Summary of Cretaceous 

Stratigraphy in Part of the 

McCarthy Quadrangle, Alaska

By D. L. JONES and E. M. MAcKEVETT, JR.

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1274-K

Marine sedimentary rocks 

of Cretaceous age are 

described and named
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

U.S. GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1969

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 15 cents
CONTENTS

Page

Abstract................................................:................................................................. Kl

Introduction........................................................................................................... 1

Purpose and scope......................................................................................... 1

Geographic setting....................................................................................... 2

Previous work and acknowledgments........................................................ 2

Geology................................................................................................................... 3

Geologic setting............................................................................................. 3

Stratigraphy.................................................................................................. 6

Kennicott Formation............................................................................ 6

Moonshine Creek Formation............................................................... 11

Schulze Formation............................................................................... 13

Chititu Formation................................................................................ 15

MacColl Ridge Formation................................................................... 17

References cited.................................................................................................... 19

ILLUSTRATIONS

Page

FIGURE 1. Index map showing location of the McCarthy quadrangle.... K2

2. Map showing generalized distribution of Cretaceous rocks in

parts of the McCarthy quadrangle............................................ 5

3. Generalized correlation chart showing relation of Cretaceous

rocks in parts of the McCarthy quadrangle............................ 7

in

CONTRIBUTIONS TO STRATIGRAPHY

SUMMARY OF CRETACEOUS STRATIGRAPHY IN PART 

OF THE MCCARTHY QUADRANGLE, ALASKA

By D. L. JONES and E. M. MACKEVETT, JR.

ABSTRACT

Cretaceous sedimentary rocks in the McCarthy A-4, B-4, B-5, B-6, C-4, C-5, 

and C-6 quadrangles, Alaska, constitute a complex stratigraphic sequence that 

is divided into the Kennicott, Moonshine Creek, Schulze, Chititu, and MacColl 

Ridge Formations. The Kennicott Formation is redefined to include only the 

lowermost rocks, and a lower sandstone and an upper siltstone member are 

recognized; the other formations are newly named. The Cretaceous rocks are 

mainly sandstone and siltstone with subordinate amounts of conglomerate, 

shale, mudstone, and porcellanite. These rocks were deposited mainly in shallow 

seas and reflect several marine transgressions and regressions. They have a 

cumulative thickness of almost 13,000 feet.

The Cretaceous rocks are separated from underlying older rocks by a pronounced angular unconformity and from overlying younger rocks by a slight 

angular discordance. They are cut by numerous felsic dikes and sills and intruded in several places by plutonic rocks. Because these Cretaceous rocks are 

locally very fossiliferous, well exposed, and only slightly deformed, they constitute an important biostratigraphic reference section for strata ranging in 

age from early Albian to late Campanian. No other area in the northeastern 

Pacific region is known to have such a complete and abundantly fossiliferous 

record preserved.

INTRODUCTION

PURPOSE AND SCOPE

This report summarizes the Cretaceous stratigraphy of the central part of the McCarthy 1-degree quadrangle. Alaska, an area 

that includes the McCarthy A-4, B-4, B-5, B-6, C-4, C-5, and C-6 

15-minute quadrangles (fig. 1). The geologic mapping was done by 

MacKevett and his coworkers in the southern Wrangell Mountains 

during 1961-65, and 1967, and more detailed stratigraphic and 

paleontologic studies were done by Jones during most of these years. 

Related laboratory investigations include petrographic and X-ray 

diffraction studies of the rocks and detailed studies of the fossils. 

Most of the fieldwork was helicopter-supported with base camps 

at McCarthy or May Creek, (fig. 2).

Kl
K2 : CONTRIBUTIONS TO STRATIGRAPHY

170° 160° 150° 140° 130° -]0°

140°

0 400 MILES

I I I I I

FIGURE 1. Location of the McCarthy quadrangle.

GEOGRAPHIC SETTING

The Cretaceous rocks described in this report underlie part of 

the south-central flank of the Wrangell Mountains and part of the 

contiguous upper Chitina Valley. These rocks crop out along the 

rugged southern flank of the range up to altitudes of about 6,000 

feet, on many of the gently-sloping hills bordering the Chitina 

Valley, and in cuts along deeply incised rivers throughout the valley 

(fig. 2). Trees and brush cover much of the lowland and persist on 

the slopes to altitudes of about 3,000 feet; they are succeeded by 

grass or flower-covered slopes and sporadic outcrops and ultimately 

by steep, bare, rocky terrain.

Topography of the region has been strongly modified by glaciation; the high mountainous terrains are characterized by perennial 

snow and ice fields, are~tes, cirques, and steep-sided ridges. Large 

valley glaciers extend down the major river drainages and have 

carved broad steep-walled valleys. Glacial deposits are also abundant 

throughout the lowland, where they mask much of the underlying 

Cretaceous rocks.

