urassic

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GEOLOGICAL SUR¥EY PROFESSIONAL PAPEft 1011
Middle Jurassic (Bathonian)

Ammonites

From Southern Alaska

By RALPH W. IMLAY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091

Studies of Bathonian ammonites from southern 

Alaska provide correlations with the arctic 

region in general, with the Pacific coast and 

western interior regions of North America, 

and with the early Bathonian of some other 

parts of the world

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1980
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY

H. William Menard, Director

Library of Congress Cataloging in Publication Data

Imlay, Ralph Willard, 1908-

Middle Jurassic (Bathonian) ammonites from southern Alaska.

(Geological Survey professional paper; 1091)

Bibliography: p.

Includes index.

1. Ammonoidea. 2. Paleontology Jurassic. 3. Paleontology Alaska. I. Title. II. Series: United States. Geological Survey.

Professional paper; 1091. 

QE807.A5I616 564'.53 78-16661

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

Washington, D.C. 20402

Stock Number 024-001-03284-8
CONTENTS

CONTENTS

Page

otieiLigi cijjiiic su.iiiin£ii*y~~~~~~~~~~~~~'"~TM'TM— "• —————— — — — — — ———— ________________ — ____________________ ^

B3.thoni3.ii 3Tmnonit^ si i cp^ssi on ————————————————————— ————— ————— ————— ————— ————— ——— ———••————— —————— - _ • _ — ———--——-— ^

West of Cook Inlet ________________________________________ 5

x cux.ee Liici _viou.nLciiiris~~~~~~'~~~"i~" — — — •- — •— — — — — ——— — — — — — — — — — — ________»_ — . — ______________ — ... — ... j^ j^

— —————————————————————————————————————————————— __ __ __ __ — . _ _________________ _ __________ _ "I JL _j, O

———————— ________ _. ——_______ _________ ....... _ .... _ ___________________ _ ___________ ~i Q

.Ammonite f3,un3J. scttintr ____ • _ • _ ———————————————————————————————————————« __ TM— — — — — — — . _ — __ ._.«_._ "i ft

Geographic distribution ———————————————————————————————————————— 1 6

HeSCT*it)tlOnS _______ ———————————————————————————————————————————— ___ ————————————. ________ "I ft

——————————— ——.«———. .————————— . _ ........ _ . ___________ _______________-._-. _ , _ ______________ 38

ILLUSTRATIONS

[Plates 1-12 follow index]

PLATE 1. Kepplerites, Phylloceras, Calliphylloceras, andMacrophylloceras.

2. Xenocephalites and Lytoceras.

3. Oppelia (Oxycerites), O. (Liroxyites), Cranocephalites, and Kepplerites.

4. Cadomites.

5. Cranocephalites.

6. Cranocephalites.

7. Cranocephalites.

8. Tuxednites, Tuxednitesl, Arctocephalites, and Iniskinites.

9. Talkeetnites.

10. Parareineckeia.

11. Parareineckeia.

12. Cobbanites.

FIGURE 1. Index map showing principal areas of outcrop of Bathonian marine rocks in southern Alaska

2. Diagram showing stratigraphic positions of ammonite localities in the Bowser Formation west of Cook Inlet between

Tuxedni Bay and Iniskin Bay ——————————————————————————————————————————————————— 8

3. Diagram showing stratigraphic positions of some Bathonian ammonite localities in the Talkeetna Mountains ——————— 10

4. Diagram showing part of the Middle Jurassic sequence exposed on northwest-trending divide at head of a tributary of 

Boulder Creek near center of NW%SE% sec. 26, T. 22 N., R. 7 E., Anchorage D-3 quadrangle, Talkeetna Mountains,

_____________ ______________________ , ________ ........ — — . ____ ... ______________ ________________ _______ ____________________ ____ . _ 1 J_

5. Diagram showing stratigraphic ranges of Bathonian ammonites in the Bowser Formation west of Cook Inlet ——————— 12

6. Diagram showing stratigraphic ranges of Bathonian ammonites in unnamed beds in the Talkeetna Mountains —————— 13

7. Chart showing correlation of Bathonian formations and faunas in southern Alaska —————————————————————— 14 

8—11. Index maps of listed Bathonian fossil localities in southern Alaska:

8. In the Wrangell Mountains ————————— - ——————————————————————————————————————— 17

9. In the Talkeetna Mountains ————————————————————————————————————————————————— 18

10. West of Cook Inlet between Tuxedni Bay and Chinitna Bay —————————————————————————————— 19

11. West of Cook Inlet on the Iniskin Peninsula ——————————————————————————————————————— 20

ill
IV CONTENTS

TABLES

TABLE 1. Bathonian ammonite genera in southern Alaska showing biological relationships and relative numbers available for study

2. Geographic distribution of Bathonian ammonites in the Wrangell and the Talkeetna Mountains, Alaska ———-——-————

3. Geographic distribution of Bathonian ammonites between Tuxedni Bay and Iniskin Bay west of Cook Inlet, Alaska————

4. Description of Bathonian fossil localities in southern Alaska————————————————————————————————

2

4

6

21

CONVERSION FACTORS

Metric unit Inch-Pound equivalent

Length

millimeter (mm) 

meter (m) 

kilometer (km)

= 0.03937 inch (in) 

= 3.28 feet (ft) 

= .62 mile (mi)

Area

square meter (m2) 

square kilometer (km2 ) 

hectare (ha)

= 10.76 square feet (ft2 ) 

= .386 square mile (mi2 ) 

= 2.47 acres

Volume

cubic centimeter (cm3 ) 

liter (L) 

cubic meter (m3 ) 

cubic meter 

cubic hectometer (hm3 ) 

liter 

liter 

liter 

cubic meter

cubic meter

= 0.061 cubic inch (in3 ) 

= 61.03 cubic inches 

= 35.31 cubic feet (ft3 ) 

= .00081 acre-foot (acre-ft) 

= 810.7 acre-feet 

= 2.113 pints (pt) 

= 1.06 quarts (qt) 

= .26 gallon (gal) 

= .00026 million gallons (Mgal or 

106 gal) 

= 6.290 barrels (bbl) (1 bbl = 42 gal)

Weight

gram (g) 

gram 

metric tons (t) 

metric tons

= 0.035 ounce, avoirdupois (oz avdp) 

= .0022 pound, avoirdupois Hb avdp) 

= 1.102 tons, short (2,000 Ib) 

= 0.9842 ton, long (2,240 Ib)

Specific combinations

kilogram per square 

centimeter (kg/cm2 ) 

kilogram per square 

centimeter 

cubic meter per second 

(ms/s)

— 0.96 atmosphere (atm)

= 35.3 cubic feet per second (ft3/s)

Metric unit

Specific

liter per second (L/s) 

cubic meter per second 

per square kilometer 

[<mVs)/km2 ] 

meter per day (m/d)

meter per kilometer 

(m/km) 

kilometer per hour 

(km/h) 

meter per second (m/s) 

meter squared per day 

(m2/d) 

cubic meter per second 

(m.3/s) 

cubic meter per minute 

( m3/min ) 

liter per second (L/s) 

liter per second per 

meter [(L/s) /in] 

kilometer per hour 

(km/h) 

meter per second (m/s) 

gram per cubic 

centimeter (g/cm3 ) 

gram per square 

centimeter (g/cm2 ) 

gram per square 

centimeter

Inch-Pound equivalent

combinations — Continued

— .0353 cubic foot per second 

= 91.47 cubic feet per second per 

square mile [ (ft3/s)/mi2 ]

= 3.28 feet per day (hydraulic 

conductivity) (ft/d) 

= 5.28 feet per mile (ft/mi)

— .9113 foot per second (ft/s)

— 3.28 feet per second

= 10.764 feet squared per day (ft2/d) 

( tran smissivity ) 

= 22.826 million gallons per day 

(Mgal/d) 

= 264.2 gallons per minute (gal/min)

= 15.85 gallons per minute 

= 4.83 gallons per minute per foot 

[(gal/min) /ft] 

— .62 mile per hour (mi/h)

= 62.43 pounds per cubic foot (lb/ft3 ) 

= 2.048 pounds per square foot (lb/ft2 ) 

= .0142 pound per square inch (lb/in2 )

Temperature

degree Celsius (°C) 

degrees Celsius 

(temperature)

= 1.8 degrees Fahrenheit (°F) 

= [(1.8x°C)+32] degrees Fahrenheit
MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM

SOUTHERN ALASKA

By RALPH W. IMLAY

ABSTRACT

The Bathonian ammonites of southern Alaska include (1) some genera characteristic of the Boreal realm, such as Kepplerites, Arctocephalites, and Cranocephalites; (2) some genera that occur nearly 

worldwide except in the Boreal realm, such as Cadomites and Siemeradzkia; and (3) many genera that are known only in the Pacific coast 

region of Alaska or in areas farther south. Those taxa found to date 

only in southern Alaska include Tuxednites n. gen., Talkeetnites n. 

gen., and Chinitnites. Those taxa found in the Pacific coast region from 

Alaska to Oregon include Parareineckeia, Cobbanites, and Iniskinites. 

Of these, Cobbanites occurs also in the western interior region. In addition, Xenocephalites occurs along the Pacific coast of both North and 

South America as well as in the western interior region of North 

America.

Ammonites of Bathonian Age in southern Alaska occur in the Bowser 

Formation west of Cook Inlet, in unnamed beds in the Talkeetna Mountains, and in the Nizina Mountain Formation in the Wrangell Mountains. These lithologic units are dated as Bathonian mainly by the presence of (1) a sequence of ammonites similar to those in northern 

Canada, northern Alaska, and East Greenland; (2) Cadomites in the 

lower part of the unnamed beds in the Talkeetna Mountains and in the 

Nizina Mountain Formation in the Wrangell Mountains; (3) Siemeradzkia in the lower part of the Bowser Formation west of Cook Inlet; 

(4) Kepplerites not associated with Cadoceras in the uppermost part of 

the Bowser Formation; (5) Cobbanites of the Leptosphinctinae 

throughout most of the Bowser Formation but mostly in the lower part; 

and (6) the lithologic units in question in the Talkeetna Mountains and 

west of Cook Inlet lying unconformably below beds of early Callovian 

Age.

More detailed dating of the Bowser Formation and equivalent units 

in southern Alaska is made possible by the ammonites that are not 

known solely from the Pacific coast region. The succession of such ammonites from the base upward is characterized (1) by many specimens 

of Cranocephalites costidensus (Imlay) in association with rare occurrences of Siemeradzkia and Cadomites; (2) next higher, by species of 

Cranocephalites similar to C. ignekensis Imlay from northern Alaska 

and to C. vulgaris Spath from the Arctic region; (3) next higher, by 

Arctocephalites similar to A. elegans Spath from the Arctic region; and 

(4) at the top, by weakly to nontuberculate species of Kepplerites that 

are not associated with Cadoceras.

Concerning this succession, the lowermost part is probably of early 

Bathonian rather than latest Bajocian Age as shown by the presence of 

Siemeradzkia and a species of Cadomites similar to C. rectelobatus 

(von Hauer). It cannot be younger than early Bathonian as indicated 

by the presence of C. cf. C. deslongchampsi (d'Orbigny). The fact that 

the associated Cobbanites belongs to the Bajocian subfamily Leptosphinctinae favors a late Bajocian Age but does not prove such an age 

because the genus also occurs much higher near the top of the Bowser 

Formation.

The next higher part of the succession characterized by the highest 

occurrences of Cranocephalites is dated as late early Bathonian on the

basis that similar species occur in East Greenland at a similar stratigraphic position. Likewise, the overlying part characterized by Arctocephalites is dated as probably middle Bathonian by comparisons with 

East Greenland. The highest part characterized by Kepplerites that is 

not associated with Cadoceras may be equivalent in East Greenland to 

the lowermost occurrence of Kepplerites in the upper part of the range 

of Arctioceras just below the lowermost occurrence of Cadoceras. Apparently the uppermost Bathonian in East Greenland that contains 

both Kepplerites and Cadoceras is represented in southern Alaska 

either by an unconformity at the base of the Chinitna Formation or by 

the basal part of the Chinitna Formation that contains the uppermost 

occurrences of Iniskinites intermedius (Imlay).

INTRODUCTION

The Bathonian ammonites of southern Alaska, partially described by the writer (Imlay, 1962a), have been 

restudied to reevaluate the stratigraphic distribution of 

genera and species, to establish regional and intercontinental correlations, and to date the lithologic units more 

precisely in terms of the standard Bathonian zones of 

western Europe. This study is based on biostratigraphic 

data compiled by Detterman and Hartsock (1966, p. 36- 

40) for the Bowser Formation west of Cook Inlet; by Arthur Grantz (1965; written commun., 1972) for equivalent 

unnamed beds in the Nelchina area of the Talkeetna 

Mountains; by R. L. Detterman and the writer, 1972 and 

1974 (unpub. data), for equivalent beds in the Boulder 

Creek area of the Talkeetna Mountains; and by E. M. 

MacKevett, Jr., (1963, unpub. data; 1969, p. A42-A45; 

1971, p. 16, 17) for the Nizina Mountain Formation in the 

Wrangell Mountains. The writer took part in field studies west of Cook Inlet with D. J. Miller in 1948 and with 

R. L. Detterman in 1974; in the Talkeetna Mountains 

with Arthur Grantz in 1952 and with R. L. Detterman in 

1972 and 1974; and in the Wrangell Mountains with E. 

M. MacKevett, Jr., in 1962. Many thanks are due all 

these geologists for collecting the fossils and for furnishing accurate fossil locality and stratigraphic data.

BIOLOGIC ANALYSIS

Southern Alaska ammonites of Bathonian, or probably 

Bathonian, Age that are discussed or described herein, 

number 343 specimens. Some of these were described in

1
MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

1962 (Imlay, 1962a), but most were obtained subsequently from the Wrangell and Talkeetna Mountains and 

from the north side of Cook Inlet between Iniskin Bay 

and Tuxedni Bay. Their distribution by genus, subfamily, and family is shown herein table 1. Among the families, the Cardioceratidae constitutes 60 percent of the total number of specimens; the Reineckeiidae?, 18 percent; 

the Perisphinctidae, nearly 8 percent; and the Phylloceratidae, 6 percent. The Cardioceratidae is dominated by 

Cranocephalites and comprises six genera, of which Tuxednites and Talkeetnites are recognized as new.

The characteristics of most of the genera and subgenera present have been described adequately in fairly 

recent publications. Liroxyites has been described by 

Imlay (1962b, p. A-8); Cadomites, by Arkell (1952, p. 

79, 80), Arkell and others (1957, p. L290), and Kopik 

(1974, p. 12, 13); Cranocephalites and Arkelloceras, by 

Arkell and others (1957, p. L301) and Imlay (1962a, p. 

C2; 1976, p. 2); Chinitnites and Iniskinites, by Imlay 

(1975, p. 17, 18, 23); and Parareineckeia, by Imlay 

(1962a, p. C-25) and Bourquin (1968, p. 160).

Cobbanites is now assigned to the subfamily Leptosphinctinae, instead of the Zigzagiceratinae, at the suggestion of John Callomon (1971, written commun.). This 

assignment is based on the presence of deep forwardly 

inclined constrictions, of slightly to strongly forwardly 

inclined ribs that arch adorally and weaken on the venter, and of lateral tubercles on the inner whorls of some 

species. Within the Leptosphinctinae, Cobbanites may 

be distinguished from Leptosphinctes proper by its much 

coarser ribbing and larger size (Buckman, 1920, pis. 160,

TABLE I.—Bathonian ammonite genera in southern Alaska 

showing biological relationships and relative numbers available for study

Family Subfamily

Calliphylloceratinae--

PseudoperisphinctinaeGenus or Number of 

subgenus specimens

Macrophylloceras — ~ 

Calliphylloceras — ~

OppeliaTOxycerites)-

Tuxednites n. gen. —

Tuxedni tes? ----------

Iniskinites ——— ----

Talkeetnites n. gen.-

2

18 

12 

2 

2 

1 

1 

4 

4 

4 

4 

2 

154 

1 

19 

5 

16 

8 

2 

60 

23 

2

161; 1921, pis. 201, 202); from Prorsisphinctes by the 

presence of tubercles on its inner whorls, much more 

compressed whorls, and considerably weaker ribbing on 

its outermost septate whorl (Buckman, 1921, pis. 200, 

247; 1922, pi. 326; 1923, pi. 366; 1927, pi. 446a, b; Sturani, 

1964, pi. 4, fig. 1); and from Vermisphinctes by its considerably larger size (Buckman, 1920, pis. 162, 190), by 

more distinct tubercles on the inner whorls of some species, by more definite weakening of ribs along the midline of the venter, and perhaps by the presence of lateral 

lappets (Arkell, 1958, p. 168).

These resemblances show that Cobbanites is closely 

related to Leptosphinctes and its subgenera and is possibly a descendant of Vermisphinctes. Nonetheless, Cobbanites is herein retained as a distinct genus because it 

does not fit precisely morphologically with either Vermisphinctes or Prorsisphinctes and occurs in beds that 

are mainly or entirely of Bathonian Age, whereas those 

subgenera are not known above beds of late Bajocian 

Age (Arkell, 1957, p. L314; Sturani, 1966, p. 9; Pavia and 

Sturani, 1968, p. 310).

STRATIGRAPHIC SUMMARY

Bathonian ammonites have been found in southern 

Alaska west of Cook Inlet, in the southern part of the 

Talkeetna Mountains, and in the southern part of the 

Wrangell Mountains (fig. 1 and tables 2-4). On the west 

side of Cook Inlet between Iniskin Bay and Tuxedni Bay, 

the Bathonian is represented by the Bowser Formation, 

which has been described and illustrated in detail by Detterman and Hartsock (1966, p. 35-40, 42, pi. 5) and is 

illustrated herein in figure 2. That formation ranges in 

thickness from 1,250 to 1,850 feet. It consists of units of 

siltstone, sandstone, and conglomerate that vary from 

thick to thin bedded, are commonly massive, change 

markedly laterally, and became less conglomeratic and 

finer grained northward. Coquinoid beds containing 

mostly Inoceramus and Trigonia are common in the 

sandstone. Ammonite-bearing concretions occur in the 

siltstone and are fairly common north of Chinitna Bay. 

The pebbles, cobbles, and boulders in the conglomerates 

consist mostly of felsite and basalt but include some 

granitic rocks. The Bowser Formation rests unconformably on the Twist Creek Siltstone or on older Bajocian 

beds. It is overlain sharply, but apparently conformably, 

by the Chinitna Formation on the Iniskin Penisula, and 

unconformably by that formation between Chinitna Bay 

and Tuxedni Bay.

In the Talkeetna Mountains, the Bathonian is represented in the Boulder Creek and Nelchina areas (fig. 3) 

by unnamed beds that are overlain unconformably by the 

Chinitna Formation of early to early middle Callovian 

Age (Imlay, 1975, p. 7, 14) and are underlain unconformably by beds ranging in age from Early Jurassic (Tal-
172° 164'

STRATIGRAPHIC SUMMARY

156° 148° 140° 132°

FIGURE 1.—Index map showing principal areas of outcrop of Bathonian marine rocks in southern Alaska. 1, Wrangell Mountains; 2, Talkeetna 

Mountains; 3, Chisik Island and peninsula between Tuxedni Bay and Chinitna Bay; 4, Iniskin Peninsula.

keetna Formation) to early late Bajocian (uppermost 

part of Tuxedni Group).

In the Boulder Creek area, the Bathonian unnamed 

beds are best exposed on a northwest-trending divide 

(figs. 3 and 4) about 6 miles N. 20° E. of the junction of 

East Boulder Creek with the main Boulder Creek. On 

that divide those beds are about 475 feet thick and consist from top to bottom of 150 feet of volcanic graywacke 

that includes some beds of coquina, 255 feet of gray to 

brown concretionary siltstone, and 70 feet of graywacke 

that includes a few beds of siltstone. Pelecypods and 

belemnites are fairly common in the coquina beds in the 

upper volcanic graywacke. Ammonites are abundant in

limestone concretions in the siltstone unit and occur 

rarely in siltstone beds within the lower unit of graywacke.

This lowermost graywacke forms a steep slope above 

a covered interval about 70 feet thick. Next lower is 30 

feet of soft brownish-gray to orange-gray, ash-bearing 

siltstone that closely resembles the Twist Creek Siltstone west of Cook Inlet (Detterman and Hartsock, 1966, 

p. 35) and contains the same early late Bajocian ammonites in limy concretions (Imlay, 1962b). Most probably 

the overlying covered interval is underlain by similar 

soft siltstone, because identical siltstone attains a thickness of at least 100 feet on a ridge about 1 mile to the
MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

TABLE 2.—Geographic distribution of Bathonian ammonites 

[Numbers 1-20 are keyed to locality numbers in figures 8 and 9.

