Geology of the 

McCarthy B-4 Quadrangle, 

Alaska 

GEOLOGICAL SURVEY BULLETIN 1333 

':}eology of the 

McCarthy B-4 Quadrangle, 

Alaska 

"y E. M. MAcKEVETT, JR. 

·-;EOLOGICAL SURVEY BULLETIN 1333 

Describes a 30,000-foot sequence of 

•

4

·edimentary and volcanic rocks which 

·VOange in age fronz, Pernz,ian and possibly 

·1lder to Quaternary, several small plutons, 

·~nd numerous sntall copper deposits 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1970 
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

Library of Congress catalog-card No. 70-609129 

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402- Price 25 cents (paper cover) 
Abstract 

Introduction 

Geologic setting and structure 

Stratigraphy and lithology_ 

Skolai Group 

CONTENTS 

Station Creek Formation 

Hasen Creek Formation_ 

Unnamed marine sedimentary rocks 

Nikolai Greenstone 

Chitistone Limestone 

Nizina Limestone 

McCarthy Formation 

Lower member 

Upper member 

Kennicott Formation 

Schulze Formation 

Moonshine Creek Formation 

Chititu Formation __ 

MacColl Ridge Formation 

Frederika Formation and Wrangell Lava 

Surficial deposits 

Intrusive rocks _ 

Gabbro 

Intermediate and mafic intrusive rocks_ 

Felsic hypabyssal rocks 

Andesitic dikes 

Summary of economic geology __ 

References 

ILLUSTRATIONS 

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FIGURE 1. Index map showing location of the McCarthy B-4 quadrangle, 

Alaska _ 2 

2. Generalized geologic map of the McCarthy B-4 quadrangle, 

Alaska ____ _ ______ ____________ _ __ 6 

TABLE 

Page 

TABLE 1. Summary of rocks in the McCarthy B-4 quadrangle, Alaska 4 

III 

GEOLOG~,. OF THE McCAI{TI-IY B-4 

QUADRANGLE, ALASKA 

By E. M. 1\IACKEVETT, ,JR. 

ABSTRACT 

This report supplements the geologic quadrangle map of the McCarthy 

B-4 quadrangle by providing additional and more detailed geologic information, particularly on stratigraphy and lithology. The McCarthy B-4 quadrangle, 

on the rugged southern flank of the Wrangell Mountains, contains a sequence 

of layered consolidated rocks more than 30,000 feet thick, scattered small 

plutons, and widespread surficial deposits. These rocks rm1ge in age from 

Permian(?) and Permian to Quarternary. 

The oldest rocks in the quadrangle, a thick sequence of Permian(?) submarine lavas and their derivative volcaniclastic rocks, are overlain by Permian 

marine sedimentary rocks practically devoid of volcanic material. Gabbro 

plutons cut both the Permian('?) and Permian rocks. Middle Triassic marine 

sedimentary rocks locally unconformably overlie the Permian rocks. The 

Nikolai Greenstone, extensive continental basaltic lavas of late Middle and(or) 

early Late Triassic age, is well exposed in the quadrangle. The Nikolai and 

most of the olde1· rocks, particularly those with volcanic affinities, show the 

effects of low-grade regional metamorphism. The Nikolai is clisconformably 

overlain by Late Triassic carbonate rocks, the Chitistone and Nizina Limestones. The carbonate rocks grade upvvard into earbonaceous shale, impure 

limestone, and chert of the ~lcCarthy Formation of Late Triassic and Early 

Jurassic age. A major reg:ional orogeny, near the close of the Jurassic or in 

the pre-Albian Cretaceous, produced the dominant structural features of the 

quadrangle. Marine Cretaceous sediments that are mainly represented by 

fine-grained clastic rocks were deposited unconformably on the older rocks, 

partly in restricted basins. The Cretaceous and older rocks were uplifted, 

mildly deformed, and eroded prior to the initial phase of Wrangell Lava volcanism in the Teritary. The subaerial Wrangell Lava and intercalated continental sedimentary rocks of the Frederika Formation are locally preserved 

in the northeastern part of the quadrangle. Other Tertiary rocks include small 

plutons of felsic hypabyssal rocks or intermediate to mafic intrusives, chiefly 

granodiorite, and a few andesite dikes and sills. The quadrangle's Quaternary 

surficial deposits are largely related to glacial processes, which have been 

important in developing the present physiography. 

The B-4 quadrangle contains numerous copper deposits, including a few 

that have been small producers, local gold placers, and a fe\v lodes or occurrences that contain gold, antimony, arsenic, or molybdenum. Silver is a minor 

constituent of most of the copper deposits. 

1 
2 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

INTRODUCTION 

This report supplements the McCarthy B-4 geologic quadrangle 

map (MacKevett and Smith, 1970) by providing additional 

stratigraphic and lithologic descriptions of the map units and short 

summaries of the structural and economic geology. (For optimum 

benefit, this report should be used with the geologic quadrangle 

map which shows graphically the discrete geologic units and structural features described in this report.) The McCarthy B-4 

15-minute quadrangle is about 260 miles east of Anchorage on the 

southern flank of the Wrangell Mountains (fig. 1). Altitudes in 

the quadrangle range from about 2,000 to 9,875 feet. To a large 

extent the quadrangle's physiography reflects glaciation and 

glacier-related erosion. Valley glaciers occupy the upper reaches of 

Glacier Creek, Toby Creek, and a few other strean1 valleys. Alpine 

glaciers and remnants of snow and ice fields are widely distributed 

throughout the higher terrain. Broad U-shaped valleys characterize 

the lower extents of the Chitistone River and a few other glacial 

streams, but most streams in the quadrangle are actively downcutting and occupy narrow V-shaped valleys. 

FIGURE 1.-Index map showing location of the McCarthy B-4 quadrangle, 

Alaska. 
GEOLOGIC SETTING AND STRUCTURE 3 

The smaller streams in the quadrangle discharge largely through 

the Nizina River into the Chitina River, which is a major tributary 

of the Copper River. During 1967 only one person lived in the 

quadrangle during most of the year, although in the summer and 

early fall the quadrangle generally is visited by a few prospectors, 

miners, and hunters. The Glacier Greek landing strip is suitable for 

small aircraft, and occasionally small fixed-wing aircraft have 

used gravel bars along the Chitistone River as landing sites. Most 

travel within the quadrangle is by foot or by helicopter. Bedrock 

outcrops are good throughout most of the quadrangle, but locally 

bedrock is masked by surficial deposits, snow, ice, or vegetation. 

The mapping was helieopter supported and used 1:48,000 scale 

cronoftex base maps. Supplementary laboratory studies consisted 

mainly of petrographic and mineralogic investigations. Grateful 

acknowledgement is given to several persons who made valuable 

contributions to the geologic studies. They include D. L. Jones, who 

was mainly responsible for the stratigraphic and paleontologic 

studies of the Cretaceous rocks; R. E. Grant, N. J. Silberling, and 

R. W. In1lay, who respectively studied the Permian, Triassic, and 

Jurassic fossils; G. R. Winkler and J. G. Smith who participated in 

the geologic mapping; the late Walter L. Holmes and his wife who 

shared their knowledge of the region and provided hospitality; and 

Jean O'Neill, who contributed information on current mining 

activities. 

The geology of the B-4 quadrangle was described previously by 

Moffit and Capps (1911) and by Moffit (1938). Reports pertinent 

to the quadrangle's economic geology include Miller (1946), Berg 

and Cobb (1967), Bateman (1932), Sainsbury (1951), and MacKevett and Smith ( 1968). Recent detailed geologic studies of 

nearby regions have resulted in geologic quadrangle maps (MacKevett, 1970a, b) and other reports that contain geologic data 

relevant to the B-4 quadrangle (MacKevett, 1970c). 

GEOLOGIC SETTING AND STRUCTURE 

The B-4 quadrangle contains a sequence of layered consolidated 

rocks more than 30,000 feet thick that ranges in age from Permian ( ?) and Permian to Tertiary, scattered intrusive rocks, and 

varied Quaternary surficial deposits (table 1 and fig. 2). 

Figure 2 is a generalized version of the geologic quadrangle map 

(MacKevett and Sn1ith, 1970). Several of the geologic units shown 

on the geologic map and described in this report have been combined and except for the main faults, structural features are not 

shown in the figure. 
4 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

TABLE 1.-Summary of rocks in the McCarthy B-4 quadrangle, Alaska 

Formation or unit 

Surficial deposits 

Andesitic dikes 

Felsic hypabyssal 

rocks. 

Intermediate to 

mafic intrusive 

rocks. 

System 

Quaternary 

Tertiary and 

Quaternary(?) 

Tertiary 

do 

Series 

'Estimated 

maximum 

thickness 

(feet) Dominant lithology 

Andesite. 

Dacite. 

Granodiorite. 

Frederika Forma- do Miocene 2,000 Varied continental 

sedimentary 

rocks and 

andesitic lava. 

tion and lower 

part of Wrangell Lava. 

MacColl Ridge Cretaceous Upper 

Cretaceous 

Sandstone and Formation. conglomerate . 2,000 

Chititu Formation do . Lower(?) and 

Upper 

Cretaceous 

Moonshine Creek 

Formation. 

Schulze Formation 

Kennicott 

Formation. 

Upper member 

of McCarthy 

Formation. 

Lower member 

of McCarthy 

Formation. 

5,000+ Mudstone and 

shale. 

do . .. .. Lower and 

Upper 

Cretaceous 250 

Siltstone. 

do . Lower(?) and Siliceous sandstone 

and siltstone. 

do 

Triassic (?) 

and 

Jurassic. 

Triassic and 

Jurassic ( ? ) 

Upper 

Cretaceous 

Lower 

Cretaceous 

Upper Traisic 

( ? ) and Lower 

Jurassic. 