PREVIOUS WORK AND ACKNOWLEDGMENTS

Cretaceous rocks in the McCarthy quadrangle have been known 

since the pioneer mapping of Rohn (1900, p. 424, 433), but he and 

most other early geologists, notably Moffit and Capps (1911, p. SI43), believed them to be of Jurassic age. Later workers, particularly
CRETACEOUS STRATIGRAPHY, MCCARTHY QUADRANGLE K3

Moffit (1938), who published a comprehensive description of these 

rocks based on his extensive reconnaissance mapping in the 

southern Wrangell Mountains and nearby regions, considered them 

to be mainly Cretaceous; however, Moffit inadvertently included 

some Jurassic rocks with those he believed to be Cretaceous and 

considered some Cretaceous rocks to be Jurassic. A more extended 

summary of early work is given by Jones and Berg (1964). Subsequent efforts to clarify and refine the age and stratigraphic 

relations of the Cretaceous rocks are founded on detailed geologic 

mapping of six 15-minute quadrangles by MacKevett and his coworkers, on the mapping of the northern half of the McCarthy A-4 

quadrangle by Miller and MacColl (1964), and especially on detailed 

mapping and stratigraphic and paleontologic studies by Jones. Besides being the basis of this report, this work has provided a description of the Cretaceous rocks in the McCarthy A-4 quadrangle (Jones 

and Berg, 1964) and in the preliminary geologic maps showing the 

distribution of Cretaceous rocks in the McCarthy A-4, B-5, C-4, C-5, 

and C-6 quadrangles (Miller and MacColl, 1964; MacKevett, 1963, 

1965a, b; MacKevett and others, 1964).

Grateful acknowledgment is made to several members of the 

southern Wrangell Mountains project who participated in mapping 

the Cretaceous rocks and collected fossils from them. These geologists include M. C. Blake, Jr., H. C. Berg, George Plafker, J. H. 

Stout, R. L. Applegate, G. R. Winkler, and J. G. Smith.

GEOLOGY

GEOLOGIC SETTING

The southern Wrangell Mountains contain diverse sedimentary 

and igneous rocks that range in age from Mississippian to Quaternary (fig. 2). Pre-Cretaceous rocks occupy a broad northwesttrending belt along the southern flank of the range. Cretaceous rocks 

overlie the older rocks with strong angular unconformity that reflects the major orogeny of the region that occurred near the close 

of the Jurassic or in the Early Cretaceous. The Cretaceous rocks 

are cut by Tertiary intrusive rocks, chiefly altered f elsic varieties, 

that form numerous sills, dikes, and small plutons, and to a lesser 

extent, by small plutons of granodiorite and by mafic dikes. Locally 

the Cretaceous rocks are overlain with slight angular unconformity 

by Tertiary continental sedimentary rocks that are intercalated 

with the basal flows of the Wrangell Lava. More commonly they are 

unconf ormably overlain by unconsolidated Quaternary surficial deposits, particularly the extensive fluvioglacial deposits that cover 

most lowland regions. The Cretaceous rocks generally have been
K4 CONTRIBUTIONS TO STRATIGRAPHY
Base from U.S. Geological Survey, 

McCarthy quadrangle, 1951

Undifferentiated

non-Cretaceous rocks

Chiefly sedimentary and volcanic rocks of Permian,

Triaasic, Jurassic, Tertiary, and Quaternary ages

FIGURE 2. Generalized distribution of Cretaceous rocks in part of th
K6 CONTRIBUTIONS TO STRATIGRAPHY

folded into series of broad, gentle folds that commonly trend northwestward, and they are slightly offset by a few faults.

STRATIGRAPHY

Cretaceous sedimentary rocks form a complex stratigraphic sequence and are widely distributed throughout the McCarthy quadrangle (figs. 2, 3). The name Kennicott Formation generally has 

been applied to all or parts of this sequence, but as Jones and Berg 

(1964, p. A5) point out^ numerous discrepancies in usage render 

the name impractical without redefinition. The Cretaceous rocks 

are dominantly shallow-water marine deposits that are separated 

by several disconformities. The oldest Cretaceous deposits in the 

area studied are basal sandstones and conglomerates of Albian age 

that are separated from older rocks by a pronounced angular unconformity. These basal deposits are older in the southern part of 

the study area than in the northern part; this distribution indicates 

that the ancestral Cretaceous seas transgressed from the south 

or southwest (fig. 3). These basal deposits are overlain by rocks 

that were formed and modified during several marine transgressions 

and regressions that included some stages of widespread uniform 

sedimentation and others of local sedimentation in isolated or restricted basins. The sedimentary record, although disrupted by 

numerous hiatuses, extends from the Albian into the upper Campanian or Maestrichtian (fig. 3).

The Cretaceous rocks are herein divided into the Kennicott, 

Moonshine Creek, Schulze, Chititu, and MacColl Ridge Formations 

(figs. 2, 3), all of which, except for the Kennicott, are new names. 

Most of these formations contain abundant marine invertebrate 

fossils, but only those fossils that provide significant age data are 

discussed in this report.

Kennicott Formation

NAME AND DISTRIBUTION

The name Kennicott was originally applied by Rohn (1900, p. 

433), who used "Kennicott Series" to designate sedimentary rocks 

in the vicinity of Fohlin and Bear Creeks (fig. 2) that were believed 

to be Jurassic in age. The name "Kennicott Formation" was introduced by Schrader and Spencer (1901, p. 33, 48-50, pi, 4), and subsequently, this name has been used several times with different 

implications and denotations. Commonly, these various usages have 

included some Jurassic rocks and some Cretaceous rocks different 

from those at Rohn's type area. Summaries of the early evolution 

of the name Kennicott Formation are given by Martin (1926, p. 

