Late Jurassic Ammonites 

From Alaska 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1190 
Late Jurassic Ammonites 

From Alaska 

By RALPH W. IMLAY 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1190 

Studies of the Late jurassic ammonites 

of Alaska enables fairly close 

age determinations and correlations 

to be made with Upper Jurassic 

ammonite and stratigraphic sequences 

elsewhere in the world 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1981 
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Library of Congress catalog-card No. 81-600164 

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304 
CONTENTS 

Page Page 

Abstract ----------------------------------------- 1 

2 

14 

14 

14 

15 

17 

17 

18 

Ages and correlations ------------------------------

Early to early middle Oxfordian ---------------

Late middle Oxfordian to early late Kimmeridgian 

19 

19 

20 

21 

21 

22 

23 

28 

36 

39 

Introduction -------------------------------------- Biologic analysis _________________________________ _ Latest Kimmeridgian and early Tithonian _____ _ Biostratigraphic summary ------------------------- Late Tithonian ______________________________ _ 

~ortheastern Alaska --------------------------

Wrangell Mountains -------------------------- Ammonite faunal setting ---------------------------

Geographic distribution ----------------------------

Talkeetna Mountains --------------------------

Tuxedni Bay-Iniskin Bay area -----------------

Systematic descriptions ___________________________ _ 

References cited ----------------------------------

Alaska Peninsula ----------------------------- Index --------------------------------------------

PLATES 1-3. 

4. 

5. 

6. 

7. 

8. 

9-11. 

12. 

Phylloceras. 

Partschiceras and Phylloceras. 

H olocophylloceras. 

Lytoceras and Partschiceras. 

ILLUSTRATIONS 

[Plates follow index] 

Aulacosphinctoides, Cardioceras, and Perisphinctes (Dichotomosphinctes). 

Cardioceras and Subplanites?. 

Cardioceras. 

Amoeboceras and Amoeboceras?. 

Page 

FIGURE 1. Generalized index map of Upper Jurassic ammonite localities in Alaska -------------------------- 2 

2-10. Detailed index maps of Upper Jurassic ammonite localities: 

2. Central part of the Mt. Michelson Quadrangle between the Canning and Sadlerochit Rivers, 

northern Alaska ----------------------------------------------------------------- 3 

3. McCarthy (C-5) Quadrangle, Wrangell Mountains, southern Alaska --------------------- 4 

4. ~elchina area of the Talkeetna Mountains, southern Alaska ---------------------------- 5 

5. Peninsula between Tuxedni Bay and Chinitna Bay, west of Cook Inlet, southern Alaska ___ 6 

6. Iniskin Peninsula west of Cook Inlet, southern Alaska --------------------------------- 7 

7. Alaska Peninsula south of Kamishak Bay and west of Cook Inlet, northwest of Augustine 

Island, southern Alaska _ _ _ __ _ _ ____ __ __ _ __ _ _ _ __ _ __ _ _ __ _ _ ___ _ _ _ ___ _ _ _ _ _ _ _ _ ___ __ _ _ _ _ 8 

8. Mt. Katmai area, Alaska Peninsula --------------------------------------------------- 9 

9. Puale Bay-Mt. Peulik-Wide Hay area, Alaska Peninsula ------------------------------- 10 

10. ~orth of Chignik Lagoon, Chignik (B-2) Quadrangle, and north of Amber Bay, Sutwik 

(D-4) Quadrangle, Alaska Peninsula ___ ------------------------------------------- 11 

11. Chart showing European ranges of Late Jurassic ammonite genera and subgenera present in Alaska 12 

12. Correlation chart of Late Jurassic ammonite faunas in Alaska ---------------------------------- 13 

III 
IV CONTENTS 

TABLES 

Page 

TABLE 1. 

2-3. 

Ammonite genera and subgenera of Late Jurassic age in Alaska -----------------------------------

Stratigraphic positions of ammonite occurrences above base of members of the Naknek Formation2. South shore of Chinitna Bay, west of Cook Inlet ---------------------------------------

3. Oil Bay and Iniskin Bay, west of Cook Inlet -----------------------·------------------------

4-6. Geographic distribution of ammonites of Late Jurassic age4. Northeastern Alaska and Wrangell Mountains ----------·-----------------------------------

5. Talkeetna Mountains and west of Cook Inlet -----------------------------------------------

6. Alaska Peninsula ________ ----- ____ ------------------------------------------------------

7. Description of Upper Jurassic ammonite localities in Alaska -------------------------------------

Metric unit 

millimeter (mm) meter (m) 

kilometer (km) 

square meter (m2) 

square kilometer (km2) 

hectare (ha) 

cubic centimeter (cma) 

liter (L) 

cubic meter (m3) 

cubic meter 

CONVERSION FACTORS 

Inch-Pound equivalent Metric unit Inch-Pound equivalent 

Length Specific combinations-Continued 

0.03937 inch (in) 

3.28 feet (ft) .62 mile (mi) 

Area 

10.76 

.386 

2.47 

Volume 

square feet (ft2) 

square mile ( mi2) acres 

cubic inch (ina) 

cubic inches 

liter per second (L/s) 

cubic meter per second 

per square kilometer 

[(ma;s)/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 

(ma;s) 

.0353 

91.47 

3.28 

5.28 

.9113 

3.28 

10.764 

22.826 

cubic foot per second 

cubic feet per second per 

square mile [ (fta;s)/ml2] 

feet per day (hydraulic conductivity) (ft/d) 

feet per mile ( ft/mi) 

foot per second (ft/s) 

feet per second 

feet squared per day (ft2/d) 

(transmissivity) 

million gallons per day 

(Mgal/d) 

14 

14 

15 

15 

16 

16 

23 

cubic hectometer (hm3) 

liter 

0.061 

6\1.03 

35.31 

.00081 

=810.7 

2.113 

1.06 

.26 

cubic feet (ft3) 

acre-foot (acre-ft) 

acre-feet 

pints (pt) cubic meter per minute 

(ma;min) 

=264.2 gallons per minute (gal/min) 

liter 

liter 

cubic meter 

cubic meter 

gram (g) 

gram 

metric tons (t) 

metric tons 

kilogram per square centimeter (kg/cm2) 

kilogram per square centimeter 

cubic meter per second 

(m3/s) 

.00026 

6.290 

Weight 

0.0::15 

.0022 

1.102 

0.9842 

quarts (qt) gallon (gal) 

million gallons ( Mgal or 106 gal) barrels (bbl) (1 bbl=42 gal) 

ounce, avoirdupois (oz avdp) pound, avoirdupois (lb avdp) 

tons, short ( 2,000 lb) 

ton, long (2,240 lb) 

Specific combinations 

0.96 atmosphere (atm) 

.98 

3::>.3 

bar (0.!)869 atm) 

cubic feet per second (fta;s) 

liter per second (L/s) 

liter per second per meter [ (L/s)/m] 

kilometer per hour 

(km/h) 

meter per second (m/s) 

gram per cubic 

centimeter (g/cma) 

gram per square 

centimeter (g/cm2) 

gram per square centimeter 

degree Celsius (°C) 

degrees Celsius 

(tern perature) 

15.85 

4.83 

.62 

2.237 

612.43 

2.048 

gallons per minute 

gallons per minute per foot 

[(gal/min) /ft] 

mile per hour (mi/h) 

miles per hour 

pounds per cubic foot (lb/ft3) 

pounds per square foot (lb/ft2) 

.0142 pound per square inch (lb/in2) 

Tern perature 

1.8 degrees Fahrenheit (°F) 

= [ (1.8 X •c) +"32.] degrees Fahrenheit 
LATE JURASSIC AMMONITES FROM ALASKA 

By RALPH w. IMLAY 

ABSTRACT 

Late Jurassic ammonites have been found in northeastern 

Alaska only in the Mt. Michelson Quadrangle from the East 

Fork of the Shaviovik River eastward about 40 miles ( 64 

kilometers) to Fire Creek. Late Jurassic ammonites have 

been found in southern Alaska, from west to east: ( 1) in 

the northern part of the Alaska Peninsula north of Chignik 

Bay; (2) along the west side of Cook Inlet, but mostly on 

the Iniskin Peninsula; (3) in the Talkeetna Mountains; and 

( 4) in the Wrangell Mountains. 

The early to early middle Oxfordian is represented by 

Cardioceras in all the areas listed above except in the 

Wrangell Mountains. Intensive collecting on the Iniskin 

Peninsula shows that the lower part of the Cardiocerasbearing beds is characterized by C. (Scarburgiceras) martini 

Reeside and the upper part by C. (C.) distans (Whitfield) in 

association with C. (Scoticardioceras) alaskense Reeside. 

Some collections, however, contain both of the first two 

species listed, which suggests that the vertical ranges of the 

two species overlap. Associated with Cardioceras on the 

Iniskin Peni~sula and in the Talkeetna Mountains are specimens of Phylloceras iniskinense Imlay, n. sp., in the lower 

part of its range. 

'I'he late middle Oxfordian to early late Kimmeridgian is 

characterized and dated in northeastern Alaska and in the 

Wrangell Mountains by an abundance of the bivalve Buchia 

concentrica (Sowerby) in association with the ammonite 

A moeboceras and its subgenera Prionodoceras and A moe bites. 

By contrast, from the Talkeetna Mountains southward to the 

middle of the Alaska Peninsula, that species of Buchia is 

not associated with A moeboceras but with two successive 

species of Phylloceras. Of these species, Phylloceras iniskinense Imlay, n. sp., near the top of its range is dated by the 

presence of Perisphinctes ( Dichotomosphinctes) as of late 

middle to late Oxfordian Age. The overlying beds containing 

Burhia concentrica are characterized by Phylloceras alaskanum Imlay, n. sp., which is likewise dated in the lower part 

of ~ts range as late middle to late Oxfordian by its association with P. (Dichotomosphinctes). The next higher beds that 

contain Phylloceras alaskanum Imlay, n. sp., associated with 

the highest occurrences of Buchia concentrica are dated as 

early Kimmeridgian to early late Kimmeridgian on the basis 

of their stratigraphic position below beds containing Buchia 

mosquensis (von Buch) and B. rugosa (Fischer); these last 

two species are not known in Eurasia in beds older than 

early late Kimmeridgian and range as high as the early 

late Tithonian. 

The uppermost Kimmeridgian and early Tithonian beds in 

Alaska are characterized by an abundance of Buchia rugosa 

(Fischer) and B. mosquen8is (von Buch). These beds are 

widespread in northern, southeastern, southern, and southwestern Alaska and on the Alaska Peninsula but are absent 

west of Cook Inlet. Ammonites are scarce throughout all 

these areas except on the Alaska Peninsula, where Phyllocera8 ala8kanum Imlay, n. sp., is common. Its association 

locally with the ammonites Subplanite8? and A ulacosphinctoides is good evidence that the beds are at least in part of 

early Tithonian Age. The beds containing B. 'rugosa and B. 

mosquensis are also dated on the basis of their stratigraphic 

position above Amoeboceras and below Buchia piochii (Gabb) 

and on the known ranges of B. rugo.<m and B. mo8quen8is in 

Eurasia. 

lJpper Tithonian beds in Alaska, which are not as widespread as beds of earlier Jurassic age, are characterized by 

the presence of Buchia piochii (Gabb), B. cf. B. fischeriana 

( d'Orbigny), B. unschen8is (Pavlow), and by an absence of 

ammonites, except for one specimen of Phylloceras from 

near Amber Bay on the Alaska Peninsula. This Phylloceras 

resembles P. knoxvillensi8 Stanton. which in California occurs with the ammonite Parodontocera8 of late Tithonian 

Ag~ (Imlav and Jones, 1970, p. B28. pl. 2, figs. 4-11). The 

RPecies of Buchia present have been dated as late Tithonian 

in arcti~ Canada by their asssociation with the ammonite 

Ora8pedites and in California, by the ammonites ParodontfJcera8 and Ko8smatia. 

The Late Jurassic ammonites present in Alaska are of 

diverse geog-raphic origin. Certain genera. including Dichotomo8phinctes, Subplanite8?, Aulacosphinctoides, Phylloceras, and 

Lytoceras are common in the Tethyan and Pacific Realms and 

apparently spread northeastward from the Pacific Ocean 

across the present site of the Alaska Peninsula, the Cook 

Inlet region, and the Talkeetna Mountains, but no farther 

east or north. Other genera, including Cardioceras and 

A moeboceras, spread southward from the Arctic Ocean across 

arct.ic Canada and thence farther south along the Pacific 

Coast. Cardioceras also spread southwestward from arctic 

Canada across southern Alaska, at least as far as the Wide 

Bay area on the Alaska Peninsula and spread southeastward 

far into the interior of North America. From the Talkeetna 

Monntains gouthwestward, Cardioceras definitely intermingled 

with ammonite genera of the Pacific or Tethyan Realm. By 

1 
2 LATE JURASSIC AMMONITES FROM ALASKA 

contrast, A moeboceras has not been found west of the 

Wrangell Mountains in Alaska or in the western interior of 

the United States. 

Associated with all these ammonite genera except Cardiocera.s is the bivalve Buchia, which in middle Oxfordian time 

spread southward from the Arctic Ocean at least as far as 

Mexico and attained maximum numbers on hard sandy to 

silty bottoms of shallow seas. Its presence suggests that the 

two different but contemporaneous ammonite faunules lived 

under similar environmental conditions. Their differences, 

however, could be reasonably ascribed to the fact that the 

marine waters southwest of the present site of the Talkeetna 

Mountains probably bordered a major ocean rather than a 

shallow sea, as attested by an abundance of Phylloceras as 

well as ammonite genera of Tethyan affinities. Apparently 

the scarcity of ammonites of latest Kimmeridgian and Tithonian Age throughout most of Alaska could be due to a slight 

shallowing of. the sea that did not affect the area now 

represented by the Alaska Peninsula. 

INTRODUCTION 

Late Jurassic ammonites (table 1) obtained from 

one area in northeastern Alaska and from nine areas 

in southern Alaska (figs. 1-10) are described herein 

in order to present evidence concerning the stratigraphic and geographic distribution of genera and 

species (tables 1-6), to evaluate their faunal setting 

in relation to the Boreal and Mediterranean regions, 

to make correlations with Upper Jurassic sequences 

elsewhere in North America, and to correlate the 

Alaskan Upper Jurassic beds and ammonite sequences with the ammonite zones of western Europe 

(figs. 11, 12). Correlation of the Upper Jurassic 

lithologic units within Alaska has been depicted in 

considerable detail by Imlay and Detterman ( 1973, 

figs. 11A, B) and is not repeated herein. 

FIGt.TRE 1.-Upper Jurassic ammonite localities in Alaska. Numbers on map refer to listing in tables 4-7. 
146°30' 146° 

R 24 E 

69°45' -

69°30' 

X 21027 

R 24 E .R 25 E 

25 

INTRODUCTION 

T 

1 

s 

T 

2 MOUNTAINS N 

R 26 E R 27 E 

Ot-l-----.----'--r----....,.....J1f MILES 

0 1

1

0 1l5 KILOMETERS 

3 

145° 

28 29 R 30 E 

MOUNTAINS 

R 29 E R 30 E R 31 E 

FIGURE 2.-Upper Jurassic ammonite localities in the central part of the Mt. Michelson Quadrangle between the Canning 

and Sadlerochit Rivers, northern Alaska. Numbers on map refer to listing in tables 4 and 7. 
4 LATE JURASSIC AMMONITES FROM ALASKA 

142°50' 45' 40' 35' 142°30' 

R 14 E R 15 E R 16 E 

6 Nizina Mtn. 

X 28577 

61°35' 

61°30' 

0 1. 2 3 4 MILES 

I I 

I 

I 

I 

I 

.I 

I 

0 3 4 5 KILOMETERS 

FIGURE 3.-Upper Jurassic ammonite localities in the McCarthy (C-5) Quadrangle, Wrangell Mountains, southern Alaska. 

Numbers on map refer to listing in tables 4 and 7. 
INTRODUCTION 

61°45't==t==============================j[==============================jt=======t======================d 0 

I 

0 

5 

I I 

10 I 

10 MILES I 

20 KILOMETERS 

5 

FIGURE 4.-Upper Jurassic ammonite localities in the Nelchina area of the Talkeetna Mountains, southern Alaska. 

Numbers on map refer to listing in tables 5 and 7. 
6· LATE JURASSIC AMMONITES FROM ALASKA 

50' 45' 40' 

TUXEDNI BAY 

0 

I 

0 

I 

3 

I 

3 MILES 

I 

4 KILOMETERS 

FIGURE 5.-Upper Jurassic ammonite locality on the peninsula between Tuxedni B'ay and Chinitna Bay, west of Cook 

Inlet, southern Alaska.- Numbers on map refer to listing in tables 5 and 7. 
INTRODUCTION 7 

20' 15' 10' 05' 153°00' 

BAY 

cHtN/TNA Gull Island 

~ 

6 Shark Tooth 

ISLAND 

0 4 5 MILES 

I 

0 3 4 

I II I 

S 6 KILOMETERS 

FIGURE 6.-Upper Jurassic ammonite localities on the Iniskin Peninsula, west of Cook Inlet~ southern Alaska. Basal boundary of Naknek Formation is indicated by dashed line. Numbers on map refer to listing in tables 5 and 7. 
8 

155°00' 

LATE JURASSIC AMMONITES FROM ALASKA 

30' 

0 

I I 0 10 

154°00' 

10 

i 

KAMISHAK BAY 

I 

20 I 

20 MILES I 

30 KILOMETERS 

30' 153°00' 

FIGURE 7.-Upper Jurassic ammonite localities on the Alaska Peninsula south of Kamishak Bay and west of Cook Inlet 

northwest of Augustine Island, southern Alaska. Numbers on map refer to listing in tables 6 and 7. 
155°00' 

0 

l 

0 

INTRODUCTION 

I 

10 

10 

i I 

20 I 

20 MILES 

I 

30 KILOMETERS 

9 

153°30' 

FIGURE 8.-Upper Jurassic ammonite localities in the Mt. Katmai area, Alaska Peninsula. Numbers on map refer to listing 

in tables 6 and 7. 
10 

157°00' 

LATE JURASSIC AMMONITES FROM ALASKA 

30' 

BECHAROF LAKE 

t:, Mt. Peulik 

X 10798 

0. 

~~+ 10795 

10796 X 

11345X 

0 

I 

0 I 

10 

156°00' 

10 

I I 

20 

~ x3136 

'?'-~ ~ 

I 

20 MILES 

I 

30 KILOMETERS 

155°30' 155°00' 

FIGURE 9.-Upper Jurassic ammonite localities in the Puale Bay-Mt. Peulik-Wide Bay area, Alaska Peninsula. Numbers 

on map refer to listing in tables 6 and 7. 
57"00' 

159°00' 

25708-25710, 257_12, 25713, 

25715, and 5799A 

30' 

0 

I 

0 

INTRODUCTION 

11359 

• 

I 

10 

15SOOO' 

10 

I 

I 

20 I 

20 MILES 

I 

30 KILOMETERS 

11 

30' 157°00' 

FIGURE 10.-Upper Jurassic ammonite localities north of Chignik Lagoon, Chignik (B-2) Quadrangle, and north of Amber 

Bay in the Sutwik (D-4) Quadrangle, Alaska Peninsula. Numbers on map refer to listing in tables 6 and 7. 
~ 

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Quenstedtoceras mariae 

Cardioceras cordatum 

Perisphinctes plicatilis 

Gregoryceras transversarium 

Perisphinctes cautisnigrae 

Decipia decipiens 

Ringsteadtia pseudocordata 

Pictonia ·bay/ei 

Rasenia cymodoce 

'Rasenia mutabilis 

Aulacostephanus eudoxus 

Aulacostephanoceras acutissiodorensis 

Virgatosphinctoides elegans 

Virgatosphinctoides scitulus 

Virgatosphinctoides wheatleyensis 

Arkellites hudlestoni 

Pectinatites pectinatus 

Pavlovia rotunda 

pavlovia pallasioides 

Zaraiskites a/bani 

Glaucolithites gorei 

Titanites giganteus 

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INTRODUCTION 

Northeastern Alaska Wrangell Mountains, Talkeetna Mountains, West of Cook Inlet 

Buchia unschensis 

and 

B. ct. B. 

fischeriima 

southern Alaska southern Alaska between Tuxedni Bay 

and lniskin Bay 

~-----------------------------4--------?------~ 

Titanites giganteus 

G/aucolithites gorei 

r------------------------------4-------?-------4 

Zaraiskites a/bani 

Pavlovia pallasioides ~------?------~------~?------~ 

Pavlovia rotunda 

Pectinatites pectinatus 

Arke/lites hudlestoni 

Virgatosphinctoides wheatleyensis 

Virgatosphinctoides sCitulus 

Virgatosphinctoides elegans 

Aulacostephanoceras acutissiodorensis 

Aulacostephanus eudoxus 

Rasenia mutabilis 

Rasenia cymodoce 

Pictonia baylei 

Ringsteadtia pseudocordata 

Decipia decipiens 

Perisphinctes cautisnigrae 

Gregoryceras transversarium 

Buchia rugosa 

and 

B. mosquensis 

? (') 

Cll 

·"=:: 

.Q 

Cll 

0 

E: 

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Amoeboceras 

(Prionodoceras ?) 

