i a 1:250,000. of Ugashik, Bristol Bay, and western Karluk quadran-
*Wilson, F.H., and Shew, Nora, 1982, Preliminary results of gles, Alaska: U.S. Geological Survey Miscellaneovs Field
K-Ar age determinations from the Ugashik quadrangle, Studies M:
a Pen in C ad, W.L, The United €, LA, 197

during 1980: ‘US. Geological Survey Circular 844, p. and eastern North
86-87. 201-233.

References 15



same_age, yet they_differ chemically. The Agripina Bay
suite has the highest K,O level (1.8 percent at 57.5
percent SiO,), whereas the Mount Becharof-Cape Igvak

groupings can be determined from the pattern of the
“star” at each sample locality. Histograms of these eight
elements are also shown. A statistical summary is also

suite has the lowest K,O level (0.9 percent at 57.5

given for the entire set of data reported by Detra and

percent SiO,) of all suites.

“others (1981).

Geochemistry (MF-1539-F, -G, -H)

A reconnaissance exploration geochemical study
was undertaken during the 1979 and 1980 field seasons.
Two diffferent media were sampled: (1) stream sedi-
ments and (2) heavy-mineral concentrates panned from
the stream sediments. A total of 585 minus-80-mesh
stream-sediment samples and 569 panned-concentrate
samples were collected from active channels of streams
draining 5-16 km”. The minus-80-mesh stream-sediment
medium reflects changes in bedrock geology and geo-

€ a ea ensive exposed-m

stream to obtain each panned-concentrate sample. Each
sample was further processed in the laboratory through
heavy liquids to remove the light-mineral fraction (sp
gr<2.8) and through a magnetic separation process to
remove magnetite as well as many of the more magnetic
mafic minerals. The nonmagnetic, heavy-mineral fraction
analyzed for this study contained high-specific-gravity,
rock-forming minerals such as apatite, zircon, rutile, and
sphene; the sulfide, sulfosalt, and some oxide minerals;
and several of the accessory minerals associated with
mineralization -and-alteration such as scheelite, fluorite,
barite, epidote, and-tourmaline. The nonmagnetic frac-

presence of ore-related minerals and therefore may be

Pan Concentrates

For the nonmagnetic heavy-mineral concentrates,
the distribution of the elements Cu, Mo, Ag, Pb, Zn, B,
Ni, and Co is shown on map A and of the elements As,
W, Au, Bi, Cd, Ba, Nb, and Sn on map B of MF-1539-G
(Frisken and others, 1988a). Thresholds were chosen
from an analysis of the distributions of each element
from the data and are shown on histograms. Three
classes of anomalous values for each clement ar= shown
using the “star” diagram; elements are grouped so that
geochemically coherent sets of elements are presented

A_of MF-— =

i igh- rt of th sediment geochemical map (MF-1539-F).

Mineralogy

Spatial distribution and abundance of pyrite, chal-
copyrite, molybdenite, galena, sphalerite, cinnat-ar, bar-
ite, gold, tourmaline, zircon, and mafic minerals are
presented in MF-1539-H (Frisken and others, 1988b).
Abundances were determined by microscopic examina-
tion of the nonmagnetic heavy-mineral concentrates.
Relative abundance is indicated by the lengtt of the
vectors of the star diagrams, and the mineral vectors are
chosen so that they correspond to the associatec vectors.

= ncentr: should reflect the on nonmagnetic heavy-mineral concentrate maps (MF-

1539-G).

useful in delineating areas of poorly exposed mineraliza-

tion. All analyses were by the semiquantitative emission
spectrographic method described by Grimes and Mar-
ranzino—(1968)—and—by Motooka_and-Grimes_(1976);
supplementary_determinations of Cu, Pb, and Zn con-
centrations were made by atomic absorption (Ward and
others, 1969). A detailed description of the geochemical
sampling, sample preparation, and analytical methods
utilized is presented, along with the tabulated geochem-
ical data and sample-locality maps, by Detra and others
(1981).

Stream Sediments

others, 1988).Anomaly thresholds we osen from
an analysis of the bedrock geochemistry and vary depend-
ing upon the bedrock. Three classes of anomalous values
for each element are shown using vectors surrounding a
central point that indicates the sample locality. Elemental

Mineral and Energy Resource Assesrsment
(MF=1539-1)

The mineral potential of the study area is summa-
rized on MF-1539- utilizing the mineral-deposit models
outlined by Cox and Singer (1986). The geothe-mal, oil
and gas, and coal resources of the area are also assessed
on MF-1539-I.

Previous mineral-exploration activity in the Ugash-
ik-Karluk area was limited largely to gold prcsvecting
near the turn of the century and to regional reconnais-
sance by major mining companies in the 1°70's for

é distribution of the elements Cu, Mo, Ag, Pb, porphy! i
i,a are shown on MF= ai er-clain e

a eld a hemical_sam b
Kennecott Corporation on the Mike and Rex frospects
were made available to the U.S. Geological Survey.
Eight tracts of land, each having somewhat differ-
ent geologic characteristics, have been outlined as poten-

Description of Component Folio Ms0s 9.



Abstract 1
Introduction 1
Purpose and scope = 1
Geography and access 1
Summary of mineral and petroleum investigations __ 3
Acknowledgments 4
Geologic investigations 5
Previous investigations 5
Present investigation 5
Description of component folio maps 6S
Geology (MF-1539-A) 6
Megafossil data (MF-1539-B)__7
Bedrock geochemistry (MF-1539-C) 7
Aeromagnetic map and interpretation (MF-1539-D) 8
Regional gravity anomalies 8
Geochronology and major-element geochemistry (MF-1539-E) 8
Geochemistry (MF-1539-F, -G, -H) 9
Stream sediments 9
Pan concentrates 9
Mineralogy 9
Mineral and energy resource assessment (MF-1539-I) 9
Bulletins 10
rati . Pan . ion,
(4537-A) 10
i etrography, chemistry, and geologic history of Yantarni volcano, Aleutian,
volcanic arc, Alaska (1761) 10
Interpretation of exploration geochemical data from the Ugashik, Bristol Bay,
and western Karluk quadrangles, Alaska (1858) ‘I
References avg

FIGURES

1, Location map showing study area on the Alaska Peninsula 2

2. Map of study area showing geographic features and physiographic
provinces 3

3. Map of study area showing claims, prospects, exploratory wells, and areas of
potential mineralization 4

TABLES

quadrangles, Alaska 2
2. Data on exploratory wells drilled for petroleum in the Ugashik and western part
of Karluk quadrangles = 5

Contents iil


SELECTED SERIES OF U.S. GEOLOGICAL SURVEY PUBLICAT ONS

Periodicals

Earthquakes & Volcanoes (issued bimonthly).
Preliminary Determination of Epicenters (issued monthly).

Technical Books and Reports

Professional Papers are mainly comprehensive scientific reports of
wide and lasting interest and importance to professional scientists and en-
‘gineers. Included are reports on the results of resource studies and of
topographic, hydrologic, and geologic investigations. They also include
collections of related papers addressing different aspects of a single scien-

tific opie.

Coal Investigations Maps are geologic maps on topographic or
planimetric bases at various scales showing bedrock or surficial geol-
ogy, stratigraphy, and structural relations in certain coal-resource areas.

Oil and Gas Investigations Charts show stratigraphic information.
for certain oil and gas fields and other areas having pet~»leum potential.

Miscellaneous Field Studies Maps are multicolor or black-and-
white maps on topographic or planimetric bases on quadrangle or ir-
regular areas at various scales. Pre-1971 maps show bedrock geology
in relation to specific mining or mineral-deposit prot ‘ems; post-1971
maps are primarily black-and-white maps on various subjects such as
environmental studies or wilderness mineral investigetions.

of, geohydrologie data of both regular and. irregular a areas; rrincipal scale

8 pe
geographic coverage than Professional Papers. They include the results
ofresource studies and of geologic and topographic investigations; as well
as collections of short papers related to a specific topic.

‘Water-Supply Papers are comprehensive reports that present sig-
nificant interpretive results of hydrologic investigations of wide interest
to professional geologists, hydrologists, and engineers. The series covers
investigations in all phases of hydrology, including hydrogeology,
availability of water, quality of water, and use of water.

Circulars present administrative information or important scientific.
information of wide popular interest in a format designed for distribution
at no cost to the public. Information is usually of short-term interest.

‘Water-Resources Investigations Reports are papers of an interpre-
tive nature made available to the public outside the formal USGS publi-
cations series. Copies are reproduced on request unlike formal USGS

is 1:24,000 and regional studies are at 1:250,000 scale or smaller.