Genus and species

Wrangell Mountains

Nizina Mountain Formation

McCarthy C-5 quadrangle

9 10 11

Phylloceras (Macrophy Hoc eras) grossicostatum Iml ay——————— — -- — -- — -- — — -- — ~ — —

(M.) cf. P_. (M.) grossicostatum Imlay—————————————— — -- -- -- -- -- -- -- -- -- -- -- --

Calliphylloceras freibrocki (Imlay)—————————————————— -- — -- -- — -- — -- — — — — --

Lytoceras sp————————————————————————————————— -- -- -- -- -- — -- -- -- -- -- -- --

Oecotraustes (Paraecotraustes?) sp——————————————————— — -- — -- -- — — — -- — -- -- --

Cadomites cf. C_. deslongchampsi (d'Orbigny) ——————— ————— -- -- -- -- -- -- -- -- -- -- -- -- --

cf. C_. rectolobatum (Hauer)————————————————————— — — -- — -- -- -- -- X -- — — —

Cranocephalites costidensus Imlay——————————————————— -- -- -- -- -- -- — -- X — X -- --

cf. C. costidensus Imlay——————————————————————— -- X -- X -- -- -- — — — — — --

alaskanus Imlay n. sp———————————————————————— -- -- — -- -- -- -- -- X -- -- -- --

cf. £. alaskanus Imlay n. sp-- — ———————————————— -- X X -- -- -- X -- -- — X -- —

cf. C. pompeckji (Madsen) ————— ----- ————— - — - — — — — — -- -- — — — -- — — — — --

globosus Iml ay n. sp———————————————————————— -- — -- — — -- -- — — -- — -- --

cf. C_. vulgaris Spath———————————————————————— -- -- -- -- -- -- — -- -- — -- -- --

Cranocephalites sp———————————————————————————— -- -- -- — — — -- X -- -- — — X

Tuxednites alticostatus (Imlay)———————————————————— -- -- -- -- — -- -- -- X -- — -- --

? S p———————————————————————————————————— -- -- -- — — — — — X -- -- — —

Chinitnites sp---- — - ————— — --- —————— ———— ————— - — — — — — -- — — — — — -- --

Talkeetnites cadiformis Imlay n. sp—————————————————— — — — -- -- -- — -- -- -- -- -- --

Parareineckeia hickersonensis Imlay—————————————————— X -- -- X — -- X X X X X -- —

nelchinensis Imlay n. sp——————————————————————— X -- X -- -- — — — X -- X X

sp——————————————————————————————.—————— ,_ x — — X X — — — — — -- —

Cobbanites talkeetnanus Imlay————————————————————— ~ X -- X -- — — — X -- — — —

striatus Imlay n. sp———————————————————————— -- -- -- -- -- -- -- -- X — -- -- --

cf. C. striatus Imlay———————————————————————— — — — X -- — — — — — — — —

southwest in the SWV4SEV4 sec. 34, T. 22 N., R. 7 E., 

and the NWV4NEy4 sec. 3, T. 21 N., R. 7 E.

Unnamed bed of Bathonian Age in the Nelchina area 

of the Talkeetna Mountains were mapped and briefly described by Grantz (1960a, b; 1965). Some descriptions 

furnished by Grantz (1959,1972, written communs.) were 

published by Imlay (1962a, p. C4; 1975, p. 2, 3, fig. 3) and 

are shown herein (fig. 4). The Bathonian sequence northwest of Limestone Hills in the upper part of the Little 

Nelchina River Valley contains some highly fossiliferous 

siltstone similar to that in the Boulder Creek area, as 

just described, but differs by consisting mostly of gray

medium- to thick-bedded sandstone and by containing 

pebbles and cobbles in its upper part. The sequence exposed from 3 to 4 miles farther north on the south side of 

the Little Oshetna River differs by consisting mostly of 

thick-bedded sandstone that is interbedded with lenses 

of conglomerate in its upper part and with coaly and 

plant-bearing beds in its lower part; it contains very few 

marine fossils.

On the southern flank of the Wrangell Mountains the 

Bathonian is represented within the Nizina Mountain 

Formation, which crops out in the McCarthy C-5 quadrangle (MacKevett, 1969, p. A42-A45; 1971, p. 16, 17,
BATHONIAN AMMONITE SUCCESSION

in the Wrangell Mountains and Talkeetna Mountains, Alaska 

Higher numbers are USGS Mesozoic locality numbers]

Talkeetna Mountains

Unnamed beds equivalent to Bowser Formation

Nelchina area Boulder Creek area

12 13 14 15 16 17 18 19 20

ir> CM

i-H CM

IT) OO

O O O

X V V V

._ _- — -_ __ ._ -- _. -- -- -- — -- V -- -- -- -- -- --

X — X — X X — X X X X X 

— X — X — — X -- - -- -- --

X X XXXXX— — XX 

„ _. „ .. .. ._ x -- -

28). That formation attains a maximum thickness of 

1,500 feet, at most places is much thinner, and locally 

pinches out. It is overlain disconformably by the Root 

Glacier Formation of late Oxfordian to middle Tithonian 

Age or by younger rocks. It is underlain disconformably 

by the Lubbe Creek Formation of Pliensbachian Age or 

by the upper member of the McCarthy Formation of earliest Jurassic Age (MacKevett, 1969, p. A44, A46; 1970; 

Imlay and Detterman, 1973, fig. 11A). It consists mostly 

of hard dark-greenish-gray fine to very fine grained medium-bedded graywacke but includes some limy shale 

and some shaly partings.

BATHONIAN AMMONITE SUCCESSION

WEST OF COOK INLET

The stratigraphic positions of many fossil collections 

within the Bowser Formation between Iniskin Bay and 

Tuxedni Bay are described herein in table 4 and are depicted in part on columnar sections (fig. 2). These data 

permit fairly accurate determinations of the stratigraphic ranges of many species relative to the top and 

bottom of the formation and to other species or genera 

(fig. 5).
MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

TABLE 3.—Geographic distribution of Bethonian ammonites 

[Numbers 21-58 are keyed to locality numbers in figures

West side of Cook Inlet between Tuxedni Bay and Iniskin Bay

Bowser Formation 

Chisik Island and Peninusla to the south

. . _ Near Lake ___________Tuxedm Bay area____________HTckerson

21 22 23 24 25 26 27 28 29 30 31 32 33 34

c\j ro ^f oo 01 o

i—) <—i i—( OS Ol O

CM C\J CM <NJ C\J <NJ CM

CM CM CM CM CM CM CM

Phylloceras cf. £. bakeri Iml ay—————————————— -- -- -- — — -- -- — -- -- -- — — -- -- —

(Macrophylloceras) grossicostatum Imlay———--—— -- -- -- -- -- -- -- -- -- — -- -- -- -- -- --

(Macrophylloceras) sp—————————————————— -- — — — -- -- -- — -- -- — -- -- -- -- --

Calliphylloceras freibrocki (Imlay)———————————— -- — -- -- -- -- -- -- -- -- X -- — -- -- --

Ly toe eras sp—————————————————————————— -- -- -- — -- -- -- -- — -- -- -- -- — — --

Oppelia (Oxycerites) sp————— ——————————— —— -- — -- -- — -- -- -- -- -- -- -- -- -- -- --

(Oxycerites) aff. (). (().) chinitnana Imlay———— -- -- — -- X -- -- -- -- -- -- -- -- — — -

(Liroxyites) cf. 0. (U) kellumi Imlay——————— -- — -- -- X -- -- -- -- -- -- -- -- -- -- --

Xenocephalites cf. X^. hebetus Imlay———————————— -- -- — — — -- -- -- -- -- -- X -- — -- —

? sp————. —————————...————————————— .. .. .. ._ .. ._ .. .. ._ _. .. ._ x -- -- --

Kepplerites sp. A———————————————————————— -- -- -- — -- -- -- — — — ~ -- -- -- -- --

sp . B ————— ----- ————— - —- ——————— -——— — — - — — — -- -- X -- — — — -- -- -

sp . c—-————————___.__—————.___....—— - „ x - - - -- -- - -- -- - - -- - -

? sp——————-—-._„...„„............ .. .. .. .. .. .. .. „ .. - - - - - - -

Cranocephalites costidensus Imlay————————————— -- -- — — -- -- — X -- — X -- -- X -- --

cf. £. costidensus Imlay———————————————— -- -- — -- -- -- -- -- -- — — -- -- -- -- --

al ask anus Imlay n. sp——————————————————— — — — -- -- — -- X -- -- -- — -- X -- --

cf. £. Imlay n. sp———————————————————— — — — — — -- — — — X X -- -- — — —

cf. C_. pompeckji (Madsen)——————————————— — — — -- -- -- X -- -- -- -- — — — -- --

globosus Imlay—————————————————————— -- — -- -- -- -- -- -- -- -- — -- -- -- -- --

sp. A————————————————————————————— — — — -- -- — — — — -- -- — — — — --

sp . B————————————————————————————— - — — — X — - - — — — — ~ — — -

sp. juv———————————————————————————— — — — — — -- — — — -- -- -- — — — —

? sp—————— —————————— - - - - - - - - - - - - - - - -

Arctocephalites cf. A. elegans Spath——————————— -- — — — -- -- -- -- -- — -- -- -- — X

Tuxednites alticostatus (Imlay)—————————————— — — -- -- -- -- -- — -- -- -- -- -- X -- --

cf. T. alticostatus Imlay——————————————— -- -- -- — — — -- -- — — — — — X -- --

? sp————————————————————————————— -- -- — — — -- -- -- -- -- -- -- -- -- -- --

Chinitnites parviformis Imlay——————————————— — -- -- -- — — — -- — ~ -- — ~ -- -- --

sp—————————————————————————————.. .. __ .. .. .. ._ .. _. _. - .- _. ._ .. .. ..

Iniskinites intermedius (Imlay)——————————————— X X -- -- -- -- — -- -- -- — — — -- -- X

cf. I_. intermedius (Imlay)——————————————— -- -- -- X -- -- -- -- -- -- -- -- -- -- -- --

sp. juv. cf. ]_. magniformis (Imlay)————————— -- — — -- -- — — — — -- — — — — — --

Parareineckeia hickersonensis Imlay——————————— -- -- -- -- -- -- -- -- -- -- -- -- -- X -- --

nelchinensis Imlay n. sp———————————————— — — — — — -- -- — — -- -- — — — — —

cf. P_. nelchinensis Imlay n. sp- —— ——— ————— -- — — — — -- — — — — -- — — — — —

Cobbanites tuxedniensis Imlay n. sp———————————— -- — — — — X -- — — — -- -- — — — —

sp—————————————————————————————— .. ._ .. .. „ .. ._ .. __ — .. ._ ._ „ — —

Siemeradzkia cf. S^. aurigera (Oppel)——————————— -- — — -- -- -- -- — — -- -- — — X -- --
BATHONIAN AMMONITE SUCCESSION

between Tuxedni Bay and Iniskin Bay west of Cook Inlet, Alaska

10 and 11. Higher numbers are USGS Mesozoic locality numbers]

West side of Cook Inlet between Tuxedni and Iniskin Bay--Continued

Bowser Bay Formation—Continued

Iniskin Peninsula

Bo.ser Creek ,„,*„ B,y ,rea

35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

^^OOOOi^i^OOVO^OOLO^^d-^'sJ-CMLOUO roro^-oororoo »—< O c\jLnor^r-*.r-*.Or-*.oor-*rx.

i— it— t CM i— i ,-H ,— i o r-*. O O C\J I-H O O O •— < O »— < OO 

C\JC\J CVJCVJCUCVJC\JCVJCVJOOC\Ji-HC\JC\JC\J'"HC\JC\JOJC\J

X V

%')('")( ______

XX -

Y Y

-- -- Y

— __ __ __ _- __ _ __ __ __ __ __ Y __ -- -_ -- __ __ _

50 51 52 53 54 55 56 57 58

po^j-ioooro^cr) ^j-^o

^j- «d-OOOOLOfr^OOOO^£>'— '

r^r^LOLOLor^r^ror^^jOOCMCMCMOOOOCM 

CM C\JC\JC\JC\jC\JCMrOCMC\J

X --

X -

Y __

-. _. -. -- -- X -- -- -- --

- X - - - - - - - - - - - - - - - - - - - - „ - - - - X X
MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

NORTH

Lake Hickerson area, sectiori on 

divide between Red Glacier 

and Boulder Creek

Tuxedni Bay area, section orj 

CHINITNA tributary of Bear Creek 

FORMATION

BOWSER 

FORMATION

TWIST CREEK 

SILTSTONE

820 feet 

Massive 

siltstone

430 feet 

Massive 

sandy 

siltstone

300 feet

Siltstone,

soft

21272 Iniskinites intermedius 

-""""" (On Chisik Island below

channel conglomerate) 

30258 Kepplerites sf/. B and C 

30263 Kepplerites sp. B and C

30261 Cobbanites tuxedniensis

30262 Iniskinites ct. I. intermedius

30257 Cranocephalites sp. B 

21284 C. cf. C. ignekensis 

22714 Xenocephalites?

22713 Xenocephalites cf. 

X. hebetus

21283 Cranocephalites 

/ costidensus and 

C. alaskanus.

-22712 Cranocephalites costidensus 

and C. cf. C. alaskanus

-22711 C. cf. C. alaskanus

12-13 MILES

130 feet 

Siltstone, 

pebbles 

near top

730 feet 

iltstone, 

interbeds of 

sandstone

150 feet 

Massive 

sandstone

690 feet 

Massive 

siltstone, 

some 

sandstone 

interbeds

410 feet

Siltstone,

soft

22700 Iniskinites intermedius

22699 Arctocephalites cf. A. 

elegans

12698 Cranocephalites costidensus, 

C. alaskanus,

Parareineckeia hickersonensis 

Siemiradzkia cf. S. aurigera, 

and Tuxednites alticostatus

18-19 MILES

FIGURE 2 —Stratigraphic positions of some Bathonian ammonite localities in the Bowser Formation west of Cook Inlet between Tuxedni 

Bay and Iniskin Bay. Data from Detterman and Hartsock, 1966, p. 37^0, pi. 5. Approximate locations of sections are shown in 

figures 10 and 11.
BATHONIAN AMMONITE SUCCESSION

Area of Tonnie Creek, Edelman Creek, 

and upper part Bowser Creek, section on Tonnie Creek

SOUTH

hinitna Bay area, ./ 

ection on ^/^ 

laikema Creek s'

180 feet 

Massive 

sandstone

220 feet 

Siltstone, 

poorly 

exposed

210 feet 

Massive 

conglomerate

180 feet 

Massive 

sandstone

610 feet 

Massive 

siltstone, 

some 

sandstone 

interbeds

120 feet 

Massive 

sandstone

420 feet 

Siltstone, 

soft

/

'21312 Iniskinites cf. I. 

intermedius, 

Macrophylloceras 

grossicostatum, 

Calliphylloceras 

freibrocki, and 

Xenocephalites 

22436 Chinitnites parviformis 

[_ and Cranocephalites sp. A. 

> 2131 1 M. grossicostatum, C.

freibrocki, and 

Phylloceras bakeri

(Fossils listed above are from Park 

Creek)

- 21308 Cranocephalites sp. juv.

-21309 Cranocephalites cf. C. 

alaskanus

4 MILES

-

"""Tsoleet 

Massive 

sandstone, 

conglomerate 

interbeds

250 feet 

Massive 

siltstone

170 feet 

Conglomerate 

and coarse 

sandstone

170 feet 

Shaly to 

thin-bedded 

sandstone

130 feet 

Sandy 

siltstone

250 feet 

Sandstone 

conglomerate 

interbeds

260 feet 

Sandy 

siltstone

70 feet 

Conglomerate

50 feet 

Siltstone

230 feet 

Sandy 

siltstone

70 feet

Sandstone

- — — — — — • — •*-*-

240 feet 

Siltstone, 

soft

inisKin t 

- — _^^____^ tribut

>21320 Chinitnites 

I 20748 Chinitnites

-21319 Kepplerites sp.A

11042 Chinitnites parviformis 

- 20746 Tuxednites alticostatus

11038 Tuxednites alticostatus 

/ and C. parviformis 

-20745 Parareineckeia cf. P. 

nelchinensis and 

Cranocephalites sp. juv.

-20011 Tuxednites 

alticostatus

\ — ——— ' ——— — . ___

-^20752 Tuxednites alticostatus 

r- 20751 Cranocephalites globosus

> 20744 Tuxednites?

20754 Cranocephalites 

I costidensis and 

/ C. cf. C. alaskanus 

'30265 Tuxednites?

(Only localities 2001 1 , 20005, 

21319, 27100, and 30265 are 

from Tonnie Creek; other fossil 

localities are from Edelman 

Creek and the upper part of 

\ Bowser Creek) 

x^20005 Tuxednites? sp. 

27100 Cranocephalites ? 

4-5 MILES

3ay area, section on 

any of Portage Creek

100 feet 

Silty 

sandstone

180 feet 

Mostly 

covered

95 feet 

Sandstone, 

siltstone

175 feet 

Covered

110 feet 

Sandstone, 

some grit

320 feet 

Covered

130 feet 

Conglomeratic 

sandstone

240 feet 

Mostly 

covered

120 feet 

Sandstone, 

thin-bedded

170 feet 

Covered

130 feet 

Sandstone, 

thin-bedded

-22416 Chinitnites

} 22536 Iniskinites cf. /. 

magnijormis

} 22538 Oppelia (Oxycerites) 

- 22553 Kepplerites ?

 20739 Lytoceras

- 1 3028 Cranocephalites sp. juv. 

Iniskinites cf. 

/. intermedius, and 

Parareineckeia 

nelchinensis

B 20736 Cranocephalites cf. 

C. costidensus

Fault at base

FIGURE 2.—Continued.
NORTH 

Little Oshetna River

on south side 

west of Conglomerate Creek

Northwest of Limestone Hills

in headwaters of 

Little Nelchina River

On divide at head of

tributary of Boulder Creek

6 miles N. 20° E. of junction with

East Boulder Creek

CHINITNA FORMATION

Unnamed beds

of 

Bathonian Age

(Cranocephalites beds)

TALKEETNA FORMATION

Conglomerate 

at base

650 feet

Sandstone, 

thick-bedded 

with some 

conglomerate 

in upper 100 

feet. Lower 

part has coaly

plants, 

siltstone, and

claystone

Volcanic rocks

/WN

} 27515 Cranocephalites 

costidensus

—24822 Cranocephalites cf. C. 

costidensus

Conglomerate 

at base

1200 feet 

or more

Sandstone

and siltstone, 

medium-to 

thick-bedded

Upper part 

has some 

conglomerate

AAA

—24118,30286 

—30287

— 24116, 24117, 30288/ 30290 

—30289

24115, 24825

Cranocephalites costidensus

occurs at all localities 

listed above;

at locality 24116, and

at locality 24117

Conglomerate 

at base

150 feet 

Volcanic 

graywacke

255 feet 

Siltstone, gray 

to brown and 

many 

limestone 

concretions; 

some 

sandstone

70 feet 

Graywacke

70 feet 

Covered

30 feet 

\Siltstone, / 

\orange-g ray/

145 feet

Siltstone, 

brown to gray

100-1 25 feet 

Covered

100 feet 

Sandstone 

and grit

150 feet 

Siltstone; 

some beds of 

graywacke

Gryphaea, Ino

and belemnite

-30274 Chinitni

! 

30275 and 305

30575 

} 30276 and 305

\ 30277 and 305

} 30278 and 305

30279 and 305

} 30580 Megasph

\ 30280 Stemma

J Chondro

i 30281 Witchell

Cranoceph

occurs at Iocs

and 30277-302

Cobbanites 

30275, 30277, 

Talkeetnites 

30277;

Parareinecke

30276; and

P. hickerson

and 30577

FIGURE 3.—Stratigraphic positions of some Bathonian ammonite localities in the Talkeetna Mountains. Data for Nelchina area furnis

Arthur Grantz, (written commun., 1972). Approximate locations of sections are shown in figure 9.
BATHONIAN AMMONITE SUCCESSION 11

Lower 

Callovian Bathonian Bajocian

Tuxedni Group

Chinitna 

Formation 

(basal part)

Unnamed beds equivalent 

to the Bowser Formation 

north of Cook Inlet

Unnamed beds equivalent at top to the 

Twist Creek Siltstone and at the bottom to the 

Red Glacier Formation north of Cook Inlet

Chinitnites 100 

. i

200

Cobbanites talkeetnanus

Cranocephalites costidensus

300

I

400 Feet

20 

I

40 

i

60 

I

100 Meters 

_i

FIGURE 4.—Partial Middle Jurassic sequence including Bathonian beds exposed on a northwest-trending divide at head of a tributary of Boulder 

Creek near center of NWV4SEV4 sec. 26, T. 22 N., R. 7 E., Anchorage D-3 quadrangle, Talkeetna Mountains, Alaska.

These ranges show that the lower two-fifths, or lower 

500-700 feet, of the formation is characterized by an 

abundance of Cranocephalites costidensus (Imlay). The 

overlying 300-450 feet of beds contain coarser ribbed 

species of Cranocephalites, which are associated with 

the lowermost occurrences of Xenocephalites and of 

Chinitnites parviformis (Imlay). The next higher 300- 

580 feet of beds at the top of the formation are characterized by species of Iniskinites including/, intermedius 

(Imlay) and some specimens of Cobbanites, Chinitnites, 

Arctocephalites, and Kepplerites. Cobbanites occurs about 

150 feet below the top of the formation near Tuxedni 

Bay. (See figs. 2, 5.) Chinitnites parviformis (Imlay) and 

Chinitnites sp. range upward into the lower part of the 

overlying Chinitna Formation (Imlay, 1975, p. 23). Arctocephalites near Lake Hickerson occurs 360-380 feet 

below the top of the formation and 170-190 feet below 

Iniskinites intermedius (Imlay). Kepplerites occurs at 

two levels from 50 to 100 feet below the top of the formation near Tuxedni Bay, 420 feet below the top at Tonnie Creek, and is probably present 360 feet below the top 

at Iniskin Bay. These occurrences of Kepplerites are 

clearly within the upper part of the range of Iniskinites.