150 

475 Sandstone, siltstone, and 

conglomerate. 

Impure limestone. 

Upper Triassic 600+ Impure limestone 

and Lower and carbonJurassic ( ? ) a ceo us shale. 

Nizina Limestone Triassic Upper Triassic 1,000 Limestone with some chert. 

Chitistone do 

Limestone. 

Nikolai do 

Greenstone. 

Unnamed marine do 

sedimentary 

rocks. 

Gabbro Permian or Triassic. 

Hasen Creek Permian 

Formation. 

Station Creek Permian(?) 

Formation. 

do 

Middle and (or) 

Upper 

Triassic 

... Middle Triassic 

. Lower Permian 

Lower 

Permian ( ?) 

1,800 

13,000 

150 

900 

4,600 

Limestone and 

dolomite. 

Basalt. 

Chert, siltstone, 

and shale. 

Gabbro. 

Varied sedimentary rocks. 

Basalt and basaltic 

andesite and 

their derivative 

volcaniclastic 

rocks. 
GEOLOGIC SETTING AND STRUCTURE 5 

The pre-Cretaceous rocks are part of a large northwest-trending 

belt that extends along the southern flank of the \Vrangell Mountains. Rocks in this belt are overlapped from the north by the 

Wrangell Lava and by Tertiary continental sedimentary rocks and 

from the south by Cretaceous n1arine sedimentary rocks or by 

Quaternary fluvioglacial deposits. 

Three crudely distinctive geologie terranes of near-equal area 

extend diagonally southeastward across the quadrangle (fig. 2). 

The northernmost terrane is characterized by a thick southwestdipping homoclinal sequence of Nikolai Greenstone and older rocks. 

The middle terrane is structurally complex and is composed of 

Nikolai Greenstone and younger Trias~ic rocks that are strongly 

faulted. and the southernmost terrane is dominated by gently 

folded Cretaceous sedimentary rocks. 

There are many steep faults in the quadrangle and one n1ajor 

and several subordinate thrust faults. Only the largest faults 

are shown in figure 2. The steep faults forn1 a well-developed 

northeast-striking set, a complementary northwest-striking set, 

and other fault sets that strike nearly north or nearly west. Dipslip components of displacement predominate on most of these 

faults, but a few of the steep faults, particularly son1e with nearwest strikes, have dmninant strike-slip displacen1ent components. 

Faults of the northeast-striking set can be traced for 8 n1iles and 

are exemplified by a fault that extends from near the southern 

boundary of the quadrangle to the Glacier Creek Glacier, by a fault 

that is well exposed near the head of Radovan Gulch, and by a 

fault along Grotto Creek in the northwest part of the quadrangle. 

The northwest- and north-striking faults are not as well developed. 

The west-striking faults are probably younger than n1ost other 

faults and are best exemplified by the faults along Copper and Dan 

Creeks that splay into a plexus of subsidiary faults near their 

eastern ends. 

The well-exposed n1ajor thrust fault in the northwest part of the 

quadrangle has been traced for n1any n1iles to the northwest in 

the McCarthy B-5 and C-5 quadrangles (l\facKevett, 1965b, and 

1970b) and is well illustrated by l\foffit (1938, pls. 8A and 9B). 

This fault cannot be mapped confidently south of the Nelson 

prospect, but its southeastward trace n1ay be represented by altered 

zones parallel to Nikolai Greenstone flows. The n1axin1um displacement on this thrust fault is probably not n1ore than a few thousand 

feet. The other thrust faults have small outcrop traces and 

displacements. 

Most of the faults probably formed during the 1najor regional 
6 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

R. 16E. 25' 

Base from U.S. Geological Survey, 1959 

"' 0 

~~29~ Ci ,::: 

z ~"'f!: UJ 0c§' 0 ~ ~'<:~ 

APPROXIMATE MEAN 

DECLINATION, 1970 

20' R. 17 E. 15' R. 18 E. 10' 142°07'30" 

Geology modified from (MacKevett and Smith, 1970) 

and based on mapping by E. M. MacKevett, Jr., 1965, 

1967, D. L. Jones, 1965, 1967, J. G. Sr:nith, 1967, 

and G. R. Winkler, 1967 

4 MILES 

FIGURE 2.-Generalized geologic map of the McCarthy B-4 quadrangle, Alaska. 
GEOLOGIC SETTING AND STRUCTURE 

EXPLANATION 

~ Surficial deposits 

Include alluvium, older alluviu-m, talus, rock gla.ciers, 

moraines, landsl1:des, and fluvioglacial deposits 

0 

Intrusive rocks 

Chiefly d(te1:te and granodiorite 

~ Lower part of Wrangell Lava 

and Frederika Formation 

Diverse continental sedimentary rocks of the Frederika 

Format·1:on and subaen:al andesitic la.vct and pyroclast?'c rocks of the Wrangell Lava 

B 

Marine sedimentary rocks 

Include, in ascending order, Kennicott, Schulze, Moonshine 

Creek, Chititu, and MacColl Ridge Formations 

I Jlim I 

McCarthy Formation 

Almost entirely rocks of lower member 

Nizina and Chitistone ~ Limestones 

Nikolai ~ Greenstone 

Unnamed marine ~ sedimentary rocks 

Gabbro 

~ 

Skolai ~ Group 

Includes Sta,tion Creek and overlying 

Hasen Creek Formations 

Contact 

Dotted where concealed; includes depositionnl 

and intrusive contacts and some fault contacts 

Steep fault 

Approximately located; dotted where corteealed 

. . . . ------ Thrust fault 

Approximately located; dotted where concealed; 

sawteeth on upper plate 

FIGURE 2.-Continued. 

}~ u 

~ (/) 

(/) 

<( 

0:: 

1-

7 
8 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

orogeny at or near the close of Jurassic or in Early Cretaceous 

time. However, since some of the steep faults cut Cretaceous rocks, 

they probably originated or were reactivated during Tertiary time. 

The dominant folds in the quadrangle trend northwestward and 

include moderately open to tight and overturned folds, mainly 

related to the Late Jurassic and(or) Early Cretaceous oror;~llY, and 

broad, gentle to moderately open post-Cretaceous folrlc:. 

The major unconformity in the quadrangle sep~~ ates Cretaceous 

from older rocks. Lesser unconformities separate Permian and 

Triassic rocks, Cretaceous and Tertiary rocks, and Quaternary 

surficial deposits from older rocks. Several di.-;conformities are 

recognized in the quadrangle's stratigraphic succession. 

STRATIGRAPHY AND LITHOLOGY 

Layered consolidated rocks in the B-4 quadrangle include submarine and subaerial volcanic rocks, abundant marine sedimentary 

rocks, and some continental sedimentary rocks (table 1 and fig. 2). 

Intrusive rocks ranging in composition from gabbro to granodiorite 

and dacite form small stocks, dikes, and sills that cut many of the 

layered rocks. Except for the Nikolai Greenstone and older rocks, 

which have undergone low-grade regional metamorphism, and 

small contact-metamorphosed zones contiguous to some plutons, 

metamorphic effects are lacking in the quadrangle. A variety of 

Quaternary surficial deposits locally mantles the bedrock. 

SKOLAI GROUP 

The Skolai Group and its subdivisions, the Station Creek and 

Hasen Creek Formations, were named and described by Smith and 

MacKevett ( 1970). The Skolai Group is well exposed in the eastcentral and northeastern parts of the quadrangle. It is weakly 

metamorphosed regionally and consists of submarine lavas and 

their derivative volcaniclastic rocks, the Station Creek Formation, 

and an overlying sequence of marine sedimentary rocks, the Hasen 

Creek Formation. 

STATION CREEK FORMATION 

The Station Creek Formation of 4500 feet maximum thickness 

is divided into a submarine volcanic flow unit and an overlying 

volcaniclastic unit which constitutes more than half the formation. 

Both units form moderately rugged outcrops. The base of the 

formation is not exposed, and its upper contact is gradational with 

the Hasen Creek Formation. Contacts between the volcanic and 

volcaniclastic units are broadly gradational. The formation is cut 

by gabbro plutons and by a few andesitic dikes. 
STRATIGRAPHY AND LITHOLOGY 9 

The volcanic unit contains basalt and basaltic andesite flows, 

subordinate coarse volcaniclastic rocks, chiefly pillow breccias and 

tuff breccias, and less abundant fine-grained volcaniclastic rocks 

and dacite or andesite flows. The lava flows are as much as 100 

feet thick, and some are n1arked by pillmv structures. Low-grade 

metan1orphic minerals widespread throughout the volcanic rocks 

have obliterated many primary textural features. Many of the lavas 

are amygdaloidal and porphyritic. More detailed petrographic 

descriptions of the Station Creek are given by Smith and MacKevett (1970). 

The upper, volcaniclastic unit contains beds between a few and 

about 100 feet thick that consist of rocks ranging from coarse volcanic breccias to finely laminated volcanilutites with volcanic graywacke predominating. A few lava flows are intercalated with the 

stratigraphically lower volcaniclastic rocks. Many beds are graded, 

and some show load casts. The volcaniclastic rocks contain abundant fragments of Station Creek volcanic rocks and assemblage of 

secondary minerals, such as albite, pun1pellyite, chlorite, epidote, 

and calcite, which reflect low-grade regional metamorphism. 

No fossils have been found in the Station Creek Formation. 

Because it gradationally underlies fossiliferous Lower Permian 

rocks, the Station Creek Forn1ation is considered to be Early 

Permian(?) in age. 