Catalogs

Permanent catalogs, as well as some others, giving comprehen-
sive listings of U.S. Geological Survey publications are available under
the conditions indicated below from the U.S. Geological Survey, Books
and Open-File Reports Section, Federal Center, Box 25425, Denver,
CO 80225. (See latest Price and Availability List.)

"Publications of the Geological Survey, 1879- 1°61" may be pur-
chased by mail and over the counter in paperback bok form and as a
set of microfiche.

“Publications of the Geological Survey, 1962- 1870" may be pur-

publications, and they are also available for public inspection at

set of microfiche.

depositories indicated in USGS catalogs.

"Publications of the U.S. Geological Survey, 1971- 1981" may be

and other material that are made available for public consultation. at
depositories. They are a nonpermanent form of publication that may be
cited in other publications as sources of information.

Maps

Geologic Quadrangle Maps are multicolor geologic maps on
topographic bases in 7 1/2- or 15-minute quadrangle formats (scales main-
ly 1:24,000 or 1:62,500) showing bedrock, surficial, or engineering geol-
ogy. Maps generally include brief texts; some maps include structure
and columnar sections only.

Geophysical Investigations Maps are on topographic or planimetric
bases at various scales; they show results of surveys using geophysical
techniques, such as gravity, magnetic, seismic, or radioactivity, which

purchased by mail and over the counter in paperback book form (two
‘volumes, publications listing and index) and as a set cf microfiche.

Supplements for 1982, 1983, 1984, 1985, 1986, ard for subsequent
years since the last permanent catalog may be purch»sed by mail and
over the counter in paperback book form.

State catalogs, "List of U.S. Geological Survey Geologic and
Water-Supply Reports and Maps For (State)," may be purchased by mail
and over the counter in paperback booklet form only.

“Price and Availability List of U.S. Geological Survey Publica-
tions," issued annually, is available free of charge in paperback book-
let form only.

Selected copies of a monthly catalog "New Publications of the U.S.
Geological Survey" available free of charge by mail or may be obtained
over the counter in paperback booklet form only. Thee wishing a free

reflect subsurface ‘structures that are of ‘eeonomicor geologic signifi cance.

are_on_planimetric_or

National Center, Reston, VA 22092.

topographic bases of regular and irregular areas at various scales; they
present a wide variety of format and subject matter. The series also in-
cludes 7 1/2-minute quadrangle photogeologic maps on planimetric bases
which show geology as interpreted from aerial photographs. Series also
includes maps of Mars and the Moon.

Note.-Prices of Government publications listed in older catalogs,
announcements, and publications may be incorrect. Therefore, the
prices charged may differ from the prices in catalogs, announcements,
and publications.



Geological Survey Open-File Report 81-173.
*Detterman, R.L., Allaway, W.H., Jr., and Rossiter, R.H.,
1981b, Locality map and scintillometer data for the
Ugashik a and Karluk quadran| les, Alaska: U.S. Geolog-

heet,

field methods for the semiquantative analysis of geologic

materials: U.S. Geological Survey Circular 591, 6 p.
+Hanson, B.M., 1957, Middle Permian limestone on Pacific
side of Alas! rT i iati =

Imlay, R.W.. 1953 Callovian (Jurassic) ammonites * from United

*Detterman, R.L., Case, J.E., Wilson, F.H., and Yount, M_E.,
1987a, Geologic map of the Ugashik, Bristol Bay, and
western part of Karluk quadrangles, Alaska: U.S. Geo-
logical_Survey—Miscellaneous_Geologic_Investigations.
Map I-1685, scale 1:250,000, 1 sheet.

*Detterman, R.L., Case, J.E., Wilson, F.H., Yount, M.E., and
Allaway, W.H., Jr., 1983, Generalized geologic map of
the Ugashik, Bristol Bay, and part of Karluk quadran-
gles, Alaska: U.S. Geological Survey Miscellaneous Field
Studies Map MF-1539-A, scale 1:250,000.

Detterman, R.L., and Miller, J.W., 1984, Late Mesozoic pale-
obiogeography-and-tectonics-of-the-Alaska-Peninsula
[abs.]: Geological Society of America Abstracts with
Programs, v. 16, no. 5, p. 278.

States and Alaska, Part 2, Alaska Peninsula and Cook
Inlet regions: U.S. Geological Survey Professional Paper
249-B, p. B41-B108.

———1975, Stratigraphic distribution and zonation of Jurassic
(Callovian) ammonites in southern Alaska: U.S. Geolog-
ical Survey Professional Paper 836, 28 p.

+1980, Jurassic paleogeography of the conte-minous
United States in its continental setting: U.S. Geological
Survey Professional Paper 1062, 134 p.

1981, Early Jurassic ammonites from Alaska: U.S. Geo-

logical Survey Professional Paper 1148, 49 p.

1984, Barlyand—Middle Bajocian_(Middle_Jurassic)

ammonites from southern Alaska: U.S. Geolog’cal Sur-
vey Professional Paper 1322, 38 p.

*Detterman, R.L. Miller, J.W., and Case J.E., 1985, Megafossil

quadrangles, Alaska: U.S. Geolonal Survey Miscella-
neous Field Studies Map MF-1539-B, scale 1:250,000, 3
sheets.

*Detterman, R.L., Wilson, F-H., Yount, M.E., and Miller, T-P.,
1987b, Quaternary geologic map of the Ugashik, Bristol
Bay, and western part of Karluk quadrangles, Alaska:
US. Geological Survey Miscellaneous Geologic Investi-
gations Map I-1801, scale 1:250,000, 1 sheet.

Detterman, R.L., Yount, M.E., and Case, J.E., 1981c, Mega-
fossil locality map, checklists, and stratigraphic sections
of the Chignik and Sutwik Island quadrangles, Alaska:
‘USS. Geological Survey Miscellaneous FieldStudies Map
MF-1053-N, 2 sheets.

Dumond, D.E., 1980, The archaeology of Alaska and the

Imlay, RW. 2 and Detterman R.L., 1973, Jurassic Paleobioge”

+ 1977, Some Lower and Middle Jurassic beds in Puale
Bay-Alinchak Bay area, Alaska: American Ascociation
of Petroleum Geologists Bulletin, v--61, no.-4, p. 607-
611.

Imlay, R.W., and Miller, D.J., 1949, Reconnaissance geology of
Wide Bay, Puale Bay, and Chinitna Bay areas, southern
Alaska: U.S. Geological Survey Administrative Report,
22 p.

Jones, D.L., and Miller, J.W., 1976, Preliminary geologic map
of Alaska Peninsula showing post-Callovian Mesozoic
fossil localities: U.S. Geological Survey Open-File Re-
port-76-76, scale-1:500,000, 2-sheets-

*Jones, D.L., Silberling, N.J., and Hillhouse, J.W., 1978, Mi-
croplate tectonics of Alaska—Significance for Mesozoic

peopling of America: Science, v. 209, no. 4460, p.

ans, OJ. Jr, 1965, Permafrost-map—of—Alaska:U-S-
Geological Survey Miscellaneous. Geologic Investiga-
tions Map I-445, scale 1:250,000.

Fisher, M.A., Bruns, T.R., and von Huene, Roland, 1981,
Transverse tectonic boundaries near Kodiak Island,
Alaska: Geological Society of America Bulletin, v. 92,
no. 1, pt. 1, p. 10-18.

*Frisken, J.G., Church, S.E., Detra, D.E., and Wilson, W.R.,
1988a, Geochemical map showing the distribution of
selected elements determined in nonmagnetic heavy-
mineral concentrates from Ugashik, Bristol Bay, and
western Karluk quadrangles, Alaska: U.S. Geological
Survey Miscellaneous Field Studies Map MF-1539-G,
‘scale 1:250,000-

alogical map showing the distribution of selected ore-

history of the Pacific coast of North America, in Howell,

Paleomtologists ‘and Mineralogists Symposium, v. 8 p.
71-16.

Keller, AS. and Reiser, H.N., 1959, Geology of the Mount
Katmai-area, Alaska: U.S. Geological Survey-Bulletin.
1058-G, p. G261-G298.

+Kellum, L.B., Davies, S.N., and Swinney, C.M., 1945, Geology
and oil possibilities of the southwéstern part of the Wide
Bay anticline, Alaska: U.S. Geological Survey C nen-File
Report, 17 p.

*Kerr, R.A., 1987, Direct measurements confirm plat> tecton-
ics: Science, v. 236, no. 4807, p. 1425-1427.

+Kienle, Juergen, Kyle, P-R., Self, Stephen, Motyka, RJ., and
Lorenz, Volker, 1980, Ukinrek Maars, Alaska;April

jon sequence, petrology, and tectonic setting:
Journal of Volcanology and Geothermal Research, v. 7,

related mineral concentrates from weshit Bristol Bay
and western Karluk q
cal Survey Miscellaneous Field I Studies Map MF- 1539-
H, scale 1:250,000.
*Grimes, D.J., and Marranzino, A-P., 1968, Direct-current arc
and alternating-current spark emission spectrographic

10. 1-2 p. TEST.

looking ‘airborne radar iSLARY Us s. Geological ‘Survey
Image Map Set, 8 sheets.