TALKEETNA MOUNTAINS

The stratigraphic occurrences of the Bathonian fossil 

collections within certain unnamed beds in the Talkeetna 

Mountains are described herein in table 4 and are depicted in columnar sections (fig. 3). This information, at 

least for the Boulder Creek area, makes possible the determination of the stratigraphic ranges of some species 

relative to each other and to the top and bottom of the 

lithologic unit in which they occur (fig. 6).

All the ammonite-bearing beds in the Nelchina area 

and most of them in the Boulder Creek area are characterized by an abundance of Cranocephalites costidensus 

and are equivalent to only the lower 500-700 feet of the 

Bowser Formation west of Cook Inlet. Also, the uppermost 65 feet of the siltstone sequence in the Boulder 

Creek area contain species of Cranocephalites that are 

similar to C. vulgaris Spath and to C. cf. C. ignekensis 

Imlay (USGS Mesozoic loc. 30275) and probably correlate with beds in the middle part of the Bowser Formation that contain similar coarsely ribbed forms of Cranocephalites (for example, USGS Mesozoic loc. 21284). 

Nonetheless, the absence of Iniskinites in the Talkeetna
12 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

Bowser Formation

Sandy siltstone Siltstone, sandstone, and conglomerate

Phylloceras cf. P. bakeri Imlay— — — —— — •

P. (Macrophylloceras) grossicostatum Imlay ———— 

Calliphylloceras freibrocki (Imlay) — — — — — —

Lytoceras sp ——— — — — — — ——— — — —

Oppelia (Oxyce rites) sp — — — — — — — — —

Oppelia(Oxycerites) aft. O. (O.) chinitnana Imlay — 

O. (Liroxyites) cf. O. (L.) kellumi Imlay — — — —

Xenocephalites cf. X. hebetus Imlay — — — — —

Kepplerites sp. A — — — — — — — — — — —

K. sp.B ——————— — —————— —————— — -

K. sp.C ————— ———————— — — ————— — •

Cranocephalites costidensus (Imlay) — — — — — ~

C. cf. C. costidensus Imlay — — — — — — — — -

C. alaskanus Imlay, n. sp — ————— — — — — -

C. cf. C. alaskanus Imlay, n. sp — — — — — — —

C. cf. C. ignekensis Imlay — — — — — — — —

C. globosus Imlay, n. sp — — —" — — — — — — ~

C. sp. A — — — — — — — — — — — — — —

C. sp. B — — — — — — — — — — — — — —

C. sp. juv — — — — — — — — — — — — —

C.? sp ————— ———————— ————— ————— —

Arctocephalites cf. A. elegans Spath — — — — —

Tuxednites alticostatus (Imlay) — — —- — — — —

Chinitnites parviformis (Imlay) ———— — — — — — —

C. sp —— — — ——— — ——— — — — — — —

Iniskinites intermedius (Imlay) — — — — — — —

/. cf. /. intermedius (Imlay) — — — — — — — —

/. sp. juv. cf./. magniformis (Imlay) — — — — — —

Parareineckeia hickersonensis Imlay — — — — —

Parareineckeia nelchinensis Imlay, n. sp — — — —

P. cf. P. nelchinensis Imlay, n. sp — — —" 

Cobbanites twcedniensis Imlay, n. sp — — — — —' 

Siemiradzkia cf. S. aurigera (Oppcl) — — — — —

FIGURE 5.—Stratigraphic ranges of Bathonian ammonites in the Bowser Formation west of Cook Inlet, Alaska.

Mountains suggests that marine beds equivalent to the 

upper part of the Bowser Formation are either absent in 

those mountains or are represented in the Boulder Creek 

area by the upper 150 feet of volcanic graywacke that has 

not furnished any ammonites.

WRANGELL MOUNTAINS

The Stratigraphic positions of many of the fossil collections within the Nizina Mountain Formation are not well 

known (table 4). Ammonites of probable early Bathonian
AGES AND CORRELATIONS 13

Unnamed Bathonian beds in Talkeetna Mountains

Graywacke 

70 feet

Gray to brown siltstone 

255 feet

Volcanic graywacke 

150 feet

Phylloceras (Macrophylloceras) grossicostatum ImlayP. (M.) cf. P. (M.) grossicostatum Imlay — ——— — —

Calliphylloceras freibrocki (Imlay) — — — — — — — -

Lytoceras sp — — — —— — — —— — — — —

Oecotraustes (Paraecotraustes?) sp — — — — — — —

Cadomites cf. C. deslongchampsi (d'Orbigny)—— — —

Cranocephalites costidensus (Imlay) — — — — — — —

C. cf. C. costidensus Imlay — — — ——— — — ————

C. cf. C. ignekensis Imlay — — — — — — — — — —

C. globosus Imlay, n. sp — — — — — — — — —— •

C. cf. C. vulgaris Spath — — — — — — — — — — •

Tuxednites alticostatus (Imlay) ~ — — — — — — — — —

Chinitnites sp — — — — — — — — — — — — — —

Talkeetnites cadiformis Imlay, n. sp — — — — — — ——

Parareineckeia hickersonensis Imlay — — — — — — —

P. nelchinensis Imlay, n. sp — — — — — — — — — —

Cobbanites talkeetnanus Imlay — — — — — — — — —

C. striatus Imlay, n. sp — — — — — — — — — —

FIGURE 6.—Stratigraphic ranges of Bathonian ammonites in unnamed beds in the Talkeetna Mountains, Alaska. Ranges bounded by question 

marks indicate fossil occurrences in the Nelchina area. Other ranges indicate fossil occurrences in the Boulder Creek area.

Age have been obtained, however, from at least the 

lower 500 feet of that formation (table 3) and represent 

the same species as are associated with Cranocephalites 

costidensus in the Talkeetna Mountains and west of Cook 

Inlet. No faunal evidence for younger faunules of Bathonian or Callovian Age has yet been found in the Wrangell Mountains. The fact that one fossil collection, obtained mostly as float (USGS Mesozoic loc. 28682), 

includes specimens of Teloceras, Normannites, and 

Chondroceras (Imlay and Detterman, 1973, p. 24) shows 

that, at least locally, the formation is basally of late middle or early late Bajocian Age.

AGES AND CORRELATIONS

The lowermost beds of Bathonian, or probable Bathonian, Age in southern Alaska are characterized by 

Cranocephalites costidensus (Imlay) and are dated as 

early Bathonian for the following reasons: (1) They rest 

unconformably on beds of early late Bajocian Age or of 

older Jurassic Age (Detterman and Hartsock, 1966, p. 

35, 40; Imlay and Detterman, 1973, p. 11, 14, 15; Grantz, 

1961, written commun.). (2) They occur west of Cook Inlet in the basal part of an ammonite sequence that is similar to Bathonian ammonite sequences in northern Alaska, 

northern Canada, and East Greenland (fig. 7), except for 

the absence of Arcticoceras (Imlay, 1975, p. 14). (3) They 

contain the ammonite Cadomites, which ranges from uppermost Bajocian through most of the Bathonian (Hahn, 

1971, p. 110), and Siemeradzkia (Imlay, 1962a, p. C20, pi. 2, figs. 9, 10), which is known only from the Bathonian (Hahn, 1969, p. 39). (4) They contain several specimens of Cadomites similar to C. deslongchampsi 

(d'Orbigny), which in Europe ranges from the uppermost Bajocian into the lower Bathonian (Sturani, 1964, 

p. 20). (5) They contain one specimen of Cadomites similar to C. rectelobatus (v. Hauer), which in Europe ranges 

from the uppermost Bajocian through most of the Bathonian but is most common in the lower Bathonian (Sturani, 1966, p. 29; Kopik, 1974, p. 21, 22). (6) They underlie 

beds containing species of Cranocephalites similar to 

those in the C. pompeckji zone of East Greenland that is 

dated by Callomon (1959, p. 508) as early, but not earliest, Bathonian.

Against this early Bathonian Age assignment of the 

beds characterized by Cranocephalites costidensus is the
14 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

Iniskin Bay to 

Tuxedni Bay

Talkeetna 

Mountains

Wrangell 

Mountains

Characteristic fossils 

in southern Alaska

Characteristic fossils in 

northern Alaska 

(Frebold,1964)

Nizina

Mountain

Formation

Cadoceras (Stenocadoceras) 

stenoloboide

Cadoceras sp.

Cadoceras 

catostoma

Iniskinites 

intermedius

Iniskinites cf. 

/. intermedius

A rctocephalites 

cf. A. elegans

Cranocephalites 

cf. C. ignekensis

8,

Cranocephalites 

costidensus

Arcticoceras ishmae

Arctocephalites 

cf. A. elegans

Cranocephalites 

ignekensis

Cranocephalites sp.

Megasphaeroceras rotundum, 

Leptosphinctes,and Normannites

Teloceras itinsae and 

Chondroceras allani

Stephanoceras kirschneri

Parabigotites crassicostatus 

and Arkelloceras Arkelloceras

_____?

Docidoceras widebayense

Erycitoides howelli and 

Pseudolioceras whiteavesi

Tmetoceras scissum

Erycitoides howelli

and Pseudolioceras 

^\whiteavesi r____/

Tmetoceras scissum

Pseudolioceras 

maclintocki

FIGURE 7.—Correlation of Middle Jurassic formations and ammonite faunas in southern Alaska with ammonite faunas of northern

Alaska, Greenland, and northwest Europe.

presence of Cobbanites, whose resemblance to Vermisphinctes of the Leptosphinctinae suggests a late Bajocian Age. Against a late Bajocian assignment, however, 

is an occurrence of Cobbanites, described herein as C. 

tuxedniensis Imlay n. sp., only 150 feet below the top of 

the Bowser Formation, 50 feet below Kepplerites, 150- 

200 feet above Cranocephalites cf. C. ignekensis Imlay, 

and 600 feet above the uppermost occurrence of Cranocephalites costidensus (Imlay). Cobbanites at that stratigraphic position must be considerably younger than Bajocian and probably as young as late middle Bathonian. 

Cobbanites is not definitely known from higher beds, although some fragmentary ammonites from the basal part 

of the Chinitna Formation were once so assigned (Imlay, 

1962a, p. C-26, C-27). That assignment now seems unreasonable because the ribs on those ammonites, originally described as Procerites by Imlay (1953, p. 102, pi. 

53, figs. 1-3), do not weaken ventrally as on the type 

species of Cobbanites at a comparable size (Imlay, 1962a, 

pi. 8).
AGES AND CORRELATIONS 15

East Greenland (Donovan, 

1957; Callomon, 1959; 

Surlyk and others, 1973)

Kosmoceras and 

Longaeviceras

Kosmoceras and 

Pseudocadoceras

Sigaloceras calloviense

Cadoceras n. sp.

Cadoceras n. sp.

Cadoceras calyx

Cadoceras variabile

Arcticoceras n. sp.

Arcticoceras ishmae

Arctocephalites greenlandicus

Arctocephalites arcticus

Cranocephalites pompeckji

Cranocephalites indistinctus

Cranocephalites borealis

Standard zones in northwest 

Europe (Callomon, 1964; 

Torrens, 1965; Gabillyand 

others, 1971; Parsons, 1974

Quenstedoceras lamberti

Peltoceras athleta

Erymnoceras coronatum

Kosmoceras jason

Sigaloceras calloviense

Macrocephalites 

macrocephalus

Clydoniceras discus

Oppelia aspidoides

Hecticoceras retrocostatum

Morrisiceras morrisi

Tulites subcontracts

Gracilisphinctes progracilis

Zigzagiceras zigzag

Parkinsonia parkinsoni

Garantiana garantiana

Stenoceras subfurcatum

Stephanoceras 

humphriesianum

Otoites sauzei

Witchellia laeviuscula

Hyperiioceras discites

Graphoceras concavum

Ludwigia murchisonae

Leioceras opalinum

FIGURE 7.—Continued.

Beds characterized by Cranocephalites costidensus 

(Imlay) are known outside Alaska only in west-central 

British Columbia and are likewise dated tentatively as 

early Bathonian (Frebold and Tipper, 1973, p. 1125- 

1130) rather than latest Bajocian. As in Alaska, the age 

evidence is not positive.

The next higher Bathonian beds west of Cook Inlet 

and in the Talkeetna Mountains of southern Alaska are 

characterized by Cranocephalites cf. C. vulgaris Spath

and C. cf. C. ignekensis Imlay. These furnish a correlation with beds that in northern Alaska contain C. ignekensis Imlay (1976, p. 15, pi. 2, figs. 9, 11, 12), that in 

northern Canada contain C. vulgaris Spath (Frebold, 

1957, p. 8, pi. 7, figs. 1, 2, pi. 8, fig. la-c), and that in 

East Greenland contain C. vulgaris Spath and C. pompeckji (Madsen) (Callomon, 1959, p. 508). All these ammonites occur in the upper part of the range of 

Cranocephalites. The beds in East Greenland that are 

characterized by C. pompeckji are considered to represent the lower Bathonian along with the underlying beds 

characterized by C. indistinctus Callomon (Surlyk and 

others, 1973, p. 9). The beds in southern Alaska that contain C. cf. C. ignekensis and C. cf. C. vulgaris are associated with the lowermost occurrences of XenocephaMtes, Iniskinites, and the species Chinitnites parviformis 

Imlay, which taxa are unknown from the other areas 

mentioned and at the present time are of little value in 

intercontinental correlations.

The overlying Bathonian beds in the upper part of the 

Bowser Formation west of Cook inlet are in part of middle Bathonian Age, as shown by the presence of one 

specimen of Arctocephalites cf. A. elegans Spath obtained 360-380 feet below the top of the formation near 

Lake Hickerson. This ammonite provides a correlation 

with Arctocephalites beds in northern Alaska (Imlay, 

1976, p. 3-5, 16) and in East Greenland (Callomon, 

1959, p. 508) that are probably of middle Bathonian Age.

The uppermost beds in the Bowser Formation are tentatively assigned a late Bathonian Age, because they 

contain Kepplerites but no Cadoceras, a genus that occurs in abundance with Kepplerites in the basal part of 

the overlying Chinitna Formation. A similar faunal relationship occurs in East Greenland, where Kepplerites appears first in the upper part of the range of Arcticoceras, 

whereas Cadoceras appears first in the overlying beds 

(zone of Cadoceras variabile) (Callomon and others, 1972, 

p. 18).

If this dating of the uppermost part of the Bowser Formation is correct and if the Bathonian-Callovian boundary in East Greenland has been correctly chosen (Callomon and others, 1972, p. 18), then the uppermost 

Bathonian zones of Cadoceras variabile and C. calyx in 

Greenland have not been identified faunally in southern 

Alaska. Those zones could be represented in southern 

Alaska by an unconformity that is well developed at the 

base of the Chinitna Formation in the Talkeetna Mountains (Grantz, 1960a, b; 1965; written commun., 1972) 

and on the west side of Cook Inlet between Tuxedni Bay 

and Iniskin Bay and is possibly represented in the Iniskin Peninsula by a sharp contact between the Bowser 

and Chinitna Formations (Detterman and Hartsock, 1966, 

p. 40, 42, pi. 5). Those zones could also be represented 

by the basal beds of the Chinitna Formation west of Cook 

Inlet, as discussed elsewhere (Imlay, 1975, p. 14).
16 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

In summation, the beds containing Cranocephalites 

costidensus (Imlay) are either earliest Bathonian or latest Bajocian Age or both. An early Bathonian Age is favored by the fact that they rest unconformably on beds 

of early Bajocian Age, by the presence of an ammonite 

that probably represents Siemeradskia, and by the presence of a species of Cadomites similar to C. rectolobatus 

(v. Hauer). The overlying beds containing Cranocephalites are dated as probably late early Bathonian because 

they contain species of that genus that are similar to species in the C. pompeckji zone in East Greenland. Somewhat higher beds that contain Arctocephalites are dated 

as middle Bathonian by comparison with the faunal sequence in East Greenland. Still higher beds in southern 

Alaska that contain Kepplerites but no Cadoceras are 

probably of late Bathonian Age by comparison with East 

Greenland. The very latest Bathonian in southern Alaska 

could be represented by an unconformity between the 

Bowser and Chinitna Formations or by the basal beds of 

the Chinitna Formation that are characterized by Iniskinites intermedius (Imlay).

AMMONITE FAUNAL SETTING

The Bathonian ammonite genera found in southern 

Alaska represent a mixed assemblage of diverse geographic origin. Ammonites characteristic of the Boreal 

Realm include Kepplerites, Cranocephalites, and Arctocephalites. Ammonites characteristic of the Pacific Realm 

from southern Alaska to Oregon include Xenocephalites, 

Cobbanites, Iniskinites, and Parareineckeia. Ammonites found to date only in southern Alaska include Tuxednites n. gen., Talkeetnites n. gen., and Chinitnites. 

Ammonites that occur nearly worldwide in the Bathonian, but are uncommon in the arctic region, include 

Phylloceras, Macrophylloceras, Calliphylloceras, and 

Lytoceras. Ammonites that occurred nearly worldwide 

except in the arctic region include Siemeradzkial, Cadomites, and perhaps Oecotraustes.

GEOGRAPHIC DISTRIBUTION

The geographic occurrences of the ammonites described herein are shown in figures 8-11 and tables 2 

and 3. Detailed descriptions of the occurrences are given 

in table 4.

SYSTEMATIC DESCRIPTIONS

Family PHYLLOCERATIDAE Zittel, 1884

Subfamily PHYLLOCERATINAE Zittel, 1884

Genus PHYLLOCERAS Suess, 1865

Phylloceras cf. P. bakeri Imlay

Plate 1, figures 6, 10

Two small specimens have ribbing identical with that 

on P. bakeri Imlay (1953, p. 72, pi. 25, figs. 10, 14) at a

comparable size and probably are immature forms of that 

species.

Figured specimen.—USNM 240705.

Occurrence.—Bowser Formation at USGS Mesozoic 

localities 21311 and 21312 on Gaikema Creek in the Chinitna Bay area. These occurrences are, respectively, 

910-930 feet and 980 feet above the base of the formation, which at that place is 1,520 feet thick.

Subgenus MACROPHYLLOCERAS Spath, 1927 

Phylloceras (Macrophylloceras) grossicostatum Imlay

Plate 1, figures 12, 13

Phylloceras (Macrophylloceras)grossicostatum Imlay, 1953, U.S. Geol. 

Survey Prof. Paper 249-B, p. 74, pi. 25, figs. 11-13, 15, 16.

This species is represented by 13 septate specimens of 

various sizes that match very well the type specimens 

from the Chinitna Formation.

Figured specimen.—USNM 240706.

Occurrence.—Bowser Formation at USGS Mesozoic 

localities 21311, 21312, and 22436 west of Cook Inlet. 

Equivalent unnamed beds in the Talkeetna Mountains at 

Mesozoic locality 30574.

Subfamily CALLIPHYLLOCERATINAE Spath, 1927 

Genus CALLIPHYLLOCERAS Spath, 1927

Calliphylloceras freibrocki (Imlay) 

Plate 1, figures 7-9, 11

Phylloceras (Calliphylloceras) freibrocki Imlay, 1953, U.S. Geol. Survey Prof. Paper 249-B, p. 73, pi. 26, figs. 7-11.

The species is represented by 12 specimens of various 

sizes; some show faint ribs or striae on the venter. These 

specimens are assigned to Calliphylloceras rather than 

Holcophylloceras because they lack distinct ribs on the 

venter and because their constrictions do not affect the 

test.

Types.—Kolotype, USNM 108006; paratypes, USNM 

108007, 108008; hypotypes, USNM 240707, 240708.

Occurrence.—Bowser Formation at USGS Mesozoic 

locality 21311, 21312, and 22712 west of Cook Inlet. 

Equivalent unnamed beds in the Talkeetna Mountains at 

Mesozoic localities 24117, 30275, and 30576^30578.

Family LYTOCERATIDAE Neumayr, 1875

Subfamily LYTOCERATINAE Neumayr, 1875

Genus LYTOCERAS Suess, 1875

Lytoceras sp.

Plate 2, figures 10-12

One septate internal mold shows evolute coiling, a 

nearly round whorl section, and crinkled riblets that incline gently forward on the flanks but cross the venter 

transversely. Constrictions are not present. The specimen closely resembles Lytoceras eudisianum (d'Orbigny)
142"45'

SYSTEMATIC DESCRIPTIONS

142°40'

17

142°35'

FIGURE 8.—Index map of listed Bathonian fossil localities in the Nizina Mountain Formation in the Wrangell Mountains, Alaska. Numbers on

map refer to those given in table 4.

as figured by J. Wendt (1963, p. 116, pi. 17, fig. 2) but 

lacks the flared ribs of the holotype as figured by 

d'Orbigny (1845, pi. 128).

Figured specimen.—USNM 240709.