-

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Cll 

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c:: 

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Buchia rugosa 

and 

B. mosquensis 

-? ,... 

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Amoeboceras 

(Prionodoceras) 

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Buchia rugosa 

and 

B. mosquensis 

-?-

Phylloceras 

a/askanum 

(rare) 

?-

Phylloceras 

iniskinense 

-

? 

m Phyl/oceras ·s alaskanum c:: 

Cll (rare) (..) 

c:: 

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13 

Alaska Peninsula 

between Kamishak 

Bay and Chignik Bay 

Buchia piochii 

r--?--?-

-

r-?-~ 

e~ ~ 2l ~ ;}a; 0 c:: 0 .... 

~~Qi E: ~ ~ ·~ ro .s ct: ·S:..!::. .g 

"0 

c 

m 

--~--~-~?-- ·~----L-----~ 

.3.cardioceras 

? ? --? .E;: :S. ? (') 

Perisphinctes plicatilis ~~rdioceras 

Cardioceras cordatum 

Ouenstedtoceras mariae 

Cardioceras ~ 

dis tans 2l distans 0 

Cardioceras Cardioceras 

--?~ ~- ~ 

ct Card1oceras 

(Scarburgiceras) (Scarburgiceras) (Scarburgiceras) martini martini 

FIGURE 12.-Correlation of Late Jurassic ammonite faunas in Alaska. 

( Verteb riceras) 

whiteavesi 
14 LATE JURASSIC AMMONITES FROM ALASKA 

This study is based mainly on fossil collections 

and stratigraphic information obtained during the 

last 70 years by many geologists of the U.S. Geological Survey, as listed by Imlay and Detterman 

(1973, p. 8, 9). It also includes fossil collections and 

data obtained by British Petroleum (Alaska), Inc., 

in 1964 in northern Alaska, by Continental Oil Co. 

in 1967 near Kamishak Bay at the south end of Cook 

Inlet, and by the Richfield Oil Co. in 1962 on the east 

shore of Puale Bay in the Alaska Peninsula. Biostratigraphic data for northern Alaska were furnished mainly in publications by Detterman and 

others (1975); for the Wrangell Mountains, by MacKevett (1969, 1970, 1971); for the Talkeetna Mountains, by Grantz (1960a, b); for the west side of 

Cook Inlet, by Detterman and Hartsock (1966); and 

for the Alaska Peninsula, by Capps (1923), Knappen 

her 233 specimens. Their distribution by family, subfamily, genus, and subgenus is shown in table 1. 

Among the families, the Gardioceratidae constitutes 

about 63 percent, the Phylloceratidae about 28 percent, the Lytoceratidae 7 percent, and the Perisphinctidae 2 percent. The characteristics of the 

genera and subgenera of Cardioceratidae have been 

discussed in detail by Arkell (1935-1948). The other 

genera and subgenera listed from Alaska have been 

described adequately by Arkell and others (1957). 

TARLE !.-Ammonite genera and subgenera of Late Jurassic 

age in Alaska 

Family Subfamily 

Genus and 

subgenus 

Number 

of 

specimens ---------------------------

(1929)' Martin (1926)' Keller and Reiser (1959)' Phylloceratidae Phylloceratinae ~~~:~~'hi~::as--========= 56 

8 

2 Smith (1925)' Smith and Baker (1924)' and,. in Lytoceratidae --- ~~~~::~~~:~ati~~-e--= z;:~~~:::;zo~~~~~--====== 16 

particular, the comprehensive study by Burk (1965) 0 Perisphinctidae -- Perisphinctinae ----- Pe(}jfc~~~~~~sphinctes) a 

1 The 1 described specimens are deposited in the type Virgatosphinctinae -- ~~~:~::;~i~ctoide;--==== 

collections of the u.s. National Museum and are Cardioceratidae -- Cardioceratinae ---- Car:::a~b:a:gi~e""r""isT-==== 

labeled "USNM." (Scoticardioceras) __ ( V ertebriceras) ____ _ 

32 

82 

" 1 A moeboceras BIOLOGIC ANALYSIS fAmoebitesJ -------- (Amoebites?J -------- Alaskan ammonites of Lake Jurassic age (Ox- (PrionodocerasJ ----

1 

1 

2 (Prionodoceras?J __ _ fordian to Tithonian) that are discussed herein num- Amoeboceras? --------- '----------------------------

23 

2 

TABLE 2.-Stratigraphic positions of ammonite occurrences above base of members of the Naknek Formation on south shore 

of Chinitna Bay, west of Cook Inlet 

South shore of Chinitna Bay 

Snug Harbor 

lower sandstone member Siltstone Member 

Stratigraphic position above base 

of members in feet (meters). 

USGS Mesozoic localities __________ 

Buchia concentrica (Sowerby) --------

sp --------------------------------- PkyUocerat~ cf. P. alaskanum Imlay, 

in~i.:i~~"-l~;y,~~-;P-~~~~~-=-~~~-=-~~ 

sp --------------------------------- Cardioceras ( Cardiocerat1) distans (Whitfield) _____________________ _ 

hyatti Reeside --------------------- cf. C. (C.) liUoetense Reeside ------- ( Scarburgiceras) martini Reeside _- _ ( Scoticardioceras) alaskense Reeside_ 

cf. C. (S.) steUa Arkell -----------

50-100 200-260 200-250 (15-30) (60-75) ( 6(}...-76) 

21350a 11002 11013 

X 

X X 

X X 

BIOSTRATIGRAPHIC SUMMARY 

NORTHEASTERN ALASKA 

200-250 

(60-75) 

11015 

X 

X 

In northeastern Alaska east of the Sagavanirktok 

River, the Upper Jurassic part of the Kingak Shale 

ranges in thickness from a featheredge to at least 

1,800 feet ( 545 m), is locally absent, and consists 

mostly of black clay shale interbedded with siltstone 

and some clay ironstone concretions (Imlay and 

Detterman, 1973, p. 5-16, figs. 6-9, 11A, 11B, 12, 

200-250 2Q0-250 200-250 200-250 450 450 800 600 600 600 ( 60-75) (60-75) (60-75) (60-75) (136) (136) (242) (181) (181) (181) 

11016 11017 11018 21782 21351 21784 21783 21352 21785 21786 

X 

X 

X 

X X X X X 

X 

X X 

X X 

X X X X X 

X 

X 

14; Detterman and others, 1975, p. 18-20, 44, fig. 7). 

On lgnek Mesa and nearby Fire Creek (table 4), 

the Kingak Shale has furnished Cardioceras (Scarburgiceras) of early Oxfordian Age. That subgenus 

on lgnek Mesa occurs 80 feet (24m) below beds of 

Early Cretaceous (Valanginian) age and 135 feet 

( 41 m) above the ammonite A rcticoceras of late 

Bathonian Age (Detterman and others, 1975, p. 18, 

44; Imlay, 1976, p. 5). 
BIOSTRATIGRAPHIC SUMMARY 15 

TABLE 3.-Stratigraphic positions of ammonite occurrences above base of members of the Naknek Formation at Oil Bay 

and Iniskin Bay, west of Cook Inlet 

Oil Bay 

Iniskin 

Bay 

lower sandstone member 

650-

68{) 

Stratigraphie position above base of 

members in feet (meters). 

50 

(16) 

98 

(30) 

16() 253 625 695 660 660 660 10 

(3) 

200-

226 

(61-

68) 

( 197-

(46) (77) (169) (180) (200) (200) (200) 206) 

USGS Mesozoic localities ---------------- 22418 3043 22426 3044 3046 3046 11066 10988 11066 20723 22460 22449 

-------------------------------------------------------------

Buchio concentrica (Sowerby) --------------

sp ---------------------------------------- Phyllocef'a.s iniskinense Imlay, n. sp ---------

L'I/f;ocera.s sp -------------------------------- X X 

Perl.phinctes ( Dichotomosphinctes) ef. P. (D.) 

muhlbachi Hyatt -------------------------- Cardioceras ( Cardioceras) distans (Whitfield) ____________________________ _ 

(C.T) spiniferum Reeside ------------------ ( Scarburoicef'a.s) martini Reeside _ _ _ _ _ _ _ _ _ X X 

X 

X X 

X 

X X 

X 

X 

X 

X 

X 

X 

X 

X 

TABLE 4.-Geographic distribution of ammonite of late Jurassic age in northeastern Alaska and in the Wrangell Mountains 

[Numbers 1-6 are keyed to locality numbers in fig. 1; higher numbers are USGS Mesozoic locality numbers] 

Northeastern Alaska Wrangell Mountains 

Kingak Shale Root Glacier 

(upper part) Formation 

Genus and species 

Buchia concentrica (Sowerby) ---------------

mosquensis (von Buch) ------------------- rugosa (Fischer) -------------------------

Phylloceras sp ------------------------------ Partschicera.s sp. A -------------------------- Cardiocera.s ( Scarburgiceras) dettermani 

Imlay, n. sp ------------------------------ Amoebocera.s (Amoebites) sp ---------------- (Amoebites1) sp -------------------------- (Prionodoceras) sp. A --------------------

sp. B ----------------------------------- (P.?) ef. A. (P.?) prorsum Spath --------

A.? sp. A ---------------------------,-------- sp. B ------------------------------------

00 

IN 

~ IN 

X 

X 

00 ";!: IN en 00 ~ U') 0 00 0 c-1 ..., en """ IN C'l IN IN 

X X X X 

X 

X 

X --

X 

In the Canning River area, the Kingak Shale has 

furnished the late Oxfordian to Kimmeridgian 

ammonite Amoeboceras (Prionodoceras) and A. 

(A moe bites) in association with the bivalve Buckia 

concentrica (Sowerby). Such mollusks were collected from about 1,040 feet (315 m) of shale exposed on the west side of the river opposite the 

mouth of Cache Creek (Imlay, 1976, p. 4). The 

lowermost occurrence (USGS Mesozoic loc. 29135) is 

about 600 feet (182 m) a'bove beds containing the 

late middle Bathonian ammonite Arctocepkalites. 

The uppermost occurrence (USGS Mesozoic loc. 

29136) is about 1,040 feet (315 m) below a fault 

contact with beds of Bajocian Age. 

Other specimens of Amoeboceras and Buckia concentrica were collected from the upper 50 feet 

(15m) of the Kingak Shale exposed on the west side 

of the Canning River about 9 miles (14.4 km) north 

I 2 I 3 I 4 5 

t- U') "' "' t- 10 "' t- t- 00 en 0 IN ~ ~ U') 

~ en en en t- t- t-

;: 00 ..., ..., ..., U') U') U') ~ en en en en ";!: ";!: ";!: 00 00 00 00 IN IN IN IN IN IN IN N N 

X X X X X 

X X X 

X 

X 

X 

X X 

X 

X X X X 

X X 

X 

X 

of Cache Creek and 2.5 miles (4 km) south of Black 

Island at USGS Mesozoic locs. 24013, 24014, 21028, 

22598, and 29882. No_ evidence has yet been found 

of the presence of Buckia rugosa (Fischer) in northeastern Alaska east of the east fork of the Shaviovik 

River, which is about 10 miles (16 km) west of the 

Canning River, except at Joe Creek near the Canadian border (Detterman and others, 1975, p. 44). 

WRANGELL MOUNTAINS 

The Root Glacier Fonnation (Upper Jurassic) has 

been described by MacKevett (1969, p. A45-A49; 

1970; 1971, p. 17, 18) and mentioned briefly by 

Imlay and Dettennan (1973, p. 8, 11). It ranges in 

thickness from a featheredge to about 3,800 feet 

(1,151 m), rests disconformably on beds of Pliensbachian to Bathonian Age, is overlain unconformably by beds of Early Cretaceous age, and consists 
16 LATE JURASSIC AMMONITES FROM ALASKA 

TABLE 5.-Geographic distribution of ammonites of Late Jurassic 

Genus and species 

:~~:e:::ctd~!~u~ sr:i!~~ >n. -;;-: :====: :==: = ==: :==: :=== = ==: ===: = === ==== := == = cf. P. ala8k11num Imlay, n. sp ------------------------------------------------

iniskinense Imlay, n. sp -----------------------------------------------------

::~:~~~=;:~~~~~~~~~~~~~~~~~~c~~~=================================== LytocerGs sp ___ ----- ___ ----- __ --------- ____________ ------- ____________________ _ 

Perisphinctes (Dichotomosphinctes) cf. P. (D.) muhlbachi Hyatt --------------

CGrdioceras (Cardioceras) distans (Whitfield) --------------------------------- hyatti Reeside _________________________________________ -- ______ ------------

liUoetense Reeside _____________________________________ --------------------

cf. C. (C.) lilloetense Reeside ---------------------------------------------- (C.?) spiniferum Reeside ------------------------------------------------- __ _ ( Scarburgiceras) martini Reeside ___________________________________________ _ dettermani Imlay, n. sp ___________________________________________________ _ 

( Scoticardioceras) alaskense Reeside ________________________________________ _ 

cf. C. (S.) stella Arkell ---------------------------------------------------

sp ------------------------------------------------------------------------

<0 c-1 

~ ~ ~ ""' c-1 c-1 

X 

X 

X 

[Numbers 6-10 are keyed to locality numbers in fig. 1; 

Talkeetna Mountains 

Naknek Formation 

6 

lO <C t- 00 iO 

~ <C 

,..;.. ~ ~ ~ 

""' ""' ""' ""' ""' c-1 c-1 c-1 c-1 c-1 

X X X 

X X 

X 

X X 

X X X 

X X X 

""' t- ..., ..., ~ 00 

""' c-1 c-1 

X 

X 

X 

X X 

X 

X 

X X 

mostly of mudstone and siltstone but includes some 

shale, graywacke, arenite, conglomerate, and limestone. It has yielded ammonites only in the McCarthy 

( C-5) Quadrangle. 

The exact stratigraphic positions of most of these 

ammonite fossil localities (table 4) in relation to the 

base of the Root Glacier Formation is not determinable because of faulting and folding. Nonetheless, 

Mesozoic loc. 28577 is about 250 feet (76 m) above 

the base; Mesozoic locs. 14495, 14496, 14497, and 

28578 are probably 1,000 to 2,000 feet (303 to 606 

m) above the base; and Mesozoic loc. 28579 is about 

1,500 feet (454 m) above the base. 

Within the McCarthy ( C-5) Quadrangle, the 

lowermost part of the Root Glacier Formation is 

dated as late Kimmeridgian by the association of 

Amoeboceras (Amoebites?) with Buchia corwentrica 

( Sowerby) at USGS Mesozoic loc. 28577. A slightly 

younger late Kimmeridgian Age is shown by the 

association of Amoeboceras (Prionodoceras) with 

Buchia mosquensis (von Buch) and (or) B. concentrica ( Sowerby) at the other listed localities, 

which are estimated to be 1,000-2,000 feet (303-606 

m) above the base of the formation. In addition, 

Buchia rugosa (Fischer) been found with the ammonite Partschiceras about 1,500 feet (455 m) above 

TABLE 6.-Geographic distribution of ammonites of Late Jurassic age in the Alaska Peninsula 

[Numbers 11-21 are keyed to locality numbers in fig. 1; higher numbers are USGS Mesozoic locality numbers] 

Staniukovicb Naknek Formation Formation Naknek Formation (lower part) 

Kamisbak Mt. Katmai Mt. Peulik-Puale Sutwik Aniakchak Chignik Island ( D-4) Crater Genus and species Bay area Bay area Quadrangle Gates Bay 

11 121 13 lal16 I 16 171 18 19 20 21 

Buchia concentrica (Sowerby) ____ -- X X X X X -- X X 

rugo11a. (Fischer) --------------- -- X X X 

mosquensis (von Bueh) --------- -- X X X X Pht~Uoceras alaskanum Imlay, n. sp_ -- X X X X X X X 

X 

X X 

X X 

X 

X X x x x x x x x 

iniskinense Imlay. n. sp -------- -- cf. P. knozvillen~~e Stanton ------ __ 

Partschiceras sp. A --------------- --

sp. B --------------------------- X Lvtoceras sp --------------------- X X Cardioceras ( V ertebriceras) 

whiteaveri Reeside -------------- -- Perisphinctes ( Dichotomisphinctes) cf. P. (D.) muhlbachi (Hyatt) -- -- X 

Aulacosphinctoides sp ------------ __ X 

Subplanites? sp ------------------- --

X 

X 

X 

X 

X 

X 

X 
BIOSTRATIGRAPHIC SUMMARY 17 

age in the Talkeetna Mountains and west of Cook Inlet 

higher numbers are USGS Mesozoic locality numbers] 

West side of Cook Inlet 

Naknek Formation-Continued 

7 I 8 9 =-ri{ .... ~ ~ ~ ~ ~ ~ 0 .... 0 a.Q ! t- ~ 0 

= ~ ~ 

= 

CQ C'l :::: .... C'l .... .... .... C'l CN 

C\4 CN CQ ..., a.Q 00 00 00 CQ ~ ~ ~ ~ CN CN C'l 

a.Q ! 00 ~ lQ :g aa 00 ~ 0) 0 ..., co ..... CQ ..., lQ CC> 00 lQ a.Q 

~ ""' a.Q CC> 

~ ~ ..., ;:!: ~ ;:!: ;:!: ~ 0 ! 

= 

t-

~ ~ ..., t-

~ :::: 0 ~ 0 CN CN CQ CQ CQ CN CN CN CQ 

X -- -- X -- -- -- X X -- -- -- -- -- -- -- X X -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- X -- X -- X X X -- X X -- -- X 

X 

-- -- -- -- -- -- X 

X -- -- -- X X 

-- -- -- -- -- -- -- -- -- -- X 

X X X -- -- X -- -- -- -- -- -- -- X -- -- -- -- X X 

X -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- X -- -- -- X X -- -- -- -- -- -- -- -- -- -- X -- -- -- X -- -- -- X X -- X X -- X -- X X -- X -- -- X X X X -- -- --

-- -- -- X -- -- -- X -- -- -- -- X -- -- -- -- -- -- -- -- X -- -- -- -- -- X -- X -- -- -- -- -- -- --

the base of the formation (USGS Mesozoic loc. 

28579) . Still younger beds of latest Kimmeridgian to 

early Tithonian Age are indicated by the presence of 

Buchia rugosa (Fischer) without ammonites at 

many localities that appear to be higher stratigraphically than those containing Amoeboceras. 

Such localities are indicated on the geologic map of 

the McCarthy ( C-5) Quadrangle ( MacKevett, 1970) 

by the numbers 65, 66, 69, 71, 72, 77, 81, and 84. 

The occurrences of Buchia mosquensis with 

Amoeboceras needs checking in the field because B. 

mosquensis has the same time range as B. rugosa 

and neither has been found elsewhere in association 

with Amoeboceras. Both occur directly above or in 

younger beds than Amoeboceras and are associated 

basally with the highest occurrence of B. concentrica. 

As most of the fossil collections from the Root 

Glacier Formation were made on fairly steep slopes, 

the specimens of Buchia mosquensis collected with 

A moeboceras may actually be float washed down 

from higher beds. 

TALKEETNA MOUNTAINS 

The Upper Jurassic in the Talkeetna Mountains 

is best exposed along the Little Nelchina River and 

its tributaries in the Talkeetna Mountains (A-1) 

and (A-2) Quadrangles. It is reported to be at least 

2,000 feet ( 606m) thick and to consist of two units. 

The lower unit is considerably thicker than the 

upper unit, consists mostly of gray siltstone and 

shale that contain limestone concretions, locally includes cobble and boulder conglomerate at its base, 

X 

as well as at higher levels, and locally in its upper 

part includes a lenticular unit consisting of sandstone, siltstone, and some coquinoid beds. The upper 

unit rests conformably on the lower unit, consists of 

sandstone and siltstone that are interbedded with 

shelly and glauconitic beds, and is overlain unconformably by beds of Valanginian Age (Grantz, 

1960a, b). 

