Middle Jurassic (Bajocian and Bathonian) Ammonites From Northern Alaska

GEOLOGICAL SURVEY PROFESSIONAL PAPER 854 Middle Jurassic (Bajocian and Bathonian) Ammonites From Northern Alaska

By RALPH W. IMLAY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 854

An ammonite succession nearly identical ivith that in northern Canada is correlated with a more varied ammonite succession in southern Alaska

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1976 UNITED STATES DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY

V. E. McKelvey, Director

Library of Congress Cataloging in Publication Data Imlay, Ralph Willard, 1908- Middle Jurassic (Bajocian and Bathonian) ammonites from northern Alaska. (Geological Survey professional paper; 854) Bibliography: p. Includes index. Supt. of Docs. no. : I 19.16:854 1. Ammonoidea. 2. Paleontology Jurassic. 3. Paleontology Alaska. I. Title. II. Series: United States. Geo­ logical Survey. Professional paper; 854. QE807.A5I615 564'.53'097987 74-20556

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington D.C. 20402 Stock Number 024-001-027305 CONTENTS

Page Abstract ______. 1 Introduction ______. 1 Biologic analysis ______. 1 Stratigraphic summary ______. 2 Stratigraphic distribution of ammonites 3 Ages and correlations ______. 5 Bajocian ammonites ______. 5 Bathonian ammonites ______7 Ammonite faunal setting ______. 7 Geographic distribution ______- 7 Systematic descriptions ______10 References cited ______. 18 Index ______. 21

ILLUSTRATIONS [Plates follow index]

PLATE 1. Pseudolioceras, Canavarella, Oppelia (Liroxyites), Arkellocerasl, and Arkelloceras. 2. Cranocephalites and Choffatial. 3. Arcticoceras, Arcticocerasl, and Erycitoides. 4. Arctocephalites and Choffatial.

Page FIGURE 1. Diagram showing occurrences and ages of fossils in Kingak Shale exposed on Canning River west of Shublik Island, northern Alaska ______-______4 2. Chart showing correlation of Bajocian and Bathonian faunas in northern Alaska _ 6 3. Generalized index map of Bajocian ammonite localities in northern Alaska _ _ -______11 4. Generalized index map of Bathonian ammonite localities in northern Alaska ______12 5. Detailed index map of Middle Jurassic ammonite localities in central part of Mt. Michelson quadrangle between the Canning and Sadlerochit Rivers ______13

TABLES

Page TABLE 1. Ammonite genera and subgenera of Bajocian and Bathonian Age in northern Alaska ______1 2. Stratigraphic position and age of fossils in Kingak Shale exposed on northwest slope of Ignek Mesa, northern Alaska ______- 3. Geographic distribution of ammonites of Bajocian and Bathonian Age in northern Alaska ______4. Description of some Middle Jurassic fossil localities in northern Alaska -

III MIDDLE JURASSIC (BAJOCIAN AND BATHONIAN) AMMONITES FROM NORTHERN ALASKA

By RALPH W. IMLAY

ABSTRACT in order to present the latest available evidence con­ Middle Jurassic ammonites of Bajocian and Bathonian cerning the stratigraphic and geographic distribu­ Age occur in northern Alaska within the Kingak Shale tion of the taxa and to show that the Bathonian throughout thicknesses ranging from 300 to 850 feet (90- 255 m) or more. Bajocian ammonites have been identified as Stage is well developed in northern Alaska. Much of far west as the Point Barrow area. Bathonian ammonites the discussion concerning the Bajocian ammonites have -been identified as far west as the Canning River and is a reinterpretation of the fossils described by the are possibly present on the Saviukviayak River. writer in 1955, but the discussion also includes some The Bajocian ammonite succession from the base upward new fossil and stratigraphic data. All these new consists of (1) Pseudolioceras maclintoeki (Haughton); (2) P. whiteavesi (White) in association with Erycitoides data, as well as most of the data concerning Bath­ howeUi (White) and Canavarella crassifalcata Imlay, n. sp.; onian ammonites, are based on fossils collected since and (3) ArkeUoceras cf. A. tozeri Frebold. P. maclintoeki in 1955 by geologists of British Petroleum (Alaska), northern Canada occurs at or near the base of the lower Inc., in 1964, by consulting geologist Marvin Man- Bajocian; P. whiteavesi and E. howelli in southern Alaska gus in 1963 and 1966, and by U.S. Geological Survey occur at the top of the lower Bajocian; and ArkeUoceras on geologists R. L. Detterman in 1969-72 and H. N. the Alaska Peninsula occurs above ammonites representing the Sonninia sowerbyi zone and near the base of an am­ Reiser in 1970. The author is grateful to all these monite sequence representing the Otoites sauzei zone. The geologists for collecting the fossils, for preparing lack of younger Bajocian ammonites anywhere in northern accurate locality maps and descriptions, and for Alaska is indicative of an unconformity. furnishing stratigraphic data. The Bathonian ammonite succession from the base upward consists of (1) Cranocephalites sp., (2) C. iguekensis Imlay, BIOLOGIC ANALYSIS n. sp., (3) Arctocephalites cf. A. elegans Spath, and (4) Arcticoceras ishmae (Keyserling). These ammonites, in com­ Northern Alaska ammonites of Bajocian and parison with the Bathonian ammonite succession in East Bathonian Age that are discussed herein number Greenland, do not represent the highest and lowest parts of 220 specimens. Their distribution by genus, sub­ the stage, as defined for Greenland, nor do they represent family, and family is shown in table 1. Among the the zone of Arctocephalites greenlandicus just below the zone of Arcticoceras ishmae. Perhaps the lack of representation on Ignek Mesa and elsewhere may be partly due to poor TABLE 1. Ammonite genera and subgenera of Bajocian and exposures. Nonetheless, an unconformity at the top of the Bathonian Age in northern Alaska Bathonian sequence in northern Alaska is indicated by the Genus and Number of nearness of Arcticoceras to the early Oxfordian ammonite Family Subfamily subgenus specimens Cardioceras on Ignek Mesa and by the scarcity of definite Hildoceratidae ____ Harpoceratinae ______Pseudolioceras ___ 65 Callovian ammonites in northern Alaska. 2 25 The Bajocian and Bathonian ammonite faunules in north­ Hammatoceratidae _ Hammatoceratinae ____ 7 Erycitoides? _____ 5 ern Alaska are closely similar to those in northern Canada Oppeliidae ______Oppeliinae __-----__-- Oppelia and lived in the same faunal province. The inclusion of (Liroxyites) ___ 1 46 some species in common with faunules of the same ages in Cranocephalites 22 Arctocephalites __ 16 southern Alaska shows that the northern and southern seas Arctocephalites? _ 6 were connected, although specifically the northern Alaskan Arcticoceras _____ 24 Perisphinctidae ___ Pseudoperisphinctinae _ 1 faunas are much less varied. New species described herein include Canavarella crassi­ falcata Imlay and Cranocephalites ignekensis Imlay. families, the Hildoceratidae composes two-fifths, the Cardioceratidae nearly one-third, and the Stephano­ INTRODUCTION ceratidae one-fifth of the total specimens. The Hil­ Middle Jurassic ammonites, representing the Ba­ doceratidae is represented mostly by Pseudolioceras jocian and Bathonian Stages, are described herein but also includes Tmetoceras and Canavarella. The BAJOCIAN AND BATHONIAN AMMONITES FEOM NOETHEEN ALASKA