HASEN CREEK FORMATION 

The Hasen Creek Formation is about 900 feet thick and typically 

forms moderately sn1ooth or subdued outcrops. It gradationally 

overlies Station Cr,eek volcaniclastic rocks and generally unde~~lies 

the Nikolai Greenstone with slight angular unconformity. Locally 

it is apparently unconformably overlain by unnamed marine sedin1entary rocks of Middle Triassic age. It is cut by nmnerous gabbro 

bodies, mainly sills, and by a few felsic Tertiary plutons. 

The formation is lithologically diverse and includes impure 

chert, shale, sandstone, conglomerate, siltstone, and limestone. 

These rocks range from light gray to grayish black and are typically thin bedded. The impure cherts consist largely of chalcedony 

and quartz and also contain argillaceous dust, scattered erystals 

of mica, chlorite, quartz, plagioclase, and fairly abundant mierofossils, ehiefly radiolarian tests and spieules. Quartz veinlets that 

eut the cherts are fringed locally by elinozoisite and pumpellyite. 

The shale is mainly fissile, carbonaceous or silieeous. Generally 

it contains abundant clay n1inerals, illite, and quartz, along with 

earbonaceous debris and scattered n1icrofossils. The sandstone 

ranges from fine to eoarse grained and in plaees shows cross or 
10 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

graded bedding. Most of the sandstone is impure lithic arkose and 

subgraywacke. These rocks contain abundant clasts, including 

lithic fragments chiefly of nonvoleanic origin, quartz, plagioclase, 

K-feldspar, and micas, chiefly biotite. The clasts are embedded in 

a microcrystalline matrix composed largely of secondary minerals. 

The coarse sandstone locally grades into granule and pebble 

conglomerates. Subrounded lithic clasts are conspicuous in the 

conglomerates and generally are composed of rocks derived from 

subjacent beds. The siltstones are mineralogically similar to the 

sandstones but are finer grained and contain better sorted and 

more rounded clasts and less abundant K-feldspar and lithic 

fragments. 

Limestones of the Hasen Creek Formation are dominantly fossiliferous wackestones (terminology of Dunham, 1962) consisting 

of worn disarticulated fossil fragments as much as 1 em ( centimeter) long in a matrix of carbonate mud that generally constitutes more than half of the rock's volume. The carbonate mud 

is mainly calcite, but it is locally dolomitic and generally contains 

some clay minerals and carbonaceous material. Calcite veinlets cut 

some of the limestones. 

Fossils are abundant in the Hasen Creek limestones and occur 

sparsely in some other rocks of the formation. They are dominantly 

crinoids, but they also include brachiopods, bryozoans, and corals. 

Numerous fossil collections from the formation in the McCarthy 

C-4 quadrangle were studied by R. E. Grant and indicate an Early 

Pennian age (Smith and MacKevett, 1970). Some of the recently 

studied Hasen Creek fossil collections from the B-4 quadrangle 

contain brachiopods indicating the Guadalupe stage (Early and 

Late Permian) (R. E. Grant, 1969, written commun.). These 

brachiopods are not definitely Late Permian indicators and, in the 

absence of more conclusive evidence, the formation is still considered Early Permian in age. 

UNNAMED MARINE SEDIMENTARY ROCKS 

Unnamed marine sedimentary rocks underlie a small area near 

the northeast corner of the quadrangle. They disconformably underlie the Nikolai Greenstone and probably unconformably overlie 

the Hasen Creek Formation, but their basal contact is poorly exposed. The sedimentary rocks, a sequence about 150 feet thick, 

form moderately smooth to subdued outcrops. These rocks consist 

of thin-bedded chert, siltstone, and fissile shale and are dark gray 

or grayish black and locally carbonaceous. 

Two fossil collections from the sedimentary rocks were studied 

by N. J. Silberling (written commun., 1968) who reports: "These 
STRATIGRAPHY AND LITHOLOGY 11 

two collections, from beds beneath the Nikolai Greenstone, are 

somewhat alike. Both contain poorly preserved impressions of 

ornate ammonites and traces of halobiicl pelecypod ribbing. On 

this basis they are no older than upper Arisian (mid lVIiddle 

Triassic). Moreover, the an1n1onites resemble trachyceratids in 

which case they are Ladinian (late lVIiddle Triassic) or younger. 

Also represented are indetenninate cylindrical or conical objects 

(possibly coleoids, i.e., 'belemnites') and fragments of bone." 

The unnan1ed marine sedimentary rocks are therefore assigned 

a Middle Triassic age. 

NIKOLAI GREENSTONE 

The Nikolai Greenstone is widespread and very well exposed in 

the quadrangle \vhere it forms moderately rugged outcrops. The 

greenstone disconfornutbly underlies the Chitistone Limestone and 

unconformably overlies Permian rocks of the Hasen Creek Formation or, rarely, the intervening unnamed 1narine sedilnentary rocks. 

Angular discordances at the base of the greenstone are generally 

less than 10 degrees. The regionally widespread Nikolai Greenstone consists of a sequence of subaerial basaltic lava flows and a 

basal conglon1erate. The fonnation reaches its 1naxin1nm known 

thickness of about 13,000 feet in this quadrangle but is typically 

about 10,000 feet thick. Nikolai lava flows are generally 1 to 12 

feet thick and conspieuously amygdaloidal. The basal conglomerate 

is about 250 feet in maxin1um thickness and is composed of beds 

2 to 15 feet thick. Typically the eontacts between the conglomerate 

and the overlying lava are sharp, but locally they are gradational 

and marked by intercalated beds and flows. 

Basal conglomerates of the Nikolai are poorly sorted darkgreenish-gray rocks that consist of abundant subrounded pebbles 

in a fine-grained matrix that generally constitutes 10 to 25 percent of the rock. Many of the conglmnerates have been sheared 

and extensively altered. The pebbles, which are largely derivatives 

of the Skolai Group, include volcanic and volcaniclastic. rocks, 

chert, limestone, gabbro, and quartzite. Matrices of the conglomerates are graywackelike assemblages dominated by secondary 

minerals such as chlorite, pumpellyite, albite, quartz, opaque dust, 

calcite, locally abundant hematite, and rare prehnite, clinozoisite, 

and dis semina ted pyrite. 

The Nikolai lavas are altered basalts that are dark greenish 

gray and weather to shades of brown. They are fine-grained slightly 

porphyritic lavas with intergranular and, uneomm·only, subophitic 

textures and eontain scattered phenocrysts between 1 and 5 mm 

(millimeter) long. Amygdules from 1-5 mn1 long and exeeptionally 
12 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

a few centin1eters long are generally rather uniformly distributed 

throughout n1ost of the flows and include spherical, ellipsoidal, and 

irregular dumbbell-shaped forms. Some of the greenstones are cut 

by calcite veinlets. 

The Nikolai basalts consist of plag·ioclase, chiefly labradorite, 

abundant clinopyroxene, less abundant relict olivine, minor to 

abundant opaque minerals, and an array of alteration products. 

The phenocrysts are chiefly plagioclase but include some corroded 

clinopyroxene. The clinopyroxene is mainly augite but some is 

probably pigeonite. Opaque minerals in the greenstone are magnetite and ilmente, subordinate hematite and pyrite, and rare flecks 

of native copper and unidentified sulfides. The alteration products 

are chlorite, including antigorite and ferrugginous serpentine 

minerals, clay minerals, sericite, and less common calcite, epidote, 

sphene, and leucoxene. The greenstone's alteration products and 

amygdule constituents indicate low-grade regional metamorphism. 

Most Nikolai amygdules contain chlorite and calcite. Chlorite is 

generally dominant and is locally represented by more than one 

variety. Some an1ygdules are characterized by quartz or chalcedony 

and epidote or by prehnite or natrolite. Less abundant to rare 

constituents of a1nygdules are pumpellyite, thomsonite, heulandite, 

native copper, tenorite, and copper carbonates. 

Except for relicts of Permian fossils in limestone clasts of the 

conglomerate, the Nikolai Greenstone is unfossiliferous. On the 

basis of its stratigraphic position, it is considered to be late Middle 

and(or) early Late Triassic in age. 

CHITISTONE LIMESTONE 

The Chitistone Limestone, which is well exposed in the westcentral and northwest parts of the quadrangle, forms rugged, bold 

outcrops that include some spectacular cliffs. Solution cavities and 

channels, including a few large caverns, are conspicuous in some 

Chitistone outcrops. Most Chitistone strata are 5 to 20 feet thick, 

although thinner beds locally intervene between the thicker beds 

and in places are dominant in zones as much as 150 feet thick. 

Thickness of the formation ranges fron1 about 500 to 1,800 feet. 

The marked contrasts in thickness indicate nonuniform deposition 

throughout Chitistone time and possibly that the subjacent Nikolai 

Greenstone was locally emergent during early stages of Chitistone 

deposition. The Chitistone Limestone disconformably overlies 

Nikolai Greenstone and gradationally underlies Nizina Limestone. 

The Chitistone Limestone consists of lime mudstone and lesser 

amounts of wackestone, crystalline limestone, and dolomite (terminology of Dunham, 1962). Some beds contain scattered generally 
STRATIGRAPHY AND LITHOLOGY 13 

spherical chert nodules less than 6 inches in diameter. Calcite 

veinlets and veins as much as 6 inches thick cut n1any of the 

Chitistone rocks and are locally abundant in strongly fractured 

rocks. Many Chitistone and Nizina limestones emit a fetid odor 

when broken. The formation's carbonate rocks range from light 

to dark greenish gray and weather light yellowish or grayish 

brown. Generally the lime n1udstones and wackestones are n1edimn 

or dark shades of gray and the crystalline carbonates light gray. 