+Le Compte, J.R., 1981, Preliminary map showing in‘erpreta-
tion of Landsat imagery of the Ugashik and Karluk

Referencss 13


Table 2. Data on exploratory wells drilled for petroleum in the Ugashik and western part of Karluk quadrangles
[U., Upper; Do. (do.), ditto]

Well Company con tied Location Depth Formation |
---- Pacific Oil & Commercial ---- 1903 NW sec. 3, T. 29 S., R. 40 W. 1,421 Sheli’of
---do.-~ 1904 SEX sec. 3, T. 29 S., R. 40 W. 1,542 D.
J.H. Costello 1903 NWS sec. 10, T. 29 S., R. 40 W. 728 D.
-~--d0.- 1904 SEX sec. 10, T. 29 S., R. 40 W. Unknown Unkrown
lLathrop #1 Standard Oil Calif. 1923 SEX sec. 17, T. 29 S., R. 43 W. 500 Nakrek
McNally #1 1925 NWS sec. 29, T. 29 S., R. 43 W. 510 D~.
Lee #1 ---- 1926 SW% sec. 20, T. 29 S., R. 43 W. 5,034 Unkrown
2Finnegan #1 1923 NE sec. 30, T. 29 S., R. 43 W. 560 Nakrek
SW* sec. 20, T.29'S., R. 43 W. Shelikof

U. Triassic

. Jrrassic
batt olith

1959

SEX sec. 35, T. 25 S., R. 50 W.

8,865 Do.

W. 12.
U. Triassic
Ugashik #1. ---- Great Basins Oil Co. ---- 1966 SEX sec. 8, T. 32 S., R. 52 W. 9,476 Mest *k
Painter Creek #1 - Cities Service Oil Co. -: 1967, NW sec. 14, T. 35 S.,R. 51 W. 7,912 Shelikof
2Becharof/State #1 AMOCO Production Co. 1985 NW% sec. 10, T. 28 S., R. 48 W. 9,023 Unknown

General location of Standard Oil wells shown on map 1539-A (Detterman and others, 1983).

Locations not shown on map.

lodging during 1982 and 1983 and aided in many phases

tion at Bear Creek anticline and Pearl Creel’ dome.

of the logistic support that made completion of the

Martin (1926) made the first major attempt to correlate

project possible. Thanks are due also to the personnel at

1979,

the Mesozoic stratigraphic units and show how they

-_Ugashik Lake Lodge, who provided similar services in relate to the rest of Alaska.

The first-mod: thesis_of the stra’ ind

~ 0 on are due ‘aptain A
“Frosty” Frothingham and the crew of the U.S. Geolog-

ti yh
xy graphy

of the Alaska Peninsula, including part of the
Ugashik quadrangle, by Burk (1965) provided the foun-

ical Survey Research Vessel Don J. Miller II, who cheer-

dation for the present geologic investigation.

fully provided us with a base of operations during the
1980 and 1981 field seasons. Our helicopter pilots Lucky
Wilson, Richard Rossiter, Edward Svec, and Tom Rob-
bins often flew in adverse weather conditions to take us
to our work sites, and we greatly appreciate their skill and
professionalism.

Present Investigation

Field work and laboratory analyses for the present
study were started in 1979 and completed in 1982. The
geologic mapping was at a scale of 1:63,360 (1 inch=1
mile). Both geologic mapping and geochemical sampling

investigation.

The first important generalized contributions to

This study was a part of the Alaska Mineral Re-

the geology of this area were by Dall and Harris (1892)

source Assessment Program (AMRAP) for the Alaska

and Dall (1896). More detailed geologic investigations by
Capps (1923), Smith and Baker (1924), and Smith (1925,
1926) were made following the early petroleum explora-

Peninsula and was supervised by R.L. Detterman. Most
of the field-mapping personnel were also responsible for
a_particular_topical_phase of the work. F.H. Wilson

Geologic Investigations 5



nt maps of the
Karluk quadrangles, A

western pal

Katmai quadrangle. Mount Peulik (1,475 m), a Holocene

U.S. Geological Survey

stratovolcano, dominates the west side of this northern

Miscellaneous Field Studies

‘Subject

~A (Detterman and others, General geolo; i ii it il

segment of mountains.

the plain are remnants of glacial moraines that rarely
exceed 100 m in elevation. Ash-flow tuff from Aniakchak
Crater to the south covers the southwestern part of the
map area, burying morainal ridges. The ash-flow-tuff
plain, extending nearly 20 km into the area, was formed
by a major eruption of Aniakchak Crater about 3,400
years ago (Miller and Smith, 1977, 1987).

Becharof Lake (1,175 km”), the second largest lake

1983)
~B (Detterman and others, Fossil locality map, checklists,
1985) and stratigraphic sections
=C (Wilson and O'Leary, Bedrock geochemistry
1986)
=D (Case and others, 1988) Aeromagnetic map and inter-
pretation
E (Wil: .d-Shi 1988) G ‘hy ? id ij

in Alaska, is mostly within the study area. Other large

element geochemistry

stream sediments

Takes include Upper Ugashit Lower U gash, and Moth-

istol Bay I Wland, The I lak I confined

-G (Frisken and others, Geochemical distribution in i i i is i
a, Pan concentrates remnants of formerly much larger lakes (Detterman and

B

-H (Frisken and others, Mineralogy of pan concen-

others, 1987b). Becharof Lake and the Ugashik Lakes

1988b) trates

=I (Church and others, 1989a) Mineral and energy resource
assessment map

Ocean side of the peninsula is dominated by the rugged
mountains of the Aleutian Range, which rise abruptly
from the sea and are cut by numerous fjords and bays.

Mount Chigina; oak, and Mount Yantarni dominate the
skyline. Mount Chiginagak (2,120 m) is the highest peak

are less than 5 m above modern sea level, and most of the
numerous other lakes and ponds are within 30 m of sea
level.

Three major river systems, the Ugashik, King
Salmon, and Dog Salmon, drain the western part of the
map area. All three empty into Ugashik Bay after follow-
ing meandering courses across a nearly flat, former
fakebed deposit (Detterman and others, 1a). The

I, um. js -
flowing stream, the Kejulik River, flows into Becharof

in the area. Small valley glaciers radiate from these
mal ice

ield lies east 0}

Lake and drains the northeastern part of the map area.
ie Egegi iver, north of the map area. runs from

Only two permanent villages exist in the map area:
Pilot Point with a population of 66, and Ugachik with 13
residents (year-round population from 1980 census).
Populations of both towns increase markedl: during the
summer months owing to commercial fishing. Numerous
hunting and fishing camps near the major lakes and rivers
are occupied seasonally. At the present time (1988) there
are no settlements on the Pacific Ocean side of the

peninsula within the map area. The former village of

Kanatak, at the head of Portage Bay, has been aban-

: WEN

yom a a
© 200 KlomeTERS
—_

Figure 1. Index map showing location of study area.

doned for many years.

Moderate-sized_twin-engine_aircraft_can_lend_at Pilot
Point and near Painter Creek, but other landing areas are
usable only by smaller aircraft. Most of the hunting and
fishing camps maintain small, private airstrips. There are

no public roads within the map area. A few miles of

2 The Alaska Mineral Resource Assessment Program: Background Information to Accompany Maps



The Alaska Mineral Resource Assessment Program:
Background Information to Accompany Folio of
Geologic and Resource Maps of the Ugashik,

Bristol Bay, and Western Part of Karluk Quadrangles,

Alaska

By R.L. Detterman, J.E. Case, S.E. Church, J.G. Frisken, F.H. Wilson, and M.E. Yount

Abstract

Program (AMRAP) by a multidisciplinary team of earth

The Ugashik, Bristol Bay,and-western_part-of-Karluk
quadrangles (1:250,000) are a part of the Alaska Peninsula in
southwestern Alaska. This circular, in conjunction with a
companion folio of MF-series maps, two I-series geologic
maps, and three bulletins, represents the results of integrated
field and laboratory studies on the geology, geophysics,
geochemistry, paleontology, geochronology, and mineral
resources of the quadrangles. These studies were undertak-
en to provide a modern assessment of the mineral and
energy resources of the quadrangles. Each map contains.
descriptive text, explanatory material, tables, diagrams, and
pertinent references. This circular provides background in-
formation for the mineral resource assessment map

general references relevant to the geology and resources 3 of

scientists. Field and laboratory studies were conducted
between 1979 and 1982.