330-349) and Jones and Berg (1964).
CRETACEOUS STRATIGRAPHY, MCCARTHY QUADRANGLE K7

Series

CRETAClousJ CRETACEOUS UPPER 

Stage

Maestrichtian

Campanian

Santonian

Coniacian

Turonian

Cenomanian

Conglomerate^ 

(age unknown)

Albian

Fohlin 

Creek-Bear 

Creek 

(C-6, B-6)

K

F

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or

 

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yp 

n

TU

 ' 

e

CO

ti

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-7

tt 

an

Southeast 

of head of 

Nikolai 

Creek (B-5)

/

F

F

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C 

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hi 

m

.h 

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^?

it 

at

Jlz 

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Kennicott 

Formation

Near 

Moonshine 

Creek 

(C-4)

Moonshine 

Creek Fm

^FrcttC]

Kenni-/!

jOtfX

Upper 

Canyon 

Creek 

(B-4)

ill

MacColl 

Ridge Fm

Chititu 

Formation

Moonshine 

yCreek Fm <^

Kennicott 

Formation

South of 

Copper 

Creek 

(B-4)

MacColl 

Ridge Fm

Chititu 

Formation

Kenn cott 

Formation

MacColl 

Ridge 

(A-4)

MacColl 

R dge Fm

Chititu 

Formation

--?-

Sch 

Form

Kenn 

Form

-?- 

ulze 

ation

icott 

ation

FIGURE 3. Generalized correlation chart showing relation of 

Cretaceous rocks in parts of the McCarthy quadrangle.

In view of the diverse previous usage of the name Kennicott 

Formation, and because none of the previous definitions are entirely 

compatible with the results of our more detailed studies, it is necessary to define the formation more precisely. The Kennicott Formation is here redefined to include the conglomerate, sandstone, 

siltstone, and shale that constitute the lowermost sequence of 

sedimentary rocks that unconformably overlies Triassic rocks in 

the McCarthy B-6 and C-6 quadrangles (fig. 2). The type locality 

is designated as the hillsides east of Fohlin Creek and north of 

Bear Creek mainly in the southwestern part of the McCarthy C-6 

quadrangle, but to a lesser extent in the northwestern part of the 

adjoining McCarthy B-6 quadrangle (fig. 2). The type locality is 

within Rohn's (1900, p. 424) loosely defined type area for his Kennicott Series.
K8 CONTRIBUTIONS TO STRATIGRAPHY

The Kennicott Formation is widely distributed throughout the 

McCarthy quadrangle (fig. 2). It is well exposed at its type locality 

and elsewhere in the southern part of the C-6 quadrangle and in 

the A-4 quadrangle -north of the Chitina River. Other good exposures of the formation are in the C-5 and C-4 quadrangles west of 

the Nizina River and south of Regal Glacier. It is exposed in parts 

of the B-5, B-6, C-4, and B-4 quadrangles as a basal unit underlying 

younger Cretaceous rocks or less commonly as isolated erosional 

remnants.

THICKNESS AND STRATIGRAPHIC RELATIONS

The Kennicott Formation ranges from a few tens of feet to almost 

500 feet in thickness. Generally the formation is bipartite and consists of a basal unit of sandstone and conglomerate as much as 100 

feet thick and an overlying unit of fine siltstone, shale, and sandstone as much as 375 feet thick. Differences in thickness characterize much of the formation, particularly its transgressive basal 

unit, which in several exposures is only a few feet or a few tens 

of feet thick. At the type locality the basal unit is about 50 feet 

thick, and the overlying upper unit about 125 feet thick. Thicker 

sections are exposed near Canyon Creek in the A-4 quadrangle and 

near the boundary between the C-5 and C-4 quadrangles west of 

the Nizina River and south of Regal Glacier (fig. 2). At both of 

these localities the basal unit is about 100 feet thick and the upper 

unit about 375 feet.

The Kennicott formation unconformably overlies older rocks, 

commonly Triassic rocks represented by the Nikolai Greenstone, 

the Chitistone and Nizina Limestones, and the lower member of 

the McCarthy Formation. Locally in the C-5 quadrangle it overlies 

Jurassic rocks including part of the upper member of the McCarthy 

Formation and the Nizina Mountain Formation. The Kennicott 

Formation overlies the Mississippian Strelna Formation in parts 

of the A-4 quadrangle and locally along the lower reaches of the 

Nizina River in the B-6 quadrangle.

Commonly the Kennicott Formation is conformably or disconformably overlain by younger Cretaceous rocks including the 

Schulze, Moonshine Creek, and Chititu Formations. Less commonly, 

as in the southwestern part of the C-6 quadrangle arid the northwestern part of the B-6 quadrangle, it is uncomformably overlain 

by unconsolidated Quaternary sediments, chiefly stratified fluvioglacial deposits. The formation is cut by dikes, sills, and small 

plutons of f elsic Tertiary intrusive rocks and uncommonly by mafic 

dikes. At its type locality the formation is locally overlain by a massive conglomerate about 80 feet thick that contains abundant shaly
CRETACEOUS STRATIGRAPHY, MCCARTHY QUADRANGLE K9

boulders derived from the lower member of the McCarthy Formation. The conglomerate is cut by a few felsic Tertiary dikes, but 

its precise age cannot be determined.

LITHOLOGY

The lower unit of the bipartite Kennicott Formation consists 

mainly of sandstone, but minor conglomerate is commonly present 

at its base. The overlying upper unit is composed of siltstone and 

subordinate amounts of shale, sandstone, and conglomerate.