The dominant carbonate n1udstones range from relatively pure 

calcite-rich rocks to dolon1itic rocks, which are confined to lower 

parts of the fonnation. Typically the n1udstones contain widely 

scattered bioclastic debris, pellets and clots of lime mud, rare 

calcite oolites, and blebs of limpid calcite, in a n1atrix of lim€ 

Inud. The bioclasts include echinoid plates and less abundant 

spherical, rodlike, and arcuate n1icrofossils. Dolon1ite is a primary 

constituent of some of the carbonate n1ud, and many of the n1udstones are neomorphic, partly or largely recrystallized. Most of 

the mud contains sparsely distributed minute opaque 111inerals, 

chiefly pyrite, and rare quartz and clay minerals. Thin stylolites cut 

a few of the mudstones. The \Vackestones are n1ineralogically and 

texturally similar to the mudstones, but they contain n1ore than 

10 percent clastic constituents. 

The crystalline carbonates consist of crystalline phases of lin1estone, dolomitic limestone, and dolomite, with crystals between 

0.1 and 0.5 m1n in dian1eter forn1ing interlocking n1osaics. Most of 

the crystalline carbonates contain sn1all quantities of quartz, pyrite, 

and hen1atite. These rocks probably represent recrystallized lime 

mudstone and wackestone. The dolomite-rich types are in lower 

parts of the formation. 

The formation's che1·ts, which are dark gray to black chalcedony 

with minor an1ounts of calcite, fracture subconchoidally. 

The Chitistone Limestone was probably deposited in shallow seas 

partly under intertidal and supratidal conditions on a carbonate 

shelf that overlaid a platforn1 of epeirogenetically submerged 

Nikolai Greenstone (Arn1strong and others, 1970). Its n1ost diagnostic fossils are sparsely distributed an1n1onites of the genus 

TTopites that indicate the late Karnian Stage of the Late Triassic 

(N. J. Silber ling, written comn1un., 1968). 

NIZIN A LIMESTONE 

The Nizina Limestone, mapped with the Chitistone in figure 2, 

is widely distributed in the west-central and northwest parts of the 

quadrangle \Vhere it forn1s moderately rugged outcrops. Its approximate thickness ranges from 700 to 1,700 feet within the quad-
14 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

rangle. The 1,700-foot estimate may be too large because of 

unrecognized structural complications; probably a more valid 

maximum thickness is about 1,000 feet. Most Nizina strata are 

between lf2 and 2 feet thick, but some are as much as 10 feet 

thick. Thin shaly limestone partings intervene between a few 

of the limestone beds. The Nizina Limestone conformably overlies the Chitistone Limestone along broadly gradational contacts 

and conformably underlies the lower member of the McCarthy 

Formation. 

The Nizina Li1nestone consists of limestone with subordinate 

local chert lenses and nodules. The limestones include abundant 

lime mudstone, fairly abundant wackestone, and rare grainstone 

(terminology of Dunham, 1962). These carbonate rocks are dark 

greenish gray or less commonly shades of medium or dark gray 

where fresh. They are yellowish brown or light brown or, rarely, 

darker shades of brown, light gray, or olive gray where weathered. 

Calcite veinlets and veins as much as 6 inches thick are abundant. 

The typical Nizina lime mudstones are composed largely of 

cloudy calcite particles 20 to 30 microns across that generally enclose widely scattered pellets and irregular clots of lime mud, bioclastic debris, chiefly echinoid plates and spicules, blebs of clear 

calcite, and flecks of pyrite and hematite. Some of the lime mudstones are neomorphic or incipiently neomorphic and contain 

crystals of clear calcite about 0.05 mm in length that have replaced 

lime mud particles. Fine stylolites have developed in some of the 

lime mudstones. Besides their dominant calcite, some lime muds 

contain minor amounts of quartz, dolomite, clay minerals, and 

carbonaceous material. 

The wackestones differ from the lime mudstones by containing 

more abundant clastic constituents, chiefly pellets of lime mud and 

bioclastic detritus enclosed in a matrix of lime mud. Some of the 

wackestones are partly recrystallized. 

The rare grainstones in the formation contain abundant oolites 

about 0.3 mm in diameter cemented by finely-crystalline calcite. 

The grainstones also contain a few nonoolitic calcite grains and 

other clasts, chiefly chert. 

The chert forms irregular nodules, usually a few inches in maximum dimension but occasionally as much as 2 feet long, a foot 

wide, and 6 inches thick, which locally coalesce to form layers of 

chert or lenses 2 to 6 inches thick. The chert is grayish-black 

to black with dull subvitreous surfaces and subconchoidal fractures 

and consists of chalcedony with sparse veinlets of calcite. 

The Nizina limestones are generally purer than similar rocks in 
STRATIGRAPHY AND LITHOLOGY 15 

the lower member of the McCarthy Formation. The Nizina Limestone differs from the underlying Chitistone Limestone in its prevalent thin beds, lack of bedded dolomite, more abundant chert, and 

typically darker colors. 

According to Armstrong, MacKevett, and Silberling (1970) the 

Nizina Limestone probably formed on the basinward slope of a 

dro\vned carbonate shelf platform of Chitistone Limestone. Some 

older Nizina Limestone is probably locally contemporaneous with 

some younger parts of the Chitistone Limestone. A similar contemporaneity is indicated between younger parts of the Nizina 

and older strata of the lower me1nber of the McCarthy Formation. 

The characteristic Nizina fossils are pelecypods of the genus 

Halobz:a. In the B-4 quadrangle, lower parts of the Nizina Limestone locally contain faunal elen1ents generally found in the Chitistone Limestone. Paleontologic studies by N. J. Silberling indicate 

that the Nizina Li1nestone is Late Triassic, with an age span from 

late Karnian to middle Norian. 

McCARTHY FORMATION 

LOWER MEMBER 

The lower n1ember of the McCarthy Formation is widely distributed in the northwestern part of the quadrangle where it is more 

than 600 feet thick. It conforn1ably overlies the Nizina Limestone 

and gradationally underlies the upper member. The lower member 

is characterized by incon1petent thin-bedded, strongly deformed 

strata that generally form subdued outcrops. 

The lower member is impure limestone with minor amounts of 

shale and in1pure chert. It contains more limestone in this quadrangle than do the McCarthy lower 1nember rocks in the McCarthy 

C-4 and C-5 quadrangles (MacKevett, 1970a, b, c). Spherical chert 

nodules, 1 to 2 inches in dian1eter, are localized in some of its 

lower strata, and narrow gash veins and veinlets of quartz or of 

quartz and calcite occupy crestal zones of some of the folds. 

The i1npure lin1estones consist of wackestone and lime mudstone 

and rare grainstone and crystalline limestone (terminology of 

Dunha111, 1962). These rocks are dark greenish gray or, exceptionally, dark gray where fresh, and light or grayish brown where 

weathered. Typically the wackestones are very fine grained, thinly 

laminateci rocks that contain scattered clasts in a microcrystalline 

matrix. Most of them contain dispersed carbonaceous material 

and fairly abundant bioclasts and qualify as carbonaceous bioclastic wackestone. The bioclasts are dominantly calcareous and 

include spherical and rodlike forms and spicules. Other clasts in the 

wackestone include grains of calcite and less abundant quartz 
16 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

and pyrite and a few clots of lime mud. The matrix is chiefly locally 

recrystallized lime mud consisting of calcite and minor dolomite 

and chalcedony. 

The lime mudstones are dense aggregates and coalesced pellets 

of lime mud and a few scattered clasts of calcareous microfosssils 

and rarely grains of calcite, quartz, and pyrite. Limpid neomorphic 

calcite has partly replaced the lime mud in some of the mudstones. 

The lime mud is dominantly calcite with lesser amounts of chalcedony, carbonaceous material, and dolomite. 

The crystalline limestone is probably a neomorphic lime mudstone. It contains scattered calcareous spherical and rodlike microfossil remains in a n1osaic of calcite crystals about 0.1 mm long. 

The rare grainstone is subrounded calcite grains from 0.1 to 0.15 

mm in diameter and minor interstitial very fine grained calcite and 

wispy carbonaceous material. The grainstone contains widely 

dispersed opaque minerals, chiefly pyrite, and a few spicules replaced by chalcedony and chlorite. 

The shales are calcareous and carbonaceous rocks that are dark 

gray to black and weather dark brown. They are thinly laminated, 

very fine grainec, and consist of quartz, calcite, clay minerals, 

carbonaceous material, and minor amounts of plagioclase, dolomite, 

and widely dispersed opaque minerals, chiefly pyrite. Most of the 

shales contain scattered relicts of microfossils. The impure cherts 

are dark-gray chalcedony-rich rocks that contain subordinate calcite, carbonaceous material, opaque minerals, and scattered microfossils. 

The lower member of the McCarthy Formation contains widespread pelecypods of the genus Manolis, which according to N. J. 

Silberling (written commun., 1968) indicate the late Norian Stage 

of the Late Triassic. In the B-4 quadrangle, lower parts of the 

member contain a faunal assemblage that includes pelecypods of 

the genus Halob1~a and other fossils generally found in the Nizina 

Limestone that are indicators of the early(?) and mid Norian 

Stages (N. J. Silberling, written commun., 1968). This faunal 

distribution substantiates the interpretation that the lower part 

of the lower member is locally a deep water temporal equivalent 

of the upper part of the Nizina Limestone. No diagnostic fossils 

were found in the uppermost 200 feet of the member, and the 

rocks of this strati~-raphic sequence may be as young as earliest 

Jurassic. 

UPPER MEMBER 

The upper member of the McCarthy Formation is not differentiated from the lower member in figure 2. Exposures of the upper 
STRATIGRAPHY AND LITHOLOGY 17 

member are confined to the northwest part of the quadrangle and 

consist of approximately 850 feet of stratigraphically lower parts 

of the member. These exposures represent the southeasternmost 

known outcrops of the member, which is well developed in the 

McCarthy C-4 and C-5 quadranges (MacKevett, 1970a, b). The 

upper member gradationally overlies the lower member. The upper 

contact of the member is not exposed in the B-4 quadrangle. Most 

strata in the member are 1;~ to 2 feet thick and form ribby outcrops 

due to differential erosion of the beds. 

