arc ridge-trench slope environments [abs.]: Geological Society of America Abstracts with Programs, v. 5, 

no. 1, p. 122-123. 

Winkler, G.R., 1973, Geologic map of the Cordova A-7 and A-8, 

B-6, B-7, and B-8 quadrangles (Hinchinbrook Island), 

Alaska: U.S. Geological Survey Miscellaneous Field 

Studies Map MF-531, 1 sheet, scale 1:63,360. 

___ 1976, Deep-sea fan deposition of the lower Tertiary Orca 

Group, eastern Prince William Sound, Alaska, in Miller, 

T.P., ed., Recent and ancient sedimentary environments in 

Alaska: Alaska Geological Society, 1975 Symposium 

Proceedings, p. Rl-R20. 

Winkler, G.R., MacKevett, E.M., Jr., and Nelson, S.W., 1977, 

Stratabound iron-copper-zinc sulfide deposits, Prince 

William Sound region, southern Alaska, in Blean, K.M., 

ed., The United States Geological Survey in AlaskaAccomplishments during 1976: U.S. Geological Survey 

Circular 751-B, p. B44-B45. 

Winkler, G.R., McLean, Hugh, and Plafker, George, 1976, 

Textural and mineralogical study of sandstones from the 

onshore Gulf of Alaska Tertiary Province, southern Alaska: 

U.S. Geological Survey Open-File Report 76-198, 51 p. 

Winkler, G.R., Miller, R.J., MacKevett, E.M., Jr., and Holloway, 

C.D., 1981, Map and summary table describing mineral 

deposits in the Valdez quadrangle, southern Alaska: U.S. 

Geological Survey Open-File Report 80-892-B, 2 sheets, 

scale 1 :250,000. 

Winkler, G.R., and Plafker, George, 1975, The Landlock faultPart of a major early Tertiary plate boundary in southern 

Alaska, in Yount, M.E., ed., United States Geological 

Survey Alaska program, 1975: U.S. Geological Survey 

Circular 722, p. 49. 

References Cited 19 
--- 1981, Geologic map and cross sections of the Cordova and 

Middleton Island quadrangles, southern Alaska: U.S. 

Geological Survey Open-File Report 81-1164, 25 p., 1 

sheet, scale 1 :250,000. 

___ in press, Geologic map of the Cordova and Middleton 

Island quadrangles, southern Alaska: U.S. Geological 

Survey Miscellaneous Geologic Investigations Series Map 

1-1984, 1 sheet, scale 1 :250,000. 

Winkler, G.R., Silberman, M L., Grantz, Arthur, Miller, R.J., and 

MacKevett, E.M., Jr., 1981, Geologic map and summary 

geochronology of the Valdez quadrangle, southern Alaska: 

20 AMRAP: Cordova and Middleton Island Quadrangles, Alaska 

U.S. Geological Survey Open-File Report 80-892-A, 2 

sheets, scale 1 :250,000. 

Wolf, L.W., Stone, D.B., and Davies, J.N., 1991, Crustal structure 

of the active margin, southcentral Alaska-An interpretation of seismic refraction data from the TransAlaska Crustal Transect: Journal of Geophysical Research, 

v. 96, no. BlO, p. 16,455-16,469. 

Zuffa, G.G., Nilsen, T.H., and Winkler, G.R., 1980, Rockfragment petrography of Upper Cretaceous Chugach terrane, southern Alaska: U.S. Geological Survey Open-File 

Report 80-713, 28 p. 

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