Occurrence.—Unnamed beds in the Talkeetna Mountains at USGS Mesozoic locality 30579. One small fragment of Lytoceras occurs also in the Bowser Formation 

on the Iniskin Peninsula at Mesozoic locality 20739.

Family OPPELIIDAE Bonarelli, 1894 

Subfamily OPPELIINAE Bonarelli, 1894

Genus OPPELIA Waagen, 1869 

Subgenus OXYCERITES Rollier, 1909

Oppelia (Oxycerites) aff. O. (O.) chinitnana Imlay

Plate 3, figures 1-5

One septate specimen differs from 0. (0.) chinitnana 

Imlay (1953, p. 74, pi. 26, figs. 3-6) from the Chinitna
18

148°30'

MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

148° 147°30' 147°

— 62°15'

61°45'

FIGURE 9.—Index map of listed Bathonian fossil localities in unnamed beds in the Talkeetna Mountains, Alaska. Numbers on map refer to

those given in table 4.

Formation in southern Alaska by having much weaker 

and more widely spaced sickle-shaped ribs on the upper 

parts of its flanks. Those ribs are stronger and appear 

earlier than in another specimen of O. (Oxycerites) from 

that formation (Imlay, 1953, p. 75. pi. 26, figs. 1, 2).

Figured specimen.—USNM 240710.

Occurrence.—Bowser Formation, 160-210 feet below 

top in the Tuxedni Bay area at USGS -Mesozoic locality 

22538.

Subgenus LIROXYITES Imlay, 1962 

Oppelia (Liroxyites) cf. O. (L.) kellumi Imlay

Plate 3, figure 6

One fragmentary ammonite differs from the most 

coarsely ribbed specimens of 0. (L.) kellumi Imlay 

(1962b, p. A-8, pi. 2, figs. 7, 10) at a comparable size

by its ribs being almost falcate and somewhat broader 

and stronger on the upper part of the flank. One spiral 

band occurs near the middle of the flank where the ribs 

bend rather abruptly. The keel is pinched at its base. The 

umbilicus is not preserved but must have been very 

small.

Figured specimen.—USNM 240711.

Occurrence.—Bowser Formation, 300 feet below top, 

at USGS Mesozoic locality 30257 in the Tuxedni Bay 

area.

Family SPHAEROCERATIDAE Buckman, 1920 

Genus CADOMITES Munier-Chalmas, 1892

Cadomites cf. C. deslongchampsi (d'Orbigny)

Plate 4, figures 1, 2, 4-12

cf. Ammonites deslongchampsi (d'Orbigny), 1846, Paleontologie 

Francaise, Terrains Jurassiques, v. 1, p. 405, pi. 138, figs. 1, 2.
SYSTEMATIC DESCRIPTIONS 19

152°55' 50' 152°35'

60°10'

60°05'

60°00'

FIGURE 10.—Index map of listed Bathonian fossil localities in the Bowser Formation on Chisik Island and on the peninsula between Tuxedni 

Bay and Cook Inlet, Alaska. Numbers on map refer to those given in table 4. Base of Chinitna Formation is indicated by dashed lines. 

Base of Bowser Formation is indicated by dotted lines.
20

153°25'

MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

20' 15' 10' 5' 150°00'

— 59°40'

FIGURE 11.—Index map of listed Bathonian fossil localities in the Bowser Formation on Iniskin Peninsula west of Cook Inlet, Alaska. 

Numbers on map refer to those given in table 4. Base on Chinitna Formation is indicated by dashed lines. Base of Bowser Formation 

is indicated by dotted lines.

cf. Cadomites cf. C. deslongchampsi (d'Orbigny). Arkell, 1952, Eng- cf. Cadomites deslongchampsi Defrance in Roman and Petourand,

lish Bathonian Ammonites, pt. 3, p. 79-81, text fig. 21, pi. 9, 1927, Travaux, Lyon Univ. Lab. Geol., pt. 11, mem. 9, p. 44, pi.

fig. 3a, b. 7, figs. 5a, b.
SYSTEMATIC DESCRIPTIONS 

TABLE 4.—Description of Bathonian fossil localities in southern Alaska

21

Number

on

figs. 

8-11

USGS

Mesozoic 

localities

Collector's

field

numbers

Collector, year of collection, description of 

locality, and strati graphic assignment

28524

28525

28527

F28

61-60

61 ABC 19

9

10

28699

28526

28692 

28698 

286%

28681

28682

28701

28683

62 AMK 48 

62 ABC 33

62 AMK 32 

62 AMK 46 

62 AMK 43 

62 AMK 52 

62 AMK 53

62 AMK 53A 

62 AMK 54A

E.M. MacKevett, D.L. Jones, and M. C. Blake, 1961. 

Wrangell Mountains. McCarthy (C-5) quad. SE. cor. 

sec. 8, T. 3 S., R. 16 E., Nizina Mountain 

Formation.

D. L. Jones, 1961. Wrangell Mountains. McCarthy 

(C-5) quad. SW. cor. sec. 9, T. 3 S., R. 16 E., 

Nizina Mountain Formation.

M. C. Blake, Jr., 1961. Wrangell Mountains. 

McCarthy (C-5) quad. SW. cor. NW% sec. 14, T. 3 

S., R. 15 E., Nizina Mountain Formation, lower 

part, a few hundred feet above the Lubbe Creek 

Formation.

R. W. Iml ay and E. M. MacKevett, 1962, Wrangell 

Mountains. Float from Nizina Mountain Formation 

at same place as locality 28527.

M. C. Blake Jr., 1961. Wrangell Mountains.

McCarthy (C-5) quad. SW%NE%NE% sec. 22, T. 3 S., 

R. 15 E., Nizina Mountain Formation about 500 ft 

above the Lubbe Creek Formation.

E. M. MacKevett, 1962. Wrangell Mountains. 

McCarthy (C-5) quad. West-central part of NE%SW% 

sec. 24, T. 3 S., R. 15 E. Float from Nizina 

Mountain Formation, probably obtained below middle,

R. W. Iml ay, 1962. Wrangell Mountains. McCarthy 

(C-5) quad. SE%NW%SW% sec. 24, T. 3 S., R. 15 E., 

Nizina Mountain Formation, float from lower part 

probably about 300 ft above base.

E. M. MacKevett, 1962. Wrangell Mountains. 

McCarthy (C-5) quad. NE. cor. SW%SW% sec. 24, T. 3 

S., R. 15 E., float from Nizina Mountain 

Formation, probably from lower part.

R. W. Iml ay, 1962. Wrangell Mountains. McCarthy 

(C-5) quad. Near creek in SE%SWJ$NW% sec. 20 T. 3 

S., R. 16 E., Nizina Mountain Formation, probably 

middle part.

R. W. Imlay, 1962. Wrangell Mountains. McCarthy 

(C-5) quad. Near creek in center SE%NW% sec. 20, 

T. 3 S., R. 16 E., Nizina Mountain Formation, 

mostly float.

E. M. MacKevett, 1962. Wrangell Mountains. About 

500 ft west of Mesozoic loc. 28682.

E. M. MacKevett, 1962. Wrangell Mountains. 

McCarthy C-5 quad. Near creek in center 

sec. 20, T. 3 S., R. 16 E., Nizina Mountain 

Formation, near base.
22 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

TABLE 4.—Description of Bathonian fossil localities in southern Alaska—Continued

Number

on

figs.

8-11

USGS

Mesozoic

localities

Collector's

field

numbers

Collector, year of collection, description of

locality, and stratigraphic assignment

11

12

28691

27515

62 AMK 28

RAL 115

13 24822 53A6 216

14 24115 52aGzl52

15 24825 53AFyl4

16 24116 52A6zl54

16

16

16

24117

24118

30286

52AGzl54A

52A6zl55

72ADtl5-l

E. M. MacKevett, 1962. Wrangell Mountains. 

McCarthy (C-5) quad. South-central part 

sec. 4, T. 4 S., R. 15 E., Nizina Mountain 

Formation, float from near base.

R. A. Lyon, 1959. Nelchina area. Talkeetna 

Mountains (A-2) quad. Lat 62oiO'36"N., long 

147040 '09" W. South of Little Oshetna River at 

altitude of 4,800 ft. Tuxedni Group, upper part. 

Conglomerate and sandstone 35-55 ft below base of 

Chinitna Formation.

Arthur Grantz and L. F. Fay, 1953, Nelchina area. 

Talkeetna Mountains (A-2) quad. Lat 

62oio'21"N., long 147°42'25"W. South of 

Little Oshetna River at altitude of 4,500 ft 

Tuxedni Group, upper part. From sandstone 325 ft 

below base of Chinitna Formation.

Arthur Grantz, R. D. Hoare, and R. W. Imlay, 1952. 

Nelchina area. Talkeetna Mountains (A-2) quad. 

Lat 620Q7 '33"N., long 147040'20"W., North fork 

of upper part of Little Nelchina River. Tuxedni 

Group, upper part, 400 ft below base of Chinitna 

Formation.

L. F. Fay and Arthur Grantz, 1953. Nelchina area. 

Talkeetna Mountains (A-2) quad. Lat 

620Q7 '15"N., long 147041 '29"W. North fork of 

upper part of Little Nelchina River. Tuxedni 

Group, upper part, about 400 ft below base of 

Chinitna Formation.

Arthur Grantz, R. D. Hoare and R. W. Imlay, 1952. 

Nelchina area. Talkeetna Mountains (A-2) quad. 

Lat 620 07'15"N., long 147° 42' 02"W. North 

side of north fork of upper part of little 

Nelchina River. Tuxedni Group, upper part, 115 ft 

below base of Chinitna Formation.

Arthur Grantz, R. D. Hoare, and R. W. Imlay, 1952. 

Same description as Mesozoic loc. 24116 except 

for location on south side of stream.

Arthur Grantz, 1952. Nelchina area. Talkeetna 

Mountains (A-2) quad., about 0.18 mile farther 

upstream than Mesozoic loc. 24116. Tuxedni Group, 

upper part, about 75 ft below base of Chinitna 

Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman, 1972. 

Nelchina area. Talkeetna Mountains (A-2) quad. 

On Cardioceras Creek in SW%SW^ sec. 31, T. 24 N., 

R. 10 E. Probably same place as Mesozoic loc. 

24118. Tuxedni Group, upper part. Graywacke and 

sandstone about 75 ft below base of Chinitna 

Formation.
SYSTEMATIC DESCRIPTIONS 

TABLE 4.—Description ofBathonian fossil localities in southern A laska—Continued

23

Number

on

figs.

8-11

USGS

Mesozoic

localities

Collector' s

field

numbers

Collector, year of collection, description of

locality, and stratigraphic assignment

16 30287 72ADtl5-2

16 30288 72ADtl5-3

16 30289 72ADtl6-l

16 30290 72ADtl6-2

17 30274 72ADtll-l

17 30275 72ADtll-2

17

17

17

30276

30276

30277

2ADtll-3

72ADtll-3

72ADtll-4

R. L. Detterman, R. W. Iml ay, and Don Hartman, 

1972. Same location as Mesozoic loc. 30286. 

Tuxedni Group, upper part. Graywacke and brown 

siltstone containing limy concretions about 100 ft 

below base of Chinitna Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman, 

1972. Tuxedni Group, upper part. Same location 

as Mesozoic loc. 30286. In siltstone containing 

limy concretions about 115 ft below base of 

Chinitna Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman, 

1972. Nelchina area. Talkeetna Mountains (A-2) 

quad. On south side of Cardioceras Creek directly 

across river from Mesozoic loc. 30288. Near 

southern boundary of south-central part of SWV>W% 

sec. 31, T. 24 N, R. 10 E. Tuxedni Group, upper 

part. Massive graywacke about 165 ft below base 

of Chinitna Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman, 

1972. Nelchina area. Talkeetna Mountains (A-2) 

quad. Near Mesozoic loc. 30289 but about 50 ft 

higher stratigraphically. Tuxedni Group, upper 

part. Siltstone 165 ft below base of Chinitna 

Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman, 

1972. Boulder Creek area. Talkeetna Mountains. 

Anchorage (D-3) quad. On ridge trending northwest 

from peak that is 1.2 miles S. 350 w. of VABM 

Snag near center of NW%SE% sec. 26, T. 22 N., R. 7 

E., Tuxedni Group, upper part. From base of 150 

ft of volcanic graywacke underlying basal 

conglomerate of Chinitna Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman, 1972. 

Boulder Creek area in Talkeetna Mountains. Same 

location as Mesozoic loc. 30274 but from 170-215 

ft below base of Chinitna Formation in gray 

siltstone bearing limy concretions.

R. L. Detterman, R. W. Imlay, and Don Hartman,

1972. Same description as Mesozoic loc. 30275 but 

from 255 to 295 ft below base of Chinitna 

Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman,

1972. Same description as Mesozoic loc. 30275 but 

from 255 to 295 ft below base of Chinitna 

Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman,

1972. Same description as Mesozoic loc. 30275 but 

from 293-375 ft below base of Chinitna Formation.
24 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

TABLE 4.—Description ofBathonian fossil localities in southern Alaska—Continued

Number

on

figs.

8-11

USGS

Mesozoic

localities

Collector's

field

numbers

Collector, year of collection, description of

locality, and stratigraphic assignment

17

17

17

17

17

17

17

17

17

18

30278

30279

30574

30575

30576

30577

30578

30579

30292

72ADtll-5 

72ADtll-6

74AI2 

74AI3

74AI4 

74AI5

74AI6 

74AI7 

RAL65 

72ADt 18

19 8573 13AMa 22

20 30271 72ADtlO-l

R. L. Detterman, R. W. Iml ay, and Don Hartman, 

1972. Same description as Mesozoic loc. 30275 but 

from 375 to 405 ft below base of Chinitna 

Formation in brown siltstone.

R. L. Detterman, R. W. Imlay, and Don Hartman, 1972. 

Same description as Mesozoic loc. 30275 but from 

405 to 475 ft below base of Chinitna Formation in 

graywacke.

R. W. Imlay and Jordan Pflaker, 1974. 

description as Mesozoic loc. 30275.

Same

R. W. Imlay and Jordan Pflaker, 1974. Same 

description as Mesozoic loc. 30275 but from 215 to 

260 ft below base of Chinitna Formation.

R. W. Imlay and Jordan Pflaker, 1974. Same 

description as Mesozoic loc. 30276, but most 

fossils are from upper 40 ft.

R. W. Imlay and Jordan Pflaker, 1974. Same 

description as Mesozoic loc. 30277, but most 

fossils are from upper 40 ft.

R. W. Imlay and Jordan Pflaker, 1974. Same 

description as Mesozoic loc. 30278.

R. W. Imlay and Jordan Pflaker, 1974. Same 

description as Mesozoic loc. 30279.

R. A. Lyons, I960?. On same ridge and same sequence 

as USGS Mesozoic Iocs. 30275-30279.

R. W. Imlay and Don Hartman, 1972. Boulder Creek 

area in Talkeetna Mountains. Anchorage (D-4) 

quad. On east side of tributary of Boulder Creek, 

5.2 miles N. 17o E. of junction of main creek 

with East Boulder Creek in south-central part of 

NW% sec. 35 T. 22 N., R. 7 E. Tuxedni Group, 

upper part. In siltstone and some interbedded 

graywacke lying at least 150 ft below base of 

Chinitna Formation.

Martin, G. C., 1913. Boulder Creek area in 

Talkeetna Mountains. Anchorage (D-4) quad. 

South-central part of NW% sec. 10, T. 21 N., R. 7 

E., at altitude of 3,400 ft on north side of knob, 

1 mile northwest of Boulder Creek and 3 miles N. 

11° E. of mouth of East Boulder Creek. Tuxedni 

Group, upper part, underlying Chinitna Formation.

R. L. Detterman, R. W. Imlay, and Don Hartman, 

1972. Boulder Creek area in Talkeetna Mountains. 

Anchorage (D-4) quad. In gully 2.6 miles N. 7o 

E. of junction of Boulder and East Boulder Creeks 

in west-central part of SW% sec. 10, T. 21 N., R. 

6 E. Tuxedni Group, upper part. Siltstonebearing cannonball concretions beneath Tertiary 

lava flows.
SYSTEMATIC DESCRIPTIONS 

TABLE 4 .—Description ofBathonian fossil localities in southern Alaska—Continued

25

Number

on

figs. 

8-11

USGS

Mesozoic

localities

Collector's

field

numbers

Collector, year of collection, description of

locality, and stratigraphic assignment

20

20

21

30272

30273

3014

72ADtlO-2

72ADUO-3

918

R. L. Detterman, R. W. Imlay, and Don Hartman, 

1972. Same place as Mesozoic loc. 30271, but 

about 30 ft lower strati graphically.

R. L. Detterman, R. W. Imlay, and Don Hartman, 

1972. Tuxedni Group, upper part. Float in gulley 

about 1,000 ft north of Mesozoic loc. 30271 in NW. 

cor. SW^ sec. 10, T. 21 N., R. 6 E.

T. W. Stanton, 1904. North side of Cook Inlet in 

Tuxedni Bay area at north end of Chisik Island; 

Kenai (A-8) quad. 1.25 miles S. 8lo E. of 

Fossil Point in sec. 19, T. 1 N., R. 19 W. Bowser 

Formation 1 ft below top, just below conglomerate 

at base of Chinitna Formation.

21

22

21272

30263

48AI 68

72ADt 8

23

24

30262

30257

72ADt 7

72ADt3

25 30261 72ADt6A

26 21284 48 A184

27 21283 48AI 82

D. J. Miller and R. W. Imlay, 1948. Tuxedni Bay 

area. Kenai (A-8) quad. Same place as Mesozoic 

loc. 3014.

R. W. Imlay and R. L. Detterman, 1972. Tuxedni Bay 

area. Kenai (A-8) quad. 1.4 miles S. 40o w. of 

mouth of small stream entering Tuxedni Channel 

from southwest opposite Chisik Island. 

South-central part of NE^ sec. 10, T. 1 S., R. 20 

W. Bowser Formation 100 ft below top in siltstone 

containing sandstone interbeds.

R. L. Detterman, and R. W. Imlay, 1972. Tuxedni Bay 

area. Kenai (A-8) quad. Near center SW^NE^ sec. 

10, T. 1 S., R. 20 W. Bowser Formation about 300 

ft below top.

R. L. Detterman and R. W. Imlay, 1972. Tuxedni Bay 

area. Kenai (A-8) quad. SW. cor. NE* sec. 10, T. 

1 S., R. 20 W., about 1.6 miles S. 43o w. of 

mouth of stream. Bowser Formation about 300 ft 

below top in brownish siltstone.

R. L. Detterman and R. W. Imlay, 1972. Tuxedni Bay 

area. Kenai (A-8) quad. SW. corn. SE^NE^ sec. 10, 

T. 1 S., R. 20 W., 1.6 miles S. 38o w. of mouth 

of stream. Bowser Formation about 150 ft below 

top in brownish siltstone.

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay 

area. Kenai (A-8) quad., 4.1 miles S. 12o w. of 

Fossil Point in NE^NW%SE% sec. 10, T. 1 S., R. 20 

W. Bowser Formation 900-950 ft above base and 

300-350 ft below top in brownish siltstone.

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay 

area. Kenai (A-8) quad. First outcrop above 

mouth of stream entering Bear Creek from southeast 

4.2 miles S. 20o w. of Fossil Point, slightly 

south of center of NE%SE^ sec. 9, T. 1 S., R. 20 

W. Bowser Formation about 500 ft above base and 

750 ft below top in gray siltstone.
26 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

TABLE 4.—Description of Bathonian fossil localities in southern Alaska—Continued

Number

on

figs. 

8-11

USGS

Mesozoic 

localities

Collector's

field

numbers

Collector, year of collection, description of 

locality, and strati graphic assignment

28 30258 72ADt 4

29 22711 51AGzl42

R. W. Imlay and D. J. Miller, 1948. Tuxedni Bay 

area. Kenai (A-8) quad., 2.1 miles S. 40o w. O f 

mouth of small stream entering Tuxedni Channel 

from southwest. North-central part of NW%SE%SW% 

sec. 10, T. 1 S., R. 20 W. Bowser Formation 50-75 

ft below top in brownish siltstone.

Arthur Grantz, 1951. Tuxedni Bay area. Kenai 

(A-8) quad., 0.38 mile above mouth of tributary 

entering Bear Creek from southeast. Near center 

SW%SE% sec. 9., T. 1 S., R. 20 W. Bowser Formation 

about 100 ft above base.

29 22712 51AGzl43

30 22713 5Agzl44

31 22714 51AGzl45

33

22698

22699

51AGzll5

51AGzll6

34 22700 51AGzll7

35 21311 48AI16

Arthur Grantz, 1951. Tuxedni Bay area. Kenai 

(A-8) quad., 0.45 mile above mouth of tributary 

entering Bear Creek from southeast. East-central 

part SWfe% sec. 9, T. 1 S., R. 20 W., Bowser 

Formation about 150 ft above base.

Arthur Grantz, 1951. Tuxedni Bay area. Kenai 

(A-8) quad., 0.62 mile above mouth of tributary 

entering Bear Creek from southeast. East central 

part SE%SW% sec. 9, T. 1 S., R. 20 W. Bowser 

Formation about 750 ft above base and 500 ft below 

top.