The folio-consists of nine-maps that provide infor-
mation on the geology, geochemistry, geophysis, geo-
chronology, paleontology, and mineral resources of the
quadrangles (table 1). The primary intent of the folio and
circular is to furnish mineral and energy resource data
for land-use planning and long-term national resource
policy decisions. Additional aims are to determine the
time and type of mineral emplacement and to increase
the geologic knowledge of an actively accreting continen-
tal margin and volcanic arc.

This circular contains references relevant to the

t-matt

the quadrangles.

INTRODUCTION

Purpose and Scope

This circular and the companion folio of related
maps area part of a series of U.S. Geological Survey
reports designed to provide an inventory of Alaska’s
mineral resources. The reports furnish information for
mineral and energy policy-making decisions by Federal
and State governments, native corporations, and industry

, pe
ances -appHcad: € UD}

In addition to the folio maps, which are printed in
black and white, two companion multicolor Miscella-
neous Geologic Investigations Series Maps (Detterman
and others, 1987a, b) have been published. Topical
studies conducted during the investigations also resulted
in three bulletins (Allaway and others, 1984; Richle and
others, 1987; Church and others, 1989b), one masters
thesis (Allaway, 1982), two circular articles (Detra and
others, 1981; Allaway and Miller, 1984), and five open-
file reports (Detterman and others, 1980, 1981I-. 1982;
Wilson, 1982; Wilson and O’Leary, 1986).

concerning th the future use of Alaskan land and resources.

Manuscript approved for publication, November 21, 1989.

The Ugashik, Bristol Bay, and western part of the
Karluk quadrangles encompass about 12,670 km? (4,892
mi’) on the Alaska Peninsula (figs. 1 and 2).

The study-area-is- bounded by 57° and-58° N. lat.
and by 155° and 158°41' W. long. (fig. 2). The Pacific

Introduct'on 1


Report 81- 716, scale 1:250,000, 2 sheets.

Geological Survey Circular 90, p. 2 17.

*Martin, G.C., 1904, Petroleum fields of Alaska and the Bering

*Smith, W.R., 1925, The Cold Bay (Puale Bay)-Katmai district,

365-382

Geological
gi y

*

1905, The petroleum fields of the Pacific coast of

€283-C209-
7 P=

* 1926, Geology and oil development of the Cold Bay

Alaska: U.S. Geological Survey Bulletin 250, 64 p.

(Puale Bay) district, Alaska: U.S. Geological Survey

'926, The Mesozoic stratigraphy of Alaska: U.S. Geo-

Bulletin 783-C, p. C6:

*McLean, Hugh, 1977, Organic geochemistry, lithology, and
paleontology of Tertiary and Mesozoic rocks from wells
on the Alaska Peninsula: U.S. Geological Survey Open-
File Report 77-813, 63 p.

*Miller, J.W., and Detterman, R.L., 1985, The Buchia zones in
Upper Jurassic rocks on the Alaska Peninsula, in
Bartsch-Winkler, Susan, and Reed, K.M., eds., The Unit-
ed States sasological Survey i in Alaska: Accomplishments

51 53.

Bay) )-Chignik district, ‘Alaska: US. Gerlogical Survey
Bulletin 755-D, p. Dis1- D218.
Stone, D.B., and Packer, D.R., 1977, Tectonic implications of
Alaska Peninsula paleomagnetic data: Tectonophysics, v.
37, p. 183-201.
*Stone, D.B., and Packer, D.R., 1979, Paleomagnetic data from
the Alaska Peninsula: Geological Society of America
Bulletin, v. 90, pt. 1, p. 545-560.

"tudes versus time for southern ‘Alaska Journal of Geo-

Miller, T.P., 1973, Distribution and chemical analyses of ther-

physical Research, v. 87, no. BS, p. 3697-3707.

mal Springs in n Alaska: U S. eclogical Survey Open-File

*Miller, Ty
flows around Aniakchak and Fisher Calderas, Alaska:

Thrupp, GA,, and Coe, R-S., 1984, 4, Peleomagnetism of Tertiary

Society of America Abstracts with Programs, v. 16, no. 5,

Geology, v. 5, p. 173-176.

Fi a i

the_eastern_Aleutian_arc, Alaska: Geology, v.15,p.
434-438.

Moore, G.W., 1967, Preliminary geologic map of Kodiak Island
and vicinity, Alaska: U.S. Geological Survey Open-File
Report 67-271, scale 1:250,000.

*Motooka, J.M., and Grimes, D.J., 1976, Analytical precision
of one-sixth order semiquantitative spectrographic anal-

is: U.S. Geological Somey Circular 738, 25 p.

plications: Canadian “Journal of Earth Sciences, v. 11, p.

p. 337.

ates Geological Survey, eromagnetic map ©

parts of the Ugashik and Karluk 1 x 2 degree quadran-

gles, Alaska: U.S. Geological Survey Open-File Report
84-351, scale 1:250,000, 2 sheets.

*Ward, F.N., Nakagawa, H.M., Van Sickle, G.H., and Harms,
T.F., 1969, Atomic absorption methods of analysis useful
in geochemical exploration: U.S. Geolog'cal Survey Bul-
letin 1289, 45 p.

+ Westerman G E. G., 1964, The ammonite fauna of the Ki-

ical Research Institution, v. 47, no. 216, p. >, 329-: 503.

976-997, + 1969, The ammonite fauna of a ‘« Formation at
, BL, » MLA, Be an c emistry o ide = laska Peninsula— Part 2, Sonninia sowerbyi
Mesozoic_and_Tertiary_plutonic_ro 0 ‘ n a a aleo a

Alaska: Geological Society of America Bulletin v. 80, p p. In titution, v. 31 no. 255 226 p.

23-43. *Wilson, F.H.,

1982, Map and tables showing preliminary

1972, Generalized geologic map of the Alaska-Aleu-
tian Range batholith showing potassium-argon ages of
the plutonic rocks: U.S. Geological Survey Miscella-
neous Field Studies Map MF-372, scale 1,000,000, 2
sheets.

1973, Alaska-Aleutian Range batholith; geochronology,
chemistry, and relation to_circum-Pacific_plutonism:
Geological Society of America Bulletin, v. 84, p. 2583—
2610.

Bulletin 1761, 27 p.

results of K-Ar age studies in Ugashik quadrangle,
Alaska Peninsula: U.S. Geological Survey Open-File
Report 82-140, scalé 1:250,000.

* 1985, The Meshik Arc—an Eocene to earliest Mio-
cene magmatic arc on the Alaska Peninsula: Alaska
Division of Geological and Geophysical Surveys Profes-
sional Report 88, 14 p.

Wilson, F.H., Detterman, R.
Alaska Peninsula terran

and Case, J.E., 1985, The
a definition: U.S. Geological

istry, Chignile and Sutwik Island quadrangles, ‘Alaska:

+Self, Stephen, Kienle, Juergen, and Huot, Jean Paul, 1980,

Research, v. “ no. 1-2, p. 39-65.
*Smith, R.LL., and Shaw, H.R., 1979, Igneous related geother-
mal systems, in Muffler, L.J-P., ed., Assessment of geo-

USS. Geological Survey Miscellaneous Field Studies Map

K sheets.

showing. data and analysis of semiquantative emission
spectrometry and atomic-absorption spectrometry of
rock samples, Ugashik and western Karluk quadrangles,

14 __ The Alaska Mineral Resource Assessment Program: Background Information to Accompany Maps


irangles. Th . is al I f the Bear
________Creek anticline where it crosses Bear Creek and Oil _ Geologic investigations in the Ugashik, Bristol Bay,
Creek. These seeps were reported as early as 1869 and western part of Karluk quadrangles were facilitated
(Capps, 1923). The oil is seeping from rocks of the greatly by the efforts of many geologists, both from the
Shelikof Formation and has formed areas of tarlike US. Geological Survey and Private industry, whose many

e i ;; sho m- wo a ory
anticline i in an area known as Pearl ‘Creek dome. Patches specialists is acknowledged on_individual_maps_in the
of bright-green, fresh oil can be seen on Ugashik Creek _ folio. The contributions of some specialists, although not
and Blue Creek. Areas of residue have formed where the _ mentioned specifically on the maps, were of great benefit
oil collected and was exposed to the air for long periods. _ to the project. Among those to whom special tribute is
These mounds of tarlike residue were used to fuel boilers due are J.A. Wolfe, R.W. Inlay, J.W. Miller, and C.D.
during early drilling operations. One additional area of _ Blome of the U.S. Geological Survey, and John Calloman
seepage was found along Simeon Creek during the of the University of London, paleontologists whose iden-
_____ current investigation. All seeps on the Ugashik anticline _tifications of many collections of invertebre‘e and plant
are from the Naknek Formation. fossils helped in determining the stratigraphic succession
In addition to seepages of oil, there are also of the sedimentary units. J.R. Riehle, M.L. Silberman,
SrePaBe of Basi in the eon Some of Which are associ- and Nora Shew made significant contributions to our

inorganic origin. Gas ‘collected
Gas Rocks seeps is about 98 percent carbon dioxide _ impossible without the willing assistance of local resi-

(Barnes and McCoy, 1979). The location and analyses of _ dents. Among those who were of great service to the
all oil and gas samples from the area were reported by _ project were the people at Painter Creek Lodge, espe-
Blasko (1976). cially J.W. Smith, who provided the project with food and

159° 158"
T T

set Area of study

PXCEIC OL 2
COSTELLO #1,2,
abe

EXPLANATION
Placer claim
Lode claim

Prospect

Exploratory well

Area of potential
mineralization

Thrust fault — Sawteeth
late. Dashed

where uncertain

0 10 20 30 40 _50 KILOMETERS

Figure 3. Area of study showing claims, prospects, exploratory wells, and areas of potential mineralization.