Sandstones of the lower unit are dominantly fine grained and 

poorly bedded. Some are crossbedded and locally may exhibit scour 

and fill relationships or show graded bedding. Very fine grained to 

very coarse grained sandstones are subordinate. Most of the sandstones are dark greenish gray on fresh surfaces and light gray or 

light pinkish brown on weathered surfaces. Fossiliferous sandy calcareous concretions, as much as 2 feet in diameter, are locally abundant. Conglomerate, which occurs mainly at the base of the lower 

unit, is well indurated and consists of subrounded to angular cobbles, pebbles, and boulders whose composition closely reflects local 

provenances. The conglomerates grade upward into the typical 

sandstones of the lower unit. Their matrices consist mainly of 

medium-grained felspathic and lithic sandstone (wacke). Locally 

the basal beds contain blocky greenstone boulders as much as 10 

feet in maximum dimension.

According to the classification of Williams, Turner, and Gilbert 

(1954, p. 290), which is used in this report, sandstones of the lower 

unit are mainly wackes and subordinately areriites. Most of the 

wackes and arenites are feldspathic; less commonly they are lithic 

or arkosic. The wackes of the lower unit are poorly to moderately 

sorted with subangular grains set in a microcrystalline matrix 

that constitutes between 10 and 35 percent of the rock's volume. 

The dominant clasts of the feldspathic wackes are quartz and plagioclase, chiefly labradorite or calcic andesine in various stages 

of alteration. The less abundant clasts include K-feldspar, lithic 

fragments, calcite, chlorite, glauconite, and opaque minerals, mainly 

leucoxene, hematite, ilmenite, and magnetite. Rare detrital clasts 

in the feldspathic wackes include apatite, clinozoisite, epidote, zircon, biotite, muscovite, and garnet. A few of the feldspathic wackes 

contain some minerals of probably authigenic origin, chiefly quartz 

overgrowths, chalcedony, secondary K-feldspar, and zeolites. Matrices of most of the wackes consist of chalcedony along with lesser 

amounts of clay minerals, chlorite, pervasive hydrous iron sesquioxides, and uncommonly sericite, calcite, siderite, ankerite, and
K10 CONTRIBUTIONS TO STRATIGRAPHY

carbonaceous debris. A few of the wackes contain sufficient glauconite to be termed "greensand".

The lithic wackes and the arkosic wackes are similar to the 

feldspathic wackes except that the lithic wackes contain between 

10 and 25 percent lithic fragments and the arkosic wackes contain 

more than 25 percent total feldspar, in contrast to lesser amounts 

of total feldspar in the feldspathic wackes.

The arenites are mineralogically similar to the wackes. They 

differ from the wackes by containing abundant calcite cement, 

which in a few specimens forms as much as 40 percent of the rock. 

Like the wackes, the arenites of the lower unit are divided into 

feldspathic, lithic, and arkosic varieties on the basis of their relative 

contents of feldspars and lithic fragments.

The dominant siltstones of the upper unit are dark gray and 

weather to diverse shades of brown, generally pinkish brown. The 

siltstones grade into or are intercalated with shale, minor amounts 

of sandstone, and less commonly, conglomerate. These rocks are 

also mainly dark gray and weather brown. Most of the conglomerate 

beds are thin and form small lenses. Sandy calcareous concretions 

similar to, but generally less f ossilif erous than those of the lower 

unit, mark several stratigraphic horizons in the upper unit.

The siltstones are principally finer grained replicas of the wackes 

and arenites. Their detritus is generally better sorted and more 

rounded than that in the wackes and arenites, and they contain 

proportionately less unstable clasts, such as feldspars, relative to 

quartz. Most of the siltstones resemble the wackes by having microcrystalline matrices, but a few siltstones are calcite cemented. 

Microfossils are fairly abundant in some of the siltstones.

The sandstones of the upper unit are similar to their counterparts in the lower unit and are mainly wackes and less commonly 

arenites. The uncommon shales in the upper unit consist of 

chalcedony-rich varieties that are aptly termed porcellanites and 

of clay-rich phases with very fine siliceous detritus. Both varieties 

are characterized by shaly partings and are rich in microfossils. 

Most conglomerates in the upper unit are well-cemented granule 

and pebble conglomerates that carry clasts of local derivation.

AGE

The Kennicott Formation, of Early Cretaceous age, can be subdivided into two well-defined faunal zones of early Albian age a 

lower Moffitites robustus zone and an upper Brewericeras hulenense 

zone (Jones, 1967, p. 2-3). In the McCarthy A-3, A-4, and B-4 quadrangles a few scattered fossil collections indicate beds of probable
CRETACEOUS STRATIGRAPHY, MCCARTHY QUADRANGLE Kll

middle Albian or early late Albian age, but fossils of these ages 

are too uncommon and the stratigraphic succession as yet too 

poorly understood to permit defining another zone in the upper 

part of the formation.

The lower unit at and near the type locality and in parts of the 

A-4 quadrangle contains abundant fossils of the pelecypod Aucellina 

as well as the ammonite Moffitites and is representative of the early 

Albian zone of Moffitites robustus. Elsewhere north of these localities, rocks of the lower unit are younger and are characterized by 

the ammonite Brewericeras and other fossils indicative of the late 

early Albian zone of Brewericeras hulenense.