Cardioceratidae is represented by nearly equal num­ Canavarella in England is recorded from the zone bers of Arcticoceras, Arctocephalites, and Crano­ of Tmetoceras scissum (Arkell and others, 1957, p. cephalites. L262) near the base of the Middle Jurassic. In The characteristics of most of the genera and sub- northern Alaska, it is associated with Pseudolio­ genera present have been adequately discussed in ceras whiteavesi (White) and Erycitoides cf. E. fairly recent publications. Pseudolioceras, Tmeto- howelli (White). ceras, and Erycitoides have been discussed by West- ermann (1964, p. 358-360, 426-432; 1969, p. 18, STRATIGRAPHIC SUMMARY 52) ; Liroxyites, by Imlay (1962b, p. A8) ; Arkello- ceras, by Frebold (1958, p. 9; 1961, p. 8-10; Fre- Middle Jurassic beds in northern Alaska have bold and others, 1967, p. 18-20) ; Cranocephalites been identified faunally in the subsurface of the and Arctocephalites, by Spath (1932, p. 14-16, 32, Point Barrow-Cape Simpson area (Imlay, 1955, p. 33), Arkell and others (1957, p. L301), and Imlay 82, 89), in a few outcrops between the Killik and (1962a, p. C2) ; Arcticoceras, by Spath (1932, p. 50- Itkillik Rivers in north-central Alaska (Patton and 53), Callomon (1959, p. 508), and Arkell and others Tailleur, 1964, p. 444), and in extensive outcrops (1957, p. L302) ; and Choffatia, by Spath (1931, p. between the Sagavanirktok and Aichilik Rivers in 325), Arkell and others (1957, p. L317), and Arkell northeastern Alaska (Imlay and Detterman, 1973, (1958, p. 211). p. 9, 12). At most places they consist of siltstone, silty shale, and pyritic clay shale that contain iron­ The ammonites Cranocephalites, Arctocephalites, stone concretions and are mostly noncalcareous. In and Arcticoceras represent a biological and strati- the Killik-Itkillik area, however, the beds consist of graphic succession. Cranocephalites is characterized interbedded tuffaceous graywacke, siltstone, clay- by a compressed to stout shell, a very small umbili­ stone, chert, and silty limestone. cus on its septate whorls, a contracted body cham­ ber, a terminal constriction, and high sharp ribbing In northeastern Alaska, the Bathonian and Ba- that persists to the aperture but may be reduced in jocian parts of the Middle Jurassic are readily dis­ strength or interrupted on the venter of the adult tinguished lithologically. The Bajocian part is body chamber. Arctocephalites differs from Crano­ typically dark gray to black, weathers nearly the cephalites mainly by having a body chamber that same color, and contains some limy concretions. remains involute or only slightly contracted and The Bathonian part differs by being mostly grayish that becomes abruptly smooth at a fairly small di­ green on fresh surfaces, by commonly weathering ameter. Arctioceras differs from Arctocephalites by reddish brown, and by containing more siltstone attaining a much larger size and by having a sharp­ beds, more ironstone concretions, and less pyritic ened venter, ribs that become sharper, coarser, and and limy material. more strongly projected on the venter, and a body Thickness of the Middle Jurassic beds ranges chamber that becomes smooth, or nearly smooth, from about 300 feet (90 m) or less in north-central and more involute. The small inner whorls of Arcti­ Alaska to 850 feet (255 m) or more in northeastern coceras greatly resemble Pseudocadoceras at the Alaska. Beds of Bathonian Age attain a maximum same size, but the middle and outer whorls are more thickness of nearly 500 feet (150 m), are highly involute, and the body whorl is much larger and is variable in thickness locally, extend west at least as generally smooth. far as the Canning River, and possibly extend to The genus Canavarella Buckman (1904, Supp. p. the Saviukviayak River. Beds of Bajocian Age at­ CXXIX), not previously recorded from Arctic tain a greater thickness than overlying Bathonian North America, is characterized by a moderately beds, are likewise highly variable in thickness involute compressed shell, a low keel, and strong locally, and extend much farther west. simple falcate ribs that project strongly forward on Within the Middle Jurassic sequence in northeast­ the venter. It differs from Cyclicoceras Buckman ern Alaska, an unconformity is demonstrated by the (1899, Supp., p. XLIX, pi. 5, figs. 5, 6; Arkell and complete lack of ammonites of late middle and late others, 1957, p. L262, L263), mainly by having sim­ Bajocian Age, by the highly variable thickness of ple instead of biplicate ribs that project forward earlier Bajocian beds within short distances, and by much more strongly on the venter. It differs from the close proximity of dated lower Bathonian to Pseudolioceras, with which it is associated in Alas­ lower or lower middle Bajocian beds. In the Killik- ka, by having a wider umbilicus, stronger ribs on Itkillik area of north-central Alaska, an even its inner whorls, and falcate instead of falcoid ribs. greater unconformity is demonstrated by an absence STRATIGRAPHIC DISTRIBUTION 3 of Jurassic ammonites and beds between the beds other areas, P. whiteavesi should occur directly containing Arkellocerasl sp. juv. of probable mid­ above P. maclintocki, and Arcticoceras ishmae dle Bajocian Age and beds containing Buchia fisch- should occur above Arctocephalites. eriana (d'Orbigny) of late Tithonian Age. The next best exposure of Middle Jurassic rocks and the most complete Bathonian ammonite suc­ STRATIGRAPHIC DISTRIBUTION OF cession known in northern Alaska occur on Ignek AMMONITES Mesa about 22 miles (35.2 km) northeast of the The stratigraphic distribution of Middle Jurassic sequence west of Shublik Island. On the northwest ammonites in northern Alaska has been difficult to slope of that mesa, the entire Jurassic section, as determine because of poor exposures, structural measured and collected by R. L. Detterman, is about complications, presence of erosional disconformities, 750 feet (225 m) thick. The section appears to be and the rather similar appearance of dark siltstones unfaulted, but contains covered intervals that are and shales ranging in age from Late Triassic to more common toward the base. Detterman collected Early Cretaceous. fossils of early Bajocian to early Oxfordian Age The best and most continuous Middle Jurassic from six different beds or units. His collections, exposures found to date are in the cliffs along the listed stratigraphically from highest to lowest, are southwest side of the Canning River from Shublik as follows: Island southeastward for about li/a miles (2.4 km). Cardioceras (Scarburgiceras) sp. (USGS Mesozoic loc. These exposures do not represent a continuous stra­ 29856) tigraphic sequence, however, as shown by the pres­ Arcticoceras sp. (USGS Mesozoic loc. 29877) Cranocephalites ignekensis Imlay, n. sp. (USGS Mesozoic ence of faults, contorted beds, and the repetition of loc. 29855) some ammonite faunules. Nonetheless, in the north­ Cranocephalites sp. (USGS Mesozoic loc. 29875) ernmost mile of exposures is a sequence at least Inoceramus cf. /. ambiguus Eichwald (USGS Mesozoic loc. 4,160 feet (1,248 m) thick in which ammonites of 29854) early Bajocian to early Kimmeridgian Age occur in /. Incifer Eichwald (USGS Mesozoic loc. 29853) normal succession. (See fig. 1.) Thus, within this From the same sequence, at the northwest end of sequence of 4,160 feet (1,248 m), early to early Ignek Mesa, the following fossils, listed stratigraph­ middle Bajocian ammonites occur throughout the ically from highest to lowest, were collected by lower 2,400 feet (720 m), and late Oxfordian to geologists of British Petroleum (Alaska) Inc.: early Kimmeridgian ammonites occur in the upper Arctocephalites cf. A. elegans Spath (USGS Mesozoic loc. 1,040 feet (312 m). Between the Bajocian and Ox­ 29144) fordian occurrences are 720 feet (216 m) of beds A. cf. A. elegans Spath and Cranocephalites ignekensis Im­ lay, n. sp. (USGS Mesozoic loc. 29143) from which the Bathonian ammonite Arctocephal- Inoceramus cf. /. Incifer Eichwald (USGS Mesozoic loc. ites was collected about 120 feet (36 m) above the 29149) highest occurrence of the middle Baj ocian ammonite /. Incifer Eichwald and Enjcitoidesl sp. (USGS Mesozoic Arkelloceras. loc. 29148) In addition to the Bajocian and Bathonian fossils From a nearby sequence 200 feet (60 m) below listed in figure 1, the same cliff exposures near their the base of the Ignek Formation at the southwest south end have furnished single specimens of the end of Ignek Mesa, Marvin Mangus collected Arcto­ late Bathonian ammonite Arcticoceras ishmae cephalites cf. A. elegans Spath and Cranocephalites (Keyserling), preserved in a hard-worn siltstone ignekensis Imlay, n. sp. (USGS Mesozoic loc. nodule, and of the early Bajocian ammonite (Pseu- 29435). At the same stratigraphic position directly dolioceras whiteavesi (White), preserved in a py- west of Ignek Mesa, he collected many specimens of ritic nodule. These were collected (USGS Mesozoic C. ignekensis and Inoceramus cf. 7. ambiguus Eich­ loc. 21023) along with 20 specimens of P. maclin- wald but did not find Arctocephalites (USGS Meso­ tocki (Haughton) preserved in grayish-black silt- zoic loc. 28817). stone. Presumably the specimens of P. maclintocki These records show that Arctocephalites definitely were collected in place, whereas those of P. white­ occurs above Cranocephalites at one locality and avesi and Arcticoceras ishmae were derived from apparently with that genus at two localities. Their float either from higher beds exposed on the cliffs association does not seem natural, however. The or from another Jurassic exposure about a mile fact that all the specimens of Arctocephalites are (1.6 km) southeast of the south end of Shublik undeformed, whereas all the specimens of Crano­ Island. On the basis of stratigraphic data from cephalites are deformed or crushed, suggests that BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

FEET 6000-

29142 (AG893) Arkelloceras Middle Bajocian

Fault and contorted beds

5000

29136 (AG887) Amoeboceras (Prionodoceras) and Buchia, concentrica Late Oxfordian to early Kimmeridgian 4000

29135 (AG882) Amoeboceras (Prionodoceras) and Buchia, concentrica, Do.

3000

29146 (AG875) Arctocephalites Bathonian 29141 (AG873) Arkelloceras _ Middle Bajocian

2000 29139 (AG868) Arkelloceras Do.

1000-

29138 (AG861) Arkelloceras Do.