4 The Alaska Mineral Resource Assessment Program: Background Information to Accompany Maps


Assessment Program: Background
Information to Accompany Folio of

Geologic and Resource Maps of the
Ugashik, Bristol Bay, and Western



Meshik arc volcanism (as defined by Wilson, 1985)
started in the late Eocene and deposited a thick sequence
of subaerial basaltic-to-andesitic fragmental volcanic

present investigation. A total of 353 collections cf marine
megafauna and 23 collections of megaflora from nonma-
rine Tertiary strata were made during the investigation,

rocks and massive lava flows from vents along the west

adding considerably to the data base for the area. Col-

side ot the modern mountains. Activity along the arc

Oligocene. ‘A thick section of these voleanic-rocks-is
exposed in the southwestern part of the map area. Owing
to the strong magnetic character of these rocks (Case and
others, 1981), it is possible, based on aeromagnetic data,
to trace them partly across the map area beneath a
mantle of glacial drift.

Volcanic activity along the Meshik arc ceased in
this area about 24 to 23 my. ago (Wilson, 1985). There-
after, these deposits, along with the older rocks, were
uplifted and reworked by erosion into the overlying
sedimentary sequence. A thick late Tertiary sedimentary
section is preserved mainly in the subsurface of the

Tections were made from rocks ranging in age { from Late

pe
graphic correlations to-be-made-for-the-various rock
units.

The Kialagvik, Shelikof, and Naknek Formations,
of Middle and Late Jurassic age, are abundantly fossilif-
erous and account for 67 percent of all fossil co"ections.
Ammonites constitute the main elements of tre mega-
fauna in the Talkeetna, Kialagvik, and Shelikof Forma-
tions, including 36 species belonging to 23 genera.
Marine bivalves of the genus Buchia are the age-diagnos-
tic fossils in the Upper Jurassic Naknek Formatiyn. Four
species from closely controlled sections permit a precise
zonation for this genera that can in be used throughout the

#2 wells and by the Ugashik #1 well (Brockway Formation were identified by J.A. Wolfe (written com-

others, 1975). A thin sequence of the Upper Miocene
Bear Lake Formation is exposed along faults near the
Ugashik Lakes.

Volcanic activity along the Aleutian volcanic arc
probably originated about 10 to 5 m.y. ago with the
renewal of igneous activity along the Alaska Peninsula.
In the Ugashik and Karluk quadrangles area this was
restricted mainly to the emplacement of quartz diorite
plutons, such as the Agripina Bay batholith, along the
Pacific coast side of the mountains. Dacite intrusions
associated—with—mineral-deposits—also-oceurred-during
this interval. Minor extrusive activity accompanied the
emplacement of these plutons. Large-scale volcanic ac-

mun., 1985) as early Eocene. This indicates that the
Tolstoi Formation in the Ugashik and Karluk quadran-
gles is equivalent to only the upper part of the same
formation exposed farther south on the peninsula (Det-
terman and others, 1981c).

Bedrock Geochemistry (MF-1539-C)

As an aid to the mineral resource assessment of the
mapped _area, 337 rock samples were collected_and
analyzed using 30-element semiquantitative emission

tivity along this part of the arc commenced about 1.9 to

spectrometry, additional atomic absorption spe7tropho-

15 my. ago at Blue Mountain, The Gas Rocks, Mount

ssibly other sites; it has contin-
ued -until the present with the eruption at Ukinrek Maars
in 1977.

Tectonic activity associated with subduction along
the proto-Aleutian Trench has resulted in numerous
high-angle reverse faults and some thrust faulting. The
Bruin Bay fault, a major fault in southern Alaska, enters
the northern edge of the study area, but disappears
beneath surficial deposits south of Becharof Lake. Trans-
verse faulting and fracturing is very common. The north-
east trend of Aleutian Range volcanoes is offset about 20
km in the Ugashik and Karluk quadrangles. This may be
due to Plumbing or structure of the downgoing slab

tometry, and other analytical methods. Sampling was
conducted throughout the area in an effort to determine
background concentrations; however, sampling was con-
centrated in areas of known or suspected mineralization
and may be somewhat biased.

Anomalous samples were collected in a number of
areas on the periphery of the Agripina Bay tatholith,
near the plutons at Mount Becharof and Cape Igvak, and
at Cape Kubugakli. Additionally, numerous an>malous
samples were collected at the Mike and Rex prospects.
No sampling or mapping was able to locate the reported
copper mineralization at the head of Puale Bay (erg and
Cobb, 1967).

The data were Statistically analyzed to select back-

Megafossil Data (MF-1539-B)

Considerable amounts of new data on the fossil
megafauna and megaflora were obtained during the

eralization with associated gold and silver. However, it
was not possible to evaluate the background levels of
metals in individual stratigraphic units because of insuf-
ficient sampling for statistical validity.

Description of Component Folio Maps 7


obtained_potassium-argon_ages forthe intrusiveand
extrusive rocks, J.E. Case was responsible for aeromag-
netic interpretations, M.E. Yount and J.R. Riehle

neath the North American plate-along- the Aleutian
Trench at arate of about 5.cm/yr (Kerr, 1987) accounts
for numerous Pleistocene and Holocene volcanoes and

mapped the Quaternary volcanic rocks, and J.W. Miller

for the earthquakes common to the area.

carried out paleontological investigations.

The oldest rocks of the Alaska Feninsula are

During the course of this study, 1,360 sites were
occupied _for—geologicdata, and-585-stream-sediment
samples.and 569 heavy-mineral pan-concentrate samples
were collected to provide a data base for the mineral
resource assessment. In addition, 337 bedrock samples
were collected at geologic stations for semiquantitative
spectrographic analysis; these include both mineralized
samples and unmineralized specimens for a background
data base. Prior to the present study, only four published
potassium-argon (K-Ar) ages were available for the
rocks of the Ugashik and western part of Karluk quad-
rangles (Reed and Lanphere, 1969, 1972; Brockway and
otbers, 1975; Wilson and d others, yo8h). 2 A * total of 57 new

the time of mineral emplacement, During the present
investigation, 376 collections of fossil megafauna and
megaflora were made from sedimentary rocks of the
quadrangles; these collections provide a strong frame-
work for relative dating of the sedimentary sequence and
form a means of correlating the potassium-argon (K-Ar)
ages from associated igneous rocks. Data from these
fossil collections were listed by Detterman and others
(1985).

Aeromagnetic surveys were flown for the eastern
part of the map area by Fugro Geometrics Inc. in 1980
and by Diversified Technical Services, Inc. in 1982 (U.S.

Geological Survey. The aeromagnetic interpretation map

exposed in this map area at Puale Bay. Fermian lime-
‘stone crops out on one smallisland at the mouth of Puale
Bay. Along the north shore of the bay-are exposures of a
thick section of Upper Triassic limestone and volcanic
rocks of an old magmatic arc. Both the Permian and
Triassic limestones were probably deposited far to the
south in seas warmer than the modern North Pacific
Ocean.

We have determined, as a result of our investiga-
tions, that_a_nearly continuous sequence of Jurassic
sedimentary rock is exposed within the Ugashik and
Karluk quadrangles. Minor hiatuses are present in the
stratigraphic record, but no major unconformities are

northward to near its present latitude. ‘Ammonites from
the Lower Jurassic strata at Puale Bay show a close
correlation to forms now found in Lower Jurassic strata
at the latitude of Mexico (Imlay, 1980). Ammonites of
Middle Jurassic age correlate more close'y with those
from areas north of Mexico. The Late Jurassic megafau-
na of the Ugashik and Karluk area consist almost entirely
of the bivalve Buchia, found worldwide only in the boreal
regions. Many changes in depositional environments
accompanied the northward shift in latitude. The Permi-
an-and- Triassic limestone was deposited on an open,
shallow-water shelf in tropical_seas. The Lower Jurassic

Geological Survey, 1984), under contract to the U.S. sediments were also deposited in shallow w:

the Middle Jurassic, deep-water turbidites were being

was compiled by Case and others (1988). Scintillometer

localities (Detterman-and_ others, 1981b, 1982).