Upper member rocks, which are dark gray and generally weather 

yellowish brown, consist of impure lin1estone and lesser quantities 

of chert and spiculite. Gradations between the member's calcareous 

and siliceous rocks are common. The dominant impure limestones 

are bioclastic wackestones (terminology of Dunham, 1962) that 

in places are partly recrystallized. These waekestones consist of 

fine clasts, generally less than 0.1 mm long, in an extremely finegrained matrix that is largely con1posed of crystalline calcite. The 

clasts include abundant bioclastic remains, chiefly calcareous or 

siliceous spheres and spicules, grains of calcite, subordinate quartz, 

plagioclase, and opaque minerals, mainly pyrite. The minor matrix 

constituents include carbonaceous material, chlorite, dolomite, and 

secondary iron oxides. 

The upper member is probably entirely Early Jurassic in age, 

although its basal strata may be Late Triassic. Fossils collected 

from near the base of the member include amn1onites that according toR. W. Imlay aln1ost certainly belong to the genus Psiloce-ras, 

indicative of the Jurassic Hettangian Stage. Stratigraphically 

higher fossil collections contain A-rietites and other ammonites 

indicative of the Jurassic lower Sinemurian Stage (R. \V. Imlay, 

written commun., 1968). 

KENNICOTT FORMATION 

The Kennicott Formation, the lowest of the five Cretaceous units 

in the quadrangle (which are combined in figure 2), is best exposed 

throughout a belt that extends from south of Dan Creek to near 

the southeastern corner of the quadrangle. It also forms scattered 

outcrops elsewhere in the quadrangle. The formation has been 

described and redefined by Jones and lVIacKevett (1969, p. K6-

K11). 

A strong angular unconformity separates the Kennicott Formation from subjacent Triassic rocks, and it is overlain by the 

Schulze Formation with disconformity or possible unconformity, 

by the Moonshine Creek Formation with disconformity, or by 

the Chititu Formation with apparent conformity or minor dis-
18 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

conformity. It is cut by a few felsic dikes and sills and by rare 

sandstone dikes. The formation ranges in thickness from a few tens 

to about 475 feet, and its strata are thin bedded to massive. 

The Kennicott Formation consists of a basal conglomerate as 

much as 75 feet thick grading upward into a sequence of sandstone, 

siltstone, and shale and containing scattered calcareous concretions 

and erratically distribut·ed wood and plant debris. The conglomerates generally form bold outcrops; other Kennicott rocks form 

moderate to subdued outcrops. 

Most of the basal conglomerate beds are 5 to 20 feet thick and 

consist of granule or pebble conglomerate, rarely of cobble or 

boulder conglomerate. The conglomerates are well indurated and 

medium dark gray, dark greenish gray, or light gray where fresh 

and diverse shades of brown where weathered. Their clasts are 

subrounded to rounded and reflect local provenances with most 

clasts being derivatives of Nikolai Greenstones or Triassic carbonate rocks. Most of the conglomerates have coarse- or mediumgrained wacke or calcite-cemeted arenite matrices which contain 

quartz, plagioclase, calcite, chlorite, chalcedony, clay minerals, 

and subordinate glauconite, carbonaceous debris, and pyrite and 

other opaque minerals. 

Sandstones of the formation include several types of wacke and 

arenite (terminology of Williams and others, 1954, p. 290-294). 

These rocks are well indurated, typically thin bedded, and locally 

flaggy or platy. They are light to dark greenish gray where fresh 

and light brown or yellowish brown where weathered. Most of the 

sandstones are fine or medium grained. The wackes include feldspathic, lithic, and arkosic varieties consisting of subangular clasts 

in microcrystalline matrices that constitute 10 to 35 percent of the 

rock. Their clasts include quartz and slightly less abundant plagioclase and lithic fragments, chiefly chert, minor to locally abundant 

K-feldspar and calcite, minor leucoxene, ilmenite, pyrite, and rare 

zircon, epidote, and barite. Matrices of the wacke consist of 

chalcedony, chlorite, and clay minerals including kaolinite, with 

subordinate calcite, brown carbonates, sericite, carbonaceous material and secondary iron oxides. 

The arenites are mainly feldspathic or lithic calcite-cemented 

arenites which contain subangular or subrounded clasts of abundant quartz, plagioclase, and lithic fragments, chiefly chert, and 

minor to rare calcite, glauconite, K-feldspar, biotite, pyrite, ilmenite, and magnetite. In addition to calcite, matrices of some arenites contain minor chlorite, clay minerals, sericite, dolomite, 
STRATIGRAPHY AND LITHOLOGY 19 

chalcedony, hematite. Alteration products of some of the clasts 

include leucoxene, hen1atite, sericite, chlorite, and clay minerals. 

The siltstones and shales are thin-bedded to fissile rocks that 

locally are finely laminated. Generally they are medium gray and 

weather yellowish or reddish brown. Most of the siltstone and 

shales consists of small clasts, chiefly quartz and subordinately 

hematite, calcite, biotite, and plagioclase, in microcrystalline matrices that contain abundant kaolinite and illite and lesser amounts 

of chalcedony, calcite, chlorite, and secondary iron oxides. 

Only the younger part of the regionally bipartite Kennicott 

Formation is represented in the B-4 quadrangle. This part of the 

formation contains a variety of fossils, mainly in concretions, that 

include diagnostic amn1onites of the late early· Albian (Early 

Cretaceous) zone of Brewericeras hulenense (Jones and MacKevett, 

1969, p. K10, K11). 

SCHUJLZE FORMATION 

The Schulze Formation, ,Jones and MacKevett, 1969, p. K13-

K15) forms small outcrops in the upland north of Boulder Creek 

near the western border of the quadrangle. These outcrops are 

probably isolated remnants of fairly extensive rocks that underlie 

uplands in the central part of the McCarthy B-5 quadrangle 

(MacKevett, 1965b). The Schulze Formation overlies the Kennicott Formation with disconformity or possibly with slight angular discordance. Its top is eroded, and its maximum thickness is 

about 150 feet. 

The formation is characterized by thin-bedded light-colored 

erosion-resistant siliceous rocks. It consists of fine and very fine 

grained sandstone, siltstone, and platy porcellanite. These rocks 

are typically light gray and weather buff or yellowish brown. The 

siliceous rocks of the forrnation contain abundant microfossils, 

but no megafossils were found. Megafossils from the formation in 

the B-5 quadrangle indicate a probable age range from late Albian 

( ?) to Cenomanian (Early('?) to late Cretaceous) (Jones and MacKevett, 1969, p. K14, K15). 

MOONSHINE CREEK FORMATION 

The Moonshine Creek Formation (Jones and MacKevett, 1969, 

p. K11-K13) is poorly exposed and sparsely distributed in the B-4 

quadrangle. It forms small outcrops that are mainly erosional 

outliers in the north-central and southeastern parts of the quadrangle. The incomplete Moonshine Creek stratigraphic sections in 

the B-4 quadrangle are 250 feet in maximum thickness, in marked 

contrast with the formation's 3,500 foot thickness at its type 
20 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

locality in the McCarthy C-4 quadrangle (MacKevett, 1970a). The 

Moonshine Creek Formation disconformably overlies the Kennicott Formation or unconformably overlies Nikolai Greenstone. 

South of Canyon Creek, the Moonshine Creek apparently disconformably underlies the Chititu Formation. Elsewhere its upper 

surfaces are being subaerially eroded. Rocks of the formation are 

mainly thin bedded and generally form moderate slopes. 

The Moonshine Creek Formation consists of fine-grained sandstone and siltstone with minor coarse-grained sandstone and conglomerate. Generally its basal unit is a pebble or granule conglomerate a few feet thick. Most of the Moonshine Creek is medium or 

dark gray and weathers light brown or orange brown. 

Siltstones of the formation are moderately well sorted and contain fine clasts, chiefly of quartz and plagioclase in microcrystalline 

clay-rich matrices. The sandstones are feldspathic or lithic wacke 

and arenite. These rocks are moderately indurated and sorted, and 

their dominant clastic constituents, quartz, plagioclase, and lithic 

fragments, are embedded in microcrystalline matrices or are cemented by calcite. 

More detailed descriptions of the formation, based largely on 

geologic studies in the McCarthy C-4 and C-5 quadrangles, are 

given by Jones and MacKevett (1969, p. K11-K13) and by MacKevett ( 1970a, c). 

The Moonshine Creek Formation contains Inoceramus and ammonites of the genus Desmoceras (Pseudouhligella) that indicate 

an age span from late Albian to late Cenomanian (Early and Late 

Cretaceous) (Jones and MacKevett, 1969, p. K13). Part of the 

formation is contemporaneous with the Schulze Formation and 

probably with some older parts of the Chititu Formation. 

CHITITU FORMATION 

The Chititu Formation, named by Jones and MacKevett ( 1969, 

p. K15), is the dominant rock unit throughout the southern part 

of the quadrangle. The formation erodes to smooth rounded slopes 

locally breached by more resistant strata or by dikes and sills. The 

Chititu Formation is from 5,000 to 9,000 feet approximately, but 

accurate estimates of its thickness are precluded by folds and by 

the lack of persistent marker beds. It overlies the Kennicott Formation with apparent conformity or minor disconformity. At one 

locality south of Canyon Creek, the Chititu apparently disconformably overlies the Moonshine Creek Formation along a poorly 

exposed contact. At a few other places marked by obscure contacts it apparently unconformably overlies pre-Cretaceous rocks. 