29157 (AG857) Pseudolioceras maclintocki Early Bajocian

FIGURE 1. Occurrences and ages of fossils in Kingak Shale exposed on Canning River west of Shublik Island, northern Alaska. Physical data furnished by British Petroleum (Alaska), Inc. Lower part of sequence probably duplicated by folding and faulting. USGS Mesozoic locality number is followed by collector's field number in parentheses. the small round undeformed specimens of Arcto­ of Callovian age. Their absence suggests that those cephalites have locally rolled down the slopes of times may be represented by disconformities. Ignek Mesa onto older beds containing somewhat The faunal succession of Bajocian Age found on flattened specimens of Cranocephalites. the Canning River near Shublik Island is supple­ On the basis of these records, the Kingak Shale mented by a partial sequence of Kingak Shale ex­ on Ignek Mesa includes a molluscan succession of posed at the head of Katakturuk Canyon which is Bajocian, Bathonian, and early Oxfordian Age, as nearly 7 miles (11.2 km) west-northwest of the shown in table 2. The Bajocian part of the litho- west end of Ignek Mesa. At this place the ammonite logic sequence is probably 200-250 feet (60-75 m) Canavarella, in association with Inoceramus lucifer thick, the Bathonian part at least 195 feet (58.5 m) Eichwald (USGS Mesozoic Iocs. 30267-30270), oc­ thick, and the Oxfordian part at least 80 feet curs 110-320 feet (33-96 m) above the base of the (24 m) thick. The sequence does not contain any Kingak Shale. Previous collections, made by geolo­ ammonites of late middle and late Bajocian age or gists of British Petroleum (Alaska), Inc., consist AGES AND CORRELATIONS

of Pseudolioceras maclintocki (Haughton) (USGS (White) with Canavarella substantiates another Mesozoic loc. 29152) below beds containing Cana- such association (USGS Mesozoic loc. 29147). It varella and Erycitoides (USGS Mesozoic loc. also shows indirectly, by comparison with the am­ 29153). monite sequence near Katakturuk Canyon that P. ivhiteavesi (White), as well as Canavarella, occurs TABLE 2. Stratigraphic position and age of fossils in Kingak higher stratigraphically than P. maclintocki Shale in exposures on northivest slope of Ignek Mesa, (Haughton). northern Alaska The exact stratigraphic position of Tmetoceras in [Positions in feet determined by R. L. Detterman] northern Alaska, where it has been found only in well cores, has not been determined with respect to Feet below base of Ignek Formation species of Pseudolioceras or of Canavarella. In (metres in parentheses) Age southern Alaska, however, Tmetoceras occurs with Cardioceras (Scarbur- 80(24) Early Oxfordian. Pseudolioceras whiteavesi (White) and Erycitoides giceras) sp. howelli (White) as well as in directly underlying Arcticoceras sp. juv __ 135(40.5) Late Bathonian. Arctocephalites cf. A. Not known ___ Middle or late beds as much as 300 feet (90 m) thick (Wester- elegans Spath. Bathonian. mann, 1964, p. 344-347, fig. 5). As its worldwide Cranocephalites ignek- 275(82.5) [Early or middle range probably corresponds to the entire lower Ba­ ensis Imlay, n. sp. f Bathonian. Cranocephalites sp .__ 310-330(93-99) jocian (Aalenian) (Westermann, 1964, p,, 432-435), Inoceramus cf. 7. 500(150) Middle Bajocian ambiguus Eichwald. to Bathonian. its occurrences in northern Alaska could represent 7. lucifer Eichwald ___ 600(180) Early to early middle any part of that substage. Bajocian. AGES AND CORRELATIONS Another partial Bajocian sequence, 150 feet (45 BAJOCIAN AMMONITES m) thick, exposed on the west bank of Kaviak All three Bajocian ammonite faunules obtained Creek, about 3 miles (4.8 km) southwest of its from outcrops in northern Alaska (fig. 2) are asso­ junction with the Sadlerochit River, is interesting ciated with Inoceramus lucifer Eichwald, which in stratigraphically because it contains the crinoid southern Alaska ranges through the Bajocian ais Pentacrinus siib angular is alaska Springer above, high as beds that correlate with the European Oto- and probably al&o below, ammonites of early Ba­ ites sauzei zone (Imlay, 1964, p. 8-10, 18, 53). The jocian Age. The evidence consists of Canavarella lowest faunule, characterized by Pseudolioceras crassifalcata Imlay, n. sp., Pseudolioceras white- maclintocki Haughton, is tentatively correlated by avesi (White), and Inoceramus cf. /. lucifer Eich­ Frebold (1960, p. 28) with the basal Bajocian zone wald (USGS Mesozoic loc. 29884) in the lower 50 of Leioceras opalinum, although it is not known feet (15 m), of the crinoid species in the middle 50 from the same bed as that species. Apparently, P. feet, and of Pseudolioceras sp. and Erycitoides! sp. maclintocki could represent either the lowest or the in the upper 50 feet (USGS Mesozoic loc. 29886). middle part of the lower Bajocian (Aalenian) or This dating does not prove that all occurrences of both. In southern Alaska, P. maclintocki and Leio­ P. subangularis alaska Springer are of early Ba­ ceras opalinum are unknown, but the time that they jocian Age. For example, an age as old as Pliens- represent probably corresponds in part to the de­ bachian is demonstrated by an occurrence near the velopment of an unconformity and the intrusion of Aichilik River of this crinoid species (USGS Meso­ the Aleutian Range batholith (Grantz and others, zoic loc. 30073) at least 100 feet (30 m) below the 1963, p. B58; Detterman and Hartsock, 1966, p. 63, ammonite Amaltheus (USGS Mesozoic loc. 30074). 69, 71). A similar age for the crinoid species at its type The second faunule above the base of the Jurassic locality on the Canning River is supported by its is characterized by Pseudolioceras whiteavesi association there with the same species of Plicatula (White), by Canavarella crassifalcata Imlay, n. sp., that occurs with Amaltheus near the Aichilik River. and by Erycitoides similar to, or identical with, E. In both localities the crinoid stems are much larger howelli (White). It is firmly dated as late early than those from lower Bajocian beds at Kaviak Bajocian because the same species of Pesudolioceras Creek (R. L. Detterman, written commun., 1973), and Erycitoides occur in southern Alaska (Wester­ a fact that may be of age significance. mann, 1964, p. 345-352, fig. 5) directly below am­ This association of Pseudolioceras ivhiteavesi monite faunas characteristic of the Sonninia sower- BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

SOUTHERN ALASKA STANDARD ZONE NORTHERN ALASKA st,age (Imlay, 1962a, b, 1964; IN NORTHWEST EUROPE (Imlay, 1955) Westermann, 1964, 1969)

Clydoniceras discus Kepplerites > 0) a Arcticoceras ishmae a Oppelia aspidoides D z Prohecticoceras retrocostatum < > 1 z 0 Morrisiceras morrisi Arctocephalites cf. A. elegans Arctocephalites cf. A. elegans I > 1 < o m o Tulites subcontracts Cranocephalites ignekensis 1 :? 00 Procerites progracilis Cranocephalites sp. -o1

Lower Inoceramus cf. Zigzagiceras zigzag Cranocephalites costidensus I. ambiguus Eichwald

Parkinsonia parkinsoni Angular unconformity on a0) Iniskin Peninsula a Garantiana garantiana D Strenoceras subfurcatum No fossil evidence Megasphaeroceras rotundum, Leptosphinctes, and Sphaeroceras Chondroceras allani, Stephanoceras humphriesianum Normannites crickmayi, and Teloceras itinsae o Stephanoceras kirschneri z < i Arkelloceras Parabigotites eras sico status o and Arkelloceras o No fossil evidence < Sonninia sowerbyi No fossil evidence m Docidoceras widebayense

Erycitoides howelli, Erycitoides howelli, 1« s Graphoceras concavum Pseudolioceras whiteavesi, and _s Pseudolioceras whiteavesi, Canavarella cras&ifalcata « and Tmetoceras scissum w Tmetoceras nocerami nocerami Ludwigia murchisonae L. (exact position unknown) 0) 5 Tmetoceras scissum o Tmetoceras scissum

Leioceras opalinum No fossil evidence

FIGURE 2. Correlation of Bajocian and Bathonian faunas in northern Alaska.