Throughout most of its range the upper unit contains Brewericeras and other ammonites characteristic of the Brewericeras 

hulenense zone, but at a few localities it contains fossils suggestive 

of middle or early late Albian ages.

Both the upper and lower units are rich in fossils, chiefly ammonites and pelecypods, and less commonly gastropods. The basal 

rocks of the lower unit commonly also contain fossil wood and plant 

debris, and the shales and siltstones of the upper unit are locally 

rich in radiolarians and foraminifers.

Moonshine Creek Formation

NAME AND DISTRIBUTION

The name Moonshine Creek Formation is here applied to the thick, 

dominantly siltstone and sandstone sequence that is well exposed 

along Moonshine Creek in the McCarthy C-4 quadrangle, herein 

designated as the type area for the formation (fig. 2). The Moonshine Creek Formation is widely distributed in the southwestern 

part of the C-4 quadrangle. It underlies small areas in the C-5 quadrangle south of Regal Glacier and west of the Nizina River and in 

the northwestern and southeastern parts of the B-4 quadrangle.

THICKNESS AND STRATIGRAPHIC RELATIONS

The best exposed section of the formation, which is at its type 

area, is about 3,500 feet thick (fig. 2). Elsewhere the formation 

ranges from a few tens to a few thousands of feet in thickness. 

Many sections of the formation have been attenuated by erosion, 

and several hiatuses document gaps in its stratigraphic record.

At its type area and in some other parts of the C-4 quadrangle, 

the Moonshine Creek Formation unconformably overlies the Nikolai Greenstone. Elsewhere it discomformably overlies the Kennicott Formation. Commonly the Moonshine Creek Formation is unconformably overlain by Tertiary nonmarine sedimentary rocks
KI2 CONTRIBUTIONS TO STRATIGRAPHY

that are intercalated with the older flows of the Wrangell Lava. At 

a few places in the southeastern part of the B-4 quadrangle, the 

Moonshine Creek Formation is overlain by the Chititu Formation. 

The Moonshine Creek Formation is cut by a few Tertiary sills and 

dikes, chiefly felsic varieties.

LITHOLOGY

The Moonshine Creek Formation consists dominantly of siltstone 

and of sandstone that is of diverse grain sizes. It is divided into six 

informal members, designated from oldest to youngest as members 

1 to 6. The basal unit, member 1, is about 900 feet thick and consists 

mainly of sandstone with minor interbedded concretionary gray 

siltstone. The sandstone grades downward into thin pebble and 

boulder conglomerates that mark the base of the formation. Member 2 is at least 700 feet thick and consists of poorly indurated 

olive-gray siltstone with abundant calcareous concretions. Member 

3 is composed of massive cliff-forming greenish-gray sandstone between 300 and 400 feet thick that contains abundant fossiliferous 

calcareous concretions. Member 4 is about 1,000 feet thick and 

mainly consists of gray siltstone with abundant calcareous concretions. Member 5 is about 200 feet thick and consists of mediumgrained green sandstone. Member 6 is also about 200 feet thick and 

is dominantly medium-grained greenish-gray sandstone with local 

conglomeratic and silty beds.

The siltstones of the Moonshine Creek Formation are moderately 

sorted, well-cemented rocks that contain subangular to subrounded 

clastic silt of quartz, plagioclase, and chlorite along with uncommon small lithic fragments and scattered opaque minerals in a clayrich matrix. Subordinate constituents of the matrices are chlorite, 

calcite, epidote, heulandite, and sericite. The sandstones are chiefly 

feldspathic wacke and to lesser extents lithic wacke and arenite. 

Most of these rocks are moderately to poorly sorted and are composed of subangular to subrounded clasts, chiefly in the fine sand 

range, set in a microcrystalline matrix. Their dominant clasts are 

quartz and plagioclase, and their less abundant clasts include calcite, chlorite, glauconite, K-feldspar, biotite, epidote, lithic fragments, opaque minerals, and zircon. Matrices of the sandstones are 

mainly chlorite, chalcedony, and clay minerals, generally with dispersed secondary iron minerals and carbonaceous debris. Sericite, 

zeolites, calcite, and siderite are also rare matrix constituents. The 

arenites contain abundant calcite cement. The shales and mudstones consist largely of argillaceous minerals with subordinate 

sand and silt. Chalcedonic tests of microfossils are common in 

some of the pelitic rocks. The conglomerates range from boulder
to granule conglomerate and commonly are gradational into sandstone. Their clasts are diverse and mainly were derived from older 

Cretaceous rocks and from Triassic rocks, particularly the Nikolai 

greenstone.

AGE

The Moonshine Creek Formation contains abundant ammonites 

and pelecypods, mainly Inoceramus; these fossils define three main 

faunal zones ranging in age from late Albian to late Cenomanian 

(Early and Late Cretaceous), These include the late Albian zone 

of Desmoceras (Pseudouhligella) dawsoni, the early Cenomanian 

zone of Desmoceras (Pseudouhligella) japonicum, and a late Cenomanian Inoceramus sp. zone. A few ammonites of possible middle 

Albian age also have been found near the base of the formation.

The formation probably was deposited in a restricted, rapidly 

sinking basin. It is partly contemporaneous with the upper part 

of the Kennicott Formation, with the much thinner Schulze Formation, and probably with the lower part of the Chititu formation.