The Chititu Formation is overlain conformably by the MacColl 
STRATIGRAPHY AND LITHOLOGY 21 

Ridge Formation and locally is cut by Tertiary plutons, chiefly 

felsic dikes and sills. Chititu rocks have been converted to hornfels 

in irregular metan1orphic aureoles near son1e of the larger plutons. 

The Chititu Formation contains abundant pelitic rocks, chiefly 

n1udstone with subordinate shale, and lesser amounts of porcellanite, sandstone, limestone, and limy concretions. Its thermally metamorphosed variants are hornfels and silicified n1udstone. Sandstone dikes locally cut the formation, generally at high angles to the 

bedding. Most of these dikes are less than 2 feet thick and are 

resistant. The concretions, which are best developed in the pelites, 

range fron1 about 2 inches to 2 feet in maximum dimension. They 

are con11nonly spherical, but a few have irregular discoidal configurations. :Most of the mudstone and shale is dark greenish gray 

or dark gray on both fresh and weathered surfaces. The mudstones are fairly n1assive, moderately to well-indurated rocks with 

a hackly fracture. The shales are finely lan1inated and typically 

fissile. The n1udstones and shales are similar in mineral content, 

being silica rich and containing scattered finely comminuted 

detrital grains, chiefly quartz, embedded in aggregates of clay 

minerals, illite, sericite, chlorite, secondary iron oxides, and chalcedony. Their less abundant detrital constituents include plagioclase, 

chert fragments, biotite, and rare K-feldspar, zircon, and magnetite. Many of the mudstones and shales contain disseminated 

pyrite, and a few are characterized by fairly abundant calcite. 

Quartz or calcite veinlets cut some of the pelites. Some of the shales 

and n1udstones contain poorly preserved remains of microfossils. 

The porcellanites are medium- to dark-gray siliceous rocks that 

are extremely fine grained and fracture subconchoidally. They 

consist n1ainly of chalcedony flecked with scattered grains of 

quartz, carbonates including calcite, dolomite, and ankerite, and 

pyrite. Most of the porcellanites contain minor amounts of carbonaceous material, chlorite, clay minerals, and secondary iron 

oxides. Son1e are cut by quartz or calcite veinlets. Spherical microfossil tests as much as 0.02 n1m in diameter are common in the 

porcellanite. The tests are mainly siliceous, but a few are calcareous. 

The sandstones include feldspathic wacke and subordinate arkosic wacke and lithic arenite (terminology of Williams and others, 

1954, p. 290-294). Typically the sandstones are fine to medium 

grained, poorly sorted, and well indurated. They are medium to 

dark gray and weather brownish gray. The feldspathic wackes 

consist of subangular grains, chiefly of quartz and plagioclase, 

embedded in a microcrystalline matrix that constitutes less than 25 
22 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

percent of the rock's volume. The matrix consists of clay minerals, 

chalcedony, chlorite, carbonaceous material, sericite, and minor 

amounts of calcite, dolomite, leucoxene, and secondary iron oxides. 

Less common grains in the feldspathic wackes are calcite, Kfeldspar, pyrite, magnetite, ilmenite, apatite, biotite, epidote, and 

lithic fragments, chiefly chert. 

The arkosic wacke is mineralogically and texturally similar to 

the feldspathic wacke but contains more abundant plagioclase and 

K-feldspar relative to quartz. All of the sandstone dikes studied 

are either lithic or arkosic wacke. 

The lithic arenite contains abundant calcite-cemented subangular to subrounded clasts including lithic fragments that resemble 

cherty rocks of the McCarthy Formation and less abundant calcite, 

quartz, plagioclase, and opaque minerals, chiefly leucoxene. The 

lithic arenites also contain rare clay minerals and chlorite. 

The limestone occurs as a few discrete beds and numerous lenses. 

It is light or medium gray with mottled gray-brown weathered 

surfaces. The limestone is impure, very fine grained, and contains 

diverse amounts of non-carbonate minerals mainly as detritus. 

Most of the limestone is closely fractured and veined by limpid 

calcite and is composed mainly of turbid microcrystalline calcite, 

and qualifies as lime mudstone in Dunham's (1962) classification. 

Some of the lime mudstone has been converted into neomorphic 

calcite. Besides the dominant lime mud the limestone contains 

sparsely distributed chalcedony, quartz, sericite, chlorite, calcite 

grains, plagioclase, pyrite, hematite, ilmenite, leucoxene, and rodlike remains of microfossils. 

The metamorphosed Chititu Formation rocks are dark gray 

weathering to a distinctive medium dark brown that distinguishes 

them in the field from the typical rocks of the formation. These 

metamorphic rocks mostly form irregular aureoles surrounding 

some of the plutons and grade from hornfels to dense silicified rocks 

and then into normal pelitic rocks outward from the pluton. All 

appear fine grained with hackly fractures, and most are tough, 

dense, well-indurated rocks. The hornfels are aggregates of clinopyroxene, epidote, calcite, chlorite, and sphene, suggesting metamorphic grade as high as the hornblende hornfels facies. The less 

metamorphosed rocks have been pervaded by quartz or calcite 

but have not been generally recrystallized. Some of the metamorphic rocks contain disseminated 1;yrite. 

The Chititu Formation contains widely distributed Inoceramus 

and less abundant ammonites, both of which substantiate its Late 

Cretaceous age. The Formation is from Cenomanian to late 
STRATIGRAPHY AND LITHOLOGY 23 

Campanian, and in places its basal rocks may )~ as old as latest 

Albian (Jones and MacKevett, 1969, p. K17). 

MacCOLL RIDGE FORMATION 

The MacColl Ridge Formation underlies a few upland areas in 

the southern part of the quadrangle where its erosion-resistant 

strata form bold outcrops or cliffs. Its excellent exposures near 

Pyramid Peak have been illustrated by Jones and Berg (1964, fig. 

4). The formation is about 2,,000 feet thick in the B-4 quadrangle, 

but its top is not exposed. It overlies the Chititu Formation with 

apparent conforn1ity and is cut by Tertiary plutons. Its strata are 

generally 1 to 3 feet thick and locall.v fiaggy. 

The MacColl Ridge Forrnation was named and described in some 

detail by Jones and MacKevett ( 1969, p. K17-K19). The formation 

consists of coarse- and medium-grained sandstone that in places 

grades into granule conglomerate, fine-grained sandstone, or, 

rarely, siltstone. Most rocks of the formation are light or medium 

gray and weather light brown. The dominant sandstones are 

arkosic, lithic, and feldspathic wacke in decreasing order of abundance (terminology of Williams and others, 1954). They are wellindurated rocks of diverse subangular clasts in chalcedony-chloriteclay matrices constituting 1J5 to 30 percent of the rock. The sandstones are distinguished by the relative abundance of their major 

clasts: plagioclase, quartz, and lithic fragn1ents, chiefly chert. Their 

less abundant clasts include K-feldspar, biotite, scattered opaque 

minerals, mainly magnetite and pyrite, and rare clinopyroxene and 

apatite. Less abundant lnatr:[x constituents and alteration products 

in the sandstones are actinolitic amphibole, sericite, hematite, 

limonite, and calcite. Some matrices contain small amounts of 

carbonaceous material. Near smne plutons the sandstones have been 

baked and slightly recrystaLlized. 

The granule conglomerate is compositionally similar to the 

coarse-grained lithic wacke. The siltstones generally contain better 

sorted and more rounded clasts, chiefly quartz, and more carbonaceous material than the wackes. 

Diagnostic fossils have not been found in the formation, but the 

field relations indicate a Late Cretaceous (Late Campanian or 

Maestrichtian) age (Jones and MacKevett, 1969, p. K18-K19). 

FREDERIKA FORMATION AND WRANGELL LAVA 

Continental sedimentary rocks of the Frederika Formation are 

intercalated with the Wrangell Lava and underlie summit regions 

in the northeastern part of the quadrangle. These rocks which 

unconformably overlie rocks of the Skolai Group and locally non-
24 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

conformably overlie gabbro are cut by a few andesitic dikes and 

sills probably related to the Wrangell Lava. The Frederika-Wrangell sequence is almost 2,000 feet thick in the quadrangle. Lithologically diverse continental sedimentary rocks of the Frederika 

Formation are dominant throughout the lower part of the sequence 

and andesites of the Wrangell Lava are dominant throughout the 

upper part. 

The Frederika Formation is conglomerate, sandstone, siltstone, 

shale, and low-rank coal. Similar rocks from nearby quadrangles 

have been described in some detail (MacKevett, 1970a, c). These 

sedimentary rocks are characteriz,ed by a wide range in lithology 

and by strongly contrasting colors and include some rocks rich in 

tuffaceous material. The few coal seams in the B-4 quadrangle are 

less than 18 inches thick and do not appear to be extensive. The 

pelitic rocks of the Frederika Formation contain scattered carbonaceous plant remains, and leaves collected from the formation in the 

C-4 and C-5 quadrangles have been dated as Miocene (MacKavett, 

1970a, b, c). 

The Wrangell Lava consists of lava flows, chiefly andesite and 

basaltic andesite, and subordinate pyroclastic rocks. The lava, 

which is more extensive in the McCarthy C-4 and C-5 quadrangles, 

has been described by MacKevett (1970a, c). Only the lower part 

of the Wrangell Lava is preserved in the B-4 quadrangle where it 

contains several flows of olivine basalt and a few pyroclastic 

layers of well-indurated lapilli and crystal tuffs or, rarely, buffcolored ash considered to be of Miocene age. Regionally, Wrangell 

volcanism extended from the Miocene well into Holocene time. 