byi zone (Westermann, 1969, p. 18, 22-30, figs. 6 Territory (Frebold and others, 1967, p. 10, 17-20, and 7) and with ammonite genera not known above pi. 3, figs. 8a, b), and Wide Bay on the Alaska the Graphoceras concavum zone (Westermann, Peninsula (Imlay, 1964, p. B53, pi. 28, figs. 7-9). 1969, fig. 8 on p. 18). Most of these occurrences have not been dated The third faunule above the base of the Jurassic closely because of lack of stratigraphic or faunal in northern Alaska is characterized by the ammonite control. The specimen from Alberta, however, is Arkelloceras which has been recorded previously associated with Stemmatoceras, which in Europe from the Canadian Arctic Islands (Frebold, 1957, p. ranges from the Otoites sauzei zone into the lower 9-11, pi. 9, figs. 1-3, pi. 10, figs. 1, 2, pi. 11, figs. 1, part of the upper Bajocian and is most common in 2; 1961, p. 8-10; 1964b, p. 18, pi. 4, fig. 4), Jasper the middle Bajocian. The specimen from the Alaska Park in Alberta (Westermann, 1964, p. 405-409, fig. Peninsula was found near the base of a sequence 2), the northern Richardson Mountains in Yukon containing many ammonites indicative of the Oto- FAUNAL SETTING ites sauzei zone (Imlay, 1964, p. B18) and above a pared with ammonites of that age in southern sequence containing ammonites indicative of the Alaska are much impoverished in numbers of indi­ Sonninia sowerbyi zone (Westermann, 1969, p. viduals and of genera and species (compare table 17-22). 3 herein with lists in Imlay, 1964, p. B11-B30) and BATHONIAN AMMONITES do not represent nearly as much of Bajocian time. Taxa not yet found in southern Alaska include Pseu- Bathonian ammonites have been collected from dolioceras maclintocki (Haughton) and Canavarella,. four different beds or units on Ignek Mesa, as shown Taxa in common with southern Alaska include in table 2. The lowest unit contains crushed frag­ Arkelloceras, Tmetoceras, Erycitoides howetti ments of a moderately ribbed species of Crano- (White), and Pseudolioceras whiteavesi (White). cephalites. The next higher unit, about 35 feet Apparently the seas in northern and southern higher, contains many well-preserved but crushed Alaska were connected, but conditions in the south­ specimens of a finely to moderately ribbed new spe­ ern seas were much more favorable for ammonite cies of Cranocephalites that differs appreciably from development. described species in the arctic region but shows Bathonian ammonites in northern Alaska are considerable resemblance to one specimen from likewise less numerous and less varied than am­ southern Alaska (Imlay, 1962a, pi. 1, figs. 9, 11-13). monites of that age in southern Alaska, but these The third highest unit contains a finely ribbed spe­ differences are not nearly as great as during Bajo­ cies of Arctocephalites identical with a species in cian time. Resemblances include a succession of at Canada described as A. elegans Spath by Frebold least two species of Cranocephalites followed by a (1961, p. 10; 1964a, p. 3; 1964b, p. 4). The highest finely ribbed species of Arctocephalites similar to unit contains immature specimens of Arcticoceras A. cf. A. elegans Spath. Differences to date with that resemble the inner whorls of specimens of A. southern Alaska include the presence of Arctico­ ishmae (Keyserling) that have been found much ceras and the absence of Kepplerites, Cobbanites, farther east in northeastern Alaska near the Aichi- Parareineckeia, Macrophylloceras, Holcophylloceras, lik River. Siemiradzkiat, Xenocephalites, Oecotraustes, and These ammonite taxa should represent most of Oppelia (Oxycerites). the arctic Bathonian as defined by Callomon (1959, These differences are too great to be explained p. 505-512, table 1) for East Greenland. Thus, the entirely by collection failure, even should some species of Cranocephalites should correspond, at genera now known only in one region be found least in part, to the Cranocephalites pompeckji zone eventually in the other. It seems evident that Bath­ in East Greenland; the finely ribbed Arctocephalites onian ammonites in southern Alaska lived under cf. A. elegans Spath, to the Arctocephalites nudus more favorable conditions than the Bathonian am­ zone; and Arcticoceras ishmae (Keyserling), clearly monites in northern Alaska but that the seas were to the A. kochi zone. Correlation of these ammonites connected, as shown by the presence of a Crano- with the Bathonian seems reasonable, but precise ceiihalites-Arctocephalites succession in both re­ correlation with its subdivisions must await future gions. faunal discoveries. Ammonites characteristic of the Boreal realm apparently include Kepplerites, Arcticoceras, Arcto­ AMMONITE FAUNAL SETTING cephalites, and Cranocephalites, but no proof exists that they actually originated in arctic seas. Am­ The Bajocian and Bathonian ammonites found in monites characteristic of the Pacific realm include northern Alaska belong mostly to the same genera Xenocephalites, Cobbanites, and Parareineckeia. and species as those found in northern Canada ex­ Most of the other genera listed occur also in the cept for the absence to date of Leioceras and the Tethyan realm. presence of Canavarella and of different species of Cranocephalites. In both regions, ammonites of these GEOGRAPHIC DISTRIBUTION ages are few in numbers: only Arkelloceras repre­ sents the middle Bajocian, and no taxon is definitely The geographic occurrences of the Bajocian and of late Bajocian Age. Evidently the Bajocian and Bathonian ammonites from northern Alaska de­ Bathonian ammonites of both regions lived in the scribed herein are shown in table 3 and figures 3-5. same faunal province. Detailed descriptions of the occurrences are given Bajocian ammonites in northern Alaska as com­ in table. 4. BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

oc 91008 ! x X t- W022 I X U3CZ i X u»tz j X Bathonianfossilloealities _*iWm X « 9CMZ X X tticz j X 8tI6Z X X -I882 X i 10 r-t 9tI6Z X 9tI6Z X X * 969ZZ H X (*n*I) 820IZ X looalitieifossilshowninfig.and8BathonianlocalitiesDetailedinfig.4.anareMiddlepositionsofJurassicfossillocalitieslistedundernumbers11.6 0 9t-S2 IH M fCI«C H > ISISS itl« > X iH MCOI MSQI ^ X LOtOl x> X _88« X 9886Z X TABLEGeographic3.distributionofBajocianBathonianammonitesandAgenorthernAlaskain e t8862 -H > X 08862 X X 09162 X o> Z986Z oo 8tI6Z X 0.208 x 69Z08 14-17,shownfig.in5]are X 89208 X >cianfossillocalitiee .9208 X t- 99I6Z X ni$2 X WI62 X S9I6Z x X Z9I6Z "3 X w 980tZ X 99Z08 X J.9I6Z v ZtI6Z X ItI62 X 68I6Z X 8CI62 X eettz v >a ivsa X 9s$n X teoi2 X (Vtwl) 82012 X X -r I69Z2 s e Z99IZ «-. I H»J- *«> e .[njo>*wlox X 1-1 X IH* »»» X -wxu»a ^t»s 0 5 (Hauffhton) __._. Imlay,n.sp,. ______[GeneralisedBajoeipositionsof (Keys«rlin«)______Imlay,n.sp-__... _____ lanavarettatsp___.___.._ Srycitoidet howeUi(White)... S.(White)ef.*.HowMi__ P.T sp_-----.______..__.. undet ___....._ Frebold ...__. .__ IrctoeephalituA.eIe_f«Mef. °.whit*av»»i(White)___... IrfceUooOTMmaeUamtef.A. D««MdoIioc«ro«'maelintoeki Jpptlia(Liro»vit»»)n.sp. Iranocephalitc*ignekentit 7anavar«U«craiiifalcata j rmetooeroesp______(Hauyhton)______. amaelintoeki cf.P.. Spath______Arcticoceratiihmae 1 ? > * °.sp _____ *1.x -^ If GEOGRAPHIC DISTRIBUTION

TABLE 4. Description of some Middle Jurassic fossil TABLE 4. Description of some Middle Jurassic fossil localities in northern Alaska localities in northern Alaska Continued

Locality USGS Collector, year of collection, description Locality USGS Collector, year of collection, description No. Mesozoic Collector's of locality, and stratigraphic No. Mesozoic Collector's of locality, and stratigraphie (figs. 3, 4) loc. No. field No. assignment (figs. 3, 4) loc. No. field No. assignment