Schulze Formation

NAME AND DISTRIBUTION

The Schulze Formation is here named for a thin sequence of 

dominantly siliceous pelitic rocks that are best exposed in the 

north-central part of the McCarthy B-5 quadrangle (fig.2). The 

name is taken from the nearby Schulze copper prospect in the B-5 

quadrangle, which is held by Henry Schulze, a pioneer prospector.

The formation has a restricted distribution. It is best and most 

extensively exposed at the type area, particularly on the upland 

north of Sourdough Peak east of the upper reaches of Nikolai 

Creek in the B-5 quadrangle (fig. 2). It underlies small areas near 

the southwest corner of the C-5 quadrangle, near the southeast 

corner of the C-6 quadrangle, and in the high terrain near the 

western border of the B-4 quadrangle south of the Chitistone River 

(fig. 2). To the south the formation crops out locally along both 

flanks of MacColl Ridge in the A-4 quadrangle (fig. 2).

THICKNESS AND STRATIGRAPHIC RELATIONS

Most exposures of the formation are in high terrain where the 

rigorous alpine environment promotes fragmentation of the formation's thin-bedded and platy rocks and produces myriad chips 

that partly obscure many of the outcrops. Consequently, details 

of the formation's stratigraphy, which apparently include rapid 

changes in facies and in thickness, are not well understood. Esti-
K14 CONTRIBUTIONS TO STRATIGRAPHY

mated thicknesses for the formation range from 100 to about 225 

feet or more.

The Schulze Formation overlies the Kennicott Formation with 

probable slight angular discordance. It is conformably overlain by 

the Chititu Formation and locally unconformably overlain by Quaternary surficial deposits. A few Tertiary felsic dikes and sills 

cut the formation.

LITHOLOGY

The Schulze Formation consists of siliceous rock that is aptly 

termed "porcellanite", of lesser amounts of interbedded sandstone, 

and of uncommon thin basal conglomerate. Most of these rocks are 

thin bedded. They are mainly light or medium gray when fresh, 

weather to pale yellow or to pale yellowish brown, and are conspicuously lighter colored than the other Cretaceous rocks of the region.

The porcellanites are dense, finely laminated, and platy rocks; 

they consist dominantly of chalcedony and grade into impure chert, 

which contains diverse amounts of very fine clastic grains that are 

widely dispersed in the chalcedonic matrix. These grains are chiefly 

calcite, but also include subordinate grains of quartz, magnetite, 

and hematite. Some of the porcellanites contain minor amounts of 

pyrite, limonite (?), carbonaceous debris, clay minerals, and sericite.

Sandstones of the formation generally are very fine grained feldspathic wackes and feldspathic arenites. The two rock types are 

compositionally similar and mainly consist of moderately well 

sorted very fine or fine grained subangular or subrounded grains 

set in a chalcedony-rich matrix that contains minor amounts of 

clay minerals, sericite, secondary iron minerals, and chlorite. The 

clasts include abundant quartz, fairly abundant plagioclase, calcite, 

glauconite, chert fragments, and chlorite, and uncommon opaque 

minerals, biotite, barite, and epidote.

The rare conglomerates at the base of the formation contain 

granules mainly derived from the Kennicott Formation set in a 

fine sandstone matrix.

AGE

Fossils in the Schulze Formation are mainly scraps of Inoceramus 

and microfossils, including calcareous tests of foraminifers and 

siliceous tests of radiolarians. Ammonites of the genus Desmoceras 

(Pseudouhligella) are common, but most shells are crushed and 

are too poorly preserved for specific determination. Several relatively undistorted specimens from the upper part of the formation 

are identified as Desmoceras (Pseudouhligella) japonicum of Cenomanian age.

The formation is contemporaneous with part of the Moonshine
CRETACEOUS STRATIGRAPHY, MCCARTHY QUADRANGLE K15

Creek and Chititu Formations and has a probable age span from late 

Albian(?) toCenomanian (Early(?) and Late Cretaceous).

The Schulze Formation probably was deposited in an isolated 

marine basin from which the abundant clastic debris of the Moonshine Creek Formation was restricted.

Chititu Formation

NAME AND DISTRIBUTION

The name Chititu Formation is applied here to the thick sequence 

of dominantly dark-gray to black pelitic rocks that are widely distributed in the McCarthy A-4, B-4, B-5, and B-6 quadrangles (fig. 2). 

The formation is named for Chititu Creek in the southeastern part 

of the B-5 quadrangle, but its type area is designated as the 

northwestern part of the McCarthy A-4 quadrangle both north 

and south of Young Creek and the southern part of the B-4 quadrangle south of the latitude of Copper Creek. Good reference sections for the formation extend north and south of Young Creek 

about 4 miles east of the western border of the A-4 quadrangle.

In the upper Chitina Valley the Chititu Formation is widely 

distributed but is largely covered by fluvioglacial deposits and is 

exposed principally in cliffs along the rivers. It is widespread in 

the northern part of the A-4 quadrangle, chiefly along the flanks of 

MacColl Ridge, and it forms the dominant rock unit in the southern 

part of the B-4 quadrangle west of Canyon Creek (fig. 2). Likewise, 

it is widespread throughout the southern part of the B-5 quadrangle 

and in the B-6 quadrangle. Small outcrops of the Chititu Formation 

are in the C-6 quadrangle near its southern boundary.