An early to early middle Oxfordian Age for the 

basal and most of the lower third of the main siltstone and shale unit is demonstrated by the presence 

of Cardioceras (table 5) at many localities (USGS 

Mesozoic locs. 24165, 24166, 24168, 24837). A slightly 

younger age for part of the lower third is indicated 

by the presence of Buchia concentrica (Sowerby) at 

several localities. The middle and upper thirds of the 

main siltstone and shale unit are definitely dated as 

late middle to late Oxfordian by the presence of 

Buchia concentrica (Sowerby) in place in the middle 

third (USGS Mesozoic loc. 24175) and Phylloceras 

iniskinense Imlay, n. sp., near the top of the unit 

(USGS Mesozoic loc. 24162). The association of 

Phylloceras alaskanum Imlay, n. sp., with Buchia 

concentrica (Sowerby) at USGS Mesozoic loc. 24156 

favors a Kimmeridgian Age younger than the beds 

containing PhyUoceras iniskinense Imlay, n. sp., in 

association with B. concentrica. I 

TUXEDNI BAY-INISKIN BAY AREA 

The Naknek Formation exposed on the west side 

of Cook Inlet between Tuxedni Bay and Iniskin Bay 

has been described in detail by Detterman and Hart. 
18 LATE JURASSIC AMMONITES FROM ALASKA 

sock (1966, p. 47-55) and was divided by them into 

four members. The Chisik Conglomerate Member at 

the base is found on Chisik Island and on the north 

side of Iniskin Bay, attains a maximum thickness of 

560 feet (170 m), and is unfossiliferous. The overlying unnamed lower sandstone member interfingers 

with the Chisik, attains a thickness of 860 feet 

(261 m), contains an assemblage of bivalves, ammonites, belemnites, gastropods, and echinoids, and 

is characterized by the ammonite Cardioceras. The 

next higher Snug Harbor Siltstone Member ranges 

from 720 to 860 feet (218 to 261 m) in thickness, 

consists mostly of dark siltstone, contains an assemblage of bivalves, ammonites, and belemnites, and 

is characterized by Phylloceras iniskinense Imlay, 

n. sp., in association with Buchia concentrica 

( Sowerby) . The Pomeroy Arkose Member at the 

top of the Naknek Formation ranges in thickness 

from 800 to 3,300 feet (242 to 1,000 m) and contains 

many siltstone beds, of which some bear the bivalve 

Buchia concentrica ( Sowerby) . 

The unnamed lower sandstone member of the 

Naknek Formation exposed between Tuxedni Bay 

and Iniskin Bay west of Cook Inlet is characterized 

faunally by the presence of the ammonites Cardioceras and Phylloceras (tables 2, 3). Cardioceras 

(Scarburgiceras) martini Reeside occurs throughout 

the lower 450 feet (136 m) of the member on the 

south side of Chinitna Bay and the lower 660 feet 

(200 m) on the north side of Iniskin Bay. C. (C.) 

distans (Whitfield) occurs 200-400 feet (60-121 m) 

above the base of the member at Chinitna Bay and 

525-660 feet (159-200 m) above the base at Oil 

Bay. C. (Scoticardioceras) alaskense Reeside and C. 

cf. C. lilloetense Reeside have ranges similar to that 

of C. distans but are less common. Phylloceras 

iniskinense Imlay, n. sp., ranges throughout the 

member and is associated with Cardioceras at three 

localities. In addition, the bivalve Buchia concentrica 

(Sowerby) was collected with Cardioceras martini 

450 feet ( 136 m) above the base of the member at, 

Oil Bay at USGS Mesozoic loc. 21784. 

This association of Buchia with Cardioceras needs 

checking in the field because outside southern Alaska, 

the two taxa have never been found associated in the 

same bed, and the next higher occurrence of Buchia 

on the Iniskin Peninsula is in the overlying Snug 

Harbor Siltstone Member, about 410 feet (124 m) 

higher. Therefore, the specimen of Buchia concentrica in question may have been washed down from 

higher beds exposed in nearby cliffs. 

The Snug Harbor Siltstone Member exposed on 

the Iniskin Peninsula west of Cook Inlet is characterized faunally by the presence of Phylloceras, 

Per·isphinctes (Dichotomosphinctes), and Cardioceras (tables 2, 3). Of these, Phylloceras iniskinense 

Imlay, n. sp., occurs about 600 feet (181 m) above 

the base of the member at Chinitna Bay and 200-225 

feet (61-68 m) above the base at Iniskin Bay. Perisphinctes (Dichotomosphinctes) is found 675 feet 

(205 m) above the base and 40 feet (12 m) below 

the top of the member at Iniskin Bay. Cardioceras 

distans (Whitfield) occurs at the very base of the 

member on the west shore of Oil Bay just above 

sandstone beds in which Cardioceras is common at 

USGS Mesozoic locs. 10988 and 11055. In addition, 

the bivalve .Buchia concentrica (Sowerby) is found 

throughout the member but is most common in its 

upper 250 feet (76 m). 

The next higher Pomeroy Arkose Member of the 

Naknek Formation contains Buchia concentrica at 

various levels in its lower part and B. cf. B. concentrica about 113 feet (34m) below its top. 

ALASKA PENINSULA 

Upper Jurassic beds on the Alaska Peninsula are 

fairly continuous as far south as the Port Moller 

area and are divided into two formations. Their 

characteristics in local areas have been described by 

many geologists (Atwood, 1911, p. 33-38; Capps, 

1923, p. 101-103; Keller and Reiser, 1959, p. 269-

273; Mather, 1925, p. 168-171; Paige, 1906, p. 101-

108; Smith, 1925, p. 198-201; Smith and Baker, 

1924, p. 178-184; Knappen, 1929, p. 182-189). Their 

overall characteristics throughout the peninsula have 

been summarized by Martin (1926, p. 203-218), described in more detail on the basis of field studies by 

Burk (1965, p. 29-44, figs. 7-9), and briefly depicted 

by Imlay and Detterman (1973, p. 8, 9, fig. 11A). 

The Naknek Formation on the peninsula comprises 

the lower part of the Upper Jurassic beds, ranges in 

thickness from 2,500 to 10,000 feet (758 to 3,030 m), 

and consists mostly of arkosic sandstone, dark siltstone, and conglomerate. From Kamishak Bay southward, the Naknek consists of three major units. At 

the base is a conglomerate that is overlain and intertongues laterally with interbedded arkosic sandstone 

and siltstone. Those beds are overlain conformably 

by a thick mass of dark siltstone interbedded with 

some fine-grained sandstone and locally with conglomerate. From Chignik Bay to Port Moller, the 

Naknek Formation consists of all these lithologic 

units, but most exposures represent the upper siltstone. 

The Naknek Formation on the Alaska Peninsula 

is characterized faunally (table 6) by the ammonite 
AGES AND CORRELATIONS 19 

Phylloceras alaskanum Imlay, n. sp., in association 

with the bivalve Buchia concentrica (Sowerby) or 

with Buchia mosquensis (von Buch) and B. rugosa 

(Fischer). P. alaskanum also occurs at one locality 

with the ammonite Aulacosphinctoides and at two 

localities with the ammonite Perisphinctes (Dichotomosphinctes) . It has not been found in association 

with Cardioceras or with Phylloceras iniskinense 

Imlay, n. sp., both of which are represented by single 

specimens on the peninsula. 

The presence of these ammonites (fig. 12), as 

discussed in the sections on Ages and Correlations, 

shows that the Naknek Formation on the peninsula 

ranges in age from early Oxfordian to early Tithonian but that the basal part of the formation at 

most places is younger than Oxfordian. For example, in the Katmai area, Buchia rugosa and B. mosquensis of latest Kimmeridgian to early Tithonian 

Age occur in siltstone overlying 80 feet (24 m) of 

marine conglomerate at the base of the Naknek 

Formation, which is about 10,000 feet (3,030 m) thick 

(Keller and Reiser, 1959, p. 271, 272). These basal 

beds should be younger than most of the fossiliferous 

beds near Mt. Peulik that contain Cardioceras of 

early to early middle Oxfordian Age, Dichotomosphinctes of late middle to late Oxfordian Age, and 

an association of Phylloceras alaskanum with Buchia 

concentrica, which should be of early to middle 

Kimmeridgian Age. The basal beds could be of the 

same age as the beds near Mt. Peulik that have furnished Phylloceras alaskanum in association with 

Buchia concentrica (USGS Mesozoic loc. 11343). 

The Staniukovich Formation constitutes the 

upper part of the Upper Jurassic beds from Wide 

Bay southward to the Port Moller area, attains a 

maximum thickness of about 2,000 feet (606 m), 

consists of siltstone and fine- to medium-grained 

sandstone, and intertongues basally with the N aknek Formation. It differs from the Naknek Formation by being uniform lithologically and by weathering tan to yellowish brown. J.t contains an abundance 

of Buchia piochii ( Gabb) of late Tithonian Age, 

locally contains B. mosquensis and B. rugosa of late 

Kimmeridgian to early Tithonian Age, and in its 

upper part contains B. crassicollis of Valanginian 

Age (Burk, 1965, p. 35, 42-44, 219). 

AGES AND CORRELATIONS 

Upper Jurassic beds of Oxfordian to Tithonian 

Age in Alaska are dated (figs. 11, 12) partly by the 

succession of species of the bivalve Buchia and 

partly by the sucession of genera and subgenera of 

ammonites (Imlay and Detterman, 1973, p. 10-13, 

19, 21). The genus Buchia in Alaska occurs throughout the Upper Jurassic beds entirely or almost entirely above those containing Cardioceras of early to 

early middle Oxfordian Age and comprises six 

species that represent three distinct Buchia zones. 

These zones, from bottom to top, are characterized 

by (1) Buchia concentrica (Sowerby), (2) B. mosquensis (von Buch) and B. rugosa (Fischer), and 

(3) B. piochii (Gabb), B. fischeriana (d'Orbigny), 

and B. unschensis (Pavlow). 

This Buchia succession is similar to that found in 

western Canada, East Greenland, parts of northern 

Eurasia, the Pacific Coast region of North America 

as far south as Baja California, and in part even in 

north-central Mexico (Imlay 1955, 1959, 1965, 1980; 

Imlay and Jones, 1970; Jones, Bailey, and Imlay, 

1969; Frebold, 1964). This similarity, coupled with 

the age evidence furnished by associated ammonites, 

permits fairly accurate correlations with some of the 

standard ammonite zones of northwest Europe 

through northern Canada (Frebold and Tipper, 

1970, p. 13-17; Jeletzky, 1966) and East Greenland 

(Donovan, 1957, p. 136-142) and with the ammonite 

zones of the Mediterranean region through California and Mexico. 

Late Jurassic ammonites in Alaska are fairly 

common in beds of Oxfordian to early late Kimmeridgian Age. They are much less common in 

younger beds that contain Buchia mosquensis (von 

Buch) of late Kimmeridgian to early Tithonian Age. 

They are rare in the uppermost Jurassic beds that 

contain B. piochii (Gabb) and B. cf. B. fischeriana 

( d'Orbigny) of late Tithonian Age. 

EARLY TO EARLY MIDDLE OXFORDIAN 

Early to early middle Oxfordian ammonites belonging to Cardioceras and its subgenera have been 

found in northern Alaska only in Ignek Valley 

(Imlay and Detterman, 1973, p. 25). In southern 

Alaska, such taxa have been found mainly in the 

Talkeetna Mountains and west of Cook Inlet between 

Tuxedni Bay and Iniskin Bay, but they are represented also on the Alaska Peninsula by one specimen 

found 5 miles (8 km) southeast of Mt. Peulik and 

16 miles (26 km) north-northwest of the northeastern end of Wide Bay. 

The earliest Oxfordian is represented by the subgenus Cardioceras (Scarburgiceras) in the Ignek 

Valley in northern Alaska, in the Talkeetna Mountains in southern Alaska, and west of Cook Inlet between Tuxedni Bay and Iniskin Bay. That subgenus 

in Europe is common in the Quenstedtoceras mariae 

zone and is rare in the lo·wer third of the next 
20 LATE JURASSIC AMMONITES FROM ALASKA 

higher Cardioceras cordatum zone. Typical species 

in Alaska include C. (S.) martini Reeside and C. 

(S.) dettermani Imlay. 

The next younger beds of early to early middle 

Oxfordian Age in Alaska are characterized by Cardioceras sensu strictu and its subgenus Scoticardioceras. Of them, Cardioceras sensu strictu in Europe 

ranges through the Cardioceras co1·datum zone and 

the lower part of the next younger Perisphinctes 

plicatilis zone. Scoticardioceras ranges through the 

upper third of the Cardioceras cordatum zone and 

all of the Perisphinctes plicatilis zone (fig. 12). The 

overlap of the ranges of these taxa is apparently 

reflected in Alaska by the association of Cardioceras 

sensu strictu with Cardioceras (Scarburgiceras) 

martini Reeside at three localities west of Cook Inlet 

(USGS Mesozoic locs. 3041 float, 11017, 21351) and 

at five localities in the Talkeetna Mountains (USGS 

Mesozoic locs. 24165, 24166, 24168, 24837, 24841). 

All beds west of Cook Inlet and in the Talkeetna 

Mountains that contain many specilnens of Cardioceras also contain specimens of Phylloceras iniskinense Imlay, n. sp., at many localities. That species, 

however, ranges higher into beds containing abundant Buchia concentrica (Sowerby), apparently 

occurs throughout all of the Oxfordian beds, and 

has never been found associated with Phylloceras 

alaskanum Imlay, n. sp. 

Cardioceras has also been collected with Buchia 

concentrica ( Sowerby) in the Talkeetna Mountains 

at USGS Mesozoic loc. 24165, whose stratigraphic 

position is unknown. On the Iniskin Peninsula, those 

taxa are associated at USGS Mesozoic loc. 21784, 

which is about 450 feet (136 m) above the base of 

the unnamed lower sandstone member of the Naknek 

Formation, and at USGS Mesozoic loc. 20723, which 

is in the basal part of the overlying Snug Harbor 

Siltstone Member. 

As Cardioceras has never been reported in association with Buchia concentrica elsewhere in the 

world, their association at these three localities 

means that the fossils were collected from different 

stratigraphic levels, or that the taxa have slightly 

different ranges in Alaska from those reported elsewhere, or that some specimens are float-derived 

from nearly cliffs. 

LATE MIDDLE OXFORDIAN TO 

EARLY LATE KIMMERIDGIAN 

Directly overlying the Cardioceras-bearing beds in 

northeastern Alaska and in the Wrangell Mountains 

are beds characterized by Amoeboceras (Prionodoceras) and A. (Amoebites) in association with the 

bivalve Buchia concentrica (Sowerby) or locally in 

the Wrangell Mountains, in association with both 

B. concentrica and B. mosquensis (von Buch). These 

fossils in association are good evidence of an age 

ranging from middle Oxfordian to early late Kimmeridgian. 

Directly overlying the Cardioceras-bearing beds 

in the Talkeetna Mountains are beds characterized 

by Phylloceras iniskinense Imlay, n. sp., in association with the bivalve Buchia concentrica 

( Sowerby) . Still higher beds contain Buchia concent rica (Sowerby) associated with Phylloceras 

alc~skanum Imlay, n. sp. These beds, on the basis of 

their stratigraphic position above Cardioceras and 

the presence of Buchia concentrica, must likewise be 

of middle Oxfordian to early late Kimmeridgian 

Age. 

On the Iniskin Peninsula west of Cook Inlet, the 

Snug Harbor Siltstone Member above the Cardioceras-bearing beds is dated as late middle Oxfordian 

to late Oxfordian by its stratigraphic position, by 

the presence of Buchia concentrica (Sowerby) and 

Dichotomosphinctes, and by the absence of Buchia 

mosquensis (von Buch) and B. rugosa (Fischer). 

Similarly, the overlying Pomeroy Arkose Member 

is dated as probably early Kimmeridgian on the 

basis of stratigraphic position and the presence of 

B. concentrica. 

On the Alaska Peninsula, the ammonite sequence 

directly overlying or slightly younger than the 

Cardioceras-bearing beds is characterized by the 

same two species of Phylloceras that occur in the 

Talkeetna Mountains and in the Iniskin Peninsula 

west of Cook Inlet. It also contains the same species 

of Perisphinctes (Dichotomospkinctes) (USGS 

Mesozoic locs. 10796 and 29899) that is found in 

the Iniskin Peninsula. The sequence differs mainly 

by having only one occurrence of Phylloceras iniskinense Imlay, n. sp., by having many occurrences of 

P. alaskanum Imlay, n. sp., and by the fact that 

Dichotomosphinctes at USGS Mesozoic loc. 10796 is 

associated with Phylloceras alaskanum instead of 

with P. iniskinense. In addition, in the peninsula, 

Buch1'a concentrica ( Sowerby) is common in the 

lower part of the range of Phylloceras alaskanum 

and is associated with Dichotomosphinctes at USGS 

Mesozoic loc. 29899. 

Of the ammonites listed, A moeboceras and its subgenus Prionodoceras are boreal in origin and in 

northwest Europe range from the Gregoryceras 

transversarium zone to the Rasenia mutabilis zone 

inclusive (that is, upper middle Oxfordian to lower 

1 upper Kimmeridgian). Amoebites ranges from the 
AGES AND CORRELATIONS 21 

Pictonia bayleyi zone to the Rasenia mutabilis zone. 

The subgenus P. (Dichotomosphinctes) is characteristic of the Mediterranean region, is also common 

in Cuba and the Gulf of Mexico region, and ranges 

through the middle and upper Oxfordian. It has also 

been found in the upper Oxfordian of California 

associated with Buchia concentrica (Imlay, 1961, 

D13, D14, D18). Phylloceras alaskanum Imlay, 

n. sp., judging by associated genera of ammonites, 

by associated species of Buchia, and by stratigraphic 

occurrences, ranges from the upper Kimmeridgian 

into the lower part of the upper Tithonian. (For 

further details concerning the ranges of Prionodoceras, Amoeboceras, and Dichotomosphinctes (fig. 

11), see Enay, Tintant, and Cariou, 1971, p. 635, 

661; Cariou, Enay, and Tintant, 1971; and Callomon, 

1964, p. 286-288.) 

LATEST KIMMERIDGIAN AND EARLY TITHONIAN 

Beds characterized by Buchia rugosa (Fischer) 

and B. mosquensis (von Buch) are widespread in 

northern, southeastern, southern, and southwestern 

Alaska and on the Alaska Peninsula but are absent 

on the west side of Cook Inlet between Tuxedni Bay 

and Iniskin Bay (Imlay and Detterman, 1973, p. 

10-13, 26, 27). 

These species on the basis of available collections 

have been found rarely with ammonites except in the 

Alaska Peninsula and in the Wrangell Mountains. 

Such ammonites in the Alaska Peninsula include 

many specimens of Phylloceras alaskanum Imlay, 

n. sp., at many localities, one specimen of Aulacosphinctoides, and the larger outer whorl of an ammonite herein assigned questionably to Suplanites. 

The beds in Alaska that contain Buchia mosquensis and B. rugosa in association are dated as 

latest Kimmeridgian to early Tithonian by their 

stratigraphic position above Amoeboceras (Amoe"-

bites) of early to early middle Kimmeridgian Age 

and below Buchia piochii ( Gabb), which species is 

associated with ammonites of late Tithonian Age in 

California (Imlay, 1961, D5, D8; Imlay and Jones, 

1970, p. B11, B12) and in Arctic Canada (Jeletzky, 

1965, 1966). This dating of B. mosquensis and B. 

rugosa (USGS Mesozoic loc. 29254) is substantiated 

by the presence of Aulacosphinctoides, a Mediterranean genus of early Tithonian Age, which elsewhere in North America has been found only in 

Mexico (Imlay, 1939, p. 22, 27-30, 38, 39, tables 7 

and 10; Burckhardt, 1906, p. 147-149; 1930, p. 

68-71) . This dating is also substantiated by the 

presence in the Alaska Peninsula of a fairly large 

ammonite that has virgatomous ribbing as in the 

subfamily Virgatosphinctinae. Within that subfamily, this ammonite shows some resemblance to 

Subplanites, a genus of early Tithonian Age, which 

in North America has been found in Mexico (Burckhardt, 1906, p. 112, pl. 32, fig. 1; Imlay, 1943, p. 533, 

pl. 91, fig. 1) and in Cuba (Judoley and Bermudez, 

1968, p. 5, 23, 109, pl. 64, fig. 1, pl. 67, fig. 1, and 

pl. 68). This dating is substantiated by the known 

ranges of Buchia mosquensis and B. rugosa in 

Eurasia (Spath, 1936, p. 166, 167) and elsewhere 

in North America (Imlay, 1955, p. 74, 75, 85). 

Thus, the highest occurrences of Buchia mosquensis (Von Buch) in Alaska could be of early late 

Tithonian Age on the basis of the occurrence of that 

spe:::ie~. in Mexico in beds containing Kossmal'ia and 

Durangites (Burckhardt, 1912, p. 206, 221, 236), 

which are correlated with the European zone of 

Zaraiskites albani. Likewise, in Milne Land, East 

Greenland, Buchia mosquensis occurs with B. rugosa 

(Fischer) in the upper part of the Glauconitic Series 

(Spath, 1936, p. 156, 157, 162-167, pl. 2, figs. la-g, 

2a, b) asso:::iated with such ammonites as Pavlovia 

and Dorsoplanites of latest early Tithonian Age and 

Glaucolithites of early late Tithonian Age (Arkell, 

1956, p. 524; Donovan, 1957, p. 140-142). These 

genera are definitely characteristic of the middle 

Volgian of the Russia Platform. Evidently, both 

species of Buchia first appeared in late Kimmeridgian time. B. mosquensis survived nntil early late 

Tithonian time, and B. rugosa survived at least 

during all of early Tithonian time. The latest survival time of either species in Alaska needs confirmation based on associated am1nonites or other 

age-diagnostic fossils. 