DESCRIPTION OF COMPONENT FOLIO MAPS

Geology (MF-1539-A)

The Ugashik, Bristol Bay, and western part of
Karluk quadrangles form a transverse segment across the
active Aleutian volcanic arc. This map area also includes
a segment of a middle Tertiary volcanic arc and plutonic
Tocks of a still older Mesozoic magmatic arc. The entire

i red to Alaska

some Mesozoic rocks of the Alaska Peninsula may y have
originated a considerable distance south of their present
latitude (Packer and Stone, 1974; Stone and Packer,
1979). Continuing subduction of the Pacific plate be-

deposited in part of the area. Upper Jurassic strata are

at many of the bedrock sample shallow-water shelf to nonmarine deposits.

Intrusive-and extrusive igneous rocks of Jurassic
age-are-also-exposed_in-the-map-area, northwest-of the
Bruin Bay fault. A small exposure of Middle Jurassic
plutonic rocks formed an island in Becharof Lake near
The Gas Rocks (Reed and Lanphere, 1969, 1972). Similar
Jurassic plutonic rocks also have been encountered in
boreholes on the Bristol Bay coastal plain (E*ockway and
others, 1975).

An extended period of erosion and nondeposition
followed the Jurassic, and thus the next overlying strata
preserved are of Late Cretaceous age. Cont‘nued tecton-
ic activity has caused the removal of most Upper Crete.
ceous shelf and s| ope leposi S, eaving no more

map area are early Eocene continental ‘deposits ¢ com-
monly containing abundant petrified logs and coal seams.
Orogenic activity during the Tertiary probably resulted
from subduction along the proto-Aleutian “rench.

6 The Alaska Mineral Resource Assessment Program: Background Information to Accompany Maps


1 mountains between Vol-

cano Creek and Dog Salmon River.

Summary of Mineral and Petroleum

Exploration for petroleum in the Ugashik and

Investigations

Karluk quadrangles has been much more intense than

gles _have_been_the_site_of intermittent_exploration for
minerals and petroleum since the early 1900’s, but no
economic deposits have been located. The earliest au-
thenticated exploration for minerals occurred in 1915,
when placer gold claims were established at Cape
Kubugakli (fig. 3). These claims were reported to have
produced about 160 ounces of gold (Smith, 1925). Noth-

section. The first wells in the area were drilled between
1902 and 1904 near oil seeps on Oil Creek (Martin, 1904,
1905; Capps, 1923; Smith, 1926). The locations of these
wells and nearly all others are shown on the gereralized
geologic map prepared by Detterman and others (1983).
Since the publication of that map, AMOCO Production
Company ¢ completed the drilling of the Becharof #1 well

ing i i ivil for exploratory wells drilled in the ma

claims, but mining equipment was found when the site

area are Tied in table 2.

was visited in 1977. Copper ore containing minor

Despite the presence of oil and gas seers in the

amounts of gold and silver was reportedly found ne near ‘the

southern part of the area. Bear Creek Mining Company

area, exploration to date has yielded only a modest show

reservoir characteristics have not been encountered in

did some diamond drilling in 1977 and 1978 on a
molybdenum porphyry prospect (Mike prospect) in the

159° 158°

drilling. Most of the oil and gas seeps are located near
faults that probably provide a pathway to the surface.

T T

we Area of study

Kejulik, y

SR field 7 F
ze Sure aang $a pT
se 1p © eT — Goeth
a res anf} ok
ap BI” Greig O vokenm § Sree 2 ff | Xe YO Bay Keturnoi

(2

on
ay Mount a
QW Becharof :

‘Cape lavak

ay pe Ig

PO Terrace |
Hartman |

5 Mount
6, _Kialagvik &

KARLUK QUAD

UGASHIK QUAD.

‘80 KILOMETERS

Figure 2. Area of study showing geographic features and physiographic provinces.

Introduction 3


DEPARTMENT OF THE INTERIOR

MANUEL LUJAN, Jr., Secretary

U.S. GEOLOGICAL SURVEY
Dallas L. Peck, Director

Any use of trade, product, or firm names in this publication
is for descriptive purposes only and does not imply
endorsement by the U.S. Government

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON

1990

Library of Congress Cataloging-in-Publication Data

The Alaska Mineral Resource Assessment Program.
(U.S, Geological Survey circular ; 1046)
Includes bibliographical references (p. _).
Supt. of Docs. no.: | 19.4/2:1046
1. Geology—Alaska—Alaska Peninsula. 2. Mines and mineral resources—
Alaska—Alaska Peninsula, 3. Alaska Mineral Resource Assessment Program.
|. Detterman, Robert L. II. Series.
QE84.A34A43 1990 553'.09798 90-3121



tial mineral resource areas. On the basis of our work in
the area the " geochemical anomalies s directly associated

Coal beds are present in the Tols‘oi Formation
near the southern peak of the suds area. Field data

and of permissive geolog! ic criteria, we estim

there is a 10-percent chance for two or more undiscov-

One tract (A5) contains several beds 1 to 2 m in thickness

ered porphyry copper deposits in the Ugashik-Karluk
study area. From the limited drilling information on the
Mike prospect, we estimate that there is a 90 percent
chance of one or more porphyry molybdenum deposits
and a 10 percent chance of two or more such deposits in
the study area. Based on the Cu/Au ratio in surface rock
samples from the Rex prospect, we estimate a 90 percent
chance of one or more porphyry copper-gold deposits in
the study area.

The estimate of the abundance of smaller deposits
is less concise because of the reconnaissance nature of
our studies. The geologic environment in many of these
tracts is permissive for polymetallic vein and epithermal

that have been seen in traverses made at 5-km spacings.
If these beds are continuous, they could Fave economic
potential.

BULLETINS

Stratigraphic Clarification of the
Shelikof Formation, Alaska Penins la

(Excerpts from Bulletin 1537-A byW.H. Allaway, Jr., R.L. Detterman,
JW. Miller, and L.B. Magoon)

Field investigations during the course of this

gold-vein deposits. The mineralization exposed on David

AMRAP investigation determined that the contact be-

Island indicates a volcanic-! hosted OPP anti-

ing g the pluton at Cape “Ievak -and the geochemical signa-
ture associated with them suggest _that_an_iron_or
tungsten skarn may be present.

Small gold placers may exist in the study area,
particularly around the area of the Rex prospect, where
gold was seen in several panned samples.

There are adequate resources of sand and gravel,
cinder, and pumice to satisfy local demand. Limestone on
Cape Kekurnoi is suitable as building stone and is
adjacent to a protected deep-water port. Given sufficient
local demand, this limestone unit is considered margin-
ally economi

10'9-10° cal) to that calculated for ‘Aniakchak Crater

tween the Shelikof Frormation and the underlying Kialag-

rather than 0 on lithostratigraphic units. This report rede-
fines the contact between the two formations.

Capps (1923, p. C97-C98) defined the Shelikof
Formation (Middle Jurassic) on the Alaska Peninsula
but did not establish a type locality. He divided the
formation into three members: a lower shale (siltstone)
member, a middle sandstone member with conglomer-
ate, and an upper shale (siltstone) member. Rapid facies
changes make these members impractical for mapping.
Capps placed the lower contact at the base of a conglom-
erate bed that occurs at the base of the lower siltstone
member at Puale Bay. This Conglomernte does not

tween the Bajocian and Callovian ‘Stages, ( Middle Juras-

(Smith and Shaw, 1979), located just 8 km south of the
study-area boundary. Ukinrek Maars, which erupted in
1977, may represent an additional geothermal resource.

Oil and_gas resources inthe study area are proba-
bly small. Twelve dry holes have been drilled in the study
area. The tract to the west (E1), which consists mainly of
Tertiary nonmarine sedimentary and volcaniclastic rocks,
has been evaluated based on the drilling. Analysis of the
rocks for hydrocarbons indicates that they are immature,
with an_organic-carbon content of less than 2 percent
(McLean, 1977). Tract E2, located on the east side of the
study area, is largely a Mesozoic sedimentary province.
Although this area has several small oil seeps located

sic).

Smith (1925) proposed to place the contact at the
base of the lowermost massive sandstone bed. This is the
most easily mapped unit and is herein defined as the base
of the Shelikof Formation. The type sectior is defined as
along the northeast shore of Puale Bay, between the
southern half of sec. 9, T. 28 S., R. 38 W. and sec. 19, T.
28 S., R. 37 W. in the Karluk C-4, C-5, and D-5
15-minute quadrangles.