1 South Barrow test well 2, lat 71°15' 7 30267 72ADt378 R. L. Detterman, 1972. Head of Ka- 51"N., long 156°37' 55"W. Kingak #1 takturuk Canyon in Ignek Valley, lat Shale at depth of 2,391 ft (717.3 m). 69°35'N., long 145°36'30"W. Fissile Early Bajocian. silty shale containing ironstone con­ cretions, 110 ft (33m) above base of 2 Topagoruk test well 1, lat 70°37'30"N., Kingak Shale. Early Bajocian. long 155°53'36"W. Kingak Shale at depth of 8,113 ft (2433.9m). 7 30268 72ADt378 R. L. Detterman, 1972. Same place as; #2 USGS Mesozoic loe. 30267, Siltstone 3 21552 49ATr352 I. L. Tailleur, 1949. Cutbank on Fort­ and shale containing ironstone beds, ress Creek about 5 miles (8 km) 240 ft (72m) above base of Kingak south-southeast of Fortress Mountain, Shale. Early Bajocian. lat 68°31'N., long 153°03'W. Medium- dark-green fine-grained graywacke 7 30269 72ADt378 R. L. Detterman, 1972. Same place ais containing much volcanic material. #3 USGS Mesozoic loc. 30267. Siltstone Early Bajocian. and shale containing ironstone beds, 295 ft (88.5m) above base of Kingak 4 22591 50AKe263 A. S. Keller, 1956, Cutbank on Tigluk- Shale. Early Bajocian. puk (Creek, lat 68°20'N., long 151°50'W. From tuffaceous gray­ 7 30270 72ADt378 R. L. Detterman, 1972. Same place as #4 USGS Mesozoic loc. 30267. Siltstone wacke. Probably middle Bajocian. and shale containing ironstone beds, 5 21023 47AGr202 George Gryc, 1947. Canning River, west 320 ft (96m) above base of Kingak (part) bank, opposite mouths of Eagle and Shale. Early Bajocian. Cache Creeks, lat 69°23'N., long 146° 8 29148 AG22 British Petroleum (Alaska) Inc., 1964. 06'W. From base of exposure of Northwest side of Ignek Mesa in pyritic black shale that contains central part of Ignek Valley, lat 69° nodules and lenses of ironstone. Early 34'N., long 145°20"W. Slightly north­ Bajocian and Bathonian. west and lower in sequence of Kingak 21024 47AGr205 George Gryc, 1947. Canning River, west Shale than USGS Mesozoic loc. 29143.. bank, lat 69°21'50"N., long 146°01' Early Bajocian. 50"W. Black shale containing iron­ 9 29852 69ADtl44 R. L. Detterman, 1969. Marsh Creek, stone beds. Middle Bajocian. 4 miles north of Mt. Weller in 22595 50AGr9 George Grye, R. W. Imlay, and Allan Sadlerochit Mountains, lat 69°41'05" Kover, 1950. Canning River, west N., long 144°50'30"W. About 500 ft bank. Same place as USGS Mesozoic (150m) above base of Kingak Shale. loc. 21023, but 150 ft (45m) above Probably early Bajocian. base of exposure. Early Bajocian. 10 29150 AG25 British Petroleum (Alaska) Inc., 1964. 22597 50AGr24 George Grye, R. W. Imlay, and Allan At Fire Creek in central part of Koyer, 1950. Canning River, west Ignek Valley, lat 69°32'N., loni? bank. Same place as USGS Mesozoic 145°09'W. Early Bajocian. loc. 21024. Black shale containing 10 29880 70ADtl67 R. L. Detterman, 1970. Fire Creek, 5.(i beds and nodules of ironstone about miles (9 km) northwest of junction 200 ft (60m) below top of exposed with Sadleroehit River, lat 69°32'20" section. Middle Bajocian. N., long 145°12'30"W. Black fissile 24033 52AKe37 A. S. Keller, 1952. Cutbank on west clay shale containing siltstone beds side of Canning River. Same as USGS and ironstone concretions. Kingak Mesozoic loc. 21024. Shale and limy Shale, about 500 ft (150m) above concretions. Middle Bajocian. base. Early Bajocian. 29138 AG861 British Petroleum (Alaska) Inc., 1964. 10 29884 70ARr414 H. N. Reiser, 1970. Kaviak Creek, West bank of Canning River west of #3 about 0.7 (1.12 km) south-southwest Shublik Island, lat 69°24'N., long of confluence with Sadleroehit River 146°10'W. Middle Bajocian. in Mt. Michelson B-2 quadrangle!, 29139 AG868 British Petroleum (Alaska) Inc., 1964. lat 69°29'N , long 145°03'W. From Canning River west of Shublik Island, lower 50 ft (15m) of 150-ft (45-m) lat 69°24'N., long 146°10'W. Middle sequence within the Kingak Shale. Bajocian. Early Bajocian. 29141 AG873 Same data as locality 29139 but about 10 29886 70ARr414 H. N. Reiser, 1970. Same place as 500 ft (150m) higher in sequence. #1 USGS Mesozoic loc. 29884 but from Middle Bajocian. upper 50 (15m) of 150-ft sequence. Probably early Bajocian. 29142 AG893 Same data as locality 29139 but about 3,900 ft (1,170 m) higher in sequence 10 29887 70ARr240 H. N. Reiser, 1970. East side of Sad- above a fault. Middle Bajocian. lerochit River. High cutbank exposin? more than 500 ft (150m) of black 29157 AG857 British Petroleum (Alaska) Inc., 1964. clay shale and minor amounts of Canning River west of Shublik Island, silty ironstone beds. NWi/i NWft lat 69°24'N., long 146°10'W. Early sec. 32, T. 2 N., R. 29 E. (unsur- Bajocian. veyed) lat 145°04'25"N., long 69°2fi' 30266 72ADt377 R. L. Detterman, 1972. Canning River, 30"W. Early Bajocian. west bank opposite Shublik Island, lat 11 10307 110 E. de K. Leffingwell, 1911. Sadlerochit 69°24'N., long 146°10'W. Siltstone and River, cut on north side, probable shale with limy concretions. Middle lat 69°33'N., long 144°43'W. In fri­ Bajocian. able black shale containing pyrite concretions about 3,000 ft (900m) 24035 52AKe46 A. S. Keller, 1952. Canning River, cut- above base of Kingak Shale. Early bank on west side, lat. 69°34'N., long Bajocian. 146°23'W., Ironstone beds, concretions, 11 10308 114a E. de K. Leffingwell, 1911. Sadlerochit and shales 1,000 1,500 ft (300-450m) River, half a mile up Camp 263 Creek, below top of Kingak Shale. Early lat 69°33'N., long 144°47'W. Fossils Bajocian. from concretions in black shale at 29152 AG807 British Petroleum (Alaska) Inc., 1964. foot of exposure and probablv ra West end of Ignek Valley near Ka- lower 100 ft (30m) of Kingak Shale. takuruk River, lat 69°35'N., long Early Bajocian. 145°36'W., Early Bajocian. 11 10309 114b E. de K. Lefflngwell, 1911. Sadlerochit River, north side, about a quarter of 7 29153 AG808 British Petroleum (Alaska) Inc., 1964. a mile downstream from Camp 263 Same description as USGS Mesozoic Creek, lat 69°33'N., long 144°46'W., loc. 29152. Early Bajocian. about 1,000 ft (300m) above base 7 29154 AG812 British Petroleum (Alaska) Inc., 1964. of Kingak Shale. Probably early West end of Ignek Valley, lat 69° Bajocian. 33'N., long 145°43'W. Early Bajocian. 11 29147 AG 19 British Petroleum (Alaska) Inc., 1964. At junction of Sadlerochit and Kekik- 7 29155 AG812A British Petroleum (Alaska) Inc., 1964. tuk Rivers, lat 69°33'N., long 144° Same description as USGS Mesozoic 43'W. Early Bajocian. loc. 29154. Early Bajocian. 11 29151 AG 538 British Petroleum (Alaska) Inc., 1964. 7 29156 AG812B British Petroleum (Alaska) Inc., 1964. At junction of Sadlerochit and Ke- Same description as USGS loc. 29154. kiktuk Rivers, lat 69°3R'N., Ion:? Early Bajocian. 144°43'W. Probably early Bajoeian. 10 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

TABLE 4. Description of some Middle Jurassic fossil TABLE 4. Description of some Middle Jurassic fossil localities in northern Alaska Continued localities in northern Alaska Continued

Locality USGS Collector, year of collection, description Locality USGS Collector, year of collection, description No. Mesozoic Collector's of locality, and stratigraphic No. Mesozoic Collector's of locality, and stratigraphic (figs. 3, 4) loc. No. field No. assignment (figs. 3, 4) loc. No. field No. assignment

12 30135 71ADt368 R. L. Detterman, 1971. On ridge west 18 30075 71ADt330D R. L. Detterman, 1971. Cutbank on of Okerokovik River, 7.6 miles west side of Aichilik River, about 2 (12.16 km) S. 80°W. of (benchmark) miles (3.2 km) N. 30° E. of VABM VABM ATTE, lat 69°29'45"N., long ATTE on northern front of Brooks 143°26'W. Early Bajocian. Range, lat 69°33'N., long 143°05'W., 13 22745 51ADUR4 R. L. Detterman, 1951. Cutback on east Demarcation Point quad. From 1,200- side of Saviukviayak River, lat 1,400 ft (360-420 m) above base of 69°00'N., long 148°04'39"W. From Kingak Shale and about 200 ft (60 concretion in hard splintery silty m) higher than beds containing shale 160 ft (48 m) above base of Amaltheus. Bathonian. Kingak Shale. 14 21023 47AGr202 George Gryc, 1947. Canning River, (part) west bank, opposite mouths of Eagle and Cache Creek, lat 69°23'N., long SYSTEMATIC DESCRIPTIONS 146°06'W. From base of exposure of pyritic black shale that contains nodules and lenses of ironstone. Early Family HILDOCERATIDAE Hyatt, 1867 Bajocian and Bathonian. Genus TMETOCERAS Buckman, 1891 14 22596 50AGrl8 George Gryc, R. W. Imlay, and Allan Kover, 1950. Canning River, west Tmetoceras sp. side, lat 69°22'10"N., long 146°02'W. Black shale containing ironstone Specimens of Tmetoceras have been found in lenses and nodules, about 2,300 ft (690 m) above base of exposed sec­ northern Alaska only in the South Barrow test well tion. Bathonian. 29146 AG875 British Petroleum (Alaska) Inc., 1964. 2 at 2,391 feet and the Topagoruk test well 1 at West side of Canning River, near Shublik Island, lat 69°24'N., long 8,113 feet (Imlay, 1955, p. 89, pi. 12, figs. 1-10). 146°10'W. Bathonian. 15 29145 AG60 British Petroleum (Alaska) Inc., 1964. Genus PSEUDOLIOCERAS Buckman, 1889 West end of Ignek Valley on north­ ern base of Shublik Mountains, lat Pseudolioceras maclintocki (Haughton) 69°33'N., long 145°50'W. NE 1^ sec. 6, T. 2 N., R. 26 E. (unsurveyed). Plate 1, figures 1-5, 7 Bathonian. 16 28817 63AMg6 Marvin Mangus, 1963. Central part of Ammonites m'clintocki Haughton, 1858, Royal Dublin Soc. Ignek Valley, near middle of sec. 6, T. 2 N., R. 28 E. (unsurveyed), west Jour., v. 1, p. 244, pi. 9, figs. 2-4. end of Isrnek Mesa, lat 69°33'30"N., long 145°20'W. Kingak Shale, 200 ft Harpoceras m'clintocki Haughton. Neumayr, 1885, K. Akad. (60 m) below base of Ignek Forma­ Wiss. Wien Denkschr., Math.-naturh. Kl., v. 50, p. 85, pi. tion. Bathonian. 16 29143 AG24 British Petroleum (Alaska) Inc., 1964. 1, figs. 5-8. Central part of Ignek Valley, near Ludwigellal cf. L. rudis (Buckman). Imlay, 1955, U.S. Geol. west end of north side of Isrnek Mesa, lat 69°34'N., long 145°20'W. Survey Prof. Paper 274-D, pi. 11, figs. 1-3. NEM, sec. 6, T. 2 N., R. 28 E. (un­ surveyed). Kingak Shale. Bathonian. Pseudolioceras whiteavesi (White). Imlay, 1955, U.S. Geol. 16 29144 AG27 British Petroleum (Alaska) Inc., 1964. Survey Prof. Paper 274-D, p. 89, pi. 12, figs. 15, 16. Central part of Ignek Valley. Same place as USGS Mesozoic loc. 29143 Ludwigia m'clintocki (Haughton). Frebold, 1958, Canada near northwest end of Ignek Mesa, Geol. Survey Bull. 41, p. 7, pi. 5, figs. 3, 4. but slightly higher in Kingak Shale. Bathonian. Pseudolioceras m'clintocki Haughton. Frebold, 1960, Canada 16 29435 66AMg29f Marvin Mangus, 1966. Central part of Geol. Survey Bull. 59, p. 20, pi. 8, pi. 9, figs. 2-4. Ignek Valley south of Ignek Mesa, near USGS Mesozoic loc. 28817. SE^i Pseudolioceras m'clintocki Haughton. Frebold, 1964a, Canada sec. 6, T. 2 N., R. 28 E. (unsurveyed), Geol. Survey Paper 63-4, p. 5, pi. 10, figs. 4a-8b, 9. lat 69°33'30"N., long 145°20'W., Kingak Shale, about 200 ft (60 m) Pseudo'lioceras m'clintocki (Haughton). Westermann, 1964, below base of Ignek Formation. Bathonian. Bulls. Am. Paleontology, v. 47, no. 216, p. 422-424. 16 29855 69ADt41A R. L. Detterman, 1969. Central part Pseudolioceras m'clintocki (Haughton). Dagis and Dagis, of Ignek Valley, 6.5 miles (10.40 km) 1967, Akad. Nauk SSSR, Sibirskoye Otdel., Inst. Geologii S.75°E. of Katakturuk Canyon at northwest end of mesa capped with i Geofiziki, p. 56-58, pi. 3, figs, la, b. Ignek Formation, lat 69°33'35"N., long 145°20'15"W. Near USGS Mes­ Pseudolioceras m'clintocki (Haughton). Westermann, 1969, ozoic loc. 29143. Kingak Shale, con­ Bulls. Am. Paleontology, v. 47, no. 216, p. 52. cretions in black clay shale about 275 ft (82.5 m) below base of Ignek Pseudolioceras maclintocki (Haughton) is repre­ Formation. Bathonian. 16 29875 70ADt215, R. L. Detterman, 1970. Central part sented in northern Alaska by 50 specimens which unit 4 of Ignek Valley, near USGS Mesozoic loc. 29855, lat 69°33'30"N., long show the same range of variation in rib coarseness 145°20'W. Siltstone and silty shale containing clay ironstone nodules. and curvature described by Frebold (1960, p. 20) Kingak Shale, about 310-330 ft (93- 99 m) below base of Ignek Forma­ for specimens from northernmost Canada. These tion. Bathonian. Alaska specimens are preserved in dark-gray to 16 29877 70ADt215, R. L. Detterman, 1970. Same place as unit 2 USGS Mesozoic loc. 29875. From black claystone or in silty claystone; most have been black fissile clay shale containing clay ironstone concretions. Kingak crushed laterally, and none shows the complete adult Shale, 135 ft (40.5 m) below base of Ignek Formation and 55 ft (16.5 body chamber. The species is characterized by a m) below Cardioceras at USGS Mes­ ozoic loc. 29856. Bathonian. highly compressed involute shell, flattened flanks 17 220S3 48AWH132 C. L. Whittington, 1948. North bank that converge gradually to the venter, a high hollow of river between Gravel and Fire Creeks, lat 69°31'N., long 145°02'W. keel, a very steep umbilical wall that rounds Dull black earthy shale. Bathonian. SYSTEMATIC DESCRIPTIONS 11