Arthur Grantz, 1951. Tuxedni Bay area. Kenai 

(A-8) quad., 0.67 mile above mouth of same 

tributary described under Mesozoic loc. 22711. 

SW. cor. SEhSEh sec. 9, T. 1 S., R. 20 W. Bowser 

Formation about 900 ft above base and 350 ft below 

top.

Arthur Grantz, 1951. Lake Hickerson area. Seldovia 

(D-8) quad., on ridge 1.5 miles N. 39o 50'E. of 

head of Lake Hickerson. NW. cor. SW^ sec. 28, T. 

2 S., R. 21 W., Bowser Formation 690 ft above base 

and 1,010 ft below top.

Arthur Grantz, 1951. Lake Hickerson area. Seldovia 

(D-8) quad., on ridge 1.62 miles N. 51° E. of 

head of Lake Hickerson. East-central part NE%SW% 

SW% sec. 28, T. 2 S., R. 21 W., Bowser Formation 

360-399 ft below top.

Arthur Grantz, 1951. Lake Hickerson area. Seldovia 

(D-8) quad., on ridge 1.7 miles N. 5lo E. of 

head of Lake Hickerson. SW. cor. SP$SW% sec. 28, 

T. 2 S., R. 21 W., Bowser Formation about 240 ft 

below top.

R. W. Imlay and D. J. Miller, 1948. Iniskin 

Peninsula. Iliamna (D-l) quad., 1.92 miles N. 

89o E. of dock at mouth of Fitz Creek. West 

central part NWW* sec. 28, T. 4 S., R. 22 W. 

Bowser Formation 550-600 ft below top and 920-970 

ft above base.
SYSTEMATIC DESCRIPTIONS 

TABLE 4.—Description ofBathonian fossil localities in southern Alaska—Continued

27

Number

on

figs.

8-11

US6S

Mesozoic

localities

Collector's

field

numbers

Collector,

locality

year of collection,

, and strati graphic

description of

assignment

35 21312 48AI17

35

36

22436

21308

50AHa32

48 All

36 21309 48AI2

37 21319 48AI36

38 20011 44AWw

39 27100 58ADt3

40 20005 44AWwF72

40 30265 72ADt 9

R. W. Iml ay and D. J. Miller, 1948. Iniskin 

Peninsula. Iliamna (D-l) quad., 1.9 miles N. 

860 E. of dock at mouth of Fitz Creek near 

center NW%NW% sec. 28, T. 4 S., R. 22 W. Bowser 

Formation about 70 ft higher than Mesozoic loc. 

21311.

J. K. Hartsock, 1950. Iniskin Peninsula. Same

description as Mesozoic loc. 21312. Bowser

Formation about 380 ft above base.

R. W. Iml ay and D. J. Miller, 1948. Iniskin 

Peninsula. Iliamna (D-l) quad., 2.4 miles S. 

840 w. of dock at mouth of Fitz Creek. SW. cor. 

SE^NWi* of sec. 27, T. 4 S., R. 23 W. Bowser 

Formation about 380 ft above base and 1,140 ft 

below top.

R. W. Iml ay and D. J. Miller, 1948. Iniskin 

Peninsula. Iliamna (D-l) quad., 2.3 miles S. 

860 w. of dock at mouth of Fitz Creek. 

West-central part SE^NW% sec. 27, T. 4 S., R. 23 

W. Bowser Formation. Float about 100 ft lower in 

gulch than at Mesozoic loc. 21308.

R. W. Iml ay and D. J. Miller, 1948. Iniskin 

Peninsula. Iliamna (D-l) quad., 0.65 mile S. 

35o E. of Tonnie Peak. Near center NE^NW^ sec. 

7, T. 5 S., R. 23 W. Bowser Formation about 410 ft 

below top.

Helmuth Wedow and L. B. Kellum, 1944. Iniskin 

Peninsula. Iliamna (D-l) quad., 1 mile up Tonnie 

Creek from trail just above crest of third falls. 

Near center NE^NW^ sec. 7, T. 5 S., R. 23 W., 

Bowser Formation about 840 ft above base and 990 

ft below top.

R. 1. Detterman, 1958. Iniskin Peninsula. Iliamna 

(D-l) quad. On Tonnie Creek, 0.94 mile N. 61o 

W. of I. B. A. No. 1 well. Near center of NE% 

sec. 7, T. 5 S., R. 23 W. Bowser Formation about 

90 ft above base.

L. B. Kellum, 1944. Iniskin Peninsula. Iliamna 

(D-l) quad. Southwest side of Tonnie Creek about 

700 ft upstream from lower cascade and 0.85 mile 

S. 56 o E. of Tonnie Peak. North central part 

NE% sec. 7. T. 5 S., R. 23 W. Bowser Formation 125 

to 150 ft above base.

R. W. Iml ay and R. L. Detterman, 1972. Iniskin 

Peninsula. Iliamna (D-l) quad. On Tonnie Creek 

0.6 mile S. 40o E. of Tonnie Peak. West-central 

part of NW^NE^ sec. 7, T. 5 S., R. 23 W. B9wser 

Formation about 300 ft above base in brownish 

siltstone.
28 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

TABLE 4.—Description of Bathonian fossil localities in southern Alaska—Continued

Number 

on

figs. 

8-11

USGS

Mesozoic 

localities

Collector's

field

numbers

Collector, year of collection, description of 

locality, and strati graphic assignment

41 22549 50AHa 63

42

43

44

11038

20754

20745

21AB46

46AKr 177

46AKr 155

45 20746 46AKrl56

46

47

48

11042

20748

21320

46AKrl58

48 A149

49 20751 46AKrl64

49

50

20752

20743

46AKrl66

46AKrl52

J. K. Hartsock, 1950. Iniskin Peninsula. Iliamna 

(C-l) quad., 4.08 miles N. 4lo f. O f Front 

Mountain on tributary to Brown Creek. NE. cor. 

SW% sec. 14, T. 5 S., R. 23 W. Bowser Formation 

280-380 ft below top.

A. A. Baker, 1921. Iniskin Peninsula. Iliamna 

(C-l) quad., about 2.2 miles N. 80 E. of Front 

Mountain. South-central part SE% sec. 20, T. 5 

S., R. 23 W. Bowser Formation 700-800 ft below top.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad., 2.0 miles N. 32ow. Of Front 

Mountain. North-central part of NW% sec. 30, T. 5 

S., R. 23 W. Bowser Formation 300 ft above base.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad. On Edelman Creek, 1.5 miles N 22o 

W. of Front Mountain. North-central part of NE% 

SE% sec. 30, T. 5 S., R. 23 W., Bowser Formation 

about 1,050 ft above base and 780 ft below top.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad. On Edelman Creek, 1.4 miles N. 220 

W. of Front Mountain. NE. cor. SE% sec. 30, T. 5 

S., R. 23 W. Bowser Formation about 1,200 ft above 

base and 630 ft below top.

A. A. Baker, 1921. Iniskin Peninsula. Iliamna 

(C-l) quad., 1.4 miles N. 150 w. of Front 

Mountain. NW^NW^SW% sec. 29, T. 5 S., R. 23 W. 

Bowser Formation about 610 ft below top.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad. Near Center NW%SW^ sec. 29, T. 5 S., 

R. 23 W. Bowser Formation 230-280 ft below top.

R. W. Iml ay and D. J. Miller, 1948. Iniskin

Peninsula. Illiamna (C-l) quad., 4.7 miles (7.5 

km) S. 150 E. of Tonnie Peak; SE^NWW* sec. 29, 

T. 5 S., R. 23 W. Bowser Formation 180-230 ft 

below top.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad., 1.4 miles N. 40° W. of Front 

Mountain; near center SE^SW^ sec. 30, T. 5 S., R 

23 W. Bowser Formation about 600 ft (183 m) above 

base and 1,230 ft below top.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad. Nearly same location as Mesozoic loc. 

20751. Bowser Formation 650-680 ft above base.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad., 1.8 miles N. 85o w. of Front 

Mountain; near center SW% sec. 36, T. 5 S., R. 24 

W. Bowser Formation 500-600 ft above base.
SYSTEMATIC DESCRIPTIONS 

TABLE 4.—Description of Bathonian fossil localities in southern Alaska—Continued

29

Number 

on

figs. 

8-11

USGS

Mesozoic 

localities

Collector 1 s

field

numbers

Collector, year of collection, description of 

locality, and stratigraphic assignment

51

52

20744

22536

46AKH54

50AHi5b

52

53

54

55

56

22538

22553

20736

20739

3038

50AHi 5a

50AHi6

46AMd32

46AKH34

933b

57

58

20764

22416

46AKrl87

50AHalO

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad., 2.7 miles S. 84o w. of Front 

Mountain. NE. cor. NWW% sec. 2, T. 6 S., R. 24 

W. Bowser Formation 500-600 ft above base.

D. M. Hill and R. W. Juhle, 1950. Iniskin 

Peninsula. Iliamna (C-l) quad. On Right Arm 

Iniskin Bay. About 4.25 miles N. 58o w. O f 

Front Mountain. South-central part of SE% sec. 

22. T. 5 S., R. 24 W. Bowser Formation 60-110 ft 

below top and 1,650-1,700 ft above base.

David Hill, 1950. Iniskin Peninsula. Iliamna

(C-l) quad. Same location as Mesozoic loc. 22536, 

but about 100 ft lower stratigraphically.

D. M. Hill, 1950. Iniskin Peninsula. Iliamna 

(C-l) quad. Right Arm of Iniskin Bay. North 

central part of NE%NE% sec. 27, T. 5 S., R. 24 W. 

Bowser Formation about 360 ft below top.

J. P. Minard, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad. East-central part of NE% sec. 28, T. 

5 S., R. 24 W. Bowser Formation 500-600 ft above 

base and 1,160-1,260 ft below top.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-l) quad., 4.65 miles N. 72o w. of Front 

Mountain. NW. cor. NE%SE** sec. 28, T. 5 S., R. 24 

W. Bowser Formation about 1,110 ft above base and 

640 ft below top.

T. W. Stanton and G. C. Martin, 1904. Iniskin 

Peninsula. Iliamna (C-2) quad., 5.25 miles N. 

74o w. of Front Mountain. Shore of Iniskin Bay 

at entrance to Right Arm. Probably south-central 

part NW% sec. 28, T. 5 S., R. 24 W. Bowser 

Formation, probably from middle part.

C. E. Kirschner, 1946. Iniskin Peninsula. Iliamna 

(C-2) quad., 5 miles N. 83o W. of Front 

Mountain. SE^NW% sec. 33, T. 5 S., R. 24 W. Float 

from Bowser Formation.

R. D. Hoare, 1950. Iniskin Peninsula. Iliamna 

(C-2) quad. East side of Iniskin Bay. SW^SW% 

sec. 4, T. 6 S., R. 24 W. Near top of Bowser 

Formation.

cf. Cadomites deslongchampi (d'Orbigny). Sturani, 1964, Univ. Padova 1st. Geolgia Mineralogia Mem., v. 24, p. 19, 20, pi. 2, fig. 

7a, b; 1966, Soc. Paleont. Italiano Boll., v. 5, p. 28, pi. 6, fig. 1.

cf. Cadomites deslongchampsi (d'Orbigny). Hahn, 1971, Geol. Jahrb.

Landesamt Baden-Wurttemberg, v. 13, Abt. 13, pi. 9, fig. 16.

This species in the Talkeetna Mountains is represented

by three specimens of which the smallest is attached to

an umbilical plug of a much larger specimen that is septate except for its outermost half whorl. The third specimen consists of the adoral part of an adult body chamber. In addition, the species may be represented by one 

laterally crushed external mold from the Wrangell Mountains.
30 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

These specimens have a coronate whorl section and a 

broad, flattened venter. Their primary ribs are sharp, 

fairly widely spaced; they become less widely spaced 

during growth, curve gently forward on the umbilical 

wall, and generally terminate in prominent nodes. The 

secondary ribs on the septate whorls are fine, closely 

spaced and average about four for each primary rib, but 

one of these four may arise freely between nodes instead 

of being attached to a node. Adorally on the body chamber the secondary ribs become fewer with respect to the 

primary ribs, and near the aperture number only two for 

each primary rib. The nodes also become variable in 

strength adorally on the body chamber.

The adoral end of the body chamber is imperfectly preserved but is marked by two single ribs that are separated and followed by broad shallow furrows.

On the largest septate specimen at a diameter of about 

55 mm, the whorl height is 21 mm and the whorl thickness is 35 mm. The ratio of whorl height to thickness is 

about 60 percent, both on the septate whorl and on the 

adult body chamber.

These Alaskan specimens of Cadomites are similar to 

C. deslongchampsi (d'Orbigny) in whorl shape and ribbing. They differ mainly by having sparser ribbing on 

their adult body chamber. That species in Europe ranges 

from the highest Bajocian zone of Parkinsonia parkinsoni into the lowest Bathonian Zigzagiceras zigzag zone 

(Westermann and Rioult, 1975, p. 876) and probably is 

most common in the highest Bajocian (Hahn, 1971, p. 

Ill; Kopik, 1974, p. 19).

Figured specimens.— USNM 240712-240715.

Occurrence.—Unnamed beds in the Talkeetna Mountains at USGS Mesozoic localities 30277, 30576, 30577 

(contains part of same ammonite as at locality 30277). 

Nizina Mountain Formation in the Wrangell Mountains 

at Mesozoic locality 28682.

Cadomites cf. C. rectelobatus (v. Hauer)

Plate 4, figure 3

One external mold of an outer whorl bears somewhat 

denser secondary ribs than the specimens herein compared with C. deslongchampsi (d'Orbigny) and is more 

similar in that respect to forms illustrated as C. rectelobatus (v. Hauer) by Sturani (1964, p. 22, pi. 2, figs. 6, 8; 

1966, p. 29, pi. 13, figs, la, b); as C. daubenyi (Gemmellaro) in Buckman (1922, pi. 311); and as C. rectelobatus 

(v. Hauer) in Hahn (1971, p. 112, pi. 9, fig. 9a, b). It also 

resembles C. exstinctus (Quenstedt) (1887, p. 630, pi. 

74, figs. 30, 32-34; Hahn, 1971, p. 110, pi. 9, figs. 10- 

13) in density of ribbing.

Of these species, C. exstinctus is reported to range 

from the uppermost upper Bajocian zone of Parkinsonia

parkinsoni into the lower part of the lower Bathonian 

zone of Zigzagiceras zigzag (Hahn, 1971, p. 59, 111) and 

is most common in the lower Bathonian. C. rectelobatus 

ranges from the uppermost Bajocian through most of the 

Bathonian but is most common in the lower Bathonian 

(Arkell, 1958, p. 232; Sturani, 1966, p. 29; Kopik, 1974, 

p. 21, 22).

Figured specimen.—USNM 240716.

Occurrence.—Nizina Mountain Formation at USGS 

Mesozoic locality 28682 in the Wrangell Mountains.

Family MACROCEPHALITIDAE Buckman, 1922 

Genus XENOCEPHALITES Spath, 1928

Xenocephalites cf. X. hebetus Imlay

Plate 2, figures 1-9

Four specimens from the Bowser Formation bear ribbing that is nearly identical with that on the type specimens of X. hebetus Imlay (1953, p. 78, pi. 29, figs. 6-8, 

11) from the Chinitna Formation of southern Alaska. 

They differ mainly by having moderately compressed to 

stout rather than globose whorls. Also, the body chamber, represented by at least three-fourths of a whorl, 

does not develop quite as strong ribbing. On the largest 

fragment of a body chamber (pi. 2, figs. 8, 9) the whorl 

section is broad and depressed, the ribbing high, sharp, 

and sparse, and the body chamber itself is markedly retracted from the inner tightly coiled septate whorls. 

These features are all similar to those on the adoral part 

of the body chamber of X. hebetus Imlay (1953, pi. 29, 

figs. 6, 7) and on the South American species, X. neuquensis (Stehn) (1924, p. 86, text fig. 11 on p. 87, pi. 1, 

fig. 3).

Figured specimens.—USNM 240717-240720.

Occurrences.—Bowser Formation, upper part, at 

USGS Mesozoic localities 21312, 22436, and 22713 west 

of Cook Inlet.

Genus CHINITNITES Imlay, 1975 

Chinitnites parviformis (Imlay)

Kheraicerasl parvif&rme Imlay, 1953, U.S. Geol. Survey Prof. Paper

249-B, p. 82, pi. 33, figs. 3, 6, 8-10, 12. 

Chinitnites parviformis (Imlay), 1975, U.S. Geol. Survey Prof. Paper

836, p. 23, pi. 3, figs. 1, 2, 5-7.

This species is represented in the Bowser Formation 

by five specimens whose characteristics have been summarized recently (Imlay, 1975, p. 23).

Types.— Holotype, USNM 108052; paratypes, USNM 

108053a-c; hypotypes, USNM 180734 and 180735.

Occurrences. —Bowser Formation, upper part at USGS 

Mesozoic localities 11038, 11042, and 22436. Chinitna 

Formation, lower part at Mesozoic localities 21334 and 

22427.
SYSTEMATIC DESCRIPTIONS 31

Family KOSMOCERATIDAE Haug, 1887 

Genus KEPPLERITES Neumayr and Uhlig, 1892

Kepplerites sp. A

Plate 1, figures 1, 2, 4, 5

cf. Kepplerites tychonis Ravn, Imlay, 1953, U.S. Geol. Survey Prof.

Paper 249-B, p. 96, pi. 48, figs. 14-17. 

cf. Kepplerites chisikensis Imlay, 1975, U.S. Geol. Survey Prof. Paper

836, p. 15, pi. 1, figs. 1-5.

This species is represented by two fragmentary immature, septate specimens. The smallest specimen is undeformed and consists of two whorls. Of these, the innermost whorl at a diameter of 15 mm has a round whorl 

section that is as wide as it is high, a nearly evenly 

rounded venter that is not distinctly flattened, and a low 

vertical umbilical wall that rounds evenly into the flanks. 

Its primary ribs are moderately low, trend radially on 

the umbilical wall, curve strongly forward on the lower 

fifth of the flanks and then pass into two or three weaker 

flexuous secondary ribs. Between rib bundles occur one 

or two secondary ribs that arise freely low on the flanks. 

All secondary ribs incline gently forward on the flanks, 

arch forward on the venter, and are strongest on the 

venter.

The next larger whorl of the smallest specimen has a 

whorl height of 21 mm, an estimated diameter of 18 mm, 

and an umbilical width of 5 mm. Its umbilical wall is 

fairly low, vertical, and rounds rather abruptly into the 

flanks. Its flanks are flattened below and round evenly 

above into a moderately broad rounded venter. Its primary ribs are weak on the umbilical wall but become 

higher and sharper ventrally. They curve backward on 

the umbilical wall, curve sharply forward low on the 

flanks, and pass into two to three somewhat weaker secondary ribs at about one-third of the height of the flanks. 

Other secondary ribs arise near the zone of furcation on 

the flanks, resulting in three to four secondary ribs for 

each primary rib. All secondary ribs incline forward on 

the flanks and become slightly stronger ventrally.

The largest fragment is much worn and represents a 

slightly later growth stage than shown on the small specimen just described. Most of it appears, however, to be 

essentially identical in umbilical width, flank shape, and 

rib characteristics. The adoral fifth of the specimen is 

nonseptate, retains very little shell material, is broken 

ventrally and bears long, weak primary ribs. Secondary 

ribs are barely visible at only one place.

This species, once compared with a finely ribbed species of Kepplerites from Greenland (Imlay, 1962a, p. C3; Ravn, 1911, p. 490, pi. 37, fig. 1), differs from most 

described species of Kepplerites by lacking a distinctly 

flattened venter. On the smallest specimen, however, 

the ventral ribs form a pattern suggestive of incipient

flattening. Also, the species greatly resembles K. chisikensis Imlay (1975, pi. 1, figs. 1-5), which occurs near 

the base of the Chinitna and Shelikof Formations, except 

for the absence of tubercles even on its inner whorls.

Figured specimens.— USNM 180716 and 240721.

Occurrence.—Bowser Formation at USGS Mesozoic 

locality 21319. The specimens were collected about 420 

feet below the top of the formation and 810 feet above 

the uppermost occurrence of Cranocephalites (Mesozoic 

locality 20751).

Kepplerites sp. B.

Plate 3, figure 9

This species is represented near the top of the Bowser 

Formation by one specimen that has a moderately stout 

adult body chamber and the crushed adoral end of the 

outermost septate whorl. The body chamber occupies 

half a whorl, terminates adorally in a broad, shallow, forwardly inclined constriction; has an ovate whorl section 

that is slightly wider than high; and retracts markedly 

from the inner septate whorls.

The ribbing on the flanks of the septate whorl is fine 

and dense. On the body chamber the primary ribs are 

narrow, incline slightly adapically on the umbilical wall, 

incline adorally on the lower third of the flanks, and terminate ventrally in weak tubercles from which pass bundles of three to four much weaker secondary ribs. Other 

ribs arise freely along the zone of tuberculation, resulting in the presence of four secondary ribs for each primary rib. All secondary ribs incline slightly adorally on 

the flanks and are eroded on the venter.