LATE TITHONIAN 

The uppermost Jurassic beds in Alaska are characterized by Buchia piochii ( Gabb) , B. jischeriana 

( d'Orbigny), and B. unschensis (Pavlow). B. cf. B. 

fisheriana occurs on the middle fork of the Okpikruak 

River in north-central Alaska. B. unschensis occurs 

on Kemik Creek near the Shaviovik River in northeastern Alaska as well as about 100 miles (160 km) 

farther east on Joe Creek near the Canadian border 

(Imlay and Detterman, 1973, p. 27). B. fischeriana 

occurs on Joe Creek in northeastern Alaska (Detterman and others, 1975, p. 20), as well as in the 

N abesna area in the southeastern part of the main 

body of Alaska (Imlay and Detterman, 1973, p. 27). 

B. piochii occurs in the southern part of the Alaska 

Peninsula nearly as far north as Wide Bay. These 

species of Buchia in Alaska have not been found 

with ammonites except for one occurrence of a 
22 LATE JURASSIC AMMONITES FROM ALASKA 

poorly preserved Phylloceras on the Alaska. Peninsula 

a little north of Amber Bay. That ammonite .is herein 

compared with P. knoxvillensis Stanton. 

Outside Alaska, in arctic Canada, B. piochii 

ranges throughout most of the beds assigned to the 

upper Tithonian, B. fischeriana ( d'Orbigny) ranges 

through the upper half of the range of B. piochii, 

and B. unschensis ranges through the upper twothirds of the range of B. fischeriana (Jeletzky, 1965, 

figs. 1, 2; 1966, p. 25-43), in association with the 

ammonite Craspedites of latest Tithonian Age. In 

British Columbia, B. fischeriana is recorded directly 

above B. piochii (Frebold and Tipper, 1970, table 1 

on p. 17; Jeletzky, 1965, fig. 2). In California, B. 

fischeriana is recorded from the upper part of the 

range of B. piochii, and both are overlain by uppermost Tithonian beds containing B. cf. B. okensis 

(Imlay and Jones, 1970). 

On the basis of these fossil records in arctic 

Canada, British Columbia, and California, the latest 

Tithonian is represented at least locally in northcentral and northeastern Alaska, in the eastern part 

of the Alaska Range in eastern Alaska, and in the 

southern part of the Alaska Peninsula. In some 

places, however, the Upper Jurassic beds are overlain unconformably by beds of Valanginian Age. For 

example, in the Talkeetna Mountains, beds of Valanginian Age rest unconformably on beds containing 

Buchia mosquensis and B. rugosa. 

AMMONITE FAUNAL SETTING 

The Late Jurassic ammonite genera in Alaska are 

of diverse geographic origin. Ammonites characteristic of the Boreal Realm include Cardioceras and 

A moeboceras and their subgenera. Ammonites characteristic of the Tethyan and Pacific Realms include 

Perisphinctes (Dichotomosphinctes), Subplanites?, 

Aulacosphinctoides, Phylloceras, and Lytoceras. All 

these taxa except Cardioceras are associated with 

the bivalve Buchia, a genus that thrived on hard 

bottoms in shallow waters (Imlay, 1959, p. 156) and 

is particularly common in the Boreal Realm. 

Of these ammonites, the genus Cardioceras of 

early to early middle Oxfordian Age is common west 

of Cook Inlet and in the Talkeetna Mountains but 

is represented elsewhere in Alaska by only one SJ?ecimen from the Mt. Peuli~ area on the Alaska Peninsula and by a few specimens from northern Alaska. 

It has been found with Phylloceras iniskinense 

Imlay, n. sp., only in the Talkeetna Mountains and 

west of Cook Inlet. Apparently Cardioceras in the 

Cook Inlet region lived in a shallow to fairly shallow 

sea, as shown by its occurrence in thin-bedded sandstone and siltstone in association with many bivalves, some echinoids, and some belemnites. Its 

association with Phylloceras iniskinense in the western part of southern Alaska shows that it lived in 

a sea that was connected with or bordered the 

Pacific Ocean. 

The next younger beds in Alaska are characterized by Buchia concentrica ( Sowerby) in association with the ammonite Amoeboceras in northeastern Alaska and in the Wrangell lVIountains but 

in association with certain species of Phylloceras 

from the Talkeetna Mountains southward to Chignik 

Bay on the Alaska Peninsula. The age of these two 

ammonite faunules, as discussed herein in detail, is 

based on their stratigraphic position, on their association with Buchia concentrica, and on the presence 

of the ammonite Perisphinctes (Dichotomosphinctes) 

of middle to late Oxfordian Age both in the upper 

part of the range of Phylloceras iniskinense Imlay, 

n. sp., and near the base of the range of Phylloceras 

alaskanum Imlay, n. sp. 

Evidently two fairly different ammonite faunules 

existed in Alaska from late middle Oxfordian to 

early late Kimmeridgian time. The faunule characterized by A moeboceras came into Alaska from the 

. north and is of boreal origin. The faunule charac1 terized by certain species of Phylloceras came into 

Alaska from the Pacific Ocean but includes Dichotomosphinctes, which is common in both the Tethyan 

and Pacific Realms. 

The next younger beds in Alaska are characterized 

by the presence of Buchia rugosa and B. mosquensis 

but have furnished few ammonites, except on Alaska 

Peninsula where Phylloceras alaskanum and Lytoceras are fairly common, Subplanites? and Aulacosphinctoides of Tethyan affinities are represented 

by single specimens, and many genera of bivalves 

are present. In contrast, equivalent beds elsewhere 

in Alaska contain a scant bivalve fauna other than 

the genus Buchia and very few ammonites. For 

example, in northeastern Alaska, only one ammonite, 

a specimen of Phylloceras (Imlay, 1955, p. 87, pl. 10, 

fig. 20), has been found with Buchia rugosa (USGS 

Mesozoic loc. 21027). In the Wrangell Mountains 

only one ammonite, herein described as Partschiceras sp. A. (pl. 6, figs. 2-7) , has been found with 

B. rugosa (USGS Mesozoic loc. 28579). Evidently 

the marine environment throughout most of Alaska 

was unfavorable for ammonites during latest Kimmeridgian and . early Tithonian time but remained 

favorable in the area of the Alaska Peninsula. Presumably,· the seas throughout most of Alaska were 

becoming too muddy or too shallow, and sedimenta-
GEOGRAPHIC DISTRIBUTION 23 

tion was too rapid for ammonites and most bivalves 

other than Buchia to thrive. 

These conditions persisted and spread during late 

Tithonian time throughout most of Alaska. Such is 

indicated by the fact that only one ammonite. 

( Cardioceras ( V ertebriceras) whiteavesi Reeside) 

of that age is present in the U.S. Geological Survey 

fossil collections, and that ammonite (pl. 7, figs. 

4-6) was obtained a little north of Amber Bay near 

the middle of the Alaska Peninsula. Evidently the 

Ia te Tithonian seas in Alaska gradually became more 

restricted, shallower, and less favorable environmentally for ammonites, even though the bivalve 

Buchia continued to flourish. 

GEOGRAPHIC DISTRIBUTION 

The geographic occurrences of the Late Jurassic 

ammonites described herein are shown in figures 

1-10 and tables 2-6. Detailed descriptions of the 

occurrences are given in table 7. 

TABLE 7.-Description of Upper Jurassic ammonite localities in Alaska 

Locality No. (fig. 1) 

1 

1 

1 

1 

1 

2 

2 

2 

3 

4 

5 

5 

USGS Mesozoic 

loc. No. 

21028 

22598 

24014 

29882 

24013 

21027 

29135 

29136 

29856 

29137 

14495 

14496 

Collector's 

field No. 

47 AGr239 _____ _ 

50AGr31 ______ _ 

52AMo50 ______ _ 

70ADt231A ____ _ 

52AMo48 ______ _ 

47 AGr8 ______ _ 

Ag 882 ---------

Ag 887 ---------

69ADt40 ______ _ 

AG 26 ---------

28AMF32 ------

28AMF33 ------

Collector, year of collection, description of locality, 

stratigraphic assignment, and age 

George Gryc, 1947. West bank of Canning River. 4 km 

south of Black Island, lat 69°30'45" N., long 146°18'45" 

W., SE. cor. sec. 19, T. 2 N., R. 24 E., Mt. Michelson 

Quadrangle. Black shale with limestone interbeds near top of Kingak Shale. Late Oxfordian to early 

Kimmeridgian. 

George Gryc, R. W Tmlay, and A. N. Kover. 1950. West 

bank of Carming River at same place as USGS Mesozoic 

loc. 21028. Kingak Shale about 61 m below top. Late 

Oxfordian to early Kimmeridgian. 

R. H. Morris, 1952. Cutbank on west side of Canning River, 

lat 69°32' N., long 146°18' W., near boundary of sees. 19 

and 20, T. 2 N., R. 24 E., Mt. Michelson Quadrangle. 

Kingak Shale about 15 m below top. Late Oxfordian to 

early Kimmeridgian. 

R. L. D~tterman, 1970. West bank of Canning River. 5.4 

km S. 10° W. of mouth of lgnek Creek, lat 69°30'45" N., 

long 146°19'30" W., Mt. Michelson Quadrangle. Shale 

containing clay ironstone concretions about 15 m below 

top of Kingak Shale. Late Oxfordian to early Kimmeridgian. 

R. H. Morris, 1952. Cutbank on west side of Canning River, 

]at 69°30'45" N., long 146°18'45" W., Mt. Michelson 

Quadrangle. Black fissile shale containing limestone 

concretions about 15 m below top of Kingak Shale. Late 

Oxfordian to early Kimmeridgian. 

George Gryc, 1947. East Fork of Shaviovik River about 16 

km west of mouth of Cache Creek at Canning River, 

lat 69°22' N., long 146°32' W., Mt. Michelson Quadrangle. 

Black shale containing limestone concretions and bed~ 

of ironstone and some limestone. Kingak Shale. isolated 

outcrop. Latest Kimmeridgian or early Tithonian. 

British Petroleum Alaska (Inc.), 1964. Canning- River near Shublik Island and about 1.6 km west of mouth of 

Cache Creek, lat 69°24' N., long 146°10' W., SE. cor. T. 1 N., R. 24 T., Mt. Michelson Quadrangle, Kingak 

Shale. Late Oxfordian to early Kimmeridgian. 

British Petroleum Alaska (Inc.) 1964. At same place as USGS Mesozoic loc. 29135. Kingak Shale. Late Oxfordian 

to early Kimmeridgian. 

R. L. Detterman. 1969. lgnek Mesa in lgnek Valley. 11 km 

S. 75° E. of Katakturuk Canyon, lat 69°33'30" N .. long 

145°20' W., east-central part of sec. 6, T. 2 N .. R. 28 E., 

Mt. Michelson Quadrangle. Fossils from concentrations 

in black silty clay shale of Kingak Shale about 24 m below top. Early Oxfordian. 

British Petroleum Alaska (Inc.), 1964. About 0.5 km south 

of Fire Creek in NW. cor. NE% sec. 13, T. 2 N .. R. 28 

E., Mt. Michelson Quadrangle, Kingak Shale. Early 

Oxfordian. 

F. H. Moffit, 1928. 0.8 km east of McCarthy <;;reek on mountain slope south of second tributary north of 

Dimond Creek, sec. 31, T. 3 S., R. 15 E., McCarthy 

(C-5) Quadrangle, Wrangell Mountains. southern 

Alaska. Root Glacier Formation. Dark-gray shale, probably 305-610 m above base of formation. Late Kimmeridgian. 

Do. 
24 

Locality No. (fig. 1) 

5 

5 

5 

5 

5 

6 

6 

6 

6 

6 

6 

6 

6 

LATE JURASSIC AMMONITES FROM ALASKA 

TABLE 7.-Description of Upper Jurassic ammonite localities in Alaska-Continued 

USGS Mesozoic Joe. No. 

14497 

28577 

28578 

28579 

28700 

24156 

24162 

24165 

24166 

24167 

24168 

24175 

24834 

Collector's 

field No. 

28AMF34 _____ _ 

61ABC27 ______ _ 

61ABC36 _____ _ 

61-17 ----------

62 AMK51 _____ _ 

52AGzl16 _____ _ 

52AGz136 _____ _ 

52AGz146 _____ _ 

52AGz147 _____ _ 

52AGz149 _____ _ 

52AGz163 _____ _ 

52AHr39 ______ _ 

53AGz261 _____ _ 

CoiJector, year of collection, description of locality, 

stratigraphic assignment, and age 

F. H. Moffitt, 1928. East side of McCarthy Creek at edge 

of west glacier, probably in SW%, sec. 13 T. 3 S., R. 14 

E., McCarthy (C-5) Quadrangle, Wrangell Mountains, 

southern Alaska. Root Glacier Formation. Probably same stratigraphic data as Mesozoic loc. 14495. Late Oxfordian to early l:1te Kimmeridgian. 

M. C. Blake, 1961. On ridge just south of a rock glacier 

in SE% SE 14 sec. 14, T. 3 S., R. 15 E., lat 61 °36'15" 

N., long 142°37'10" W., McCarthy (C-5) Quadrangle, 

Wrangell Mountains, southern Alaska. Root Glacier Formation, about 76 m above the top of the Nizina Mountain Formation. Early Kimmeridgian. 

M. C. Blake, 1961. Same data as USGS Mesozoic loc. 

14495. 

D. L. Jones, 1961. About 2.4 km east of McCarthy Creek 

and 0.8 km north of Lubbe Creek in NE 14 NW% sec. 5, T. 4 S., R. 15 E. McCarthy Creek (C-5) Quadrangle, 

Wrangell Mountains, southern Alaska. Root Glacier 

Formation, about 457 m above contact with Nizina 

Mountain Formation. Late Kimmeridgian to early 

Tithonian. 

E. M. Mackevett, Jr .. 1962. West of Nizina River and 

northeast of West Fork in SE% SE%, sec. 19. T. 3 S., 

R. 16 E., McCarthy (C-5) Quadrangle. Wrangell 

Mountains, southern Alaska. Root Glacier Formation. 

Dark-gray sandstone and a few limy beds less than 305 m above contact with Nizina Mountain Formation. Late 

Kimmeridgian. 

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

62°10.0' N., long 147°22.0' W., Talkeetna Mountains 

(A-1) Quadrangle, southern Alaska. Lower(?) third 

of main siltstone and shale member of Naknek Formation. Early Oxfordian. 

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

Lat 62°06.3' N., long 147°36.7' W .. Talkeetna Mountains (A-2) Quadrangle, southern Alaska. Near top of 

main siltstone and shale member of Naknek Formation. 

Kimmeridgian to early Tithonian. 

Arthur Grantz, R. D. Hoare, and R. W. Imlay. Lat 62°09.4' 

N., long 147°35.8' W., south side of Little Nelchina 

River, Talkeetna Mountains (A-2) Quadrangle. southern 

Alaska. Lower third of main siltstone and shale member 

of Naknek Formation. Early Oxfordian. 

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

62°07.5' N., long 147°35.0' W., on north side of Little 

Nelchina River, Talkeetna Mountains (A-2) Quadrangle, 

southern Alaska. Lower third of main siltstone and shale 

member of Naknek Formation. Early Oxfordian. 

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

62°09.4' N., long 147°38.6' W., on north side of Little 

Nelchina River. Talkeetna Mountains (A-2) Quadrangle, southern Alaska. Lower third of main siltstone and 

shale member of Naknek Formation. Late middle to late 

Oxfordian. 

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

62°08.5' N., 147°44.3' W., Talkeetna Mountains (A-2) 

Quadrangle, southern Alaska. Near base of main siltstone and shale member of Naknek Formation. Early 

Oxfordian. 

R. D. Hoare, 1952. Lat. 62°07.49' N., long 147°44.7' W., 

Talkeetna Mountains (A-2) Quadrangle. southern 

Alaska. Middle third of main siltstone and shale mem- ber of Naknek Formation. Buchia concentrica (Sowerby) found in place. Ammonites occur as float derived 

from higher beds. Late Oxfordian to early Kimmeridgian. 

Arthur Grantz and L. F. Fay, 1953. Lat 62°07.7' N., long 

147°41.9' W., Talkeetna Mountains (A-2) Quadrangle, 

southern Alaska. Float from lower third of main siltstone and shale member of Naknek Formation. Late 

middle to late Oxfordian. 
Locality No. (fig. 1) 

6 

6 

6 

7 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

8 

9 

GEOGRAPHIC DISTRIBUTION 25 

TABLE 7.-Description of Upper Jurassic amnwnite localities in Alaska-Continued 

USGS Mesozoic Joe. No. 

24837 

24841 

8575 

22701 

11002 

11013 

11015 

11016 

11017 

11018 

21350 

21351 

21352 

21782 

21783 

21784 

21785 

21786 

3041 

Collector's 

field No. 

53AGz272 _____ _ 

53AFy17 ______ _ 

Martin 24 _____ _ 

51AGz123 _____ _ 

AFf11 ---------

ABF21 -------- ABf22 --------- ABf23 --------- ABf24 --------- ABf25 --------- 48AI24 --------

48AI27 _______ _ 

48AI85 _______ _ 

· 49AGz15 -------

49AGz35 ______ _ 

49AGz36 ______ _ 

49AGz37 

49AGz45 ______ _ 

934a -----------

Collector, year of collection, description of locality, 

stratigraphic assignment, and age 

Arthur Grantz and L. F. F'ay, 1953. Lat 67°07.25' N., 

long 147°32.7' W., Talkeetna Mountains (A-2) Quadrangle, southern Alaska. Lower third of main siltstone 

and shale member of Naknek Formation. Early 

Oxfordian. 

L. F. Fay, 1953. Lat 62°06.7' N., long 147°43.5' W. and 

also at a point 46 m farther west, Talkeetna Mountains (A-2) Quadrangle, southern Alaska. Lower third 

of main siltstone and shale member of Naknek Formation. Early Oxfordian. 

G. C. Martin, 1913. From concretions on talus across the 

stream from the lowest outcrop on the creek entering 

Boulder Creek from the northwest 9 km upstream from 

mouth of East Boulder Creek, Anchorage ( D-3) Quadrangle, Naknek Formation. Early Oxfordian. 

Arthur Grantz, 1951. South side of Red Glacier. 0.3 km 

above presP.nt tP.rminuR 11ear ce11ter of west half of sec. 36, T. 2 S., R. 21 W., Seldovia (D-8) Quadrangle. 

On Peninsula between Tuxedni Bay and Chinitna Bay 

west of Cook Inlet. Naknek Formation, unnamed lower 

sandstone member 30.5-53 m above base. Early 

Oxfordian. 

A. A. Baker, 1921. Chinitna Bay area, south shore, a little east of Sea Otter Point in NW1

.4 sec. 14. T. 4 S., 

R. 22 W., Iliamna (D-1) Quadrangle. Naknek Formation, unnamed lower sandstone member, 61-76 m above 

base. Early Oxfordian. 

Do. 

Do. 

Do. 

Do. 

Do. 

R. W. Imlay, 1948. Near head of first stream entering 

Chinitna Bay east of Park Creek. Center of SE 1,4 sec. 22, T. 4 S., R. 22 W., Iliamna (D-1) Quadrangle. 

Naknek Formation, unnamed lower sandstone member, 

15-31 m above base. Early Oxfordian. 

R. W. Imlay, 1948. Eight km N. 71 o E. of dock at mouth 

of Fitz Creek and slightly southeast of Mesozoic loc. 

11002. Naknek Formation, unnamed lower sandstone 

member, 137 m above base. Early Oxfordian. 

R. W. Imlay, 1948. South shore of Chinitna Bay, 8 km 

N. 74° E. of dock at mouth of Fitz Creek, and 0.8 km 

southeast of Mesozoic loc. 21350 in east-central nart of same section. Naknek Formation, Snug Harbor Siltstone 

Member, 183 m above base. Late middle to late 

Oxfordian. 

Arthur Grantz, 1949. South shore of Chinitna Bay, 1.3-1.4 

km west of Gull Island at same place as Mesozoic loc. 

11002. Naknek Formation, unnamed lower sandstone 

member, 61-76 m above base. Early Oxfordian. 

Arthur Grantz, 1949. South shore of Chinitna Bay, 1 km 

west of Gull Island and 0.3 km southwest of Mesozoic 

loc. 21351. Naknek Formation, unnamed lower sandstone member, 244 m above base. Early Oxfordian. 