Petrography, Chemistry, and
Geologic History of Yantarni Volcano,
Aleutian Volcanic Arc, Alaska

along the crest of two large anticlines, analysis of the

indicates poor reservoir characteristics for most o!
content of the Mesozoic rocks is low. Of the 12 dry holes
in the study area, eight have been drilled near the surface
oil seeps on the crests of these two anticlines.

T.P. Miller)

In-1979, during the-course-of this AHMRAP study,
R.L. Detterman_and_J.E.-Case_discovered_a_previously.
unknown Quaternary volcano near the south boundary of

10 The Alaska Mineral Resource Assessment Program: Background Information to Accompany Maps


Alaska: U.S. Geolo jical Surve Ope en-! File Repe ort T1- Cobb. i as

169-H, scale 1:1,000,000. Bristol Bay quadrangle, Alaska: U.S. Geological Survey
‘Barnes, Ivan, and McCoy, G.A., 1979, Possible role of mantle- Miscellaneous Field Studies Map MF-456, scale

derived-CO, i g two-phreatic explosions in Alas- 1:250,000-

ka: Geology, v. 7, no. 9 p. 434-435, 1972b, Metallic_mineral f-the-Karluk
Beikman, H.M., 1975, Preliminary geologic map of Alaska quadrangle, Alaska: U.S. Geological Survey Miscella-

Peninsula and Aleutian Islands: U.S. Geological Survey neous Field Studies Map MF-459, scale 1:250,000.

lumley, .. and Thrupp,
1:1,000,000, 2 sheets. "G. A. 1985, Paleomagnetic results from Alaska and their
“Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits tectonic implications, in Howell, D.G., ed., Tectonostrat-
of ‘Alaska: US. Geological Survey Bulletin 1246, 254 p. igraphic terranes of the circum-Pacific region: Circum-
“Blasko, D.P., 1976, Oil and gas seeps in Alaska, Alaska Pacific Council for Energy and Mineral Resources, Earth
Peninsula, western Gulf of Alaska: U.S. Bureau of Mines Science Series No. 1, p. 85-108.

Report of Investigations RI 8122, 78 Pp. Cox, D.P., Detra, D.E., and Detterman, R.L., 1981, Mineral
“Brockway, R.G., Alexander, Bryan, Day, Paul, Lyle, W.M., resources of the Chignik and Sutwik Island quadrangles,
Hiles, RM. » It Decker, William, Polski, William, and Saska: US. Reological Survey Mise llaneous Field

y : sheets.
relation section southwest Alaska: ‘Anchorage, Alaska. *Cox, DP. a vd Sin ger, DA. ds. 198 in neral-deposit

The Alaska Geologic Society. models: U.S. Geological Survey Bulletin 1693, 379 p.
Bruns, T.R., and von Huene, Roland, 1977, Sedimentary basins *Dall, W.H., 1896, Report of coal and lignite of Alaska: U.S.
‘ "i eed- eological Survey 171] nual Report, pt. 1, p. 763—

Offs: -

ference, Houston, Texas, May 2-5, 1977,
1 Neogene: U.S. Geological Survey Bulletir 84, 349

it i . 1980, AMRAP geochemistry, Bristol Bay,
ica Memoir 99, 250 p. Ugashik. and Karluk quadrangles, Alaska, in Reed,

*Capps, S.R., 1923, The Cold Bay District, in Brooks, A.H., ed., KM., ed., U.S. Geological Survey in Alaska 1980 pro-
Mineral resources of Alaska: U.S. Geological Survey gram: US. Geological Survey Circular 823A, p. A52.
Bulletin 739-C, p. C77-C117. +Detra, D.E., Detterman, R.L., Cox, D.P., and Wilson, F.H.,

——— 1934, Notes on the geology of the Alaska Peninsula and 1982, Reconnaissance geochemical stud‘es in Bristol
Aleutian Islands: U.S. Geological Survey Bulletin 857- Bay, Ugashik, and Karluk quadrangles, Alaska, in Coon-
D, p. D141-D153. rad, W.L., ed., The United States Geological Survey in

*Case, J.E., Cox, D-P., Detra, DE., Detterman, R.L., and Alaska: Accomplishments during 1980: U.S. Geological

> P-

, FH. 7 7 urvey Circular

Map MF- 1053-B, scale 1:250,000, 2 summary from analysis of stream-sediment and heavy-
sheets. mineral-concentrate samples collected ir Bristol Bay,

0 Chuchel, B-A.,and gashik, and -Karluk quadrangles, Alaska: US. Geolog-
Yount, ME, 1988, Maps showing aeromagnetic surv i = =

and geologic interpretation of the Ugashik and part of _ Detterman, R.L., 1985, The Alaska Peninsula A~2 transect, in

Sarluk quadrangles, Alaska: U.S. Geological Survey von Huene, Roland, ed., Continent-oceans transect A-2:
Miscellaneous Field Studies Map-MF-1539=D, scale Kodiak to Kuskokwin, Alaska: Geological Society of
1:250,000, 2 sheets. America Transect Series Map A-2, scale 1:500,000.
*Church, S.E., Detterman, R.L., and Wilson, F.H., 1989a, *Detterman, R.L., Allaway, W.H., Jr., Day, G.W., Hopkins,
Mineral and energy resource assessment of the Ugashik, DM., O'Leary, R.M., and Svec, Edward, 1982, Locality
Bristol Bay, and western Karluk quadrangles, Alaska: map for scintillometer and analytical data collected in
USS. Geological Survey Miscellaneous Field Studies Map 1981, Ugashik and Karluk quadrangles, Alaska: U.S.
MF-1539-I, scale 1:250,000. Geological_Survey Open-File Report 82-53, scale
*Church, S.E., Frisken, J.G., Detra, D.E., and Wilson, W.R., 1:250,000, 1 sheet.

“Detterman, RI

1988, Geochemical mp howing distribution of select- Allway, WH, Jr, O'Leary, E.M,, Gruzen-

US. Geological Survey Miscellaneous Field Studies May ap lected j in 1979, Ugashik and Karluk quadrangles, Alaska:
MF-1539-F, scale 1:250,000. US. Geological Survey Open-File Report 80-142, scale

Bristol Bay, and western Karluk quadrangles, ‘Alaska: ton, David, and Risoli, DA, josia, ‘Sample location

US. Geological Survey Bulletin 1858, 45 p. map and analytical data for rock samples collected in
Coats, R-P., 1950, Volcanic activity in the Aleutian arc: U.S. 1980, Ugashik and Karluk quadrangles, Alaska: U.S.

12 __ The Alaska Mineral Resource Assessment Program: Background Information to Accompany Maps


___The Alaska Mineral Resource ees
__ Assessment Program: Background
Information to Accompany Folio of
Geologic and Resource Maps of the
Ugashik, Bristol Bay, and Western
_ Part of Karluk Quadrangles, Alaska

. T



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Aeromagnetic Map and Interpretation
(MF-1539-D)

western part of Ka q were flow
and 1982. The data obtained from the two surveys were

Regional Gravity Anomalies
Gravity data are sparse in the mountairous parts of

ne hows.a negative
10 mGal in the southwestern part of the Bristol Bay

combined, and some data from National Uranium Re-
source Evaluation (NURE) surveys were incorporated to
produce a smoothed final map for publication.

Over the Bristol Bay Lowland, broad ovoid highs of
200 to 500 gammas are produced by deep-seated granit-
oid plutonic bodies, which are thought to be part of the
Alaska-Aleutian Range batholith of Jurassic to Tertiary
age (Reed and Lanphere, 1969, 1972). Gentle gradients
on the flanks of the anomalies indicate that the sources of
the anomalies are buried at depths of 3 to 4 km or more.
One of the anomalies, near Cape Greig, coincides witha
positive gravity anomaly of about 15 mGal (Barnes,
1977b), and the source may be a dense and magnetic

Lowland, continuing northeast to near the Kejulik River.
This low is caused by the thick accumulation (3 to 4 km
or more) of Tertiary sedimentary rocks of low density.
The relative-gravity-high- of 10-to—15-2r Gal-in-the
northwest, near Cape Greig, may indicate a mafic pluton
at depth, or shallower depth to basement.

A positive anomaly of 30 to 50 mGal t-ends north-
east along the mountainous part of the per‘nsula. This
positive anomaly is an extension of the major gravity high
over the Aleutian Islands and may be caused by oceanic
crust_at- depth (Case_and others, 1981).

phase of the batholith, perhaps dioritic or gabbroic.