160° 156° 152° 148° 140°

68

50 0 50 100 150 MILES

50 0 50 100 150 KILOMETRES

FIGURE 3. Generalized index map of Bajocian ammonite localities in northern Alaska. abruptly or sharply into the flanks, and variably Not Pseudolioceras whiteavesi (White). Imlay, 1955, U..S. weak to strong falcate ribs that become stronger Geol. Survey Prof. Paper 274-D, p. 89, pi. 12, figs. 15, 16. ventrally but fade out before reaching the keel. Pseudolioceras m'clintocki whiteavesi (White). Westermann, r?/pes. Hypotypes, USNM 192125-192130. 1964, Bulls. Am. Paleontology, v. 47, p. 421-425, pi. 68, Occurrences. Kingak Shale at USGS Mesozoic fig. 2, pi. 69, figs. 1-6, pi. 70, figs. 1-5, pi. 71, figs. 1, 2, text-figs. 30, 31. Iocs. 21023, 22595, 24035, 30135, 29152, and 29157. Turgites whiteavesi (White). Kalacheva and Sey, 1970, The species is possibly represented also at USGS Akad. Nauk SSSR Doklady, v. 193, no. 2, p. 450-451, pi. Mesozoic Iocs. 10307, 29880, and 29887. It is asso­ 1, figs. 1-3. ciated with Oxytoma jacksoni (Pompeckj) at USGS This species, represented in northern Alaska by Mesozoic loc. 24035 and with Inoceramus lucifer only four specimens, differs from P. maclintocki Eichwald at USGS Mesozoic loc. 21023. In northern­ (Haughton) solely by having a narrow raised um­ most Canada, O. jacksoni has been found with, and bilical edge (Frebold, 1960, p. 21; Westermann, a little below, Pseudolioceras maclintocki (Haugh- 1964, p. 423). Associated mollusks include Inocera­ ton) (Frebold, 1960, p. 28). mus lucifer Eichwald and Canavarella crassifalcaia Pseudolioceras whiteavesi (White) Imlay, n. sp. Plate 1, figures 16-18 ZVpes. Hypotypes, USNM 192131-192133. Ammonites (Amaltheus) whiteavesi White, 1889, U.S. Geol. Survey Bull. 51, p. 69-90, pi. 13, figs. 1-5. Occurrences. Kingak Shale at USGS Mesozoic Harpoceras whiteavesi (White). Kellum, Daviess, and Swin- Iocs. 10307, 21023, 29147 and 29884. The species is ney, 1945, U.S. Geol. Survey Prelim. Kept, on geology and associated with Inoceramus lucifer Eichwald at oil possibilities of the southwestern part of the Wide Bay anticline, figs. 4e, f. USGS Mesozoic Iocs. 10307 and 21023. 12 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

160° 156° 152° 148° 144° 140°

50 0 50 100 150MILES I I 50 0 50 100 150 KILOMETRES FIGURE 4. Generalized index map of Bathonian ammonite localities in northern Alaska.

Family GRAPHOCERATIDAE Buckman, 1905 This species of Canavarella from northern Genus CANAVARELLA Buckman, 1904 Alaska is similar in appearance to C. belophora Canavarella crassifalcata Itnlay, n. sp. Buckman (1904, Supp. p. CXXIX, pi. 22, figs. 22- Plate 1, figures 6, 8-14 24) from England, but has much stouter ribs on its The species is represented by 25 laterally com­ body chamber and slightly broader saddles. pressed internal molds that show various growth Canavarella differs from Pseudolioceras, with stages. It is characterized by a moderately involute, which it is associated in Alaska, by having a wider compressed shell; gently rounded flanks that pass umbilicus, stronger ribs on its inner whorls, and gradually into the umbilical slope and the venter; a more falcate ribs that project forward more low keel; and strong simple falcate ribs. These ribs strongly on the venter. begin at the umbilical seam, become stronger ven- Types. Holotype, USNM 192134; paratypes, trally, are strongest on the ventral margin, and USNM 192135-192140. then fade out before reaching the keel. Fairly strong falcate ribbing is visible on some specimens at diam­ Occurrences. Kingak Shale, USGS Mesozoic Iocs. eters of only 8-10 mm. The body chamber is not 29147, 29153-29156, 29884, and 30267-30270. The completely preserved but occupies at least half a species ranges from 110 to 320 feet above the base whorl. of the Kingak Shale exposed near the head of Meaningful measurement cannot be made because Katakturuk Canyon in the western part of Ignek of deformation. The suture line is simple, has Valley. In that sequence it is associated throughout broader saddles than lobes, and its auxiliaries as­ with Inoccramns lucifer Eichwald and locally with cend to the umbilical seam. Erycitoides (Mesozoic loc. 29153). SYSTEMATIC DESCRIPTIONS 13