Arthur Grantz, 1949. South shore of Chinitna Bay, 1.3 

km west of Gull Island at same general location as Mesozoic loc. 21351. Naknek Formation. unnamed lower 

sandstone member, 168 m above base. Early Oxfordian. 

Arthur Grantz, 1949. South shore of Chinitna Bay at same place as Mesozoic loc. 21352. Naknek Formation, Snug 

Harbor Siltstone Member, 183 m above base. Late middle to late Oxfordian. 

Arthur Grantz, 1949. South shore of Chinitna Bay, 1 km 

west of Gull Island, a little southeast of Mesozoic loc. 

21783 in the same section, Iliamna ( D-1) Quadrangle. 

Naknek Formation, Snug Harbor Siltstone Member, 183 m above base. Oxfordian. 

T. W. Stanton, 1904. East shore of Oil Bay near a large 

waterfall. SE1,4 sec. 12, T. 6 S., R. 24 W., Iliamna 

(C-1) Quadrangle, west of Cook Inlet, southern 

Alaska. Naknek Formation, float from higher beds ex- posed in cliffs. Kimmeridgian. 
26 

Locality No. (fig. 1) 

LATE JURASSIC AMMONITES FROM ALASKA 

TABLE 7.-Description of Upper Jurassic ammonite localities in Alaska-Continued 

USGS Mesozoic loc. No. Collector's 

field No. Collector, year of collection, description of locality, stratigraphic assignment, and age 

----------------------- -------

9 3043 

9 3044 

9 3045 

9 3046 

9 10988 

9 11050a 

9 11055 

9 11056 

9 20723 

9 22418 

9 22426 

9 22449 

9 22450 

10 30764 

934c __________ _ 

934d 

934e 

934f -----------

ABF 61 _______ _ 

ABF66, 67 ____ _ 

ABF69 ________ _ 

46AKr102 _____ _ 

50AHa21 ______ _ 

50AHa21a _____ _ 

50AGz12 ______ _ 

AGz16 ---------

74ADt9 --------

T. W. Stanton, 1904. East shore of Oil Bay, west-central 

margin of sec. 18, T. 6 S., R. 23 W., Iliamna (C-1) 

Quadrangle, west of Cook Inlet, southern Alaska. N aknek Formation, unnamed lower sandstone member, 4.6 m above base of bed no. 8 and 30 m above base of mem- ber drawn at base of bed no. 14 (Martin, 1926, p. 173). 

Oxfordian. 

T. W. Stanton. 1904. Slightly south of Mesozoic locality 

3043 and 62 m above base of unnamed lower sandstone 

member of the Naknek Formation. Early Oxfordian. 

T. W. Stanton, 1904. Slightly south of Mesozoic locality 

3044. Nakr:ek Formation, unnamed lower sandstone 

member, 24 m above base of bed no. 7 and 160 m above 

base of member. Late early Oxfordian. 

T. W. Stanton, 1904. Slightly south of Mesozoic locality 

3044. Naknek Form::ttion, 46 m above hase of bed no. 7 

and 181 m above base of unnamed lower sandstone 

member (Martin, 1926, p. 173). Early Oxfordian. 

F. H. Moffit, 1921. West shore of Oil Bay about 0.8 km 

from head on point near center of SE 14 sec. 14, T. 6 S., 

R. 24 W., Iliamna (C-1) Quadrangle, west of Cook 

Inlet, southern Alaska. Naknek Formation. at top of 

unnamed lower sandstone member. Early Oxfordian. 

A. A. Baker, 1921. Probably at head of Edelman Creek in 

east-central part of sec. 32, T. 5 S., R. 23 W., Iliamna 

(C-1) Quadrangle, west of Cook Inlet, southern Alaska. 

Naknek Formation, talus from below Chinitna-Naknek 

contact. Early Oxfordian. 

A. A. Baker, 1921. West shore of Oil Bay at second point 

down bay from gravel spit near mouth of Bowser 

Creek, near center of SE14 sec. 14, T. 6 S., R. 24 W., 

Iliamna ( C-1) Quadrangle, west of Cook Inlet, southern 

Alaska. Naknek Formation, at top of unnamed lower 

sandstone member, but possibly reworked. Early 

Oxfordian. 

A. A. Baker, 1921. East shore of Oil Bay, N. 61 o E., from 

Mt. Pomeroy, a little south of Mesozoic loc. 3046, in 

SW% sec. 18, T. 6 S., R. 23 W., Iliamna (C-1) Quadrangle, west of Cook Inlet, southern Alaska. Naknek 

Formation, near top of unnamed lower sandstone mem- ber. Early Oxfordian. 

C. E. Kirschner, 1946. East shore of Oil Bay at about same place as USGS Mesozoic locality 11056. Naknek 

Formation, near base of Snug Harbor Siltstone Member. Oxfordian. 

R. D. Hoare and J. K. Hartsock, 1950. West shore of 

Oil Bay, NE cor. SE14 SE14 sec. 14. T. 6 S .. R. 24 W., 

Iliamna (C-1) Quadrangle, west of Cook Inlet. southern 

Alaska. Naknek Formation, about 15 m above base of 

unnamed lower sandstone member. Early Oxfordian. 

R. D. Hoare and J. K. Hartsock. 1950. West shore of Oil 

Bay, about 213 m south of USGS Mesozoic loc. 22418 

and 427 m south of first major point down bay from 

gravel spit near mouth of Bowser Creek. SE corner SE 1,4 sec. 14, T. 6 S., R. 24 W .. Iliamna (C-1) Quadrangle, west of Cook Inlet. Naknek Formation, 48 m above base of unnamed lower sandstone member. Early 

Oxfordian. 

Arthur Grantz, 1950. East shore of Iniskin Bay northeast 

of Scott Island on southwest tip of Iniskin Peninsula, 

NE% sec. 19, T. 6 S., R. 24 W., Iliamna (C-2) 

Quadrangle west of Cook Inlet, southern Alaska. Naknek 

Formation, 198-206 m above base and 12 m below top 

of Snug Harbor Siltstone Member. Late Oxfordian. 

Arthur Grantz, 1950. East shore of Iniskin Bay in NE cor. NE%. sec. 19, T. 6 S., R. 24 W., about 0.3 km north 

of Mesozoic loc. 22449 in Iliamna ( C-2) Quadrangle. 

Naknek Formation, 61-69 m above base of Snug Harbor 

Siltstone Member. Late middle to late Oxfordian. 

R. L. Detterman, 1974. On peninsula between Ursus Cove 

and Bruin Bay 91 m north of mouth of Sunday Creek, 

northwest of Augustine Island, Iliamna (B-2) Quadrangle, west of Cook Inlet, southern Alaska. Naknek 

Formation, upper part. 
Locality No. (fig. 1) 

11 

11 

11 

11 

11 

12 

13 

13 

14 

15 

16 

16 

17 

18 

18 

18 

18 

18 

GEOGRAPHIC DISTRIBUTION 27 

TABLE 7.-Description of Upper Ju'rassic amm.onite localities in Alaska-Continued 

USGS Mesozoic Joe. No. 

3096 

25832 

25833 

29253 

29899 

26003 

29254 

29255 

10249 

12077 

3124 

3128 

3136 

10795 

10796 

10798 

10817 

11345 

Collector's 

field No. 

940a -----------

CEK776 ________ 

CEK787 --------

65AP363 -------

14828.2 --------

CEK 800 ______ _ 

65AP 375 _____ _ 

65AP376 ______ _ 

F --------------

4 --------------

3 --------------

5a -------------

12 -------------

1-82 -----------

1-83 -----------

1-89 -----------

1-122 ----------

7 --------------

Collector, year of collection, description of locality, 

stratigraphic assignment, and age 

T. W. Stanton and G. C. Martin, 1904. South side of 

Kamishak Bay on west bank of Douglas River about 1.6 

km above its mouth, Iliamna (A-3) Quadrangle, at 

head of Alaska Peninsula. Naknek Formation. 

C. E. Kirschner, 1955. South side of Kamishak Bay on west end of Douglas Island, Iliamna (A-3) Quadrangle, 

at head of Alaska Peninsula. Naknek Formation. Early 

Tithonian. 

C. E. Kirschner, 1955. South side of Kamishak Bay near mouth of Douglas River, coordinates 19.8-0.9 on the 

Iliamna (A-3) Quadrangle, ·at head of Alaska Peninsula, Naknek Formation. Early Tithonian. 

Marvin Mangus, 1965. South side of Kamishak Bay about 

1.6 km from beach and 19.5 km S. 67° E. of V ABM 

McNeil, Iliamna (A-3) Quadrangle, at head of Alaska 

Peninsula. Naknek Formation. Early Tithonian. 

Continental Oil Company, 1967. South side of Kamishak 

Bay on east tip of westernmost island that is 1.6 km 

N. 40° E. of mouth of Douglas River, Iliamna (A-3) 

Quadrangle, at head of Alaska Peninsula. Naknek Formation. Kimmeridgian. 

C. E. Kirschner, 1955. On ridge east of the Kamishak 

River, coordinates 16.0-13.3. Mt. Katmai Quadrangle on Alaska Peninsula. Naknek Formation. Kimmeridgian or early Tithonian. 

Marvin Mangus, 1965. From small island 1.1 km S. 18° 

E. of abandoned site of Kaguyak in the Shelikof Strait, 

Afognak Quadrangle, on Alaska Peninsula. Naknek 

Formation. Early Tithonian. 

Marvin Mangus, 1965. From same island as USGS 

Mesozoic loc. 29254. Naknek Formation. Early Tithonian. 

C. N. Fenner, 1919. From sandstone in place and in loose 

slabs on shore south of Iliuk Arm of Naknek Lake near Savanoski camp (abandoned), Mt. Katmai Quadrangle, on Alaska Peninsula. Naknek Formation. Kimmeridgian or early Tithonian. 

W. R. Smith, 1923. East side of Kejulik Pass below Gas 

Creek, Mt. Katmai Quadrimgle, on Alaska Peninsula. 

Naknek Formation. Kimmeridgian or early Tithonian. 

Lawrence Martin, 1904. West side of Katmai Bay, 0.8 km 

north of camp on west side of Shelikof Strait, Mt. 

Katmai Quadrangle, on Alaska Peninsula. Naknek Formation. Late Oxfordian to early Tithonian. 

Lawrence Martin, 1904. On north shore of Katmai Bay, 

1.6 km north of camp on west side of Shelikof Strait, 

Mt. Katmai Quadrangle, on Alaska Peninsula. Naknek 

Form·ation. 

Lawrence Martin, 1904. Froin 0.8 km up creek entering 

marshes at head of Puale Bay, Karluk (D-5) Quadrangle, on Alaska Peninsula. Naknek Formation. Late 

middle Oxfordian or Kimmeridgian. 

S. R. Capps. 1921. 1.6 km west of shore of Becharof Lake, 

and 4.8 km southeast of Mt. Lee, Ugashik ( C-1) 

Quadrangle, on Alaska Peninsula. Naknek Formation, 

about 305 m above its base. Lower Kimmeridgian. 

S. R. Capps, 1921. 1.6 km southeast of Mesozoic loc. 

10795, Ugashik (C-1) Quadrangle. on Alaska Peninsula. Naknek Formation. about 305 m above its base. 

Kimmeridgian or early Tithonian. 

S. R. Capps, 1921. Eight km south of Mt. Peulik. Ugashik 

( C-2) Quadrangle, on Alaska Peninsula. Naknek Formation . .Early to early middle Oxfordian. 

S. R. Capps, 1921. Southeast shore of Becharof Lake between extreme south end of lake and the fishing village, 

Ugashik (C-1) Quadrangle, on Alaska Peninsula. Naknek Formation. Kimmeridgian. 

W. R. Smith, 1922. Creek across divide (south of) Ugashik 

Creek. Ugashik ( C-1) Quadrangle, on Alaska Peninsula. Naknek Formation. Latest Kimmeridgian. 
28 LATE JURASSIC AMMONITES FROM ALASKA 

TABLE 7.-Description of Upper Jurassic ammonite localities in Alaska--Continued 

Locality No. (fig. 1) 

19 

20 

21 

21 

21 

21 

21 

21 

21 

USGS Mesozoic 

loc. No. 

31492 

11359 

25708 

25709 

25710 

25712 

25713 

25715 

5799a 

Collector's 

field No. 

78ACe34 ______ _ 

33 -------------

55-AKe-12 ____ _ 

55-AKe-13 ____ _ 

55-AKe-14 ____ _ 

55-AKe-16a ___ _ 

55-AKe-17 -----

55-AKe-19 

58A -----------

Collector, year of collection, description of locality, 

stratigraphic assignment, and age 

Jim Case and Tom Ovenshine, 1978. On hill 154 m high 

about 3.2 km northwest of ocean in S.E cor. sec. 3, T. 

38 S., R. 49, Sutwik Island (D-4) Quadrangle, on Alaska Peninsula. Staniukovich Formation. Late 

Tithonian. 

W. R. Smith, 1922. Gates of Crater Aniakchak at head of 

Aniakchak River. West-central part of sec. 8, T. 38 S., 

R. 55 W., Chignik (D-1) Quadrangle, on Alaska 

Peninsula. Naknek Flormation. 

A. S. Keller, 1955. Beach on north side of Chignik Lagoon. 

East-central part of sec. 33, T. 44 S., R. 59 W., Chignik 

( B-2) Quadrangle, on Alaska Peninsula. From green 

slabby calcareous siltstone and thin beds of limestone near top of upper 30.5 m of exposed Naknek Formation. 

Kimmeridgian. 

A. S. Keller, 1955. Same place as USGS. Mesozoic loc. 

25708 but from near middle of upper 30.5 m of exposed 

Naknek Formation. Kimmeridgian. 

A. S. Keller, 1955. Same place as USGS Mesozoic loc. 

25708 but from near base of upper 30.5 m of exposed 

Naknek Formation. Kimmeridgian. 

A. S. Keller, 1955. Beach on north side of Chignik Lagoon. 

About 0.5 km west of USGS Mesozoic loc. 25708 in 

north-central part of S.E% sec. 33, T. 44 S., R. 59 W., 

Chignik ( B-2) Quadrangle, on Alaska Peninsula. Naknek Formation. Kimmeridgian or early Tithonian. 

A. S. Keller, 1955. Same place as USGS Mesozoic loc. 

25712 but from 15 m of gray-green slabby siltstone 

containing calcareous concretions and thin beds of limestone from 14-27 m above lowermost part of the Naknek 

Formation. Kimmeridgian. 

A. S. Keller, 1955. Same place as USGS Mesozoic loc. 

25712 but from 50-63 m above lowermost exposures. 

Kimmeridgian. 

W. W. Atwood, 1908. Opposite Alaska Packers cannery on north side of Chignik Lagoon. Naknek Formation. Kimmeridgian or early Tithonian. --------------~--------------------------------------

SYSTEM A TIC DESCRIPTIONS 

Family PHYLLOCERATIDAE ZiHel, 1884 

Subfamily PHYLLOCERATINAE ZiHel, 1884 

Genus PHYLLOCERAS, Suess, 1884 

Phylloceras alaskanum Imlay, n. sp. 

Plates 1 and 2 

This species is represented in northern Alaska by 

34 specimens. It has a discoidal compressed form, 

highly elliptical whorls, which are widest a little 

below the middle of the flanks, and a very narrow 

umbilicus. Its body chamber is not preserved. 

Its ornamentation consists of fine, gently flexuous 

ribs, which become a little stronger ventrally, and 

conspicuous radial folds. These folds are weak near 

the umbilicus, become fairly strong near the middle 

of the flanks, and then fade out adorally as they pass 

into three to five fine ribs. These fine ribs, as exposed 

on the upper third of the flanks, outnumber the 

radial folds 7 to 10 times. Both ribs and folds curve 

forward on the lower third of the flanks, recurve on 

the middle of the flanks, curve forward on the upper 

third of the flanks, and then arch forward slightly 

on the venter. All ribs are separated by somewhat 

wider interspaces. 

Most of the specimens cannot be measured accurately because of lateral crushing. The holotype at 

a diameter of 7 4 mm, has a whorl height of 42 mm, 

a whorl thickness of 22 mm, and an umbilical width 

of 7 mm. A somewhat larger specimen (pl. 2, figs. 2, 

3) at a whorl height of 52 mm, has a whorl thickness of 29 mm. These measurements indicate that 

the whorls are nearly twice as high as they are thick. 

The suture line is similar to that of P. appenninicum Canavari in Burckhardt (1906, pl. 28, fig. 4). 

This species in shape and in fineness of ribbing 

resembles Phylloceras knoxvillense Stanton ( 1896, 

p. 72, pl. 14, figs. 1-3; Imlay and Jones, 1970, p. B28, 

pl. 2, figs. 4-11) but differs by lacking pronounced 

constrictions on its internal mold and by having 

much stronger radial folds. Its ribbing appears to 

be identical with that on Phylloceras apenninicum 

Canavari in Burckhardt (1906, p. 106, 153, 182, pl. 

28, figs. 1-5) from lower Tithonian beds in northcentral Mexico. It differs, however, by having a 

smaller umbilicus and a higher more compressed 
SYSTEMATIC DESCRIPTIONS 29 

whorl section. Its radial folds are much stronger and 

extend higher on its flanks than do those on P. subplicatius Burckhardt (1906, p. 40, pl. 8, figs. 1-6) 

from the Kimmeridgian I doc eras-bearing beds at 

San Pedro del Gallo in northern Mexico. Its radial 

folds appear to be somewhat stronger and much 

more flexuous than are those on the type specimen 

of P. plicatum Neumayr (1871, p. 313, pl. 12, figs. 

7a, b, pl. 13, fig. 2) from the Oxfordian of Europe. 

Phylloceras alaskanum Imlay, n. sp., is associated 

with Buchia concentrica (Sowerby) at USGS Mesozoic locs. 10795, 10817, 25708, 25710, 25713, 25715, 

29899, and 24156. It is associated with Buchia mosquensis (Von Buch) at USGS Mesozoic locs. 11345, 

25832, and 25833 and with B. rugosa (Fischer) at 

Mesozoic loc. 25832, 25833. 

Type.-Holotype, USNM 256879; paratypes, 

USNM 256875-256878. 

Occurrences.-N aknek Formation in Talkeetna 

Mountains at USGS Mesozoic loc. 24156; and on 

Alaska Peninsula at Mesozoic locs. 3124, 5799A, 

10249, 10795, 10796, 10817, 11345, 12077, 24156, 

25708-25710, 25712, 25713, 25715, 25832, 25833, 

26003, and 29899. 

Phylloceras cf. P. alaskanum Imlay 

Two fragmentary ammonites differ from Phylloceras alaskanum Imlay, n. sp., in that their ribs are 

less flexuous on their flanks. They differ from P. 

iniskinense Imlay, n. sp., by having stronger radial 

folds. Their general appearance is similar to that of 

P. plicatum Neumayr (1871, p. 313, pl. 12, figs. 7a, 

b, pl. 13, fig. 2) from the Oxfordian of Europe. 

Occurrences.-Naknek Formation, unnamed lower 

sandstone member, on south shore of Chinitna Bay 

at USGS Mesozoic loc. 11018; float at base of cliff 

near a large waterfall on east shore of Oil Bay at 

Mesozoic loc. 3041. 

Phylloceras iniskinense Imlay, n. sp. 

Plate 3, figures 1-9 

This species is represented in southern Alaska by 

17 septate specimens that are similar in size and 

shape to Phylloceras alaskanum n. sp. Its ribs are 

very fine, gently flexuous, and become a little 

stronger ventrally. Faint radial folds occur only on 

the lower parts of the flanks on some whorls but are 

absent or inconspicuous on most whorls. 

The holotype, at a diameter of 87 mm, has a 

whorl height of 50 mm, a whorl thickness of 24 mm, 

and an umbilical width of 6 mm. 

The suture line is not well preserved. 

This species differs from P. alaskanum Imlay, n. 

sp., by having finer radial ribbing and inconspicuous 

radial folds. It differs from P. knoxvillense Stanton 

(1896, p. 72, pl. 14, figs. 1-3; Imlay and Jones, 1970, 

p. B28, pl. 8, figs. 4-11) from northern California 

and Oregon by lacking constrictions on its internal 

molds. It differs from P. glennense Anderson (1945, 

p. 976, pl. 11, figs. 1, 2; Imlay and Jones 1970, p. 

B28, pl. 1, figs. 9, 10) from California by having 

weaker radial folds, a little finer ribbing, and a 

smaller umbilicus. It differs from P. aff. P. consanguineum Gemmellaro in Burckhardt (1906, p. 71, 

pl. 18, figs. 8-11) by having a higher whorl section 

and weaker radial folds. 

P. iniskinense Imlay, n. sp., apparently occurs at 

a different stratigraphic position than does P. 

ala,skanum Imlay, n. sp., as indicated by their nonassociation .. A lower stratigraphic position for I. 

iniskinense is indicated by its association with 

Buchia concentrica (Sowerby) at USGS Mesozoic 

locs. 22450, 24165, or 24167 but not with B. rugosa 

(Fischer) or B. mosquensis (von Buch), whereas P. 

alaskanum occurs with all three species of Buchia. 