Geochronology and Major-element

Conglomerate and sandstone derived by erosion of
rma-
tion.The—conglomerate—and—some—of—the—sandstone
contain__a_high proportion_of _magnetite.__Elongate.
northeastern-trending magnetic highs of 200 to 500 gam-
mas are produced by magnetite-rich sandstone in the
Naknek near the Ugashik Lakes. Another northeast-
trending high of 400 gammas over covered areas to the
northwest is interpreted to be caused by the Naknek on
the northwest limb of an anticline.

Volcanic rocks of the Meshik Formation (Eocene
and Oligocene) produce elongate positive anomalies as
much as 1,000 gammas in amplitude along the north-
western front of the mountain belt. Other Tertiary vol-

ocks and —Karlu

Many of the Tertiary granitoid plutons cause ovoid
magnetic highs of 200 to 1,000 gammas or more. Similar
anomalies are in water-covered areas east of Cape
Kilokak, east of Hartman and Terrace Islands, and
elsewhere, and these are interpreted to result from
Tertiary plutons. Most of the known ore deposits, pros-
pects, and geochemical anomalies of the area are associ-
ated with the Tertiary plutons or their hornfelsed and
altered wall rocks. Thus, the ovoid magnetic anomalies
constitute guides to exploration, as in the Chignik and
Sutwik Island-quadrangles to the south (Case-and-others,
1981). A few magnetic lows or_magnetically flat_areas

may indicate hornfelsing or hydrothermal alteration and

Geochemistry (MF-1539-E)

A-total-of 57-new-K-Ar-ages-were-determined-in
conjunction with the AMRAP mapping studies and help
to provide a well-constrained time scale for Tertiary and
Quaternary events and stratigraphic relations. In addi-
tion, 54 new and 12 previously reported major-element
chemical analyses were compiled and analyzed.

The ages are approximately evenly divited in num-
ber between the late Tertiary Aleutian magmatic arc and
samples representative of the Meshik (early Tertiary)
and Jurassic magmatic arcs. A number of samples were
collected to date hydrothermal alteration associated with
mineralization. Significant among these were samples
collected e periphery of the tate Pliocene Agrip

yielded Oligocene ages, equivalent to that of the Meshik
arc, which suggests that the area of the batholith was the
site of magmatic activity and alteration during the time-
span of both Tertiary magmatic arcs. Age determinations
of Meshik-age plutonic rocks at the Rex prospect indi-
cate hydrothermal and magmatic activity occurred in
multiple phases, spanning approximately 4.5 m.y.
Major-element chemical analyses shcw rocks of
both arcs to be of calc-alkaline affinity, though a few
samples, including some from the Kejulik vol-anic center
of Quaternary-age, lie-in-the-tholeiitic field-on-a SiO,
versus-FeQ*/MgO_plot.The-samples_collected-can_be

associated with Tertiary intrusive and extrusive rocks divided into_a number of suites on the basis of age and

geologic setting. These suites are chemically distinct on

may serve as a secondary guide to exploration.

many elemental plots and indicate varying ranges and

Quaternary volcanic centers at Mount Chiginagak,
Mount Kialagvik, Mount Peulik, and Blue Mountain
cause short-wavelength positive anomalies of 200 to
1,000 gammas or more.

trends of major elements with respect to silica. Both the
Agripina Bay batholith suite and the suite cf plutons at
Mount Becharof-and-Cape-Igvak-intrude-si~ailar-rocks,
are compositionally similar, and_are_of_escentially_the

8 The Alaska Mineral Resource Assessment Program: Background Information to Accompany Maps



the_map_area, subsequently named_Yantarni_after_the
nearby bay of the same name. Yantarni volcano and
neighboring Mounts Chiginagak and Kialagvik are locat-
ed along the axis of the Wide Bay-Bear Creek anticline
an it ne ig] rangle ‘aul

at extends southwe:

Aleutian volcanic. arc along which the volcanoes are.
approximately 35 _km_ closer to the Aleutian Trench than
those on either side. The Mike prospect, a locus of late
Tertiary volcanism, is 5 km north of Yantarni dome.

Volcanic activity at Yantarni began in middle Pleis-
tocene time with the eruption of andesite flows that now
cap ridges to the west and south of the present summit. A
catastrophic Holocene eruption (possibly 3,500 to 2,000
years ago; Riehle and others, 1987) breached the small,
late Pleistocene stratocone, produced the present dome,
and filled the valley to the east with approximately 1 km’
of pyroclastic flow deposits.

that small batches of magma feeding the volcanic system
have occasionally intercepted one another beneath the
volcano and mixed to form hybrid magmas (Riehle and
others, 1987).

Although there is no historical record of activity at
Yantarni, the possibility of future eruptions cannot be
discounted.

Interpretation of Exploration Geochemical
Data From the Ugashik, Bristol Bay, and
Western Karluk Quadrangles, Alaska

(Excerpts from Bulletin 1858 by S.E. Church, J.G. Frisken, and

metal anomalies. Aeromagnetic data suggest that there
are several buried plutons in the area benezth the
geochemical a anomalies of the Mike prospect (Cese and
others, urther €

with an_area at Cape Tavak that shows possible hydro-
thermal vein or skarn mineralization, possibly associated
with a pluton of Pliocene age. Gold, antimony, lead, and
molybdenum mineralization at Cape Kubugakli appears
to be restricted to quartz veins within the outcrop pattern
of intrusive rocks. The intrusive rocks appear, from the
aeromagnetic anomaly, to extend offshore to the east.

REFERENCES

The asterisks (*) denote references cited in this report.
Plus signs(+) indicate uncited references that mainly or
entire! ly pertain to the gas ik, Bristol Bay, and wester:

material relevant to the quadrangles.

+Albert, N-R.D., 1982, Preliminary photogeologic interpreta-
tion-map~ of -side-looking-airborne—radar—imagery— of
Bristol Bay, Ugashik, and Karluk quadrangles, Alaska:
US. Geological Survey Open-File Report 82-141, scale
1:250,000, 2 sheets.

*Allaway, W.H., Jr., 1982, Sedimentology and petrolozy of the
Shelikof Formation, Alaska Peninsula: San Jose, Calif.,
San Jose State University, M.S. thesis, 88 p.

*Allaway, W.H., Jr., Detterman, R.L., Miller, J.W., and Ma-
goon, L.B., 1984, Stratigraphic clarification of the She-
likof Formation, Alaska Peninsula, in Stra*igraphic
notes, 1983: U.S. Geological Survey Bulletin 1537-A, p.

F-H. Wilson)

A21-A27.

The integration of the geochemical results from the

*Allaway, W.H., Jr., and Miller, J. W., 1984, Newly reognized

geochemical maps (MF-1539-C, —F, —G, —H) are pre-
sented in an interpretative report in U.S. Geological
Survey Bulletin 1858. Both drainage-basin analysis and
factor-analysis-of the-entire-data-sets_are-covered, and
conclusions are drawn regarding the type of mineraliza-
tion present.

Analysis of the geochemical data obtained from
exploration geochemical studies has helped to define the
limits of several porphyry Cu-Mo target areas, some of
which were previously unknown. Widespread geochemi-
cal_anomalies_and_ hydrothermal _alteration_halos_are
associated with an inferred Oligocene to Pliocene intru-
sive complex in the southern part of the Ugashik-Karluk

sedimentary environments in_the-Shelikof-Fe-mati

Alaska, in Coonrad, W.H., and Elliot, R.L., eds., The
United States Geological Survey in Alaska: Accomplish-
ments during 1981: U.S. Geological Survey Circular 868,
p. 34-37.

Andreason, G.E., Dempsey, W.J., and Vargo, JL. 1963a,
Aeromagnetic map of part of the Naknek quadrangle,
Alaska: U.S. Geological Survey Geophysical Investiga-
tion Map GP-353, scale 1:125,000.

1963b, Aeromagnetic map of parts of Ugashik and
Karluk quadrangles, Alaska: U.S. Geological Survey
Geophysical Investigation Map GP-354, scale 1:125,000.

Atwood, W.W., 1911, Geology and mineral resources of parts
of the Alaska Peninsula: U.S. Geological Surve-’ Bulletin

study area. Two of these areas are the Rex prospect, a

467,137

Barnes, D.F., 1967, Four preliminary gravity maps of parts of

porphyry Cu-Mo system associated with composite Oli-
gocene intrusive "

ty Mo system associated-with Pliocene intrusive act
Both areas_are outlined by Cu-Mo-W_ anomalies sur-
rounding drainage basins that show base- and precious-

Alaska: U.S. Geological Survey Open-File Report,
[67-10], 5 p.
1977a, Bouguer gravity map of Alaska: U.S. Geological
Survey_Geophysical Investigations Map GP-13, scale
1:2,500,000.

References 11