SURFICIAL DEPOSITS 

Quaternary surficial deposits in the quadrangle are alluvium and 

older alluvium, talus, rock glaciers, several kinds of moraines, landslides, fluvioglacial deposits, and thin veneers of soil, slope wash, 

or colluvium that were not mapped. Except for the fluvioglacial deposits, the mapped surficial deposits are similar to those described 

from the nearby McCarthy C-4 and C-5 quadrangles (MacKevett, 

1970a, b, c.). Rock glaciers and a variety of moraines are especially 

well developed in the B-4 quadrangle. 

Fluvioglacial deposits as much as 200 feet thick are exposed 

along the valley walls of the Chitistone River and the tributaries of 

Young Creek near the southern boundary of the quadrangle. They 

unconformably overlie older consolidated rocks and locally are 

overlain by other surficial deposits. The fluvioglacial deposits are 

poorly consolidated and generally well stratified. They form layers 

as much as 12 feet thick that are composed of moderately well-
INTRUSIVE ROCKS 25 

sorted sand and silt and lesser amounts of clay, granules, pebbles, 

and boulders. Typically the larger clasts are subangular and the 

smaller ones subrounded. Fluv] oglacial deposits in the B-4 quadrangle represent the northeasternmost extent of vast deposits underlying large parts of the Chitina Valley west and southwest of 

the quadrangle. The ftuvioglacial deposits probably originated in a 

periglacial lacustrine environrnent where overloaded proglacial 

streams discharged large quant.ties of sediments into a Pleistocene 

lake. 

INTRUSIVE ROCKS 

Intrusive rocks in the quadr<c1ngle include gabbro of Permian or 

Triassic age and intermediate to mafic, felsic hypabyssal, and 

andesitic rocks of Cenozoic age. 

GABBRO 

Gabbro forms sills and discordant plutons in the northeastern 

part of the quadrangle where it intrudes rocks of the Skolai Group. 

Its outcrops range from masses several miles long and about a half 

mile wide to narrow sills and dikes a few feet thick. Locally gabbro 

is nonconformably overlain by ·:he Frederika Formation or cut by 

felsic dikes. 

The gabbros are medium-· to coarse-grained rocks composed of 

minerals 2 to 7 mm long. They are bluish-gray or greenish-gray 

rocks, weathering to rusty brovvn or greenish black, and have been 

altered in various degrees. The gabbros are hypidiomorphic granular or subophitic with rare, generally finer-grained, intergranular 

phases. Their dominant primary minerals, plagioclase (labradorite) and clinopyroxene, probably augite, generally occur in nearequal amounts and constitute a:; much as 90 percent of the rock's 

volume. Other primary minerals include opaque minerals, mainly 

magnetite and ilmenite, and rare quartz and apatite. Alteration 

products, abundant in some of the gabbros, include diverse ferruginous serpentine minerals and related chlorites, biotite, uralitic 

hornblende, sericite, quartz, sphene, pumpellyite, clay minerals, 

clinozoisite, epidote, and secondary iron oxides. A few of the gabbros contain sparsely disserrtinated pyrite and pyrrhotite(?). 

Although the precise age of the gabbro is not known, it is considered to be Permian or Trias~;ic because it cuts the fossiliferous 

Lower Permian Hasen Creek Formation and because gabbro pebbles are local components of the basal conglomerate of the Triassic 

Nikolai Greenstone. 

D. H. Richter (written commun., 1969) states that gabbro cuts 

the lower part of the Triassic Nikolai Greenstone in the Nabesna 
26 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

quadrangle, which borders the McCarthy quadrangle on the north. 

Richter's observations, along with field evidence in the McCarthy 

B-4 and C-4 quadrangles, suggest that the gabbro may have 

formed during more than one intrusive stage in the Triassic and 

possibly Late Permian, but conclusive evidence for multiple episodes of gabbro intrusion is lacking in the B-4 quadrangle. 

INTERMEDIATE AND MAFIC INTRUSIVE ROCKS 

A few stocks and small satellite cupolas of Tertiary intermediate 

and mafic intrusive rocks cut the Cretaceous Chititu and MacColl 

Ridge Formations in the southern part of the quadrangle. Pelites 

of the invaded Chititu Formation have been metamorphosed near 

some intrusive masses forming aureoles as much as several thousand feet wide. In a few places the intermediate and mafic rocks 

are cut by felsic hypabyssal plutons. The stocks and related smaller 

intrusive masses form bold outcrops underlying rugged terrain. 

The intermediate and mafic intrusive rocks are largely mediumgrained hypidiomorphic granular rocks, granodiorite, quartz diorite, and subordinate diorite and gabbro, that weather dark gray 

or dark greenish gray. The stock near Pyramid Peak is crudely 

zoned with a border zone of gabbro a few hundred feet wide, a 

dioritic intermediate zone of similar width, and a central zone of 

quartz diorite and granodiorite. The other intrusive masses consist 

of granodiorite and quartz diorite without apparent zoning. 

The quartz diorite contains abundant plagioclase, mainly calcic 

andesine, fairly abundant quartz, clinopyroxene (augite), biotite, 

and hornblende, and minor to trace amounts of sphene, zircon, apatite, K-.J!'?.ldspar, and opaque minerals, chiefly magnetite. Its secondary rjnerals include uralitic hornblende, chlorite, sericite, calcite, 

and clay minerals. The granodiorite differs from the quartz diorite 

in containing sodic andesine, more abundant K-feldspar, and only 

trace amounts of clinopyroxene. 

Diorite in the intermediate zone of the stock near Pyramid Peak 

is composed of abundant plagioclase, chiefly normally zoned sodic 

labradorite-calcic andesine, and abundant brown hornblende 

formed partly at the expense of clinopyroxene, which is present as 

scattered frayed relict crystals. Its minor to rare constituents are 

quartz, biotite, sphene, and magnetite, and its alteration products 

include uralitic hornblende, sericite, chlorite, and clay minerals. 

The border zone gabbro is locally xenomorphic granular in texture. It is composed of abundant normally zoned labradorite, augite, hypersthene, and olivine, and minor to trace amounts of 

apatite, sphene, K-feldspar, quartz, ilmenite, and magnetite. Its 

alteration products are biotite, uralitic hornblende, chlorite and 
INTEUSIVE ROCKS 27 

related ferruginous serpentine minerals, sericite, and clay minerals. 

Th intern1ediate and mafic intrusive rocks are late Tertiary in 

age. In the McCarthy C--6 and C-5 quadrangles similar intermediate intrusive rocks cut the lower (Tertiary) part of the Wrangell 

Lava (MacKevett, 1965a, 19?0b, c). Granodiorite from a stock near 

the western border of the adjacent McCarthy B-3 quadrangle 

north of Glacier Creek Glaeier that is probably coeval with the 

intermediate intrusive rock:; in the B-4 quadrangle yielded concordant potassiun1-argon ages of 8.4 ± 0.25 m.y. (million years) 

on both hornblende and biotite. This radiometric age, indicative of 

the Pliocene, is surprisingly young for a plutonic rock and implies 

substantial and probably rapid Quaternary uplift and erosion. 

Data pertinent to the age determinations follow. Potassium 

analyses were done by Lois Schlocker on a Baird Flame photometer 

using a lithium internal standard. Argon analyses were made by 

J arel Von Essen using sta::1dard techniques of isotope dilution. 

Ages were calculated using the following constants: 

K40 decay constants: 

Ae = 0.585 X 10- 10 year- 1 

Af3 = 4.72 X 10- 10 year- 1• 

Abundance ratio: 

K40/K = 1.19 X 10- 4 atom per atom. 

Argon analyses and age calculation: 

Mineral Percent KzO A40 rad 

(moles/gm) 

A40 rad Apparent age 

A40 total (millions of years±2.0) 

Hornblende 0.534 } .... 0.535 0.534 6.657 X 10-12 0.18 8.4 ± 0.25 

Biotite 8.53 } 8.58 1.064 X 10-10 8.64 0.20 8.4 ± 0.25 

FELSIC HYPABYSSAL ROCKS 

Felsic hypabyssal rocks are widespread in the Cretaceous terrane in the southern part of the quadrangle and cut the Chititu 

Formation and, less cmYlmonly, other Cretaceous rocks and Tertiary intermediate to mafic intrusive rocks. Elsewhere in the quadrangle a few felsic dikes eut pre-Cretaceous rocks. The felsic hypabyssal rocks generally form bold outcrops accented by the subdued 

slopes of their main host rock, the Chititu Formation. Locally their 

outcrops are highly fragn1ented and masked by aggregates of chips 

and slabs. The felsic hypabyssal rocks form dikes and sills and a 

few small stocks. Most of the dikes and sills are 2 to 10 feet thick; 

a few of the sills are as mueh as 150 feet thick. The felsic hypabyssal rocks have locally baked and welded the invaded Cretaceous 
28 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

rocks, and less commonly they contain partly digested inclusions 

of hornfelsed Cretaceous pelites. 

The felsic rocks are mostly dacite but include rare quartz diorite 

and felsite. They are light gray to pinkish gray and weather light 

gray to brown. The rocks are typically porphyritic, or locally glomeroporphyritic in some of the dacites, with abundant phenocrysts 

in a very fine grained intersertal or felty groundmass. The phenocrysts in the porphyritic dacite are 1 to 2 mm long and consist 

chiefly of plagioclase, mainly oscillatory zoned andesine and calcic oligoclase and less commonly quartz or partly resorbed mafic 

minerals including clinopyroxene, amphibole, and biotite. The 

groundmass of the dacites is dominated by plagioclase microlites 

and alteration products including chlorite, calcite, sericite, epidote, 

clay minerals, chalcedony, leucoxene, and secondary hydrous iron 

oxides. The groundmass may also contain quartz and minor to rare 

K-feldspar, sphene, apatite, and opaque minerals, chiefly pyrite and 

ilmenite. Most of the dacite contains sparsely disseminated pyrite 

and is cut locally by calcite or quartz veinlets. The quartz diorite 

and felsite are mineralogically similar to the dacite but differ in 

texture. 