es O

T7T Z < 3-* m10 r-l 00 Z (T> (T> D Cvl Cvl o on od

CO Z < Z D O

^o COes

CD D I CO

Q 14 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

Family HAMMATOCERATIDAE Buckman, 1887 Occurrence. Kingak Shale at USGS Mesozoic Genns ERYCITOIDES Westermann, 1964 loc. 29435 in association with Cranocephalites and Erycitoides cf. E. howelli (White) rare Arctocephalites. Plate 3, figures 5, 6, 10 Family STEPHANOCERATIDAE Neumayr, 1875 Erycitoides is definitely represented in northern Genus ARKELLOCERAS Frebold, 1957 Alaska by five fragments of outer septate whorls. Of Arkelloceras cf. A. maclearni Frebold these, the best preserved has been illustrated pre­ Plate 1, figures 21-26 viously as E. howelli (White) Imlay, 1955, pi. 13, Reineckeia (Reineckeites) cf. R. (R.) stuebeli Steinmann. figs. 12, 13) because it closely resembles comparable- Imlay, 1955, U.S. Geol. Survey Prof. Paper 274-D, p. 91, sized specimens of that species from the Alaska pi. 13, figs. 1-7. Peninsula (White, 1889, pi. 12, figs. 1, 2, pi. 14, figs. This species, represented by 46 laterally crushed 1-3; Westermann, 1964, pis. 44-57). The other four specimens from the banks of the Canning River, is specimens are more fragmentary and are, therefore, nearly identical in side view with described species only compared herein with that species. One of of that genus from northern Canada. Some finely these (pi. 3, figs. 5, 6) appears to be a typical repre­ ribbed specimens match very well in side view with sentative of the species. The other (pi. 3, fig. 10) A. tozeri Frebold (1958, p. 10, pi. 9, figs, la-d, 2a, has long weak primary ribs and closely spaced sec­ b, 3a, b; pi. 10, figs, la-c, 2a, b; pi. 11, figs, la-c, ondary ribs as in a specimen figured by Westermann 2a, b; 1961, p. 8, pi. 3, fig. 1, pi. 4, figs. 1, 2a, b, (1964, pi. 58, fig. 1). pi 5, figs, la-c) and with A. elegans Frebold, in Figured specimens. USNM 192141, 180730. Frebold, Mountjoy, and Templeman-Kluit (1967, p. Occurrences. Kingak Shale at USGS Mesozoic 17. pi. 3, figs. 8a, b). Other coarsely ribbed speci­ loc. 10308. The species is probably represented also mens match closely in side view with A. maclearni at Mesozoic Iocs. 29150, 29153, and 29880. Frebold (1958, p. 11, pi, 12, figs, la-c, 2a-g, 3a-c, pi. 13, figs, la-d, 2a-c, 3a, b; 1961, p. 8, pi. 4, figs. Family OPPELHDAE Bonarelli, 1894 Genus OPPEL1A Waagen, 1869 3a, b). As these specimens occur in the same collec­ Subgenus L1ROXY1TES Imlay, 1961 tions and are associated with others bearing ribbing Oppelia (Liroxyites) n. sp. undet. of intermediate coarseness, all are herein considered Plate 1, figure 15 to represent a single species. On the whole they re­ The subgenus is represented by one laterally com­ semble A. maclearni more than A. tozeri in coiling, pressed internal mold that bears some shelly ma­ coarseness of ribbing, and in the presence of swell­ terial and represents an adult body whorl. It has a ing or tubercles at the ventral ends of the primary discoidal, highly involute compressed shell; a fairly ribs. sharp keel that is pinched basally; a body chamber Definite identification of this species with any of that occupies about three-fifths of a whorl; an aper­ the described species of Arkelloceras from Canada ture that terminates abruptly in a forwardly in­ will not be possible until specimens are found that clined falcoid curve; falcoid ribs that arise near the show the characteristics of the venter. A venter middle of the flanks, are fairly strong on the last similar to that on Arkelloceras (Frebold, 1958, p. 9) septate whorl, become lower and broader adorally, is suggested, however, by the fact that the ribs on and persist almost to the aperture; fine f alcoid several small specimens pass ventrally into weak striae that cover the entire surface; and a faint tubercles or into laterally compressed swellings. spiral band that occurs at about three-fifths of the One feature that may differentiate the species of height of the whorl. Arkelloceras found near the Canning River, Alaska, The preservation of the specimen is not sufficient from those found in northern Canada is the pres­ to make accurate measurements or to trace the su­ ence of lateral tubercles on the small septate whorls ture line. This species differs from O. (Liroxyites) of the coarsely ribbed Alaskan specimens. These kellumi Imlay (1962b, p. A8, pi. 2) in having some­ tubercles are conical on the innermost septate what coarser ribbing on its body chamber and much whorls, become radially elongate and weaker dor- coarser ribbing on the septate part of its body sally, and are absent at diameters greater than about whorl. In this respect it shows more resemblance to 50 mm. In contrast, on the described specimens a specimen from Canada described by Frebold from Canada, only slight or moderate swellings at (1957, p. 54, pi. 28, fig. 2) as Oppelia (Oxycerites) the ventral ends of the primary ribs were reported ex. gr. fallax Gueranger. by Frebold (1958, p. 12, pi. 12, figs. 2a, g; Frebold Figured specimen. USNM 192142. and others, 1967, p. 18, pi. 3, fig. 8a). SYSTEMATIC DESCRIPTIONS 15

The present assignment of the specimens under ternal molds, most of which are laterally com­ discussion to Arkelloceras instead of Reineckeia pressed. It is characterized by a very small umbili­ (Reineckeites) is based on the lack of constrictions cus on septate whorls, a contracted body chamber and on the presence of tubercles on the venters of that occupies nearly three-fourths of a whorl, a several small specimens. The alternate arrangement fairly deep apertural constriction that inclines for­ of ribs on the venters of small specimens of Arkel­ ward and is bordered adorally by a swelling, and loceras, as described by Frebold (1958, p. 9), is distinct forwardly inclined ribs that become quite different from the arrangement on the venter stronger adorally and persist to the apertural con­ of Reineckeia (Reineckeites) . striction without fading. The presence of Arkelloceras implies an early These ribs vary considerably in strength and middle Bajocian Age (Frebold, in Frebold and density, incline adapically on the umbilical wall, in­ others, 1967, p. 20), which is in accord with its cline adorally on the flanks, cross the venter trans­ stratigraphic position above Pseudolioceras on the versely or with a gentle forward arching, and gen­ Canning River (fig. 1). erally bifurcate at one-fourth to one-third the height Figured specimens. USNM 192143-192148. of the flanks. Some primary ribs remain simple, and Occurrences. Kingak Shale at USGS Mesozoic some secondary ribs arise freely a little below the Iocs. 21024, 22597, 24033, 29138, 29139, 29141, middle of the flanks. The primary ribs are higher 29142, and 30266. and sharper than the secondary ribs along the fur­ cation zone. The secondary ribs, however, become Arkelloceras? sp. juv. broader and higher ventrally and adorally, are Plate 1, figures 19, 20 strongest on the venter, and near the aperture are One small external mold shows one flank and part wider than the interspaces on some specimens. of the venter of a small immature ammonite. Its Among the 22 specimens available, five have ribs primary ribs are strong, trend radially and termi­ that are fine and fairly closely spaced, five have ribs nate ventrally in weak tubercles or swellings a little that are coarse and fairly widely spaced, and 14 below the middle of the flanks. From the swellings have ribs that are intermediate or moderate in pass pairs of slightly weaker secondary ribs, some coarseness and spacing. of which are weakly connected with the primary The suture line has broad saddles and fairly short ribs. All secondary ribs become fairly strong ven­ lobes, and its auxiliaries ascend toward the umbili­ trally and then weaken abruptly along the margin cal seam. of the venter. The midventral area is apparently Meaningful measurements cannot be made be­ nearly smooth. cause all specimens are deformed or crushed. The characteristics of this specimen suggest that These specimens, in spite of appreciable differ­ it may be an immature form of Arkelloceras Fre­ ences in coarseness of ribbing, are herein considered bold (1958, p. 9). It resembles the inner whorls of to represent a single species because all three vari­ A. maclearni Frebold (1958, p. 11, pi. 12, figs. 2d- ants occur together at two localities (USGS Meso­ g, 3a, b) rather than those of A. tozeri Frebold zoic Iocs. 28817 and 29143), two variants occur (1958, p. 10, pi. 9, figs. Ib, c, 3a) in having fairly together at two other localities (USGS Mesozoic strong primary ribs that terminate ventrally in Iocs. 29435 and 29885), and both finely and mod­ swellings or tubercles. It also resembles A. elegans erately ribbed variants occur on opposite sides of a Frebold in Frebold, Mountjoy, and Tempelman- single slab (pi. 2, figs. 1, 7). Kluit (1967, p. 17-20, pi. 3, figs. 8a, b) in strength of ribbing and in that its ribs fork below the mid­ The most coarsely ribbed specimens (pi. 2, figs. dle of the flanks. 11, 12) of Cranocephalites ignekensis Imlay, n. sp., Figured specimen. USNM 192149. show some resemblance to C. pompeckji (Madsen) (1904, p. 189, pi. 8, figs. 5, 6; Spath, 1932, p. 16, Occurrence. Kingak Shale at USGS Mesozoic pi. 4, figs. 9a, b, 10, pi. 5, figs. 6a, 7, pi. 13, figs, la, loc. 22591. b; Donovan, 1953, pi. 17, figs. 2, 3) except for hav­ Family CARDIOCERATIDAE Siemiradzki, 1891 ing slightly broader ribs on their septate whorls, Genus CRANOCEPHALITES Spath, 1932 appreciably broader ribs on their body chambers, Cranocephalites ignekensis Imlay, n. sp. and a deeper apertural constriction. The moderately Plate 2, figures 1-9, 11, 12 ribbed specimen (pi. 2, figs. 5-7, 9) has ribs that This species is represented in collections from the are much finer than on any described specimen of central part of Ignek Valley by 22 internal and ex­ C. pompeckji (Madsen) but are similar to those on 16 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA one septate specimen of C. vulgaris Spath (1932, pi. All these specimens from the Arctic region of 4, figs. 3a, b) from East Greenland. The typical Alaska are characterized by a medium size for the finely ribbed specimens (pi. 2, figs. 1-4) likewise genus, a moderately compressed shell, a very nar­ resemble a Greenland variant of C. vulgaris Spath row umbilicus, and sharp forwardly inclined ribs (1932, pi. 4, fig. 1) in fineness and density of ribbing that bifurcate or trifurcate below the middle of the on their septate whorls. All three variants from flanks and cross the venter nearly transversely. northern Alaska differ markedly from C. vulgaris Also, in all specimens the adult body chamber be­ in retaining distinct ribbing on all parts of the adult comes abruptly smooth or nearly smooth near its body whorl and in having stronger ribbing on the adapical end and then terminates adorally in a pro­ venter than on the flanks of the body whorl. nounced forwardly inclined constriction. The moderate to coarsely ribbed variants of C. Assignment of these finely ribbed specimens to ignekensis Imlay, n. sp., also resemble a certain Arctocephalites elegans Spath seems reasonable specimen of Cranocephalites from southern Alaska when comparison is made with the monotypic holo- (Imlay, 1962a, pi. 1, figs. 9, 11-13) except that they type from East Greenland (Spath, 1932, pi. 10, figs. attain a smaller adult size and have a more compli­ 4a, b). Nonetheless, the validity of that assignment cated suture line. They could represent the same must await studies showing the range of variation species. within the species of Arctocephalites in Greenland. Type. Holotype, USNM 192151; paratypes, The possibility that A. elegans Spath may be a vari­ USNM 192152-192160. ant of some earlier named species is suggested by Occurrences. Kingak Shale at USGS Mesozoic the fact that it was obtained from the same locality Iocs. 28817, 29143, 29435, and 29855. These were (Spath, 1932, p. 135) and ammonite zone (Callo- collected 200-275 feet below the top of the forma­ mon, 1959, p. 508) as several other described species tion in the central part of Ignek Valley. The highest of the genus. occurrences (Mesozoic Iocs. 29143, 29435) also con­ Figured specimens. USNM. 192160-192162. tain Arctocephalites that are undeformed, whereas Occurrences. Kingak Shale at USGS Mesozoic all the specimens of Cranocephalites are deformed Iocs. 29143, 29144, 29145, 29146, and 29435. or crushed. Arctocephalites cf. A. arcticus (Newton and Teall) Genus ARCTOCEPHALITES Spath, 1928 Plate 4, figure 10 Arctocephalites cf. A. elegans Spath One compressed fragment bears sharp fairly Plate 4, figures 1-8 sparse ribbing like that on the outermost septate cf. Arctocephalites elegans Spath, 1932, Medd. Gr0nland, v. whorl of A. arcticus (Newton and Teall, 1897, pi. 87, no. 7, p. 37, pi. 10, figs. 4a, b. 40, figs, la, b; Whitfield, 1906, pi. 18, fig. 2; Spath, Arctocephalites elegans Spath. Frebold, 1961, Canada Geol. 1932, pi. 12, fig. 2). Its ribbing appears to be a Survey Bull. 74, p. 10, pi. 9, fig. 1, pi. 10, figs. 1, 2; pi. 11, figs. 1-4. little weaker and less sparse than that on A. pilae- Arctocephalites elegans Spath. Frebold, 1964b, Canada Geol. formis Spath (1932, p. 33; Newton and Teall, 1897, Survey Bull. 119, p. 3, pi. 1, figs. 1-3, pi. 2, figs. 1, 2. pi. 40, figs. 2, 2a) and A. callomoni Frebold (1964b, Arctocephalites elegans Spath. Frebold, 1964a, Canada Geol. pi. 5, fig. 3, pi. 7, fig. 3). Survey Paper 63-4, p. 4, pi. 23, figs. 1, 2, 4. lArctocephalites aff. A. elegans Spath. Efimova and others, Figured specimen. USNM 192163. 1968, Polevoy atlas Yurshoy fauny i flory Severe-Vostoka Occurrence. Kingak Shale at USGS Mesozoic SSSR, p. 125, pi. 94, figs, la, b, 2a-c. loc. 29146. This species in northern Alaska is represented by seven specimens that closely re&emble and show the Genus ARCTICOCERAS Spath, 1924 same range of variation as the specimens of A. ele­ Arcticoceras ishmae (Keyserling) gans Spath described by Frebold (1961, p. 10; Plate 3, figures 7-9, 11-22 Ammonites ishmae Keyserling, 1846, Wissenschaftliche Beo- 1964b, p. 3) from the Arctic region of Canada. One bachtungen auf einer Reise in das Petschora-Land im finely ribbed specimen (pi. 4, figs. 1-3) is nearly Jahre 1843, p. 331, pi. 20, figs. 8-10. identical in ribbing with one Canadian specimen Macrocephalites ishmae Keyserling. Sokolov, 1912, Com. (Frebold, 1961, pi. 11, figs, la, b). The other six geol. St. Petersbourg Mem., new ser., v. 76, p. 15, 49, pi. specimens from northern Alaska bear slightly 1, fig. 1, pi. 3, fig. 12. Arcticoceras ishmae (Keyserling). Spath, 1932, Medd. Gr0n- coarser ribbing, similar to that on several Canadian land, v. 87, no. 7, p. 50, pi. 15, figs. 7a, b. specimens (Frebold, 1961, pi. 10, figs. 1, la, pi. 11, Arcticoceras sp. Imlay, 1955, U.S. Geol. Survey Prof. figs. 2, 3; 1964b, pi. 1, figs, la, b, 2a, b). Paper 274-D, p. 90, pi. 12, figs. 11, 19. SYSTEMATIC DESCRIPTIONS 17