The body whorl of this species bears a general resemblance to that of Kepplerites mcevoyi (McLearn) (1928, 

p. 20, pi. 4, figs. 1, 2; Imlay, 1953, p. 97, pi. 51, figs. 3, 

5-8) but has much weaker tubercles, fewer secondary 

ribs, and a more strongly retracted body chamber. K. 

multus (McLearn) (1929, p. 7, pi. 3, fig. 2) has a more 

inflated whorl section, a higher umbilical wall, and 

stronger tubercles. K. chisikensis Imlay (1975, p. 15, pi. 

1, figs. 1-5) has a more compressed whorl section, finer, 

denser ribbing, and much weaker tubercles.

Figured specimen.—USNM 240722.

Occurrence.—Bowser Formation, 50-70 feet below 

top at USGS Mesozoic locality 30258 south of Tuxedni 

Bay.

Kepplerites sp. C.

Plate 1, figure 3

One nucleus of Kepplerites from the Bowser Formation has more evolute coiling and stronger ribbing than 

other specimens of Kepplerites found in that formation. 

It bears some resemblance to the innermost known whorls
32 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

of K. gitinsi (McLearn) as figured by Imlay (1953, pi. 52, 

figs. 1, 2).

Figured specimen.—USNM 240723.

Occurrence.—Bowser Formation, upper part, about 

100 feet below top, at USGS Mesozoic locality 30263 

south of Tuxedni Bay.

Family CARDIOCERATIDAE Siemiradzki, 1891 

Subfamily CADOCERATINAE Hyatt, 1900 

Genus CRANOCEPHALITES Spath, 1932

Cranocephalites costidensus (Imlay)

Plate 7, figures 1-12

Arctocephalites (Cranocephalites)costidensus Imlay, 1962a, U.S. Geol. 

Survey Prof. Paper 374-C, p. C-24, pi. 2, figs. 11-19.

Arctocephalites (Cranocephalites) costidensus Imlay. Frebold and Tipper, 1973, Canadian Jour. Earth Sci., v. 10, no. 7, p. 1115, pi. 2, 

fig. 2; pi. 4, fig. 2-7.

This species is represented in the U.S. Geological Survey collections by 108 specimens of which 15 are from 

west of Cook Inlet, 85 from the Talkeetna Mountains, 

and 8 from the Wrangell Mountains. It is characterized 

by having fine dense ribbing on its septate whorls and on 

most body chambers such as on the holotype (Imlay, 

1962a, pi. 2, figs. 14, 15). Some moderately stout to stout 

specimens (pi. 7, figs, 5, 8, 11; Imlay, 1962a, pi. 2, fig. 

19) have somewhat coarser ribs on their adult body 

chambers than those found on most specimens of the species.

Types.—Holotype, USNM 130745; paratypes, USNM 

130746, 130748, and 130749; hypotypes, USNM 240724- 

240728.

Occurrences.—Bowser Formation west of Cook Inlet 

at USGS Mesozoic localities 20754, 21283, 22698, and 

22712 and probably at Mesozoic localities 20736 and 20754. 

Unnamed beds in the Talkeetna Mountains at Mesozoic 

localities 8573, 24117, 27515, 30271, 30273, 30276^30278, 

30286^30290, and 30575^30579 and probably at Mesozoic localities 24822, 24825, 30279, and 30292. Nizina 

Mountain Formation in the Wrangell Mountains at Mesozoic localities 28681 and 28682, and probably at Mesozoic localities 28525 and 28699.

Cranocephalites alaskanus Imlay n. sp.

Plate 5, figure 1-5

Arctocephalites (Cranocephalites)pompeckji (Madsen) of Imlay, 1962a, 

U.S. Geol. Survey Prof. Paper 374^C, p. C-23, pi. 1, figs. 4, 

6, 8, 10 (not figs. 7, 9, 11-12).

Associated with Cranocephalites costidensus (Imlay) 

(1962a, p. C-24, pi. 2, figs. 11-19) in southern Alaska 

is a much less common species that has much higher and 

sparser ribs and fewer secondary ribs per primary rib. 

This species was formerly identified by Imlay (1962a, p. 

C-23) as C. pompeckji (Madsen) (1904, p. 189, pi. 8, 

figs. 5, 6a, b; Spath, 1932, p. 16, pi. 4, figs. 8-10, pi. 5,

figs. 6-8, pi. 13, figs, la, b; Donovan, 1953, p. 83, pi. 

17, figs. 2a, b, 3a, b). It differs, however, by having finer 

denser ribs on its septate whorls; lower, blunter, and 

sparser ribs on its adult body chamber; and by attaining 

a much smaller adult size. In these respects it is intermediate between C. pompeckji (Madsen) and C. indistinctus Callomon (1959, p. 510, pi. 17, figs. 3, 4, pi. 18, 

figs. 1, 2) from East Greenland.

Types. —Holotype, USNM 240729; paratypes, USNM 

130752 and 130753.

Occurrences.—Bowser Formation, lower two-fifths, 

west of Cook Inlet at USGS Mesozoic localities 21283 

and 22698 and possibly at Mesozoic localities 20754, 

21309, 22711, and 22712. Nizina Mountain Formation in 

the Wrangell Mountains at Mesozoic locality 28682 and 

possibly at Mesozoic localities 28525, 28527, 28681, and 

28698.

Cranocephalites cf. C. ignekensis Imlay

Plate 5, figures 9-11

Arctocephalites (Cranocephalites) pompeckji (Madsen) of Imlay, 1962a, 

U.S. Geol. Survey Prof. Paper 347-C, p. C-23, pi. 1, figs. 1, 

11-13 (not figs. 5-8, 10).

cf. Cranocephalites ignekensis Imlay, 1976, U.S. Geol. Survey Prof. 

Paper 854, p. 15, 16, pi. 2, figs. 1-9, 11, 12.

In southern Alaska only two ammonites similar to C. 

pompeckji (Madsen) have been found above the range of 

C. costidensus (Imlay). One of these (pi. 5, fig. 9), an 

external mold of the adoral part of a body chamber, bears 

coarse, fairly broad, forwardly inclined ribs of which 

about half bifurcate fairly low on the flanks and all cross 

the venter transversely without diminution in strength. 

The other specimen (pi. 5, figs. 10, 11; Imlay, 1962a, pi. 

1, figs. 9, 11-13) has identical coarse ribbing on its body 

chamber. It differs from some specimens, herein described as C. alaskanus Imlay n. sp., by attaining a 

larger adult size and by having slightly coarser ribbing 

on its adult body chamber. Compared with the holotype 

of C. pompeckji (Madsen, 1904, pi. 8, figs. 6a, b), it appears to have finer ribbing on the septate part of the 

adult body whorl, blunter ribbing on the nonseptate 

part, and a less strongly retracted body chamber.

These two specimens from southern Alaska are likewise similar to Cranocephalites ignekensis Imlay (1976, 

pi. 2, figs. 1-9, 11, 12) that occurs in northern Alaska 

just below beds containing Arctocephalites. They differ 

mainly by attaining a larger adult size, by having blunter 

and sparser ribbing on the adult body chamber, and by 

having a slightly more complicated suture line. They may 

be within the range of variation of that species.

Figured specimens.— USNM 130751 and 240730.

Occurrences.—Bowser Formation, near base of upper 

fourth, west of Cook Inlet at USGS Mesozoic locality
SYSTEMATIC DESCRIPTIONS 33

21284. Unnamed beds in the Talkeetna Mountains at 

Mesozoic locality 30275.

Cranocephalites globosus Imlay n. sp.

Plate 6, figures 1-3, 5, 6, 8-13

This species is represented by three specimens. It is 

characterized by a globose form; by much depressed 

whorls that are widest at about one-fourth of their height; 

by fairly coarse ribbing on its smallest whorls; by fine, 

sharp, fairly dense ribbing on its outer whorls; by a very 

narrow, funnel-shaped umbilicus on its septate whorls; 

and by a scaphitoid body chamber. Its umbilical wall is 

vertical basally but rounds fairly evenly into the flanks. 

Its adult body chamber represents about three-fifths of 

a whorl. The aperture is marked by a constriction that is 

followed by a swelling.

On septate whorls the primary ribs trend nearly radially and divide at about the top of the lower fourth of the 

flanks into two or three much weaker secondary ribs that 

cross the venter transversely or with a slight forward 

arching. Other secondary ribs arise freely near the zone 

of furcation, resulting in about three secondary ribs for 

each primary.

No ribbing is preserved on the adapical part of the 

body whorl. Near the aperture, however, are found several strong widely spaced primary ribs that are most 

prominent where the whorl section is widest and that 

fade out gradually ventrally. The midventral area near 

the aperture bears several patches of smooth shelly material.

This species resembles Cranocephalites costidensus 

(Imlay) (1962a, p. C-24, pi. 2, figs. 11-19) in the fineness of ribbing on its outer whorls. It differs, however, 

by being much more globose and by certain features of 

its primary ribs. Those ribs fork much lower on the 

flanks, are stronger relative to the secondary ribs, and 

are much more prominent near the adult aperture. Arctocephalites orientalis Krimholz (1939, p. 32, 59, pi. 2, 

figs. 5, 6) has similar fine ribbing but has a more compressed whorl section that is widest at about half of the 

whorl height.

Types.—Holotype, USNM 240731; paratypes, USNM 

240732 and 240733.

Occurrence.—Bowser Formation, 620 feet above base, 

at USGS Mesozoic locality 20751 on the Iniskin Peninsula; unnamed beds in the Talkeetna Mountains at Mesozoic localities 24116 and 24117.

Cranocephalites cf. C. vulgaris Spath

Plate 3, figures 7, 8, 10, 11

This species is represented by one undeformed internal mold of an adult body whorl. It has a compressed 

whorl section, a highly arched venter, flattened flanks, a

low nearly vertical umbilical wall that rounds rather abruptly into the flanks, and a contracted body chamber 

that occupies three-fifths of a whorl and is terminated by 

a shallow constriction.

The ribs on the septate part of the body whorl are 

sharp and fairly closely spaced. The primary ribs trend 

backward on the umbilical wall, curve forward on the 

lower third of the flanks, and give rise to pairs of slightly 

weaker secondary ribs. These secondary ribs incline forward on the flanks but cross the venter transversely.

On the body chamber are found long simple ribs that 

either bifurcate at about the top of the lower third of the 

flanks or alternate with one of two short intercalated 

ribs. The simple ribs on the lower third of the flanks are 

sharp, widely spaced, curve adapically at the umbilical 

edge, and curve adorally rather strongly on the flanks. 

All ribs incline forward on the upper two-thirds of the 

flanks, cross the venter transversely, become weaker 

and broader above the middle of the flanks, and almost 

fade out on the venter. This reduction in strength does 

not appear to be due to weathering or abrasion.

The specimen, at an estimated maximum diameter of 

90 mm, has a whorl height of 37 mm, a whorl thickness 

of 33 mm, and an umbilical width of 20 mm. About onethird of a whorl adapically, the same dimensions are 72, 

32, 28, and 13 mm.

This species is characterized by its compressed shape, 

by the presence of fine, sharp ribs on the septate part of 

the shell, and by the faintness of all ribs on the venter of 

the adult body chamber. The last feature distinguishes it 

from all other known species of Cranocephalites in Alaska 

but is fairly common in species of that genus in the Arctic 

region (Spath, 1932, p. 14; Voronets, 1962, pis. 5, 6). For 

example, the Alaskan species under discussion matches 

fairly well a compressed variant of C. vulgaris Spath 

(1932, pi. 5, figs, la, b) from East Greenland except for 

having somewhat weaker ribbing. It also greatly resembles the holotype of C. vulgaris Spath (1932, pi. 1, figs. 

4a, b) except for being more compressed.

Figured specimen.—USNM 240734.

Occurrence.—Unnamed beds in the Talkeetna Mountains at USGS Mesozoic locality 30275.

Cranocephalites sp. A.

Plate 5, figures 6-8

One worn adult specimen differs from the specimen 

herein figured (pi. 3, figs. 7, 8, 10, 11) as C. cf. C. vulgaris Spath by having a stouter whorl section and somewhat stronger primary ribs and by its secondary ribs 

arching adorally on the venter near the aperture.

Figured specimen.—USNM 240735.

Occurrence.—Bowser Formation at USGS Mesozoic 

locality 22436 on the Iniskin Peninsula.
34 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

Cranocephalites sp. B.

Plate 6, figures 4, 7

One undeformed body whorl shows most of the septate 

part and a little of the adoral end of the body chamber. 

This whorl is ovate and slightly wider than it is high. Its 

aperture is marked on the flanks by a deep constriction. 

Its umbilicus is extremely narrow but widens appreciably near the aperture as the body chamber contracts. 

Apparently the body chamber occupies about half a whorl.

The ribbing on the septate part of the shell is sharp 

and moderately spaced. Its primary ribs trend radially 

and divide at one-fourth to one-third of the height of the 

flanks into two or three slightly weaker secondary ribs. 

A few secondary ribs arise freely between the forked 

ribs. All secondary ribs incline adorally on the flanks and 

then cross the venter transversely.

The ribbing near the aperture consists only of faint, 

broad, primary ribs and even fainter secondary ribs that 

are barely visible on the venter.

This Alaska specimen was obtained at nearly the same 

stratigraphic position as a specimen herein described as 

Cranocephalites cf. C. ignekensis Imlay that was collected nearby on another tributary of Bear Creek. It differs, however, by being smaller and more robust, by 

having more secondary ribs per primary rib, and by its 

ribbing becoming faint near the aperture. These features 

match much better those of some robust specimens of C. 

vulgaris Spath (1932, p. 1, figs. 3a, b, 4a, b, pi. 4, figs. 

3a, b, pi. 8, figs, la, b) from East Greenland.

Figured specimen.—USNM 240736.

Occurrence.—Bowser Formation, 300 feet below top 

at USGS Mesozoic locality 30257 near Tuxedni Bay.

Genus ARCTOCEPHALITES Spath, 1928 

Arctocephalites cf. A. elegans Spath

Plate 8, figures 18-21

Arctocephalites is represented in southern Alaska by 

one ammonite that consists of a fairly complete septate 

finely ribbed whorl and about one-third of a nonseptate 

nearly smooth outer whorl.

The septate whorl has a fairly narrow umbilicus, a 

subquadrate whorl section that is as wide as it is high, 

and fine, rather closely spaced ribs that incline strongly 

forward on the lower half of the flanks but cross the venter transversely. The primary ribs trend radially on the 

umbilical wall, curve forward low on the flanks and divide into two or three slightly weaker secondary ribs at 

about the top of the lower fourth of the flanks. Other ribs 

arise freely along the zone of furcation, resulting in about 

three secondary ribs for each primary rib.

The nonseptate whorl is fragmentary and worn, and 

its junction with the septate whorl is not preserved by 

half a whorl. Its surface, exposed at several places, is

nearly smooth except for the presence of a few weak primary ribs low on the flanks.

This ammonite shows considerable resemblance to some 

ammonites from northern Canada that have been assigned to Arctocephalites elegans Spath by Frebold (1961, 

p. 10, 11, pis. 9-11 in part; 1964, p. 3, pis. 1 and 2 in 

part). The ribbing on its septate whorl appears to be 

slightly finer and denser than on most of the Canadian 

specimens but matches fairly well with that on the adapical end of one specimen (Frebold, 1961, pi. XI, figs, la, 

b). The smoothness of its outer whorl matches very well 

with that of the body whorl of A. elegans Spath. The 

presence of weak primary ribs on the flanks of the nonseptate whorl suggest that the fragment is the adapical 

part of the adult body chamber of Arctocephalites. It appears, therefore, that the ammonite from west of Cook 

Inlet is either a finely ribbed variant of A. elegans Spath 

as defined by Frebold (1961, p. 11) or a closely related 

species. This is borne out by comparisons with a specimen of A. cf. A. elegans Spath from northern Alaska 

(Imlay, 1976, p. 16, pi. 4, figs. 1-3).

Figured specimen.—USNM 180743.

Occurrence.—Bowser Formation, upper part, at USGS 

Mesozoic locality 22699 west of Cook Inlet. The specimen 

was collected 360-380 feet below the top of the formation, 170-190 feet below an occurrence of Iniskinites 

(Mesozoic loc. 22700) and about 850 feet above Cranocephalites costidensus (Imlay) (Mesozoic loc. 22698).

Genus TUXEDNITES Imlay n. gen.

Tuxednites is characterized by fairly small, moderately compressed to stout shells; a fairly small umbilicus 

that does not become wider on the body whorl; an adult 

body chamber that occupies about three-fourths of a 

whorl; an apertural constriction that is conspicuous only 

low on the flanks; and high, sharp, gently flexuous ribs 

that cross the venter transversely. The primary ribs become high on the lower fourth of the flanks where most 

of them pass into pairs of weaker secondary ribs that become high and sharp on the venter. The suture line is 

poorly preserved and cannot be traced accurately. Tuxednites alticostatus (Imlay), described previously as 

Arctocephalitesl alticostatus Imlay (1962a, p. C-22), is 

designated as the type species.

Tuxednites differs from Chinitnites (Imlay, 1975, p. 

17, 18) by its septate whorls having stronger primary 

ribs and a slightly wider umbilicus and by its adult body 

whorl not contracting from the septate whorls.

Tuxednites alticostatus (Imlay)

Plate 8, figures 1-9

Arctocephalitesl alticostatus Imlay. 1962a, U.S. Geol. Survey Prof.

Paper 374-C, p. C-22, pi. 2, figs. 1, 2, 4-8 [not fig. 3]. 

This species is represented by 18 specimens that vary 

considerably in coarseness of ribbing and in stoutness in
SYSTEMATIC DESCRIPTIONS 35

ways similar to that shown by Chinitnites chinitnaensis 

Imlay (1975, p. 22, pi. 2). It does not include a specimen 

from USGS Mesozoic locality 24116, referred to previously (Imlay, 1962a, p. C-23), which may represent the 

inner whorls of Cranocephalites globosus Imlay n. sp. 

from the same locality. Similarly the small specimen 

from USGS Mesozoic locality 21308 (see Imlay, 1962a, 

pi. 2, fig. 3) may represent the inner whorls of a globose 

form of Cranocephalites. The other specimens of T. alticostatus (Imlay) that were previously illustrated are all 

stout to fairly stout, are coarsely ribbed, and are representative of 13 of the 18 specimens herein assigned to 

the species. The other five specimens, present only at 

USGS Mesozoic localities 20746 and 30290, differ only by 

being a little less stout and a little finer ribbed. (See pi. 

8, figs. 3, 4.)

The species is possibly also represented by an even 

more finely ribbed, more compressed specimen that was 

once illustrated (Imlay, 1962a, pi. 1, fig. 7) as Arctocephalites (Cranocephalites) pompeckji (Madsen). That 

specimen, refigured herein on plate 8, figures 16, 17, is 

considerably finer ribbed and more compressed than the 

holotype of Tuxednites alticostatus (Imlay), with which 

it is associated at USGS Mesozoic locality 22698, but is 

only a little finer ribbed than some specimens that are 

herein assigned to that species (compare pi. 8, figs. 3, 4).

Types.—Rolotype, USNM 103757; paratypes, USNM 

103758 and 103759; hypotypes, 240737-240739.

Occurrence.—Bowser Formation, lower part at USGS 

Mesozoic localities 11038, 20011, 20746, 20752, and 22698 

west of Cook Inlet; at Mesozoic localities 30288 and 

30290 in the Talkeetna Mountains, and at Mesozoic locality 28682 in the Wrangell Mountains. This species ranges 

from the upper part of the beds characterized by Cranocephalites costidensus through the overlying beds containing other species of Cranocephalites into the lower 

part of the range of Chinitnites parviformis (Imlay) at 

USGS Mesozoic localities 11038 and 20746.

Tuxednites? sp. ind.

Plate 8, figures 10-15

Tuxednites is possibly represented by a number of 

small globose narrowly umbilicate sharply ribbed immature ammonites that occur in the beds characterized by 

Cranocephalites costidensus (Imlay). These ammonites 

show some resemblance to Xenocephalites but differ by 

having a wider umbilicus and much stronger, sharper 

ribs on their septate whorls. They show more resemblance to Tuxednites alticostatus (Imlay) (1962a, p. C22, pi. 2, figs. 3-8) in coiling and in rib plan but differ 

by being much stouter and by having sparser, stronger, 

less flexuous ribs. Their features suggest that they belong to Tuxednites, but their preservation does not permit a definite taxonomic assignment. Also, the fact that

none of the specimens bears an apertural constriction 

suggests that all of the specimens may be immature 

forms and, therefore, could represent the early growth 

stages of much larger ammonites such as Cranocephalites globosus Imlay n. sp., as described herein.

Figured specimens.—USNM 240741 and 240742.

Occurrence.—Bowser Formation, lower part at USGS 

Mesozoic localities 20005, 20744, and 30265 west of Cook 

Inlet; at Mesozoic locality 24116 in the Talkeetna Mountains; and at Mesozoic locality 28682 in the Wrangell 

Mountains.

Genus INISKINITES Imlay, 1975 

Iniskinites cf. I. intermedius (Imlay)

Plate 8, figures 22, 26-28

cf. Kheraiceras intermedium Imlay, 1953, U.S. Geol. Survey Prof. Paper 249-B, p. 81, pi. 31, figs. 1-4, pi. 32, figs. 2, 3, 5, 7, 8.

cf. Iniskinites intermedius (Imlay), 1975, U.S. Geol. Survey Prof. Paper 836, p. 24, pi. 3, figs. 3, 4.