Types.-Holotype, USNM 256880; paratypes 

USNM 256881-256884. 

Occurrences.-N aknek Formation in the Talkeetna Mountains at USGS Mesozoic locs. 24162, 

24165, and 24167; west side of Cook Inlet at Mesozoic locs. 11017, 11056, 21350, 21352, 21782, 21783, 

21786, and 22450; Alaska Peninsula at Mesozoic 

loc. 3124. 

Pbylloceras cf. P. knoxvillense Stanton 

Plate 4, figure 10 

This genus is represented in the Staniukovich Formation on the Alaska Peninsula by a single large 

internal mold that is crushed laterally, is mostly 

septate, and bears ribbing identical with that on 

P. knoxvillense Stanton (1896, p. 72, pl. 14, figs. 

1-3; Anderson, 1945, p. 976, pl. 11, fig. 5; Imlay and 

Jones, 1970, p. B28, pl. 2, figs. 4-11) . 

Its surface bears very fine, closely spaced, gently 

flexuous ribs that become a little coarser ventrally. 

On the venter of the nonseptate part of the shell, the 

ribs became considerably wider than the interspaces. 

The suture line is imperfectly preserved on the venter 

because of the crushing, but it definitely has a triphyllic second lateral saddle. 

Figured specimen.-USNM 256936. 

Occurrence.-Staniukovich Formation on the 

Alaska Peninsula at USGS Mesozoic loc. 31492. 
30 LATE JURASSIC AMMONITES FROM ALASKA 

Phylloceras sp. Figured specimens.-USNM 256889-256892 . 

Plate 4, figs. 9-11 

One specimen is highly involute. Its whorl section 

is subovate and is widest a little below the middle 

of the flanks. Its surface, wherever the shell is preserved, bears very fine riblets or lirae that are faint 

near the umbilicus but become slightly stronger ventrally. These lirae curve forward strongly on the 

lower third of the flanks, recurve a little near the 

middle of the flanks, and then cross the venter transversely. 

The specimen at a diameter of 72 mm, has a whorl 

height of 44 mm, and a whorl thickness of 30 mm. 

It differs from Phylloceras? contrarium Imlay and 

Jones (1970, p. B28, pl. 1, figs. 1-8) mainly by 

having a subovate instead of a subelliptical whorl 

section and by the fact that its ribs cross the venter 

transversely. 

Figured specimen.-USNM 256885 . 

Occurrence.-N aknek Formation in Talkeetna 

Mountains at USGS Mesozoic loc. 24841 and on the 

south shore of Chinitna Bay at Mesozoic loc. 21785, 

and in northeastern Alaska at Mesozoic loc. 21027. 

The same species is probably represented by five 

faintly striate much smaller specimens from the 

Talkeetna Mountains at Mesozoic loc. 8575. 

Genus PARTSCHICERAS Fucini, 1923 

Partschiceras sp. A 

Plate 6, figures 2-7 

One species, represented by three specimens, is 

similar to P. (P) subobtusiforme Pompeckj (Imlay, 

1953, p. 73, pl. 35, figs. 1-3, 8) from the Chinitna 

Formation west of Cook Inlet, Alaska, but differs by 

having slightly stronger and sparser ribbing on the 

upper part of its flanks. It is associated with Buchia 

concentrica (Sowerby) at USGS Mesozoic loc. 3136. 

Figured specimen.-USNM 256886-256888. 

Occurrences.-Naknek Formation on the Alaska 

Peninsula at USGS Mesozoic loc. 3136; Naknek 

Formation, northwest of Augustine Island on west 

side of Cook Inlet between Ursus Cove and Bruin 

Bay at Mesozoic loc. 30764; Root Glacier Formation 

in the Wrangell Mountains at Mesozoic locality 

28579; possibly represented in the Kingak shale by 

one immature specimen from west bank of Canning 

River in northern Alaska at Mesozoic loc. 24013 (see 

Imlay, 1955, p. 86, pl. 10, figs. 18, 19). 

Partschiceras sp. B 

Plate 4, figures 1-8 

This species, represented by four crushed specimens, has smooth inner whorls, but during growth, 

it develops coarse, widely spaced, radial trending 

ribs on the venter and upper parts of the flanks. 

Occurrences.-Naknek Formation on Alaska Peninsula at USGS Mesozoic locs. 11359 and 29253. 

Subfamily CALLIPHYLLOCERATINAE Spath, 1927 

Genus HOLCOPHYLLOCERAS Spath, 1927 

Holocophylloceras cf. H. mesolcum (Dietrich) 

Plate 5, figures 1-3 

This species is represented by two septate specimens, of which the smaller is compressd laterally 

and the larger is much worn on one side. It has a 

discoidal compressed form. Whorls are elliptical and 

are widest at about the top of the lower third of the 

flanks. The umbilicus is fairly narrow and has a low 

vertical wall that rounds rather abruptly into the 

flanks. 

Ornamentation consists mostly of acutely sigmoid 

to tongue-shaped constrictions on both the test and 

the internal mold and partly of weak radial ribs on 

the upper parts of the flanks wherever the shell is 

preserved. The smaller specimen has nine constrictions; the incomplete larger specimen has seven constrictions on an inner whorl and eight constrictions 

on the incomplete outer whorl. 

The suture line is imperfectly preserved. 

The inner whorl of the larger specimen, at a 

diameter of 93 mm, has a height of 49 mm and a 

thickness of 30 mm. The outer whorl, at a diameter 

of about 190 mm, has a height of 108 mm and an 

estimated thickness of 70 mm. 

This species in shape, constrictions, and fine ventral ribbing greatly resembles H olcophylloceras 

mesolcum Dietrich (1925, p. 8, pl. 1, figs. 4, 5;·Spath, 

1930, p. 24, pl. 1, figs. 2a-d; Collignon, 1959, pl. 96, 

fig. 366) from near Mombasa in Kenya, east Africa. 

Figured specimens.-USNM 256893 and 256894. 

Occ'w~rences.-N aknek Formation in the Talkeetna Mountains at USGS Mesozoic locs. 24165 and 

24834. 

Family LYTOCERATIDAE Neumayr, 1875 

Subfamily LYTOCERATINAE Neumayr, 1875 

Genus L YTOCERAS Suess, 1865 

Lytoceras sp. 

Plate 6, figures 1, 8-10 

Sixteen fragmentary specimens of Lytoceras have 

been collected at nine localities in southern Alaska. 

Some have crinkled riblets, and some have more 

closely spaced riblets than others. Those that are not 

crushed have round whorls. Their preservation is 

not sufficient to permit recognition of species. 

Figured specimens.-USNM 256895-256898. 
SYSTEMATIC DESCRIPTIONS 31 

OccuTrences-N aknek Formation west of Cook 

Inlet at USGS Mesozoic locs. 3043, 20723, and 22418; 

in the Talkeetna Mountains at Mesozoic locs. 24166 

and 24175; and in the Alaska Peninsula at Mesozoic 

locs. 3090, 3128, and 25833. 

Family PERISPHINCTIDAE Steinmann, 1890 

Subfamily PERISPHINCTINAE Steinmann, 1890 

Genus PERISPHINCTES Waagen, 1869 

Subgenus DICHOTOMOSPHINCTES Buckman, 1926 

Perisphinctes (Dichotomosphinctes) cf. P. (D.) muhlbachi Hyatt 

Plate 7, figures 7-12 

Perisphinctes (Dichotomosphinctes) cf. P. (D.) muhlbachi 

Hyatt. Imlay 1961, U.S. Geological Survey Professional 

Paper 374-D, p. D24, pl. 4, fig. 6. 

The subgenus Dichotomosphinctes is represented 

by three specimens from southern Alaska. The two 1 

largest specimens were collected on the Alaska 

Peninsula in association with Buchia concentrica 

(Sower by) . The smallest specimen was collected on 

the west end of Cook Inlet in association with Buchia 

sp. 

These specimens are characterized by evolute 

coiling, by moderately spaced, high narrow ribs, and 

by deep constrictions. The ribs incline forward 

gently on the flanks, most of them bifurcate high on 

the flanks, and all cross the venter transversely. 

Some pairs of secondary ribs are separated by single 

ribs that arise freely along the zone of furcation. 

The dimensions of the largest specimen are not 

determinable because of lateral crushing. The next 

smaller specimen has also been crushed laterally but 

haf:'. a whorl section that is slightly wider than high. 

On the smallest specimen at one place, the whorl 

height is 23 mm and the whorl thickness is 28 mm. 

These specimens are nearly identical in shape and 

ornamentation with P. (D) muhlbachi Hyatt 

(Crickmay, 1933, p. 57, pl. 18, figs. 1, 2) from California and with P. (D.) durangensis Burckhardt 

(1912, p. 16, pl. 3, figs. 1, 2, pl. 4, fig. 6) from northcentral Mexico. 

Figured specimens.-USNM 130789, 256899, and 

256900. 

Occurrence.-N aknek Formation on the Alaska 

Peninsula at USGS Mesozoic locs. 10796 and 29899 

and on the Iniskin Peninsula west of Cook Inlet at 

USGS Mesozoic loc. 22449. 

Subfamily VIRGATOSPHINCTINAE Spath, 1923 

Genus SUBPLANITES Spath, 1925 

Subplanites? sp. 

Plate 8, figure 15 

One fragment of a large ammonite has many 

strong, widely spaced, forwardly inclined ribs that 

branch at two levels ( virgatotomous) on the middle 

part of the flank. Constrictions are not present. 

The presence of virgatotomous ribs suggests that 

the specimen belongs to the subfamily Virgatosphinctinae (Arkell and others, 1957, p. L328) and 

probably represents part of the outer whorl of Subplanites or Pachysphinctes. An assignment to Subplanites is favored by the fact that most of the ribs 

are virgatotomous, whereas most of the ribs of 

Pachysphinctes are biplicate. 

Figured specimen.-USNM 256901. 

Occurrence.-N aknek Formation on the Alaska 

Peninsula at USGS Mesozoic loc. 29255. 

Genus AULOCOSPHINCTOIDES Spath, 1923 

Aulacosphinctoides sp. 

Plate 7, figures 1-3 

The genus Aulacosphinctoides is represented by 

one laterally crushed specimen on which some shelly 

material is preserved. Its whorls are fairly evolute 

and rounded. The outermost preserved whorl embraces about half of the preceding whorl and bears 

fairly sharp biplicate ribs. These ribs curve backward on the umbilical wall, curve forward on the 

lower part of the flanks, curve backward on the 

upper part of the flanks, and then cross the venter 

transversely. The next smaller whorl bears similar 

biplicate ribs, which are exposed at one place (pl. 7, 

fig. 3) where the outer whorl has been deformed by 

crushing. Constrictions are not evident on the outer 

whorl. One constriction may be present on the next 

inner whorl. 

This specimen in lateral view resembles A. infundibulum (Uhlig) (1910, p. 371, pl. 72, figs. 1a-e, 

2a, and 4 a, b) in coiling and in having fairly sharp, 

strongly curved, biplicate ribbing. The much narrower appearance of its venter is due at least in part 

to crushing. 

Figured specimen.-USNM 256902. 

Occurrence.-N aknek Formation on the Alaska 

Peninsula at USGS Mesozoic loc. 29254 in association with Buchia mosquensis (von Buch) and B. 

rugosa (Fisher). 

Family CARDIOCERATIDAE Siemiradzki, 1891 

Subfamily CARDIOCERA TINAE Siemiradzki, 1891 

Genus CARDIOCERAS Neumayr and Uhlig, 1881 

Cardioceras (Cardioceras) distans (Whitfield) 

Plate 8, figures 1-14 

Ammonites cordiformis var. distans Whitfield, 1880, U.S. 

Geographical and Geological Survey of the Rocky Mountain Region, p. 380, 381, pl. 6, fig. 25. 
32 LATE JURASSIC AMMONITES FROM ALASKA 

C. distan8 (Whitfield). Neumayr, 1883, K. Akademie der 

Wissenschaften, Wien, Mathematisch-N aturwissenschaftliche Klasse, Denkschriften, v. 4 7, p. 302. 

C. distans (Whitfield) Reeside, 1919, U.S. Geological Survey 

Professional Paper 118, p. 24, pl. 15, figs. 18-21, pl. 16, 

figs. 1-6. 

C. distans (Whitfield) var. depressum Reeside, 1919, U.S. 

Geological Survey Professional Paper 118, p. 24, pl. 15, 

figs. 22-24, pl. 16, figs. 7-11. 

This species is represented in Alaska by 20 specimens. It is characterized by a subquadrate whorl 

section that is as high or nearly as high as wide; by 

a moderately wide umbilicus; by sharp, prominent, 

widely spaced primary ribs that become stronger 

ventrally; by sharp but less prominent secondary 

ribs, most of which arise in pairs from the primary 

ribs near the middle of the flanks, but some arise 

freely higher on the flanks, and all curve strongly 

forward on the venter; and by a coarsely nodose 

pinched keel on the venter. 

Types.-Paratypes, USNM 32335, 32336, 32338; 

hyptotypes, 256903-256907. 

Occurrences.-N aknek Formation on the Iniskin 

Peninsula west of Cook Inlet at USGS Mesozoic locs. 

3045, 11002, 11013, 11017, 11056, 20723, and 21351; 

in the Talkeetna Mountains at Mesozoic locs. 24165, 

24166, 24168, 24837, and 24841. 

Cardioccras (Cardioceras) hyatti Reeside 

Plate 9, figure 6 

Cardioceras hyatti Reeside, n. sp., 1919, U.S. Geological Survey Professional Paper 118, p. 26, pl. 15, figs. 1-4. 

C. (Anacardiocera8) hyatti Reeside. Maire, 1938 Societe 

Geologique de France Memoires, new series, v. 15, no. 

2/3 (Memoire 34), p. 75, pl. 13, fig. 2. 

This species in Alaska is represented by a single 

specimen that attains a larger size than the holotype 

but has identical ribbing, except near its adoral end, 

where the ribs branch a little lower on the flanks. 

The species is characterized by its compressed form 

and by regular ribs that are only slightly stronger 

on the lower part of the flanks than on the upper. 

Types.-Holotype ,USNM 32326; hypotype, USNM 

256908. 

Occurrence.-N aknek Formation west of Cook 

Inlet at USGS Mesozoic loc. 11015. 

Cardioceras (Cardioceras) lilloetense Reeside 

Plate 9, figures 1-5 

Cardioceras lilloetense Reeside 1919, U.S. Geological Survey 

Professional Paper 118, p. 27, pl. 17, figs. 20-23. 

C. (Cardioceras) lilloetense Reeside. Maire, 1938, Societe 

Geologique de France Memoires, new series, v. 15, no. 

2/3 (Memoire 34), p. 96, pl. 13, figs. 10, lOa. 

This species is represented in Alaska by one 

specimen that is crushed laterally. The outer whorl 

of the holotyp~ has a subquadrate whorl section that 

is higher than wide; flattened flanks; a weakly 

shouldered venter; a moderately wide umbilicus; and 

sharp radial-trending, widely spaced primary ribs 

that terminate near the middle of the flank in weak 

tubercles, from which arise pairs of weaker ribs. 

One or two additional secondary ribs arise between 

the forked ribs. The secondary ribs outnumber the 

primary ribs nearly four to one, all bend forward 

on the venter, many fork again near the keel, and 

all pass into crenulations on the venter. The outer 

whorl of the smaller specimen has slightly finer 

ribbing than that on the holotype at a comparable 

size. 

Types.-Holotype, USNM 32347; hypotype USNM 

256909. 

Occurrences.-Naknek Formation in Talkeetna 

Mountains at USGS Mesozoic loc. 24841. The holotype was collected from the head of Big Creek in the 

Chilcotin River area, near Lilloet, British Columbia. 

Cardioceras (Cardioceras) cf. C. (C.) lilloetense Reeside 

Plate 9, figures 7-21 

Nine laterally crushed ammonites differ from 

C. (C.) lilloetense Reeside by having shorter primary ribs, fewer and stronger secondary ribs, and 

a rounded instead of a weakly shouldered venter. 

Their general appearance is similar to that of C. 

(C.) persecans (S. Buckman), as illustrated by 

Arkell (1946, p. 315, pl. 68, figs. 10-12, pl. 69, figs. 

5, 6), but they differ by having a narrower umbilicus. 

Figured specimens.-USNM 256910-256917. 

Occurrence.-N aknek Formation west of Cook 

Inlet at USGS Mesozoic locs. 11002, 11017, and 

21351. 

Cardioceras (Cardioceras ?) spiniferum Reeside 

Plate 11, figures 8, 9 

Cardioceras spiniferum Reeside, n. sp., 1919, U.S. Geological 

Survey Professional Paper 118, p. 30, 31, pl. 18, fig. 4, 

pl. 19, figs. 1-3. 

This species to date is represented only by the 

holotype, on which are exposed part of a septate 

whorl and an adjoining nonsepta te whorl but none 

of the inner whorls. These whorls show that the 

shelJ is compressed, the umbilicus is fairly narrow, 

and the venter terminates in a high sharp keel that 

is not bordered by furrows. The septate whorl bears 

strong sharp primary ribs that become stronger 

ventrally and that terminate in laterally con1pressed 

tubercles at or a little above the middle of the flanks. 

From these tubercles arise two or three weak secondary ribs that arch forward on the upper part of 

the flanks. In addition, two to three similarly weak 
SYSTEMATIC DESCRIPTIONS 33 

forwardly arched ribs arise freely near the middle 

of the flanks between the tubercles. All secondary 

ribs appear to pass into striae on the keel. 

The nonseptate whorl is fairly smooth, but on its 

lower half, it bears weak, broad, widely spaced 

swellings, and throughout, it bears rather weak 

striae that trend nearly radially, except near the 

keel where they arch gently forward. 

This species is assigned to Cardioceras rather than 

A moeboceras on the basis of the absence of furrows 

bordering the keel. Its preservation, however, is not 

sufficient to make a subgeneric assignment. 

H olotype.-USNM 32348. 

Occurrence.-N aknek Formation on east side of 

Oil Bay on the Iniskin Peninsula west of Cook Inlet 

at USGS Mesozoic loc. 3046. This occurrence is 70 

feet (21 m) higher than that of Cardioceras distans 

(Whitfield) at Mesozoic loc. 3045, 417 feet (126 m) 

higher than C. (Scarburgiceras) martini Reeside at 

Mesozoic loc. 3044, and 550 feet (167 m) below an 

occurrence of Bnchia concentrica (Sowerby) (see 

Martin, 1926, p. 173). 

Subgenus SCARBURGICERAS Buckman, 1924 

Cardioceras (Scarburgiceras) dettermani Imlay, n. sp. 

Plate 10, figures 1-11 

This species is represented by 12 specimens. The 

smallest specimens (Pl .. 10, figs. 1-3, 7, 8), at diameters less than 25 mm, have a narrow umbilicus, 

a subovate whorl section that is a little higher than 

wide, a narrowly rounded venter, and fairly strong 

ribs that trend radially on the lower half of the 

flanks, bifurcate in part near the middle of the 

flanks, curve slightly forward on the upper half, and 

cross the venter without becoming nodose. 

On a somewhat larger specimen (pl. 10, figs. 5, 6), 

the whorl section becomes higher, the venter becomes sharp and weakly nodose, the pri1nary ribs 

bifurcate below the middle of the flanks, simple unforked ribs become common, all ribs arch strongly 

forward on the upper part of the flanks and on the 

venter, and some ribs bifurcate high on the venter. 

Striations occur in places on the flanks and on the 

venter. 

On the largest specimens (pl. 10, figs. 9-11), forwardly arched striations become common, and the 

venter becomes nodose but apparently is not compressed at its base. 

This species differs from immature specimens of 

C. (S.) martini Reeside by having a smaller umbilicus, coarser and sparser ribs that arch forward 

more strongly, a venter that does not become sharpened or keeled until a much larger size is attained, 

and striations at a smaller size. Its ribbing and the 

shape of its inner whorls resemble those features on 

C. (S) scarburgensis (Young and Bird) (Arkell, 

1939, p. 156, pl. 10, figs. 1a, b; Arkell and others, 

1957, p. L307, figs. 379, 2a, b). It differs, however, 

by havjng a smaller umbilicus and a narrowly 

rounded instead of a sharp venter. It likewise resembles Lamberticeras lamberti Sowerby (Arkell 

and others, 1957, p. L303, figs. 372, 1a, b) except 

for having a narrower umbilicus and finer ribbing 

and by developing ventral crenulations. 

Types.-Holotype, USNM 256919; paratypes, 

USNM 256920-256925. 

Occurrences.-Kingak Shale in Ignek Valley of 

northeastern Alaska at USGS Mesozoic locs. 29137 

and 29856. Naknek Formation west of Cook Inlet in 

southern Alaska at Mesozoic loc. 11050a (float). 