Field relationships indicate that the felsic hypabyssal rocks are 

probably late Tertiary, although their upper age limit is equivocal. 

Their lower age limit is documented by the fact that felsic hypabyssal rocks cut through leaf-bearing Miocene strata in the McCarthy C-4 quadrangle (MacKevett, 1970a) and by the indicated 

Pliocene age of intermediate intrusive rocks cut by the felsic 

plutons. 

ANDESITIC DIKES 

Sparsely distributed andesitic dikes, which are not shown in 

figure 2, crop out in the northeastern part of the quadrangle where 

they cut the Frederika Formation and older rocks. The dikes dip 

steeply and are between 2 and 10 feet thick. They are altered porphyritic andesites characterized by plagioclase and less abundant 

clinopyroxene phenocrysts in fine-grained, generally intersertal 

groundmasses rich in plagioclase. The andesitic dikes are similar 

to those described from the McCarthy C-4 and C-5 quadrangles 

(MacKevett, 1970a, c). They are probably genetically related to 

Wrangell Lava volcanism, which extended from late TerUary well 

into Quaternary time. 

SUMMARY OF ECONOMIC GEOLOGY 

The general region is best known for the massive copper sulfide 

lodes in the lower part of the Chitistone Limestone at the Kenne-
SUMMARY OF ECONOMIC GEOLOGY 29 

cott mines (mainly in the :YicCarthy C-5 quadrangle). The B-4 

quadrangle contains nun1erous copper deposits, including a few in 

geologie settings similar to those of the Kennecott deposits, local 

gold placers, and a few lodes or occurrences of gold, antimony, 

arsenic, or molybdenum. Silver is a n1inor constituent of most of 

the copper deposits, but except for the rare native silver associated 

with some of the native copper, no discrete silver 1ninerals have 

been found. The only signiftcant mineral production in the quadrangle has been frmn gold placers, which probably is less than a 

third of the Nizina Distriet's placer gold production of about 

143,440 ounces (Koschn1ann and Bergendahl, 1968, p. 14). 

A report by MacKevett and Sn1ith ( 1968) sumn1arizes the quadrangle's economic geology and gives analytical data for samples 

collected throughout the quadrangle. Other reports describing the 

quadrangle's mineral deposits are by l\1offit and Capps (1911), 

Bateman (1932), Miller (19"16), and Sainsbury (1951). 

The copper lodes are widely distributed in the Nikolai Greenstone and in places are localized in the lower, 1nainly dolomitic, 

parts of the Chitistone Limestone; they are rare in the other rocks 

of the quadrangle. The deposits in the greenstone forn1 veins, altered zones, and uncommon mineralized an1ygdules and interflow 

lenses. The veins, which generally are narrow and discontinuous, 

typically contain chalcopyrite, bornite, or chalcocite as their chief 

copper minerals and quartz as their dominant gangue. Most of the 

altered zones are less than :20 feet wide and are characterized by 

splotchy, scattered surficia1 coatings of secondary copper minerals, chiefly malachite. Mineralized an1ygdules in the greenstone 

contain native copper and generally s1naller quantities of other 

copper minerals. At the Eriekson 1nine, native copper and tenorite 

forn1 a few slabby interflow lenses in the greenstone. Small masses 

of native copper are also localized in fractures in the Nikolai 

Greenstone near the Erickson mine. In the Chitistone Limestone, 

copper deposits forn1 veins and small lenticular n1asses. The dominant copper 1nineral is chaleocite or, exceptionally, as at the Westover prospect, bornite. 

Copper-bearing altered zones in the Station Creek Formation are 

similar to those in the Nikolai Greenstone. Minor an1ounts of chalcopyrite are associated with a few quartz veinlets that cut Tertiary 

plutons and hornfelsed Chititu Formation. Nuggets of native copper are found locally in the gold placers. 

The gold placers, which have been v.,rorked intennittently since 

1903, are along Dan and Copper Creeks and their northwardflowing tributaries that drain terrane largely underlain by the 
30 GEOLOGY OF THE McCARTHY B-4 QUADRANGLE, ALASKA 

Chititu Formation. Exc-ept for a few bench placers that extend into 

the quadrangle along Dan Creek, the placers are shallow and are 

the products of modern erosion. Gold is a minor constituent of 

quartz veinlets at the Taylor prospect, and it probably occurs elsewhere in similar veinlets genetically related to the Tertiary 

plutons. 

Stibnite, which is a constituent of quartz v·eins and altered zones 

cutting the Nizina Limestone north of the head of Eagle Creek, is 

sporadically distributed in a few other veins and altered zones in 

the quadrangle. Samples from the deposits north of the head of 

Eagle Creek also contain minor amounts of tungsten. 

Molybdenite-bearing quartz float, derived from lodes in the 

McCarthy B-3 quadrangle, was found on the moraines of Canyon 

Creek Glacier. Molybdenite is an uncommon mineral in a few 

quartz veinlets associated with Tertiary plutons in the southern 

part of the quadrangle. 

Realgar and subordinate orpiment are minor constituents of the 

mineralized fault zone at the Radovan Low-Contact prospect. Arsenic, generally in small amounts, was detected in samples from 

many of the copper deposits. 

Carbonate rocks of the Chitistone and Niziila Limestones may 

warrant economic interest in the future. The few coal seams in the 

Frederika Formation are too small, lean, and remotely situated for 

exploitation. 

REFERENCES 

Armstrong, A. K., MacKevett, E. M., Jr., and Silberling, N. J., 1970, The 

Chitistone and Nizina Limestones of part of the southern Wrangell 

Mountains, Alaska-a preliminary report stressing carbonate petrography and depositional environments, in Geol. Survey Research 1969: 

U.S. Geol. Survey Prof. Paper 650-D, p. D49-D62. 

Bateman, A. M., 1932, Notes on a Kennecott type of copper deposit, Glacier 

Creek, Alaska: Econ. Geology, v. 27, no. 3, p. 297-306. 

Berg, H. C., and Cobb, E. H., 1967, Metalliferous lode deposits of Alaska: 

U.S. Geol. Survey Bull. 1246, 254 p. 

Dunham, R. J., 1962, Classification of carbonate rocks according to depositional texture, in Ham, W. E., ed., Classification of carbonate rocks-a 

symposium: Am. Assoc. Petroleum Geologists Mem. 1, p. 108-121. 

Jones, D. L., and Berg, H. C., 1964, Cretaceous stratigraphy of the McCarthy 

A-4 quadrangle, southern Alaska: U.S. Geol. Survey Bull. 1180-A, 18 p. 

Jones, D. L., and MacKevett, E. M., Jr., 1969, Summary of Cretaceous stratigraphy in part of the McCarthy quadrangle, Alaska: U.S. Geol. Survey 

Bull. 127 4-K, p. K1-K19. 

Koschmann, A. H., and Bergendahl, M. H., 1968, Principal gold-producing 

districts of the United States: U.S. Geol. Survey Prof. Paper 610, 283 p. 
REFERENCES 31 

MacKevett, K M., Jr., 1965a, A preliminary geologic map of the McCarthy C-6 

quadrangle, Alaska: U.S. Gt:ol. Survey Misc. Geol. Inv. Map I-444, scale 

1:63,360. 

---1965b, Preliminary geologic map of the McCarthy B-5 quadrangle, 

Alaska: U.S. Geol. Survey 1\iisc. Geol. Inv. Map I-438, scale 1:63,360. 

---1970a, Geologic map of the McCarthy C-4 quadrangle, Alaska: U.S. 

Geol. Survey Geol. Quad. M2.p GQ-844, scale 1:63,360. [In press.] 

---1970b, Geologic map of the McCarthy C-5 quadrangle, Alaska: U.S. 

Geol. Survey Geol. Quad. Map G-89~), scale 1:63,360 [In press]. 

---1970c, Stratigraphy and g·eneral geology of the McCarthy C-5 quadrangle, Alaska: U.S. Geol. Survey Bull. 1323. [In press.] 

MacKevett, E. M., Jr., and Smith, J. G., 1968, Distribution of gold, copper 

and some other metals in the McCarthy B-4 and B--5 quadrangles, Alaska: U.S. Geol. Survey Circ. 604, 25 p. 

---1970, Geologic map of the McCarthy B-4 quadrangle, Alaska: U.S. 

Geol. Survey Quad. Map GQ-943, scale 1 :63,360 [In press.] 

Miller, D. J., 1946, Copper deposits of the Nizina district, Alaska: U.S. Geol. 

Survey Bull. 947-F, p. 93-1:~0. 

Moffitt, F. H., 1938, Geology of the Chitina Valley and adjacent area, Alaska: 

U.S. Geol. Survey Bull. 894, 137 p. 

Moffitt, F. H., and Capps, S. R., 1911, Geology and mineral resources of the 

Nizina district, Alaska: U.S. Geol. Survey Bull. 448, 111 p. 

Sainsbury, C. L., 1951, Geology of the Nelson and Raclovan copper prospects, 

Glacier Creek, Alaska: U.S. Geol. Survey open file rept., Oct. 1951, 18 p. 

Smith, .J. G., and MacKevett, K M., Jr., 1970, The Skolai Group in the 

McCarthy B-4, C-4, and C-Ei quadrangles, Wrangell Mountains, Alaska: 

U.S. Geol. Survey Bull. 127Ll-Q, p. Q1-Q26. 

Willian1s, Howel, Turner, F. J., and Gilbert, C. M., 1954, Petrography-an 

introduction to the study of rocks in thin sections: San Francisco, Calif., 

W. H. Freeman and Co., 40() p. 

*U.S. GOVERNMENT PRINTING OFFICE: 1970 0-403-445