Iniskinites intermedius (Imlay) is represented (1) at 

the very top of the Bowser Formation on Chisik Island 

by the holotype (Imlay, 1953, pi. 31, figs. 3, 4) at USGS 

Mesozoic locality 21272; (2) probably 240 feet below the 

top near Lake Hickerson (see pi. 8, fig. 26) at Mesozoic 

locality 22700; (3) probably 300 feet below the top (pi. 8, 

figs. 22, 27, 28) at Mesozoic locality 30262 on an unnamed 

creek east of Bear Creek south of Tuxedni Bay; and (4) 

probably about 540 feet below the top at Mesozoic locality 21313 on Park Creek near Chinitna Bay.

Types.—See listing in Imlay (1975, p. 24); figured 

specimens USNM 240743 and 240744.

Iniskinites cf. .1. magniformis (Imlay)

Plate 8, figures 23-25

Two immature specimens of Iniskinites have very fine 

dense ribbing and a globose form as on the inner whorls 

of I. magniformis Imlay (1975, pi. 4, figs. 2, 7). The inner whorls of I. abruptus (Imlay) (1953, pi. 33, figs. 1, 7; 

1975, pi. 5, figs. 1, 2) have slightly coarser ribbing.

Figured specimen.—USNM 240745.

Occurrence.—Bowser Formation at USGS Mesozoic 

locality 22536 near Iniskin Bay on the Iniskin Peninsula.

Genus TALKEETNITES Imlay n. gen.

Talkeetnites is characterized by fairly large shells that 

change during growth from globose to cadicone; by a 

deep, rather narrow funnel-shaped umbilicus; by a slightly 

retracted body chamber; by a vertical umbilical wall that 

rounds evenly into the flanks; by its septate inner whorls 

bearing sharp ribs that bifurcate along the line of greatest whorl thickness and become sharper ventrally; by its 

outermost whorls bearing secondary ribs that weaken 

adorally and primary ribs that become stronger adorally; 

by the lack of tubercles on the septate whorls; and by the
36 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

primary ribs becoming swollen and comma shaped on the 

body chamber. The suture line is poorly exposed.

Talkeetnites cadiformis Imlay, described herein, is 

designated as the type species.

Talkeetnites resembles cadicone species of Tulites and 

Cadoceras in the shape of its outer whorl. Its inner 

whorls differ from those of Tulites, however, by lacking 

a sharp or distinct umbilical edge, by not bearing nodes, 

and by bearing sharp ribs (compare Arkell, 1952, pi. 9, 

figs. 4a, b, 6a, b, pi. 11, figs. 6a-d; 1954, pi. 12, figs. 2a, 

b, 4a, b, pi. 13, figs. 6a, b). Its body whorl differs from 

that of Cadoceras by lacking a distinct umbilical edge and 

by contracting from the septate whorls. Its small inner 

whorls are more tightly coiled than in Cadoceras but are 

comparable in that respect with those of Cranocephalites 

with which they are associated. Overall the genus appears to be more closely related to Cranocephalites than 

to Cadoceras or Tulites.

Talkeetnites cadiformus Imlay n. sp.

Plate 9, figures 1-10

This species is represented by two specimens whose 

outer whorls are extremely wide and depressed (cadicone) and whose inner whorls are globose. Umbilicus 

deep, moderately narrow, funnel shaped. Umbilical wall, 

vertical at base, gently inclined above, rounding evenly 

into flanks on all whorls but becoming more narrowly 

rounded on body whorl. Body chamber incompletely preserved, but occupies at least three-fifths of a whorl on 

the largest specimen, and its adoral part is slightly retracted from the septate whorls. Aperture unknown.

On the smallest preserved whorls, the ribs are sharp, 

high, moderately spaced, and gently flexuous. Primary 

ribs trend nearly radially on the umbilical wall and generally bifurcate along the line of greatest whorl thickness. Secondary ribs are slightly sharper than the primary ribs, curve forward on the flanks, and then cross 

the venter transversely or with a slight forward arching.

Adorally on the penultimate and body whorls, the secondary ribs gradually become weaker on the venter but 

persist to the end of the largest specimen and arch forward considerably on the body chamber. The primary 

ribs, by contrast, gradually become stronger adorally 

along the line of greatest whorl thickness, and near the 

adoral end of the body chamber develop into commashaped swellings from which pass broad faint secondary 

ribs.

The dimensions of the holotype, in millimeters, and ratios of the diameter are as follows:

Diameter

31 — . ——— .. —————

55. — - — . — .. ———

Q1

Whorl 

height

—— 15 (0.48)

—— £O \ •^c-l

-— 32 ( .39)

Whorl 

thickness

97 I f\ Q7 ^

51 ( .93)

80 ( ,99)

Umbilical 

width

6.5 (0.21)

10.0 ( .18)

25.0 ( .31)

The suture line cannot be traced.

Types.—Rolotype, USNM 240746; paratype, USNM 

240747.

Occurrence.—Unnamed beds in the Talkeetna Mountains at USGS Mesozoic locality 30277.

Family REINECKEIIDAE Hyatt, 1900 

Genus PARAREINECKEIA Imlay, 1962

Parareineckeia hickersonensis Imlay

Plate 10, figures 1-10

Parareineckeia hickersonensis Imlay, 1962a, U.S. Geol. Survey Prof.

Paper 374-C, p. C-25, pi. 7, figs. 1-6.

IParareineckeia cf. P. hickersonensis Imlay. Frebold and Tipper, 

1973, Canadian Jour. Earth Sci., v. 10, p. 1119, pi. 6, fig. 6.

This species, in addition to the holotype from the Lake 

Hickerson area west of Cook Inlet, is represented by 4 

septate and 1 adult specimen (microconch) from the Talkeetna Mountains and 22 fragmentary, compressed specimens from the Wrangell Mountains. These show that 

the rib pattern as preserved on the holotype gradually 

becomes stronger during further growth. On the largest 

specimen available (pi. 10, fig. 10), the body chamber occupies three-fifths of a whorl and terminates simply. On 

one of the small specimens (pi. 10, fig. 3), some tubercles 

form the base of prominent spines that project ventrally.

Types. —Holotype, USNM 130756; hypotypes, USNM 

240748-240752.

Occurrence.—Nizina Mountain Formation in the 

Wrangell Mountains at USGS Mesozoic localities 28524, 

28681, 28682, 28696, 28698, and 28701. Unnamed 

beds in the Talkeetna Mountains at Mesozoic localities 

30272, 30576, and 30577. Bowser Formation west of 

Cook Inlet at Mesozoic locality 22698.

Parareineckeia nelchinensis Imlay n. sp.

Plate 11, figures 1-16

Parareineckeia cf. P. shelikofana (Imlay), 1962a, U.S. Geol. Survey

Prof. Paper 374-C, p. C-26, pi. 7, fig. 6, 7. 

Parareineckeia cf. P. shelikofana (Imlay), Frebold and Tipper, 1973,

Canadian Jour. Earth Sci., v. 10, p. 1117, pi. 4, fig. 1, pi. 6, figs.

3-5.

This species is represented by 30 specimens of which 4 

are from the Talkeetna Mountains, 25 from the Wrangell 

Mountains, and 1 from the Iniskin Peninsula. These specimens, although most are crushed and fragmentary, do 

represent various growth stages including part of an 

adult body chamber. They show that the species is intermediate in characteristics between P. hickersonensis 

Imlay (1962a, p. C-25, pi. 7, figs. 1-5) and P. shelikofana (Imlay) (1953, p. 101, pi. 55, figs. 1, 8). It differs 

from P. hickersonensis Imlay by having considerably 

weaker and denser ribbing and a slightly higher whorl 

section. It differs from P. shelikofana (Imlay) by having 

slightly sparser and sharper ribs at comparable sizes and 

by its lateral tubercles persisting to a much later growth 

stage.
SYSTEMATIC DESCRIPTIONS 37

Types.—Holotype, USNM 240753; paratypes, USNM 

130750, 240754-240760.

Occurrences.—Nizina Mountain Formation in the 

Wrangell Mountains at USGS Mesozoic localities 28524, 

28527, and 28681-28683. Unnamed beds in the Talkeetna Mountains at Mesozoic localities 24117, 30272, 

and 30276. Bowser Formation in the Iniskin Peninsula at 

Mesozoic locality 3038 and possibly at 20745. The species 

is commonly associated with Cranocephalites costidensus (Imlay) and Parareineckeia hickersonensis Imlay. 

These occurrences, however, are much lower stratigraphically than those with P. shelikofana (Imlay, 1953, 

p. 101, 102).

Family PERISPHINCTIDAE Steinmann, 1890

Subfamily LEPTOSPHINCTINAE Arkell, 1950

Genus COBBANITES Imlay, 1962

Cobbanites talkeetnanus Imlay

Plate 12, figures 2-4, 7-9

Cobbanites talkeetnanus Imlay, 1962a, U.S. Geol. Survey Prof. Paper

374-C, p. C-27, pi. 7, figs. 8-13, pi. 8, fig. 1.

Cobbanites talkeetnanus Imlay. Frebold and Tipper, 1973, Canadian 

Jour. Earth Sci., v. 10, no. 7, p. 1123, pi. 7, figs. 1^.

This species is represented by 7 fairly well preserved 

specimens from the Talkeetna Mountains and 12 fragmentary septate specimens from the Wrangell Mountains. Its characteristic features, as shown on the original type specimens, are herein supplemented by views of 

inner septate whorls. Note particularly that on the smallest specimen (pi. 12, figs. 8, 9) the primary ribs terminate ventrally in weak swellings and that the ribs are 

reduced in strength along the midline of the venter.

The outer septate whorl of this species bears considerable resemblance to that of Leptosphinctes (Yermisphinctesl) reparator Buckman (1923, p. 366), which Arkell (1958, p. 168) assigns to Prorsisphinctes, but is 

more compressed, more involute, and its ribs more widely 

spaced. The inner septate whorls of C. talkeetnanus Imlay in comparison with L. (V.) vermiformis Buckman 

(1920, pi. 162) are more involute and have sparser, weaker 

ribs that arch forward more strongly on the venter.

Types.— Holotype, USNM 130743; paratype, USNM 

130744; hypotypes, USNM 240761-240763.

Occurrences.—Nizina Mountain Formation in the 

Wrangell Mountains at USGS Mesozoic localities 28525, 

28682, and 28699; unnamed beds in the Talkeetna 

Mountains at Mesozoic localities 24116, 30277, 30574, and 

30578.

Cobbanites striatus Imlay n. sp.

Plate 12, figures 1, 5, 10, 11

This species is represented by one moderately small 

septate specimen and by one smaller fragment. It is distinguished from C. talkeetnanus Imlay by having much 

finer, weaker, and denser ribbing and by its secondary

ribs outnumbering the primary ribs about 3 to 1 instead 

of 2 to 1. On the adoral end of the largest preserved septate whorl the secondary ribs are only faintly connected 

with the primary ribs. This ribbing is appreciably finer 

and denser than in Leptosphinctes (Vermisphinctes) subdivisus Buckman (1920, pi. 190) from the upper Bajocian 

of England or on Cobbanites talkeetnanus var. densicostatus Frebold and Tipper (1973, p. 1125, pi. 7, figs. 5, 6) 

of British Columbia.

Holotype.— USNM 240764; paratype, UCLA 4988.

Occurrences.—Nizina Mountain Formation in the 

Wrangell Mountains at USGS Mesozoic localities 28682 

and probably 28699; unnamed beds in the Talkeetna 

Mountains at Union Oil Co. locality RAL 65 in association with Cranocephalites costidensus (Imlay).

Cobbanites tuxedniensis Imlay n. sp.

Plate 12, figures 6, 12-15

This species is represented by one septate specimen 

that shows nearly five whorls at diameters between 12 

and 112 mm. Shell compressed and moderately involute. 

Whorls embrace from one-third to two-fifths of the preceding whorl and become more evolute and more compressed during growth. At the diameter of 56 mm, the 

whorl section is subquadrate and 16 mm in height and 

width. Half a whorl adorally at a diameter of 78 mm the 

whorl section is 24 mm in height and 19 mm in width. 

Umbilicus very wide and shallow. Umbilical wall low and 

steeply inclined. Flanks gently convex on innermost exposed whorls but become nearly flat on outer septate 

whorls. Venter evenly rounded on inner whorls but becomes moderately arched on largest septate whorl.

The ornamentation, as exposed in the umbilicus, consists of stout radially trending primary ribs and some 

weak constrictions. These primary ribs are nearly as 

wide as the interspaces, thicken slightly ventrally, and 

are mostly not tuberculate, although most furcation points 

are hidden by the succeeding whorls.

On the outer two septate whorls the primary ribs likewise trend radially, become slightly weaker adorally, 

generally pass into pairs of slightly weaker secondary 

ribs at about three-fifths of the height of the flank, and 

are slightly swollen at the furcation points. Some secondary ribs arise freely on the flanks near the zone of furcation and others are indistinctly connected with the primary ribs. All secondary ribs arch forward moderately 

on the venter, but this arching becomes less pronounced 

during growth. Six weak to moderately strong constrictions occur on the outermost complete whorl. Slight reduction of ribbing along the midventral line is apparent 

at a few places.

The suture line, exposed only on the lower two-thirds 

of the flank, has long slender lobes similar to that on Cobbanites talkeetnanus Imlay (1962a, pi. 7, fig. 8).
38 MIDDLE JURASSIC (BATHONIAN) AMMONITES FROM SOUTHERN ALASKA

This species is intermediate in most characteristics between Cobbanites talkeetnanus Imlay from Alaska (Imlay, 1962a, p. C-27, pi. 7, figs. 8-13) and C. aff. C. 

talkeetnanus Imlay from eastern Oregon (Imlay, 1964, 

p. D-16, pi. 4, figs. 10-13). It differs from both by having somewhat weaker constrictions; longer, denser, 

nearly radial primary ribs that bifurcate higher on the 

flanks; and fewer and stronger secondary ribs. Its general appearance is similar to that of the paratype of C. 

engleri Frebold (1957, p. 65, 76, pi. 40, figs, la, b) from 

western Alberta, but it has weaker constrictions, apparently higher points of rib furcation, and more distinct 

arching of ribs on its venter. It likewise resembles Leptosphinctes (Vermisphinctes) reparator Buckman (1923, 

pi. 366) at a comparable size but differs in having nearly 

radial primary ribs and in being more involute. In those 

features it resembles L. (Prorsisphinctes) omphalicus 

Buckman (1922, v. 4, pi. 326).

Holotype.— USNM 240765.

Occurrence.—Bowser Formation, about 150 feet below top at USGS Mesozoic locality 30261 west of Cook 

Inlet.

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and the south third of Talkeetna Mountains (B-l) quadrangle. 

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Hahn, Wolfgang, 1969, Die Perisphinctidae Steinmann (Ammonoidea) 

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1-9, 11 figs.

———1971, Die Tulitidae S. Buckman, Sphaeroceratidae S. Buckman 

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

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25-55, figs. 3-9.

———1962a, Jurassic (Bathonian or early Callovian) ammonites from 

Alaska and Montana: U.S. Geol. Survey Prof. Paper 374-C, 32 

p., 8 pis.

———1962b, Late Bajocian ammonites from the Cook Inlet region, 

Alaska: U.S. Geol. Survey Prof. Paper 418-A, 15 p., 5 pis., 4 

figs.

———1964, Upper Jurassic mollusks from eastern Oregon and western 

Idaho: U.S. Geol. Survey Prof. Paper 483-D, p. D1-D21, pis. 

1-4, 3 figs.

———-1975, Stratigraphic distribution and zonation of Jurassic (Callovian) ammonites in southern Alaska: U.S. Geol. Survey Prof. Paper 

836, 28 p., 6 pi. 

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northern Alaska: U.S. Geol. Survey Prof. Paper 854, 22 p., 4 pis.

Imlay, R. W., and Detterman, R. L., 1973, Jurassicpaleobiogeography 

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Kopik, Janusz, 1974, Genus Cadomites Munier-Chalmas, 1892 (Ammonitina) in the upper Bajocian and Bathonian of the Cracow-Wielun Jurassic range and the Gory SwietkrzysWe Mountains (southern Poland) in Z badan stratygraficznopaleontologicznych w Polsce, 

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REFERENCES CITED 39

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———1970, Geologic map of the McCarthy C-5 quadrangle, Alaska: 

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INDEX

[Italic page numbers indicate descriptions and major references]

abruptus, Iniskinites ___________________________ 35

alaskanus, Cranocepkalites _________________ 32, pi. 5

Alberta ___________________________ 38 

cdticostatus, Arctocephalites _____________________ 34

Tuxednites _________________________ 34,35, pi. 8

ammonites _______________________ 3 

Bajocian ________________________ 3 

Bathonian ____________________ 5,12,13 

deslongchampsi ____________________________ 18

Arcticoceras _______________________________ 13, 15

Arctocephalites ________________ 11,15,16, 32, 34, pi. 8

alticostatus ________________________________ 34

(Cranocephalites) costidensus _________________ 32

(Cranocephcdites) pompeckji _______________ 32, 35

elegans ____________________________ 15, 34, pi. 8

orientalis _________________________________ 33

Arkelloceras ___________________________________ 2

B

Bajocian Age ____________ 2, 3,13,14,15,16, 30 

ammonites _______________________ 3 

assignment ______________________ 14 

beds ________________________ 2 

of England _____________________ 37 

bakeri, Phylloceras ________________________ 16, pi. 1

Bathonian Age 1, 2,3, 4,13,14,15,16, 21, 22, 23, 24,25,

26, 27, 28, 29, 30

ammonites _________________ 1, 2, 12, 13 

beds __________________________ 15 

Bear Creek _____________________ 34, 35 

Belemnites _______________________ 3 

Boreal realm _____________________ 1, 16 

Boulder Creek _______________ 1, 2, 3, 4,11,12 

Bowser Formation __ 1, 2, 5,11,12,14,15,16,17,18, 30,

31, 32, 33, 34, 35, 36, 37, 38 

British Columbia __________________ 15,37

cadiformus, Talkeetnites ____________________ 36, pi. 9

Cadoceras ______________________________ 15, 16, 36

calyx _____________________________________ 15

variable __________________________________ 15

Cadoceratinae _______________________ 32 

Cadomites __________________ 2, 13, 16, 18, 20, 30, pl.4

daubenyi__________________________________ 30

deslongchampsi ____________ 13, 18, 20, 29, 30, pi. 4

exstinctus _________________________________ 30

rectelobatus _____________________ 13, 16, 30, pi. 4

Calliphylloceras _______________________________ 16

freibocki ______________________________ 16, pi. 1

Phylloceras, freibocki _______________________ 16

Calliphylloceratinae ___________________ 16 

Callovian Age __________________ 2,13,15 

calyx, Cadoceras _______________________________ 15

Canada _____________________ 13, 15, 34 

Cardioceratidae ___________________ 2, 32 

Chinitna Bay ____________________ 2,16, 35 

Chinitna Formation _____ 2, 14, 15,16, 17, 18, 30, 31 

chinitnaensis, Chinitnites _______________________ 35

chinitnana, Oppelia (Oxycerites) _____________ 17, pi. 3

Chinitnites ________________________ 2, 11, 16, 30, 34

chinitnaensis ______________________________ 35

parviformis _______________________ 11,15, 30, 35

Chisik Island ________________________ 35 

chisikensis, Kepplerites _________________________ 31

Chondroceras _________________________________ 13

Cobbanites _________________________ 2, 11,14, 16, 37

engleri ___________________________________ 38

striatus _____________________________ 37, pi. 12

talkeetnanus ______________________ 37, 38, pi. 12

tuxedniensis ______________________ 14, 37, pi. 12

Cook Inlet _ 1, 2, 3, 7,11,13,15,16,30, 32, 34, 35,36, 38 

Coquinoid __________________________ 2 

costidensus, Arctocephalites (Cranocephalites) ______ 32

Cranocephalites _ 11,13,14,15,16, 32, 33, 34,35, 37,

pi. 7 

Cranocephalites __ 2, 11, 13, 14,16, 31, 32, 33, 34, 35, 36,

pis. 3, 5 

alaskanus ____________________________ 32, pi. 5

Arctocephalites costidensus ___________________ 32

Arctocephalites pompeckji _________________ 32, 35

costidensus _ 11, 13,14,15,16, 32, 33, 34, 35, 37, pi. 7 

globosus ___________________________ S3, 35, pi. 6

ignekensis ________________ 11, 14, 15, 32, 34, pi. 5

indistinctus ____________________________ 15, 32

pompeckji ________________________ 13, 15, 16, 32

vulgaris _____________________ 11, 15, 33, 34, pi. 3

D

daubenyi, Cadomites ___________________________ 30

densicostatus _________________________________ 37

deslongchampsi, ammonites ______________ 18 

Cadomites _________________ 13, 18, 20, 29, 30, pi. 4

E

Early Jurassic ______________________ 2,5 

East Boulder Creek ____________________ 3 

East Greenland _____________ 13,15,16,33, 34 

elegans, Arctocephalites _________________ 15, 34, pi. 8

engleri, Cobbanites _____________________________ 38

eudisianum, Lytoceras _________________________ 16

exstinctus, Cadomites ___________________________ 30

freibocki, Calliphylloceras __________________ 16, pi. 1

Phylloceras (Calliphylloceras) ________________ 16

G

Gaikema Creek _____________________ 16 

gitinsi, Kepplerites _____________________________ 31

globosus, Cranocephalites ________________ 33, 35, pi. 6

grossicostatum, Phylloceras (Macrophylloceras) _ 16, pi. 1

H

hebetus, Xenocephalites _____________________ 30, pi. 2

hickersonensis, Parareineckeia __________ 36, 37, pi. 10

Holcophylloceras ______________________________ 16

I

ignekensis, Cranocephalites _____ 11, 14, 15, 32, 34, pi. 5

indistinctus, Cranocephalites _________________ 15, 32

Iniskin Bay ______________ 1, 2, 5, 7, 11, 15, 35 

Iniskin Peninsula ________ 2, 15, 17, 33, 35, 36, 37

Page

Iniskinites _________________ 2, 11, 15, 16, 34, 35, pi. 8

abruptus __________________________________ 35

intermedius _____________________ 11, 16, 35, pi. 8

magniformus _________________^_____ 35, pi. 8

Inoceramus ____________________________________ 2

intermedium, Kheraiceras ______________________ 35

dius, Iniskinites ______________ 11, 16, 35, pi. 8

Jurassic Age ________________________ 13

K

kellumi, Oppelia (Liroxyites) ________________ 18, pi. 3

Kepplerites ___________ 11,14, 15, 16, 31, pis. 1, 3 

chisikensis ________________________________ 31

gitinsi ____________________________________ 31

mcevoyi___________________________________ 31

multus ___________________________________ 31

tychonis __________________________________ 31

Kheraiceras intermedium ________________ 35 

parviforme ________________________________ 30

Kosmoceratidae ______________________ 31

Lake Hickerson _______________ 11, 15, 35, 36 

Leptosphinctes (Prorsisphinctes) omphalicus ________ 38

(Vermisphinctes) reparator ________________ 37,38

(Vermisphinctes) subdivisus __________________ 37

(Vermisphinctes) vermiformis ________________ 37

Leptosphinctinae _________________ 2, 14, 37 

Limestone Hills ______________________ 4 

Liroxyites __________________________________ 2, 18

Oppelia ______________________________ 18, pi. 3

Oppelia kellumi ________________________ 18, pi. 3

Little Nelchina River Valley _______________ 4

Oshetna River ___________________ 4

Lubbe Creek Formation _________________ 5

Lytoceras _________________ ___________ 16, 17, pi. 2

eudisianum _______________________________ 16

Lytoceratidae _______________________ 16 

Lytoceratinae _____________________ 16

____ 30 

__ 16

Macrocephalitidae ____________________

Macrophylloceras ____________________.