Cardioceras (Scarburgiceras) martini Reeside 

Plate 10, figures 12-22 

For synonymy. see Imlay. 1964. U.S. Geological Survey Professional Paper 483-D, p. D15. 

This species is represented in Alaska by about 70 

specimens. It is characterized by its compressed 

form. a vertical umbilical wall on the larger septate 

specimens, flattened and high flanks, a pinched venter, and fine, sharp, rather closely spaced ribs, of 

which many bifurcate a little below the middle of 

the flanks. Other ribs remain single, a few trifur<~ate, 

and some arise freely near the middle of the flanks. 

The primary ribs arise low on the umbilical wall on 

small specimens, arise near the top of the wall on 

larger specimens, and trend slightly forward on the 

flanks. The secondary ribs curve strongly forward 

on the venter and are continuous with prominent 

serrations on the keel. The adoral half of the largest 

preserved who~l, which is entirely septate, is marked 

by an abrupt change from fairly strong ribbing to 

faint striations that likewise curve forward on the 

venter. The adapical ribbed half of the same whorl 

is marked near the keel by faint striae that incline 

forward more strongly than the ribs. 

The immature forms of this species, including the 

holotype, greatly resemble C. (S.) bukowski Maire 

(1938, p. 64, pl. 7, fig. 8; Arkell, 1946 (Monograph), 

p. 305, text-figs. 105-2 and 108-1; Malinowski, 1963, 

p. 44, pl. 16, figs. 87-90). They differ by having a 

more compressed whorl section, somewhat weaker 

primary ribs that do not become swollen near the 

middle of the flanks, and some trifurcated ribs 

(Arkell, 1946 (Monograph), p. 306). The immature 

forms of C. (S.) ma.rtini have much weaker primary 

ribs than do some specimens from Wyoming that 
34 LATE JURASSIC AMMONITES FROM ALASKA 

Reeside (1919, pl. 8, figs. 4-7) assigned to C. (S.) 

cordiforme (Meek and Hayden) and Maire (1938, 

p. 61) assigned to a new species, C. reesidei. 

Types.-Holotype, USNM 32317; hypotypes 

USNM 132360, 256926-256930. 

Occurrences.-Naknek Formation, west of Cook 

Inlet at USGS Mesozoic locs. 93041, 3044, 10988, 

11016, 11017, 11055, 21350a, 21351, 21782, 21784, 

22418, 22426, 22701; Talkeetna Mountains and upper 

part of Matanuska Valley at Mesozoic locs. 8575, 

24165, 24166, 24168, 24837, and 24841. 

Subgenus SCOTICARDIOCERAS Buckman, 1925 

Cardioceras (Scoticardioceras) alaskense Reeside 

Pia te 11, figures 1-6 

Cardioceras alaskense Reeside, 1919, U.S. Geological Survey 

Professional Paper 118, p. 18, pl. 6, figs. 7-10. 

This species, now represented in Alaska by four 

specimens, was originally described on the basis of 

a single septate fragment, whose outermost preserved whorl bears features characteristic of the 

subgenus Scoticardioceras (Arkell, 1956, p. 548). 

Such features include a very small umbilicus, a 

vertical umbilical wall, a laterally compressed trigonal-shaped whorl section, a tall serrated keel, and 

ribbing that fades out adorally within about twofifths of a whorL Such fading, starting near the 

umbilicus, is typical of the outer septate whorl of 

the subgenus (Arkell, 1941, p. LXXVI). 

Several smaller whorls are partly exposed within 

the umbilicus of the holotype. The largest of these 

whorls is mostly covered but has a steep umbilical 

wall, a round umbilical edge, and sharp, widely 

spaced, radial-trending ribs. The next smaller whorl, 

as described by Reeside (1919, p. 18), is subovate, 

a little higher than wide, sharp ventered, and bears 

low ribs that bifurcate near the middle of the flanks, 

arch forward in the venter, and pass into crenulations on the keel. 

The species is also represented by smaller septate 

specimens (pl. 11, figs. 1, 6) whose adoral parts are 

similiar in size, shape, and ribbing to the adapical 

part of the holotype. In contrast, the adapical parts 

of the smaller specimens bear sharp, widely spaced, 

radially trending primary ribs that becon1e stronger 

ventrally and pass near the middle of the flanks 

into two or three weaker secondary ribs. One or two 

secondary ribs also arise freely near the middle of 

the flanks between the forked ribs. All secondary 

ribs arch strongly forward and become faint on the 

venter some divide into two ribs, and all pass into ' crenulations on the keel. 

The ribbing on the adapical end of these smaller 

specimens is similar to that on small specimens of 

C. (S.) exca'uatum (J. Sowerby) figured by Arkell 

( 1941, pl. 49, figs. 3, 5). The ribbing on the adoral 

end of these specimens as well as on the holotype is 

similar to that on some larger specimens of C. (A.) 

excavatum (J. Sowerby) (Arkell, 1941, pl. 49, figs. 

1a, b, pl. 50, fig. 9). C. (S.) alaskense Reeside differs 

mainly by having a s.maller :umbilicus and by losing 

its ribbing at an earlier growth stage. 

Types.--Holotype, USNM 32306; hypotypes 

USNM 256931.-256933. 

Occurrences.-N aknek Formation on west side of 

Cook Inlet at USGS Mesozoic locs. 3041 (float), 

11015, 21351, and 22426. 

Cardioceras (Scoticardioceras) cf. C. (S.) stella Arkell 

Plate 11, figures 7, 10 

One laterally crushed, mostly septate specimen is 

nearly identical in appearance with Cardioceras 

(Scoticardioceras) stella Arkell (1947, p. 333, pl. 73, 

figs. 4a, b) : It has a tall, coarsely serrated keel, 

prominent sharp ribbing, a narrow umbilicus, and 

a low vertical umbilical wall. Within the umbilicus 

are exposed parts of two inner whorls that bear 

sharp, widely spaced primary ribs. On the outer 

whorl, the primary ribs are short and terminate in 

sharp tubercles. On the adapical half of the outer 

whorl, these tubercles give rise to pairs of ribs that 

become a little stronger ventrally and are separated 

from other pairs by one, or in places by two intercalary ribs that begin near the middle of the flanks. 

On the adoral half of the outer whorl, the primary 

ribs fade out rather abruptly and the secondary 

ribs fade a little. On the venter of the outer whorl, 

all secondary ribs swing sharply forward, become 

very fine, and then pass into prominent serrations 

on the keel. 

This specimen differs from the holotype of C. 

(S.) stella Arkell by having a slightly smaller umbilicus and by the fact that its ribs fade out at a 

smaller shell size. It could be within the range of 

variation of that species. 

Figured specimen.-USNM 256934. 

Occurrence.-N aknek Formation west of Cook 

Inlet at USGS Mesozoic loc. 21351. 

Subgenus VERTEBRICERAS Buckman, 1920 

Cardioceras (Vertebriceras) whiteavesi Reeside 

Pia te 7, figures 4-6 

Cardioceras whiteavesi Reeside, 1919, U.S. Geological Survey 

Professional Paper 118, p. 33, pl. 17, figs. 1-4. 

One uncrushed external mold from 5 miles ( 8 km) 

east-southeast of Mt. Peulik on the Alaska Peninsula 

differs from the holotype of C. whiteavesi Reeside 

only by being somewhat larger and by the adoral 
SYSTEMATIC DESCRIPTIONS 35 

secondary ribs of each pair being indistinctly connected with the primary rib. 

Hypotype .. -USNM 256935. 

Occurrence.-N aknek Formation on the Alaska 

Peninsula at USGS Mesozoic loc. 10798. 

Genus AMOEBOCERAS Hyatt, 1900 

Subgenus AMOEBITES Buckman, 1925 

Amoeboceras (Amoebites) sp. 

Plate 12, figure 1 

A moe bites is represented by one small laterally 

crushed fragment of an inner whorl. The ribs on 

the flanks are sharp, fairly straight, and moderately 

spaced, incline slightly forward, and terminate ventrally in tubercles. The venter is poorly exposed but 

is marked along its midline by a serrated keel that 

appears to be bounded laterally by shallow narrow 

furrows. These features are similar to those on a 

small specimen of A. (A.) dubium (Hyatt) (Reeside, 

1919, pl. 24, fig. 7) from California and on A. (A.) 

rasenense Spath (1935, p. 29, pl. 1, figs. 6a, b) from 

England. 

Figured specimen.-USNM 256941. 

Occurrence.-Kingak Shale in northern Alaska at 

USGS Mesozoic loc. 24014. 

Amoeboceras (Amoebites?) sp. 

Plate 12, figure 2 

One external mold is characterized by a fairly 

narrow umbilicus and by moderately spaced ribs 

that are mostly simple, that incline forward gently 

on the flanks, and that terminate ventrally in small 

tubercles. One rib bifurcates a little above the middle of the flank. The venter is not exposed. The 

general appearance of the specimen is similar that 

of A. (A.) irregulare Spath (1935, p. 32, pl. 1, figs. 

1a, b) from East Greenland. 

Figured specimen.-USNM 256942. 

Occurrence.-Root Glacier Formation in Wrangell 

Mountains at USGS Mesozoic loc. 28577 associated 

with Buchia concentrica ( Sowerby) . 

Subgenus' PRIONODOCERAS Buckman, 1920 

Amoeboceras (Prionodoceras) sp. A 

Plate 12, figures 3-12 

Six Alaskan specimens have a fairly small umbilicus, a subquadrate whorl section that is as wide 

as high, and a fairly high moderately serrate keel 

that is bordered by narrow smooth furrows. Their 

ribs are sharp, bear fairly prominent lateral and 

ventral tubercles, incline gently forward on the 

flanks, curve strongly forward on the margin of the 

venter, and terminate at the ventral furrows. Most 

of the ribs are simple, but some bifurcate at the 

lateral tubercles, and some secondary ribs arise 

freely near the middle of the flank. There are two 

serrations on the venter for every rib that borders 

the ventral furrows. 

This species has much sparser and coarser ribs 

and tubercles than the species herein compared with 

A. (P.) prorsum Spath. A. (P.) cf. quadratoides 

(Nikitin) of Sokolov (1912, pl. 2, figs. 7-9) has a 

more finely serrated keel and weaker lateral tubercles that are higher on the flanks. 

The two smallest specimens resemble a small 

specimen from East Greenland that Spath (1935, 

p. 19, pl. 1, fig. 5) described as Amoeboceras 

(Prionodoceras) sp. juv., and that he suggested 

might be a young form of A. (P.) transitorium 

Spath (1935, p. 17, pl. 1, fig. 8). The four larger 

specimens, however, bear ribbing that is a little 

weaker than that in A. (P.) transitorium. 

Amoeboceras (Prionodoceras) sp. A. is assoqt~ted 

with Buchia mosquensis (von Buch) at USGS Mesozoic. locs. 14495, 14496, and 28700. It is also associated with Buchia concentrica (Sowerby) at Mesozoic locs. 14495 and 14496. 

Figured specimens.-USNM 256937, 256939, and 

256943-256946. 

Occurrence.-Root Glacier Formation in the 

Wrangell Mountains at USGS Mesozoic locs. 14495, 

14496, 28578, and 28700. 

Amoeboceras (Prionodoceras} sp. B 

Plate 12, figures 13-~5 

Two specimens differ from A. (P.) sp. A in that 

their keel is more finely serrated and their ribs are 

finer, more closely spaced, and more nearly radial on 

the flanks. Compared with the specimens compared 

herein with A. (P.) prorsum Spath, their ribs are 

higher, denser, and straighter on the flanks but curve 

forward more strongly on the venter, and their lateral tubercles are stronger. 

Figured specimens.-USNM 256938 and 256947. 

Occurrence.-Root Glacier Formation in the 

Wrangell Mountains at USGS Mesozoic locs. 14496 

and 14497. 

Amoeboceras (Prinodoceras ?) cf. A. (P.?) prorsum Spath 

Plate 12, figures 16-18 

Amoeboceras (Prionodoceras?) sp., Imlay 1955, U.S. Geological Professional Paper 274-D, p. 90, pl. 12, figs. 2-6. 

A previous comparison of 20 small fragmentary 

ammonites from northern Alaska (Imlay, 1955, p. 

91) with A. (P. ?) pr01·sum Spath (1935, p. 24, pl. 

5, figs. 4a, b) from East Greenland is supported by 

the discovery of sev~ral larger specimens that closely 

resemble the holotype from East Greenland. The 
36 LATE JURASSIC AMMONITES FROM ALASKA 

Alaskan specimens have a fairly narrow umbilicus, 

flattened flanks, and a fairly high finely crenulated 

keel that is bordered by narrow smooth furrows. 

The specimens bear sharp ribs that incline gently 

fonvard on the flanks, curve strongly forward on 

the ventral margin, and rarely bifurcate. Weak 

tubercles are present on most ribs near the middle 

of the flanks. Fairly sharp tubercles are present 

near the ventral ends of all ribs. 

Figured specimens.-USNM 108772, 108773, 

256948-256950. 

Occurrences.-Kingak Shale in northern Alaska 

at USGS Mesozoic locs. 21028, 22598, and 29135 in 

association with Buchia concentrica (Sowerby). 

Amoeboceras? sp. A. 

Plate 12, figures 20, 21 

One poorly preserved specimen from northern 

Alaska is characterized by fairly evolute coiling and 

by strong rather widely spaced ribs that swing forward on the upper part of the flanks and on the 

venter. Some of these ribs merge ventrally with a 

low serrated keel. Serrations outnumber the ribs 

about two to one. 

The assignment to A moeboceras is questioned because the serrated keel is not separated from the 

ribs by furrows. Otherwise, the specimen shows 

some resemblance to A moeboceras (Prionodoceras) 

transitorium Spath (1935, p. 17, pl. 1, figs. 8a, b). 

An assignment to Cardioceras or any of its subgenera is questioned because the specimen was found 

near the top of the Kingak Shale associated with 

Buchia concentrica (Sowerby) and near occurrences 

of A moeboceras at USGS Mesozoic locs. 21028 and 

24014. 

Figured specimen.-USNM 256940. 

Occurrences.-Kingak Shale in northern Alaska at 

USGS Mesozoic loc. 29882, in 1ssociation with 

Buchia concentrica ( Sowerby) . 

Amoeboceras? sp. B. 

Plate 12, figure 19 

One laterally compressed specimen has fairly 

evolute coiling. The outermost preserved whorl has 

moderately spaced, moderately strong ribs that incline forward slightly on the flanks, arch forward 

on the venter, and bear weak tubercles on the middle 

and upper parts of the flanks. The next inner whorl 

has much stronger and more widely spaced ribs that 

bear fairly strong lat_eral tubercles. The venter has 

a serrated keel, which does not appear to be bordered by furrows but which is too poorly preserved 

for a definite generic determination. 

Figured specimens.-USNM 256918. 

Occurrence.-Kingak Shale in northern Alaska at 

USGS Mesozoic loc. 29136, in ::1.ssociation with 

Buchia concentrica (Sowerby). 

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38 LATE JURASSIC AMMONITES FROM ALASKA 

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A 

Page 

Alaska, northeastern ----------------------------11' Alaska Peninsula ___________________ 18, 19, 20, 21, 22 

Alaska Range ----------------------------------22 alaskanum, Phylloceras _____________ 14, 16, 17, 19, 20, 

21, 22, ~8,£9; pis. 1, 2 

alaskense, Cardioceras (Scoticardioceras) _____ 14, 16, 18, 

94; pl.11 

alba.ni, Zaraiskites, zone -------------------------21 

Amber Bay ---------------------~--------------22 Ammonites cordiformis distans ___________________ 31 

(Amoebites), Amoeboceras ____________ 14, 16, 20, 21, 85 

dubium, A moeboceras ________________________ 35 

irregulare, A moeboceras ______________________ 35 

rasenense, Amoeboceras ___________________ ..;. __ 35 

sp., Amoeboceras ____________________ 15, 85; pl. 12 

A moeboceras ____________________ 14, 17, 21, 22, 33, 85 

sp. A ------------------------------15, 86; pl. 12 

sp. B ------------------------------15, 86; pl. 12 (Amoebites) _____________________ 14, 16, 20, 21,85 

dubium ---------------------------------35 

irregulare ------------------------------35 

rasenense -------------------------------35 sp. _____________________________ 15, 85; pl. 12 

(Prionodoceras) _________________ 14, 16, 20, 21, 85 

prorsum _______________________ 15, 85: cl. 13 

quadratoides ----------------------------35 transitorium _________________________ 35, 36 

sp. A __________________________ 15, 85; pl. 12 

sp. B ---------------------------15,95; pl. 12 

(A nacardioceras) hyatti, Cardioceras _______________ 32 

Aniakchak Crater Gates _________________________ 16 

appenninicum, Phytwceras -----------------,------28 

A rcticoceras -----------------------------------14 

Arctocephalites ---------------------------------15 Aula.cosphinctoides __________________ 14, 19, 21, 22, 31 

infundibulum -------------------------------31 

sp; --------------------------------16, 81; pl. 7 

B 

bayleyi, Pictonia, zone ---------------------------21 

Bibliography -----------------------------------36 

Black Island -----------------------------------15 

Buchia ----------------------------------------22 concentrica _________________ 14; 15, 16,.17, 18, 19, 

20, 21, 22, 24, 29, 30, 31, 35 

crassicollis ---------------------------------19 

fischeriana ---------------------------19, 21, 22 mosquensis _________ 15, 16, 17, 19, 20, 21, 22, 29,35 

okensis ------------------------------------22 piochii ______________________________ 19, 21, 22 

rugosa ___________________ 15, 16, 17, 20, 21, 22, 29 

unschensis ---------------------------19, 21, 22 

sp -------------------------------------14, 31 

succession of -------------------------------19 lrukowski, Cardioceras (Scarburgiceras) ____________ 33 

c 

Cache Creek -----------------------------------15 

Canning River ---------------------------------15 Cardioceras _______________ 14, 17, 18, 19, 20, 22, 81, 36 

cordatum zone ------------------------------20 

reesidei ------------------------------------34 

sp ----------------------------------------16 (A nacardioceras) hyatti ______________________ 32 

INDEX 

[Italic page numbers indicate major references] 

Page 

(Cardioceras) distans ________ 14, 15, 16, 18, 81; pl. 8 

hyatti ________________________ 14, 16, 811; pl. 9 

lilloetense _________________ 14, 16, 18, 811; pl. 9 

persecans -------------------------------32 spiniferum __________________ 15, 16, 811; pl. 11 

(Scarburgiceras) -----------------------14, 19,98 

lrukowski -------------------------------33 

cordiforme ------------------------------34 

dettermani _______________ 15, 16, 20, 88; pl. 10 

martini ____________ 14, 15, 16, 18, 20, 89; pl. 10 

(Scoticardioceras) _____________________ 14, 20, 81, 

alaskense _________________ 14, 16, 18, 91,; pl. 11 

euavatum ------------------------------34 stella _______________________ 14, 16, 81,; pl. 11 

(Vertebriceras) ---------------------------14, 81, whiteavesi ____________________ 16, 23, 81,; pl. 7 

(Cardioceras) distans, Cardioceras _14, 15, 16, 18, 81;pl. 8 

hyatti, Cardioceras ________________ 14, 16, 911; pl. 9 

lilloetense, Cardioceras __________ 14, 16, 18, 8~; pl. 9 

persecans, Cardioceras _______________________ 32 

spiniferum, Cardioceras __________ 15, 16, 811; pl. 11 

Chignik Bay -----------------------------16, 18, 22 

Chinitna Bay -----------------------------------14 

Chisik Conglomerate Member, Naknek Formation ____ 18 

Chisik Island -----------------------------------18 concentrica, Buchia _________________ 14, 15, 16, 17, 18, 

19, 20, 21, 22, 24, 29, 30, 31, 35 cO'nBanguineum, PhylWceras ______________________ 29 

contrarium, Phylloceras -------------------------30 

Cook Inlet -------------------------17, 19, 20, 21, 22 cordatum, Cardioceras, zone ______________________ 20 

cordiforme, Cardioceras (Scarburgiceras) ___________ 34 

cordiformis distans, Ammonites ___________________ 31 

Craspedites ------------------------------------22 

crassicollis, Buchia -----------------------------19 

D 

dettermani, Cardioceras. (Scarburgiceras). _______ 15, 16, 

20, 88; pl. 10 

(Dichotomosphinctes) _________________________ 19, 20 

Perisphinctes _____________ 14, 18, 19, 20, 21, 22, 81 

durangensis, Perisphinctes _____________ 31 

muhlbachi, Perisphinctes ____ 15, 16, 81; pl. 7 

distans, Ammonites cordiformis ------------------ 31 

Cardioceras (Cardioceras) ____ 14, 15, 16, 18, 81; pl. 8 

Dorsoplanites ----------------------------------21 dubium, Amoeboceras (Amoebites) _________________ 35 

durangensis, Perisphinctes (Dichotomosphinctes) _____ 31 

Durangites ------------------------------------21 

E 

excavatum, Cardioceras (Scoticardioceras) __________ 34 

F 

Faunal setting, ammonite ------------------------~11 

Fire Creek ------------------------------------14 fischeriana, Buchia _______________________ 19, 21, 22 