Stratigraphic measurements of the Chititu Formation are impaired by the lack of continuously exposed sections and marker 

horizons and by minor folds and faults. At its reference sections 

the formation's apparent thickness is about 5,500 feet. Thicknesses 

of similar magnitude are indicated at other places where large sections of the formation are exposed, as elsewhere in the southern 

part of the B-4 quadrangle and the southeastern part of the B-5 

quadrangle.

At most places the Chititu Formation overlies the Kennicott 

Formation with apparent conformity. The contact between the 

Kennicott and Chititu Formations is well exposed in cliffs bordering 

the lower part of the Nizina River in the B-6 quadrangle and south 

of Copper Creek in the B-4 quadrangle (fig. 2). Locally in the A-4 

and B-5 quadrangles the Chititu Formation conformably overlies
K16 CONTRIBUTIONS TO STRATIGRAPHY

the Schulze Formation. In the southeastern part of the B-4 quadrangle it appears to overlie the Moonshine Creek Formation, although relationships there are obscure.

In the A-4 quadrangle and locally in the B-4 and B-5 quadrangles, 

the Chititu Formation is conformably overlain by the MacColl 

Ridge Formation. Throughout much of the lowland terrane the formation is unconf ormably overlain by stratified unconsolidated Quaternary fluvioglacial deposits. At a few places other Quaternary 

surficial deposits mantle the Chititu Formation.

Throughout much of its range the formation is cut by small 

plutons of granodiorite or felsic hypabyssal intrusive rocks, both 

of Tertiary age. Swarms of dikes and sills of the felsic intrusive 

rocks are abundant and extensive in much of the Chititu terrane, 

particularly the southeastern part of the B-5 quadrangle and the 

northern part of the B-6 quadrangle. The formation is also cut by 

a few dikes with intermediate or mafic affinities.

LITHOLOGY

The Chititu Formation consists mainly of pelitic rocks, chiefly 

mudstone and shale. It contains minor amounts of porcellanite, 

impure chert, and fine-grained sandstone, and uncommon thin beds 

and lenses of impure limestone. Calcareous concretions of diverse 

sizes are locally abundant. Sandstone dikes, generally less than 2 

feet thick, transect parts of the formation, notably in the southeastern part of the B-5 quadrangle. Commonly the sandstone dikes 

cut the bedding at high angles. Adjacent to the granodiorite plutons, near Williams Peak and near Pyramid Peak (fig. 2), rocks of 

the Chititu Formation have been baked, silicified, and partly recrystallized. These altered rocks occupy contact aureoles as much 

as a mile wide that surround the plutons, and they weather to 

medium or dark brown in contrast to the dark-gray or black surfaces characteristic of most unaltered rocks of the formation.

The dominant mudstones and shales of the formation are mineralogically similar. The mudstones are massive, blocky, and commonly have hacky fracture, whereas the shales have fine partings 

or fissility. Many of the pelitic rocks, particularly the shales, are 

finely laminated. They generally contain subordinate silt clasts, 

chiefly of quartz, scattered throughout a microcrystalline matrix 

that consists mainly of chalcedony and clay minerals, mainly illite. 

The porcellanites and impure cherts are mainly microcrystalline 

rocks that consist almost entirely of chalcedony.

The arenaceous rocks of the formation include feldspathic wackes 

and lithic arenites. They consist of poorly to moderately sorted
CRETACEOUS STRATIGRAPHY, MCCARTHY QUADRANGLE K17

fine-grained clasts set in a chalcedony- or calcite-rich matrix. Commonly the clasts are subangular and are composed of quartz and 

plagioclase and subordinately of lithic fragments, opaque minerals, 

K-f eldspar, calcite, dolomite, epidote, muscovite, zircon, and sphene. 

The carbonate rocks of the formation include limestone breccias 

and impure micritic limestones. The limestone breccias contain 

small fragments of micritic limestone that are cemented by sparry 

calcite. The micritic limestones are extremely fine grained and 

composed of cloudy calcite that locally is cut by veinlets of limpid 

calcite. Most of the limestones contain widely scattered detrital 

grains, chiefly of quartz and opaque minerals.

AGE

Fossils in the Chititu Formation consist mainly of Inoceramus 

and less commonly of ammonites that are generally enclosed in 

concretions. Microf ossils, chiefly radiolarians, are abundant in some 

of the silica-rich pelites and less common in the other rocks. The 

megafossils indicate that the formation is mainly Late Cretaceous, 

with an age span extending from at least Cenomanian to Late Campanian. The base of the formation appears to vary in age from place 

to place, and may be as old as early Albian along the lower Nizina 

River, latest Albian near Copper Creek, and as young as Coniacian 

on MacColl Ridge.

MacColl Ridge Formation

NAME AND DISTRIBUTION

A coarse sandstone sequence that is well exposed on MacColl 

Ridge in the McCarthy A-4 quadrangle is named here the MacColl 

Ridge Formation. The type section is about 3 miles east of the west 

boundary of the A-4 quadrangle (fig. 2) and trends southward 

from the contact with the Chititu Formation to near the crest of 

MacColl Ridge where the uppermost exposed strata of the formation occupy the core of a syncline.