Phylloceras, grossicostatum, ______________ 16, pi. 1

magniformus, Iniskinites ___________________ 35, pi. 8

McCarthy C-5 quadrangle ________________ 4 

McCarthy Formation ___________________ 5 

mcevoyi, Kepplerites ___________________________ 31

Mesozoic locality __ 16,17, 30, 31, 32, 33, 35, 36, 37, 38,

pis. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 

Middle Jurassic _____________________ 11 

multus, Kepplerites ____________________________ 31

N

Nelchina ________________________ 1, 2, 4 

nelchinensis, Parareineckeia _______________ 36, pi. 11

Nizina Mountain Formation ____ 1, 4,12, 30,32, 36, 37 

Normannites __________________________________ 13

41
42 INDEX

o

Oecotraustes __________________________________ 16

ompkalicus, Leptosphinctes (Prorsisphinctes) _______ 38

Oppelia ______________________________________ 17

(Liroxyites) ___________________________ 18, pi. 3

(Liroxyites) kellumi ____________________ 18, pi. 3

(Oxycerites) ___________________________ J7, pi. 3

(Oxycerites) chinitnana _________________ i7, pi. 3

Oppeliidae _______________________ 17 

Oppeliinae ______________________ 17 

Oregon ________________________ 38 

orientalis, Arctocephalites _______________________ 33

Oxfordian Age _______________________ 5 

Oxycerites ____________________________________ 17

Oppelia ______________________________ JS, pi. 3

Oppelia, chinitnana ____________________ J7, pi. 3

Pacific Realm _______________________ 16 

Parareineckeia ___________________________ 2, 16, 36

hickersonensis _____________________ 36, 37, pi. 10

nelchinensis __________________________ 36, pi. 11

shelikofana _____________________________ 36, 37

Park Creek ______________________ 35 

parkinsoni, Parkinsonia ________________________ 30

Parkinsonia parkinsoni ________________________ 30

parviforme, Kheraiceras ________________________ 30

parviformis, Chinitnites _______________ 11, 15, 50, 35

Pelecypods _______________________ 3 

Perisphinctidae _____________________ 2, 37 

Phylloceras _______________________________ 16, pi. 1

bakeri ________________________________ 16, pi. 1

(Calliphylloceras) freibocki ___________________ 16

(Macrophylloceras) grossicostatum ________ 16, pi. 1

Phylloceratidae 2, 16 

Phylloceratinae 16 

Pliensbachian Age _____________________ 5 

pompeckji, Arctocephalites (Cranocephalites) _____ 32, 35

Cranocephalites __________________ 13, 15, 16, 32

Procerites ____________________________________ 14

Prorsisphinctes _____________________________ 2, 37

Leptosphinctes ompkalicus ___________________ 38

R

rectelobatus, Cadomites _______________ 13, 16, 30, pi. 4

Reineckeiidae ____________________ 2, 36 

reparator, Leptosphinctes (Vermisphinctes) ______ 37,38

Root Glacier Formation __________________ 5

Shelikof Formation ____________________________ 31

shelikofana, Parareineckeia __________________ 36, 37

Siemeradzkia ______________________________ 13, 16

Sphaerocerotidae .18 

striatus, Cobbanites _______________________ S7, pi. 12

subdivisus, Leptosphinctes (Vermisphinctes) ________ 37

Talkeetna Formation __________________ 2, 3 

Mountains 1, 2, 4, 5, 11, 12, 13, 15, 16, 17, 29, 30, 32,

33, 35, 36, 37 

talkeetnamis, Cobbanites ___________________ 37, pi. 12

Talkeetnites ___________________________ 2, 16, 35, 36

cadiformus ___________________________ 36, pi. 9

Teloceras _____________________________________ 13

Tithonian Age ________________________ 5 

Tonnie Creek _____________________ 11

Page

Trigonia _____________________________________ 2

Tulites ___________________________________ 36

Tuxedni Bay _____ 1, 2, 5, 7, 11, 15, 18, 31, 32, 34, 35 

Tuxedni Group _____________________ 3 

tuxedniensis, Cobbanites ________________ 14, 37, pi. 12

Tuxednites ______________________ 2, 16, 34, 35, pi. 8

alticostatus ________________________ 34, 35, pi. 8

Twist Creek Siltstone __________________ 2, 3 

•s, Kepplerites ___________________________ 31

variable, Cadoceras ___________________ 15 

vermiformis, Leptosphinctes (Vermisphinctes) ______ 37

Vermisphinctes ______________________________ 2,14

Leptosphinctes reparator _________________ 37, 38

Leptosphinctes subdivisus ____________________ 37

Leptosphinctes vermiformis __________________ 37

vulgaris, Cranocephalites __________ 11,15, SS, 34, pi. 3

W

Wrangell Mountains __ 1, 2, 4, 5, 13, 29, 30, 32, 35, 36, 37

Xenocephalites ___________ 11,15, 16, 30, 35, pi. 2 

hebetus _______________________________ SO, pi. 2

zigzag, zigzagiceras ____________________________ 30

Zigzagiceras zigzag ____________________________ 30

Zigzagiceratinae ______________________ 2
PLATES

Contact photographs of the plates in this report are available,

at cost, from U.S. Geological Survey Library, Federal Center,

Denver, Colorado 80225
PLATE 1

[Figures natural size unless otherwise indicated]

FIGURES 1, 2, 4, 5. Kepplerites sp. A (p. 31).

1, 2, 4. Figured specimens USNM 240721 from Mesozoic loc. 21319. Figures

1 and 2 (x 2) represent inner whorl of specimen shown on figure 4.

5. Figured specimen, USNM 180716 from USGS Mesozoic loc. 21319.

Note absence of lateral tubercles. 

3. Kepplerites sp. C (p. 31).

Lateral view (x 2). Figured specimen, USNM 240723 from USGS Mesozoic 

loc. 30263. 

6, 10. Phylloceras cf. P. bakeri Imlay (p. 16).

Figured specimen, USNM 240705 from USGS Mesozoic loc. 21311. 

7-9, 11. Calliphylloceras freibrocki Imlay (p. 16).

7. 11. Hypotype, USNM 240708 from USGS Mesozoic loc. 30578.

8. 9. Hypotype, USNM 240707 from USGS Mesozoic loc. 21311. 

12, 13. Phylloceras (Macrophylloceras) grossicostatum Imlay (p. 16). 

Hypotype, USNM 240706 from USGS Mesozoic loc. 30574.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 1

11 12 ~ 13

KEPPLERITES, PHYLLOCERAS, CALLIPHYLLOCERAS, AND MACROPHYLLOCERAS
PLATE 2

[All figures are natural size]

FIGURES 1-9. Xenocephalites cfX. hebetus Imlay (p. 30).

1-3. Figured specimen, USNM 240719 from USGS Mesozoic loc. 21312. 

4, 5. Figured specimen, USNM 240717 from USGS Mesozoic loc. 22436. 

6, 7. Figured specimen, USNM 240718 from USGS Mesozoic loc. 21312. 

8, 9. Figured specimen, USNM 240720 from USGS Mesozoic loc. 22713. Shows

part of adult body chamber. 

10-12. Lytoceras sp. (p. 16).

Figured specimen, USNM 240709 from USGS Mesozoic loc. 30579.
PROFESSIONAL PAPER 1091 PLATE 2

XENOCEPHALITES AND LYTOCERAS
PLATE 3

[All figures are natural size]

FIGURES 1-5. Oppelia (Oxycerites) aff. 0. (0.) chiniinana Imlay (p. 17).

Figured specimen, USNM 240710 from USGS Mesozoic loc. 22538. 

6. Oppelia (Liroxyites) cfO. (L.) kellumi Imlay (p. 18).

Figured specimen, USNM 240711 from USGS Mesozoic loc. 30257. 

7, 8, 10, 11. Cranocephalites cf. C. vulgaris Spath (p. 33).

Figured specimen, USNM 240734 from USGS Mesozoic loc. 30275. Shows aperatural, ventral, cross-sectional, and lateral views of adult body chamber. 

9. Kepplerites sp. B (p. 31).

Figured specimen, USNM 240722 from USGS Mesozoic loc. 30258. Shows adult 

body chamber.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 3

OPPELIA (OXYCERITES), 0. (LIROXYITES), CRANOCEPHALITES, AND KEPPLERITES
PLATE 4

[All figures are natural size]

FIGURES 1, 2, 4-12. Cadomites cf. C. deslongchampsi (d'Orbigny) (p. 18).

1, 2, 4, 5. Nonseptate specimens, USNM 240714 from USGS Mesozoic loc. 

30576. Shows lateral views (figs. 1 and 2), ventral view (fig. 4), 

and rubber latex imprint of dorsal surface of adoral part of adult 

body chamber (fig. 5).

6, 7. Septate specimen, USNM 240713 from USGS Mesozoic loc. 30577. 

This small specimen was part of an umbilical plug that was detached from the specimen shown in figures 9-12. 

8. Rubber imprint of external mold of specimen, USNM 240715 from

USGS Mesozoic loc. 28682.

9-12. Ventral and lateral views of specimen, USNM 240712 from 

USGS Mesozoic loc. 30277. Note that the adoral end has been 

crushed vertically. 

3. Cadomites cf. C. rectelobatus (v. Hauer) (p. 30).

Rubber imprint of laterally crushed external mold of specimen, USNM 

240716 from USGS Mesozoic loc. 28682.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 4

11

CADOMITES
PLATE 5

[All figures are natural size]

FIGURES 1-5. Cranocephalites alaskanus Imlay n. sp. (p. 32),

1-4. Lateral, apertural, and ventral views of holotype, USNM 240729 from

USGS Mesozoic loc. 22698.

5. Immature paratype, USNM. 130753 from USGS Mesozoic loc. 22698. 

6—8. Cranocephalites sp. A (p. 33).

Lateral and ventral views of specimen, USNM 240735 from USGS Mesozoic loc.

22436. 

9—11. Cranocephalites cf. C. ignekensis Imlay (p. 32).

9. Rubber imprint of external mold of specimen, USNM 240730 from USGS Mesozoic loc. 30275. 

10,11. Lateral views of specimen, USNM 130751 from USGS Mesozoic loc. 21284
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 5 

t ¥^ L ><*.-
PLATE 6

[All figures except suture line are natural size]

FIGURES 1-3, 5, 6, 8-13. Cranocephalites globosus Imlay n. sp. (p. 33).

1-3. Cross-sectional, ventral and lateral views of paratype, USNM

240732 from USGS Mesozoic loc. 20751.

5,6. Paratype, USNM 240733 from USGS Mesozoic loc. 24117. 

8-13. Holotype, USNM 240731 from USGS Mesozoic loc. 24116. Figure 9 shows suture line (x 2) drawn at diameter of 53 mm, 

whorl height of 15 mm, and whorl thickness of 43 mm. On Figures 10 and 13 note smoothness of venter near the apertural 

constriction. On Figure 11 note persistence of ribs on the flanks 

almost to the apertural constriction. 

4, 7. Cranocephalites sp. B (p. 34).

Lateral and apertural views of specimen, USNM 240736 from USGS 

Mesozoic loc. 30257.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 6

13

CRANOCEPHALITES
PLATE 7

[All figures natural size except suture lines]

FIGURES 1-12. Cranocephalites costidensus (Imlay) (p. 32).

1-3, 6. Hypotype, USNM 240724 from USGS Mesozoic loc. 30273 has a compressed form and moderately strong ribbing. Figure 6 shows suture 

lines (x 2) drawn at adapical end of body chamber.

4, 12. Hypotype, USNM 240727 from USGS Mesozoic loc. 30277, has a compressed form and fairly fine ribbing. 

5, 8. Hypotype, USNM 240725 from USGS Mesozoic loc. 30289, has a fairly

stout form and moderately strong ribbing. 

7. Suture line ( x 2) on hypotype, USNM 240728 from USGS Mesozoic loc.

30277.

9-11. Hypotype, USNM 240726 from USGS Mesozoic loc. 30277, has a very 

stout form and fairly fine ribbing.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 7

CRANOCEPHALITES
PLATE 8

[All figures are natural size]

FIGURES 1-9. Tuxednites alticostatus (Imlay) (p. 34).

1, 2. Holotype, USNM 130757 from USGS Mesozoic loc. 20752. 

3, 4. Hypotype, USNM 240739 from USGS Mesozoic loc. 30290. 

5, 6. Hypotype, USNM 240738 from USGS Mesozoic loc. 30288. 

7-9. Hypotype, USNM 240737 from USGS Mesozoic loc. 11038. 

10-15. Tuxednites? sp. ind. (p. 35).

10, 11. Ventral and lateral view of internal mold of specimen, USNM 240742

from USGS Mesozoic loc. 30265. 

12, 13. Rubber cast of external mold of same specimen shown in figures 10 and

11.

14, 15. Nonseptate specimen, USNM 240741 from USGS Mesozoic loc. 20744. 

16, 17. Tuxednites cf. T. alticostatus (Imlay) (p. 35).

Specimen, USNM 240740 from USGS Mesozoic loc. 22698. Whorl section is slightly

crushed. 

18-21. Arctocephalites cf. A. elegans Spath (p. 34).

Specimen, USNM 108743 from USGS Mesozoic loc. 22699. Partial, nearly smooth 

body chamber is shown in figures 18 and 21. On figure 21 the adoral end of body 

chamber is pointed upward. 

22, 26-28. Iniskinites cf. I. intermedius (Imlay) (p. 35).

22, 27, 28. Ventral and lateral views of specimen, USNM 240744 from USGS Mesozoic loc. 30262.

26. Specimen, USNM 240743 from USGS Mesozoic loc. 22700. 

23-25. Iniskinites cf. I. magniformis (Imlay) (p. 35).

23, 25. Crushed immature septate specimen, USNM 240745a from USGS Mesozoic loc. 22536.

24. Ventral view of uncrushed specimen, USNM 240745b from USGS Mesozoic loc. 22536.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 8

TUXEDNITES, TUXEDNITES1, ARCTOCEPHALITES, AND INISKINITES
PLATE 9

[All figures are natural size]

FIGURES 1-10. Talkeetnites cadiformis Imlay, n. sp. (p. 36).

1-4, 6, 8-10. Holotype, USNM 240746 from USGS Mesozoic loc. 30277. Shows 

ventral, cross-sectional, and apertural views of incomplete body 

whorl. On Figure 1 the adoral part of the body chamber is 

pointed downward. Figure 4 is a line drawing cross-sectional 

view. Figures 9 and 10 represent the adoral half of the holotype 

split along the crack shown in figure 6. Figures 2, 3, and 10 show 

the ribbing on a small inner whorl.

5, 7. Paratype, USNM 240747 from USGS Mesozoic loc. 30277. Lateral 

and ventral views of intermediate-sized septate whorl.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 9

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• J,

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-.* ?^" & . x :.?-'*' -*"*"1 , -*^T**^-

^3- * - y^- "*-"- •** >

' A'*"-*"." tVV, ^ i^!l J&«ti-5JJ *ia^!'^

TALKEETNITES
PLATE 10

[Figures natural size unless otherwise indicated]

FIGURES 1—10. Parareineckeia hickersonensis Imlay (p. 36).

1, 4, 6, 7, 9. Hypotype, USNM 240751 from USGS Mesozoic loc. 30576. Figures

6 and 7 (x 2) depict three inner whorls whose place of attachment

is shown on Figure 9. Figures 1, 4, and 9 depict the outermost

whorl of a microconch as shown by presence of a lateral lappet.

2. Rubber imprint of external mold of laterally crushed hypotype,

USNM 240750 from USGS Mesozoic loc. 28682. 

3, 8. Ventral and lateral views of hypotype, USNM 240752 from USGS

Mesozoic loc. 30272. Note prominent spines in figure 3. 

5. Rubber imprint of laterally crushed external mold of hypotype,

USNM 240749 from USGS Mesozoic loc. 28682.

10. External and internal molds of laterally crushed hypotype, USNM 

240748 from USGS Mesozoic loc. 28682. At least two-fifths of the 

outer whorl is nonseptate.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1091 PLATE 10
PLATE 11

[All figures are natural size]

FIGURES 1—16. Parareineckeia nelchinensis Imlay n. sp. (p. 36).

1. Rubber imprint of external mold of paratype, USNM 240754 from

USGS Mesozoic loc. 28527.

2-5. Internal mold of immature paratype, USNM 240760 from USGS Mesozoic loc. 3038. 

6. Laterally crushed paratype, USNM 240756 from USGS Mesozoic loc.

28682.

7, 13-16. Holotype, USNM 240753 from USGS Mesozoic loc. 30272. Figures 7 

and 14 represent the septate whorls. On figure 16 about half of outer 

whorl is nonseptate.

8. Laterally crushed paratype, USNM 240755 from USGS Mesozoic loc. 

28527. Probably represents part of adult body chamber.

9. Laterally crushed paratype, USNM 240759 from USGS Mesozoic loc.

28524.

10, 11. Paratype, USNM 240758 from USGS Mesozoic loc. 28682. 

12. Paratype, USNM 240757 from USGS Mesozoic loc. 28682.
GEOLOGICAL SUKVE PROFESSIONAL PAPER 1091 PLATE 11

,,-X • t
PLATE 12

[All figures natural size except suture lines]

FIGURES 1, 5, 10, 11. Cobbanites striatus Imlay n. sp. (p. 37).

1. Internal and external molds of holotype, USNM 240764 from

USGS Mesozoic loc. 28682. 

5, 10, 11. Internal mold of immature paratype, UCLA 4988 at loc. RAL

65. 

2-4, 7—9. Cobbanites talkeetnanus Imlay (p. 37).

2-4. Hypotype, USNM 240761 from USGS Mesozoic loc. 30277. 

7. Hypotype, USNM 240762 from USGS Mesozoic loc. 28699. 

8, 9. Hypotype, USNM 240763 from USGS Mesozoic loc. 28525. 

6, 12-15. Cobbanites tuxedniensis Imlay n. sp. (p. 37).

Holotype, USNM 240765 from USGS Mesozoic loc. 30261. Figure 6 shows 

suture line (x 2) drawn at diameter of 80 mm. Figure 12 shows a ventral 

view at diameter of about 67 mm. Figure 13 shows a ventral view at diameter of 80 mm.
GEOLOGICAL SURVEY

12

COBBANITES

.S. GOVERNMENT PRINTING OFFICE: 1980 O—311-344/21