G 

Geographic distribution --------------------------23 

Glauconitic Series -------------------------------21 

glennense, Phytwceras ---------------------------29 Gregoryceras transversarium zone ________________ 20 

Page 

H 

Holcophytwceras _____________________________ 14, 90 

mesolcum ---------------------------16, 80; pl. 5 hyatti, Cardioceras (A nacardioceras) _______________ 32 

Cardioceras (Cardioceras) __________ 14, 16, 811; pl. 9 

Ignek Mesa ------------------------------------14 

Ignek Valley -----------------------------------19 infundibulum, A ula.cosphinctoides _________________ 31 

Iniskin Bay ---------------------------15, 17, 19, 21 

Iniskin Peninsula ----------------------------18, 20 

iniskinense, Phytwceras ___________________ 14, 15, 16, 

17. 18, 19, 20, 22, 119; pl. 3 

irregulare, A moeboceras (A moebites) _______________ 35 

J 

Joe Creek ----------------------------------15, 21 

K 

Kamishak Bay ------------------------------16, 18 

Katmai ---------------------------------------19 

Kemik Creek -----------------------------------21 

Kimmeridgian, late ---------------------------110, ~1 

Kingak Shale -------------------------------14, 15 

kmxl:villense, Phylloceras, ___________ 16, 22, 28, 119; pl. 4 

Kossmatia -------------------------------------21 

L 

Lamberti, Lamberticeras _________________________ 33 

Lamberticeras Lamberti __________________________ 33 

lilloetense, Cardioceras (Cardioceras) _14, 16, 18, 9~; pl. 9 

Little Nelchina River ----------------------------17 

Lytoceras --------------------------------14,22,80 

sp ------------------------------15, 16, 90; pl. 6 

M 

mariae, Quenstedtoceras, zone ____________________ 19 

martini, Cardioceras (Scarburgiceras) __________ 14, 15, 

16, 18, 20, 98; pl. 10 

mesolcum, Holcophylloceras _______________ 16, 90; pl. 5 

Milne Land, Greenland --------------------------21 

mosquensis,Buchia _____ 15,16,17,19, 20, 21, 22, 29,35 

Mt. Katmai ------------------------------------16 Mt. Peulik :_ ______________________________ 16, 19, 22 

muhlbachi1, Perisphinctes (Dichotomosphinctes) ____ 15, 

16, 81; pl. 7 

mutablis, Rasenia, zone ------------------------- 20 

N 

Nabesna --------------------------------------21 

Naknek Formation ________________________ 16, 17, 18 

Chisik Conglomerate Member of _______________ 18 

lower sandstone member of __________ 14, 15, 18, 20 

Pomeroy Arkose Member of ________________ 18, 20 

Snug Harbor Siltstone Member of _____ 14, 15, 18, 20 

39 
40 

Page 

0 

Oil Bay ------------------------------------15, 18 

ok6718is, Buchia ---------------------------------22 

Okpikruak River --------------------------------21 

Oxfordian, early --------------------------------19 

.middle ----------------------------------19, fO 

p 

Partschiceras -------------------------------14, 90 

(Partschiceras) subobtusijorme _________________ 30 

sp. A _________________________ 15, 16, 22, 90; pl. 6 

sp. B -------------------------------16, 90; pl. 4 

(Partschiceras) subotusijorme, Partschiceras ________ 30 

Pavlovia --------------------------------------21 

Persphinctes plicatilis zone -----------------------20 

(Dichotomosphinctes) _______ 14, 18, 19, 20, 21, 22, 91 

duranensis -----------------------------31 muhlbachi ____________________ 15, 16, 91; pl. 7. 

persecans, Cardioceras (Cardioceras) ------------~--32 

Phylloceras ------------------------------14, 22, fB 

alaskanum __ 14, 16, 17, 19, 20, 21, 22, fB, f9; pis. 1, 2 

appenninicum ------------------------------28 

consanguineum -----------------------------29 

contrarium --------------------------------30 

glennense ----------------------------------29 iniskinense ____ 14, 15, 16, 17, 18, 19, 20, 22, f9; pl. 3 

kno:will6718e ___________________ 16, 22, 28, f9; pl. 4 

plicatum -----------------------------------29 

subplicatius --------------------------------29 

sp ---------------------------14, 15, 16, 90; pl. 4 

Pictonia bayleyi zone ----------------------------21 

piochii, Buchia ---------------------------19, 21, 22 

plicatilis, Perisphinctes, zone _____________________ 20 

plicatum, Phylloceras ---------------------------29 

Pomeroy Arkose Member, Naknek Formation ____ 18, 20 

LATE JURASSIC AMMONITES FROM ALASKA 

Page 

Port Moller ---------------------------------18, 19 

(Prionodoceras), Amoeboceras _________ 14, 16, 20, 21,85 

prorsum, Amoeboceras _______________ 15, 85; pl. 12 

quadratoides, A moeboceras ____________________ 35 

transitorium, Amoeboceras ________________ 35, 36 

sp. A, Amoeboceras __________________ 15, 85; pl. 12 

sp. B, Amoeboceras __________________ 15, 95; pl. 12 

prorsum, A moeboceras (Prionodoceras) _____ 15, 95; pl. 12 

Puale Bay -------------------------------------16 

Q 

quadratoides, Amoeboceras (Prionodoceras) _________ 35 

Quenstedtoceras mariae zone _____________________ 19 

R 

rasen6718e, Amoeboceras (Amoebites) ________________ 35 

Rasenia mutabilis zone __________________________ 20 

reesidei, Cardioceras ----------------------------34 

Root Glacier Formation ____________________ 15, 16, 17 

rugosa, Buchia _______________ 15, 16, 17, 20, 21, 22, 29 

s 

Sagavanirktok River ----------------------------14 

(Scarburgiceras), Cardioceras _______________ 14, 19, 89 

bukowski, Cardioceras _______________________ 33 

cordijorme, Cardioceras ______________________ 34 

dettermani, Cardioceras ________ 15, 16, 20, 89; pl. 10 

martini, Cardioceras ____ 14, 15, 16, 18, 20, 98; pl. 10 

(Scoticardioceras), Cardioceras ______________ 14, 20,94 

alask6718e, Cardioceras _________ 14, 16, 18, 94; pl. 11 

excavatum, Cardioceras ______________________ 34 

steUa, Cardioceras _______________ 14, 16, 84; pl. 11 

Shaviovik River --------------------------------21 

Page 

Snug Harbor Siltstone Member, Naknek Formation __ 14, 

15, 18,20 

spiniferum, Cardioceras (Cardioceras) __ 15, 16, 8f; pl. 11 

Staniukovich Formation ______________________ 16, 19 

steUa, Cardioceras (Scoticardioceras) ___ 14, 16, 84; pl. 11 

subobtusijorme, Partschiceras (Partschiceras) _______ 30 

Subplanites ___________________________ 14, 21, 22, 91 

sp ---------------------------------16, 81; pl. 8 subplicatius, Phylloceras _________________________ 29 

Sutwik Island ----------------------------------16 

T 

Talkeetna Mountains ________________ 16, 17, 19, 20, 22 

Tithonian, early ________________________________ f1 

late _______________________________________ f1 

transitorium, Amoeboceras (Prionodoceras) ______ 35, 36 

transversarium, Gregoryceras, zone _______________ 20 

Tuxedni Bay -----------------------------17, 19, 21 

u 

unsch6718is, Buchia ________________________ 19, 21, 22 

v 

(Vertebriceras), Cardioceras ___________________ 14, 84 

whiteavesi, Cardioceras ____________ 16, 23, 34; pl. 7 

Virgatosphinctinae -----------------------------21 

w 

Wide Bay ----------------------------------19, 21 

whiteavesi, Cardioceras (Vertebriceras) __ 16, 23, 94; pl. 7 

Wrangell Mountains _______________________ 15, 20, 22 

z 

Zaraiskites albani zone --------------------------21 
PLATES 1-12 

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 1 and 3 are X 9/10; figure 2 is natural size] 

FIGURES 1-3. Phylloceras alaskanum Imlay, n. sp. (p. 28). 

1, 3. Holotype, USNM 256879, from USGS Mesozoic loc. 25832. 

2. Paratype, USNM 256875, from USGS Mesozoic loc. 25832. See plate 2, figure 1, for lateral view. 

PLATE 2 

[All figures are natural size] 

FIGURES 1-6. Phylloce'ras alaskanwn Imlay, n. sp. (p. 28). 

1. Paratype, USNM 256875, from USGS Mesozoic loc. 25832. See plate 1, figure 3, for ventral view. 

2, 3. Paratype, USNM 256877, from USGS Mesozoic loc. 24156. 

4. Paratype, USNM 256876, from USGS Mesozoic loc. 10796. 

5, 6. Paratype, USNM 256878, from USGS Mesozoic loc. 29899. 
GEOLOGICAL SURVEY PHOFES::;JOJ\AL P.\PER 1190 PLATE ~ 

PHYLLOCERAS 
PLATE 3 

[All figures are natural size] 

FIGURES 1-9. Phylloceras iniskinense Imlay, n. sp. (p. 29). 

1, 8. Paratype, USNM 256884, from USGS Mesozoic loc. 21783. 

2-4. Lateral, ventral and cross-sectional views of paratype, USNM 256883, from USGS Mesozoic loc. 

11056. 

5. Paratype, USNM 256881, from USGS Mesozoic loc. 21352. 

6. Paratype, USNM 256882, from USGS Mesozoic loc. 21352. 

7, 9. Holotype, USNM 256880, from USGS Mesozoic loc. 24162. 
GEOLOGICAL Sl'RVEY PROFESSIONAL PAPER 1190 PLATE il 

1 

PHYLLOCERAS 
PLATE 4 

[Figures natural size unless otherwise indicated] 

FIGURES 1-8. Partschiceras sp. B. (p. 30). 

1, 2. Distorted specimen, USNM 256892, from USGS Mesozoic loc. 11359. 

3, 4. Laterally compressed specimen, USNM 256889, from USGS Mesozoic loc. 29253. 

5, 6. Specimen, USNM 256890, from USGS Mesozoic loc. 29253. 

7, 8. Crushed specimen, USNM 256891, from USGS Mesozoic loc. 29253. 

9, 11. Phylloceras sp. (p. 30). 

Septate specimen, USNM 256885, from USGS Mesozoic loc. 24841. 

10. Phylloceras cf. P. knoxvillense Stanton (p. 29). 

Specimen, USNM 256936, from USGS Mesozoic loc. 31492 (X 9/10). 
GEOLOGICAL SUR\'EY 

PROFESSIO~AL l'AP~~H I!HO PLATE .J 

PARTSCHICERAS AND PHYLLOCERAS 
PLA'rE 5 

[Figures 1, 2 are X 9/10; figure 3 is natural size] 

FIGURES 1-3. Holcophylloceras cf. H. mesolcum (Dietrich) (p. 30). 

1, 2. Two whorls of specimen, USNM 256893, from USGS Mesozoic loc. 24165. The smaller whorl shown in 

figure 2 is exposed on the much weathered side opposite that shown on figure 1. 

3. Specimen, USNM 256894, from USGS Mesoizoic loc. 24834. 
GEOLOGiCAL SURVEY PROFESSlOJ'\AL PAPEH 1190 PLATE :> 

2 3 

HOLCOPHYLLOCERAS 
PLATE 6 

[All figures are natural size] 

FIGURES 1, 8-10. Lytoceras sp. (p. 30). 

1. Laterally crushed specimen, USNM 256897, from USGS Mesozoic loc. 24175. 

8, 9. Specimen, USNM 256896, from USGS Mesozoic loc. 3090. 

10. Specimen, USNM 256895, from USGS Mesozoic loc. 3043. 

2-7. Partschiceras sp. A. (p. 30). 

2, 3. Specimen, USNM 256887, from USGS Mesozoic loc. 3136. 

4, 7. Specimen, USNM 256886, from USGS Mesozoic loc. 28579. 

5, 6. S.pecimen, USNM 256888, from USGS Mesozoic loc. 30764. 
GEOLOGICAL SUR\.EY PROFESSIONAL PAPER lHlO !'LATE fi 

LYTOCERAS AND PARTSCHICERAS 
PLATE 7 

[All figures are natural size] 

FIGURES 1-3. Aulacosphinctoides sp. (p. 31). 

Views of a slightly distorted specimen, USNM 256902, from USGS Mesozoic loc. 29254. 

4-6. Oardioceras (Vertebriceras) whiteavesi Reeside (p. 34). 

Views of rubber cast of external mold, hypotype, USNM 256935, from USGS Mesozoic loc. 10798. 

7-12. Perisphinctes (Dichotomosphinctes) cf. P. (D.) muhlbachi Hyatt (p. 31). 

7, 12. Specimen, USNM 256899, from USGS Mesozoic loc. 29899. 

8, 10, 11. Specimen, USNM 256900, from USGS Mesozoic loc. 22449. Figure 11 is a ventral view of an 

inner whorl. 

9. Specimen, USNM 130789, from USGS Mesozoic loc. 10796. 
GEOLOGICAL SCR\ 'EY PROFESSIONAL PAPER 1190 PLATE 7 

AULACOSPHINCTOIDES, CARDIOCERAS, AND PERlSPHINCTES (DICHOTOMOSPHINCTES) 
PLATE 8 

[All figures are natural size] 

FIGURES 1-14. Cardioceras (Cardioceras) distans (Whitfield) (p. 31). 

1, 2. Paratype, USNM 32336, from USGS Mesozoic loc. 3045. 

3, 4. Hypotype, USNM 256903, from USGS Mesozoic loc. 3045. 

5-7. Hypotype, USNM 256904, from USGS Mesozoic loc. 21351. 

8, 9. Hypotype, USNM 256905, from USGS Mesozoic loc. 11013. 

10, 11. Hypotype, USNM 256906, from USGS Mesozoic loc. 11002. 

12. Paratype, USNM 32335, from USGS Mesozoic loc. 3045. 

13, 14. Paratype, USNM 32338, from US.GS Mesozoic loc. 3045. 

15. Subplanites? sp. (p. 31). 

Lateral view of specimen, USNM 256901, from USGS Mesozoic loc. 29255. 
00 

w 0') E--

<! 

.....:l 

0.. 

~ ~ 

w 

0.. 

<! 

0.. 

.....:l 

<! 

z 

0 

w 

•r:n 

w 

0 """' 

p:; 

0.. 
PLATE 9 

[All figures are natural size] 

FIGURES 1-5. Cardioceras (Cardioceras) lilloetense Reeside (p. 32). 

1-3. Lateral and ventral views of holotype, USNM 32347, from near Lilloet, British Columbia. 

4, 5. Hypotype, USNM 256909, from USGS Mesozoic loc. 24841. 

6. Cardioceras (Cardioceras) hyatti Reeside (p. 32). 

Hypotype, USNM 256908, from USGS Mesozoic loc. 11015. 

7-21. Cardioceras ( Cardioceras) cf. C. (C.) lilloetense Reeside ( p. 32). 

7, 8. Specimen, USNM 256916, from USGS Mesozoic loc. 21351. 

9, 10. Specimen, USNM 256915, from USGS Mesozoic loc. 21351. 

11, 12. Specimen, USNM 256917, from USGS· Mesozoic loc. 21351. 

13, 14. Specimen, USNM 256914, from USGS Mesozoic loc. 21351. 

15, 16. Specimen, USNM 256912, from USGS Mesozoic loc. 21351. 

17-19. Specimen, USNM 256913, from USGS Mesozoic loc. 21351. Figure 17 is a rubber cast of an external mold preserved on opposite side of specimen shown in figure 19. 

20. Specimen, USNM 256910, from USGS Mesozoic loc. 11002. 

21. Specimen, USNM 256911, from USGS Mesozoic loc. 21351. 
GEOLOGICAL SURVEY 

1 

7 8 9 

13 14 

18 19 

2 

\ 

I 

_, 

3 

15 

CARDIOCERAS 

PROFE::-iSIO!\AL PAPER lHlO PLATE H 

6 

12 
PLATE 10 

[Figures natural size unless otherwise indicated] 

FIGURES 1-11. Cardioceras (Scarburgiceras) dettermani Imlay, n. sp. (p. 33). 

1-3. Paratype, USNM 256925, from USGS Mesozoic loc. 29137 (X 2). 

4. Paratype, USNM 256920, from USGS Mesozoic loc. 29137. 

5, 6. Holotype, USNM 256919, from USGS Mesozoic loc. 11050a. 

7. Paratype, USNM 256924, from USGS Mesozoic loc. 29856. 

8. Paratype, USNM 256923, from USGS Mesozoic loc. 29137. 

9, 10. Paratype, USNM 256922, from USGS Mesozoic loc. 29137. 

11. Paratype, USNM 256921, from USGS Mesozoic loc. 29137. 

12-22. Cardioceras (Scarburgiceras) martini Reeside (p. 33). 

12. Hypotype, USNM 256930, from USGS Mesozoic loc. 8575. 

13. Hypotype, USNM 256929, from USGS Mesozoic loc. 8575. 

14-17. Holotype, USNM 32317, from USGS Mesozoic loc. 8575. 

18, 19. Hypotype, USNM 256928, from USGS Mesozoic loc. 21784. 

20, 21. Hypotype, USNM 256926, from USGS Mesnoic loc. 24837. 

22. Hypotype, USNM 256927, from USGS Mesozoic loc. 24837. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1190 PLATE 10 

9 

13 

CARDIOCERAS 
PLATE 11 

[All figures are natural size] 

FIGURES 1-6. Cardioceras (Scoticardioceras) alaskense Reeside (p. 34). 

1, 2. Hypotype, USNM 256931, from USGS Mesozoic loc. 21351. 

3, 4. Holotype, USNM 32306, from USGS Mesozoic loc. 3041. 

5. Hypotype, USNM 256933, from USGS Mesozoic loc. 22426. 

6. Hypotype, USNM 256932, from USGS Mesozoic loc. 11015. 

7, 10. Cardioceras (Scoticardioceras) cf. C. (S.) stella Arkell (p. 34). 

Specimen, USNM 256934, from USGS Mesozoic loc. 21351. 

8, 9. Cardioceras (Cardioceras?) spiniferum Reeside (p. 32). 

Holotype, USNM 32348, from USGS Mesozoic loc. 3046. 
GEOLOGICAL SURVEY PROFESSIONAL PAPER !HlO PLATE 11 

CARDIOCERAS 
PLATE 12 

[All figures are natural size] 

FIGURE 1. Amoeboceras (Amoebites) sp. (p. 35). 

Specimen, USNM 256941, from USGS Mesozoic lo~. 24014. 

2. Amoeboceras (Amoebites?) sp. (p. 35). 

Specimen, USNM 256942, from USGS Mesozoic lo:::. 28577. 

3-12. Amoeboceras (Prinonodoceras) sp. A. (p. 35). 

3, 4. Specimen, USNM 256945, from USGS Mesozoic loc. 14496. 

5, 6. Specimen, USNM 256944, from USGS Mesozoic loc. 14495. 

7. Specimen, USNM 256939, from USGS Mesozoic loc. 28700. 

8, 9. Specimen, USNM 256946, from USGS Mesozoic loc. 14495. 

10, 11. Specimen, USNM 256943, from USGS Mesozoic loc. 14495. 

12. Specimen, USNM 256937, from USGS Mesozoic loc. 28578. 

13-15. Amoeboceras (Prinodoceras) sp. B. (p. 35). 

13, 14. Specimen, USNM 256947, from USGS Mesozoic loc. 14497. 

15. Rubber cast of external mold, USNM 256938, from USGS Mesozoic loc. 14496. 

16-18. Amoeboceras (Prionodoceras?) cf. A. (P. ?) prorsum Spath (p. 35). 

16. Specimen, USNM 256949, from USGS Mesozoic loc. 29135. 

17. Specimen, USNM 256948, from USGS Mesozoic loc. 29135. 

18. Specimen, USNM 256950, from USG~ Mesozoic loc. 29135. 

19. Amoeboceras? sp. B. (p. 36). 

Specimen, USNM 256918, from USGS Mesozoic loc. 29136. 

20, 21. Amoeboceras? sp. A. (p. 36). 

Specimen, USNM 256940 from USGS Mesozoic loc. 29882. 

-k U.S. GOVERNMENT PRINTING OFFICE: 1981-361-614/266 
GEOLOGICAL SURVEY 

1 

19 20 

AMOEBOCERAS AND AMOEBOCERAS? 

PROFESS IONAL PAPER 1190 PLATE 12 

21