The formation is not extensively distributed, and it is largely 

.confined to high mountainous terrain where its erosion-resistant 

strata form bold outcrops (see Jones and Berg, 1964, figs. 3-5). 

Besides capping much of MacColl Ridge, the formation is exposed 

in the summit areas and flanks of some of the higher peaks in the 

southern part of the B-4 quadrangle and to a lesser extent in the 

southeastern part of the B-5 quadrangle.

THICKNESS AND STRATIGRAPHIC RELATIONS

The thickness of the entire formation is not determinable because 

its top is not preserved. The formation is about 2,500 feet thick at
K18 CONTRIBUTIONS TO STRATIGRAPHY

its type section (fig. 3), and similar maximum thicknesses are 

known elsewhere.

The MacColl Ridge Formation overlies the Chititu Formation 

with apparent conformity. It is not in contact with any postCretaceous consolidated sedimentary rocks. Near Pyramid Peak 

and elsewhere in the southwestern part of the B-4 quadrangle the 

formation is cut by Tertiary granodiorite plutons, and also by a 

few dikes and sills of Tertiary felsic intrusive rocks. Locally the 

formation is overlain by unconsolidated Quaternary surficial deposits and by permanent snow and ice.

LITHOLOGY

The MacColl Ridge Formation consists dominantly of coarsegrained sandstone which locally grades into very coarse grained 

sandstone and granule to pebble conglomerate or into medium- or 

fine-grained sandstone and siltstone. Most rocks of the formation 

are light or medium gray when fresh and diverse shades of brown 

when weathered, but the siltstone is dark gray to black when 

fresh and dark brown when weathered.

The sandstone includes feldspathic, lithic, and arkosic wacke. 

These rocks consist of subangular clasts set in chalcedony-chloriteclay matrices that constitute between 10 and 35 percent of their 

volumes. The wackes are poorly sorted, and their clasts have size 

differentials between ten and a hundredfold.

The dominant clasts in most of the wackes are lithic fragments, 

quartz, and plagioclase. Their less abundant clasts include K-feldspar, chlorite, biotite, and opaque minerals; their rare clasts are 

calcite, apatite, actinolite, hornblende, epidote, muscovite, zircon, 

sphene, and augite. Their lithic fragments are chiefly chert and 

less commonly porphyritic intrusive rocks, siltstone, and diverse 

metamorphic rocks. Except for containing coarser clasts and a 

preponderance of lithic clasts the conglomerate is similar to most 

of the wackes. Clasts in the siltstones are finer than those in the 

sandstones and are predominantly of stable constituents. Some 

of the siltstones contain carbonaceous debris. Near the granodiorite pluton, rocks of the formation have been baked and partly 

recrystallized.

The formation's limited distribution, together with the coarseness of the clasts and the abundance of the lithic fragments, indicates rapid deposition, probably adjacent to a locally uplifted area.

AGE

The precise age of the MacColl Ridge Formation cannot be 

ascertained because of the lack of diagnostic fossils. On the basis
CRETACEOUS STRATIGRAPHY, MCCARTHY QUADRANGLE K19

of its superposition above Campanian strata and on the basis of 

its relation to intrusive Tertiary rocks, the MacColl Ridge Formation is considered to be of Late Cretaceous (late Campanian or 

Maestrichtian) age. The only -fossils that have been found in the 

formation are poorly preserved plant remains, fragments of 

Inoceramus, and possibly reworked fragments of unidentifiable 

ammonites.

REFERENCES CITED

Jones, D. L., 1967, Cretaceous ammonites from the lower part of the Matanuska

Formation, southern Alaska, with a stratigraphic summary by Arthur

Grantz: U.S. Geol. Survey Prof. Paper 547, 49 p. 

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. 

MacKevett, E. M., Jr., 1963, Preliminary geologic map of the McCarthy C-5

quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-406, scale

1:63,360. 

___1965a, Preliminary geologic map of the McCarthy B-5 quadrangle,

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

_1965b, Preliminary geologic map of the McCarthy C-6 quadrangle,

Alaska: U.S. Geol. Survey Misc. Geol. Inv. Map 1-444, scale 1:63,360. 

MacKevett, E. M., Jr., Berg, H. C., Plafker, George, and Jones, D. L., 1964,

Preliminary geologic map of the McCarthy C-4 quadrangle, Alaska: U.S.

Geol. Survey Misc. Geol. Inv. Map 1-423, scale 1:63,360. 

Martin, G. C., 1926, The Mesozoic stratigraphy of Alaska: U.S. Geol. Survey

Bull. 776, 493 p.

Miller, D. J., and MacColl, R. S., 1964, Geologic map and sections of the northern part of the McCarthy A-4 quadrangle, Alaska: U.S. Geol. Survey

Misc. Geol. Inv. Map 1-410, scale 1:63,360. 

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

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

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

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

Rohn, Oscar, 1900, A reconnaissance of the Chitina River and the Skolai

Mountains, Alaska: U.S. Geol. Survey 21st Ann. Rept., pt. 2, p. 393-440. 

Schrader, F. C., and Spencer, A. C., 1901, The geology and mineral resources

of a portion of the Copper River district, Alaska: U.S. Geol. Survey Spec.

Pub., 94 p. 

Williams, 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 Co., 406 p. [Reprinted 1958.]

U. S. GOVERNMENT PRINTING OFFICE : 1969 O - 334-796