Arcticoceras kochi Spath, 1932, Medd. Gr0nland, v. 87, no. variations as A. kochi Spath from East Greenland 7, p. 53-56, pi. 12, fig. 1, pi. 13, fig-s. 4, 5, pi. 14, figs. 1-3, but also closely resemble A. ishmae (Keyserling) pi. 15, figs. 1, 4-6. from Petchora-Land and Canada. This agrees with Arcticoceras kochi Spath. Frebold, 1961, Canada Geol. Sur­ vey Bull. 74, p. 16, pi. 9, fig. 3, pi. 12, figs, la, b, pi. 13, the observations of John Callomon (written com- figs. 4, 5, pi. 14, figs. 1-3, pi. 15, figs 1, 4-6. mun., 1972) that in East Greenland the topotypes of Arcticoceras ishmae Keyserling. Frebold, 1961, Canada Geol. A. kochi Spath occur in the same bed as A. ishmae Survey Bull. 74, pi. 10, fig. 3, pi. 13, figs, la, b, pi. 14, figs. (Keyserling) and are within the range of variation 1, 3a, b. of that species. Arcticoceras kochi Spath. Frebold, 1964a, Canada Geol. Sur­ vey Bull. 63-4, pi. 25, figs. 1, 2. Hypotypes. USNM 192164-192176. This species is represented by 22 specimens, of Occurrences. Kingak Shale at USGS Mesozoic which 18 are from USGS Mesozoic locality 30075. Iocs. 21023, 22596, and 30075. The specimen of Most of them are small and septate, and only one Arcticoceras from loc. 21023 is considered to be (Imlay, 1955, pi. 12, fig. 19) represents an adult float because it is preserved in a hard brown silt- body chamber. Among the septate specimens, six stone, whereas most of the other specimens from have fine closely spaced ribs (pi. 3, figs. 7-9, 11, that locality are preserved in a softer black shale 12), eight have coarse broadly spaced ribs (pi. 3, and consist mostly of Pseudolioceras maclintocki figs. 19-22), and seven have ribs of intermediate (Haughton) and Inoceramus lucifer Eichwald of coarseness and spacing (pi. 3, figs. 13-18). The ribs early Bajocian Age (Imlay, 1955, p. 80, 86). are sharp, trend radially or incline slightly back­ ward on the umbilical wall, incline forward on the Arcticoceras sp. juv. flanks, and project strongly forward on the venter. Plate 3, figures 1, 2 Most ribs bifurcate near or below the middle of the Two immature specimens of Arcticoceras from Ig- flanks, but some ribs remain simple and are sepa­ nek Mesa (see table 2) have ribbing and a sharp­ rated by short ribs that arise near the middle of the ened venter identical with those on immature speci­ flanks. The venter is narrowly arched on most of the mens of the moderately ribbed variant of Arctico­ septate specimens and apparently becomes less so ceras ishmae (Keyserling) as just described. These during growth, except on the smallest whorls. specimens also resemble an even smaller ammonite In comparisons with Arcticoceras in East Green­ (pi. 3, figs. 3, 4) from the Saviukviayak River. That land, the finely ribbed variant from northern Alaska ammonite was once described as Pseudocadoceras is similar to specimens that Spath (1932, p. 55, pi. grewingki (Pompeckj) because of its resemblance 14, figs. 2, 3, pi. 15, fig. 6) considered to be a variant to immature specimens of that species in southern of A. kochi Spath and named pseudolamberti. The Alaska (Imlay, 1955, p. 90, pi. 12, fig. 1). It now moderately ribbed variant from Alaska greatly re­ appears, however, that small immature specimens of sembles certain Greenland specimens described as Pseudocadoceras and Arcticoceras are very much A. aff. A. kochi Spath (1932, p. 55, pi. 15, figs. 4a, alike, a resemblance which was discussed by Spath b, 5). The most coarsely ribbed variant from Alaska (1932, p. 57) and confirmed by John Callomon bears ribbing comparable with that on the adapical (written commun., 1972). In contrast, adult speci­ part of the outer whorl of the holotype of A. kochi mens of Pseudocadoceras differ from adult speci­ Spath (1932, pi. 15, fig. 1). In addition, the nearly mens of Arcticoceras in the following ways: (1) smooth body chamber of one Alaska specimen (Im­ they are much smaller and more evolute; (2) their lay, 1955, pi. 12, fig. 19) resembles that of an adult ribs project forward less strongly on the venter; of A. kochi Spath (1932, pi. 14, fig. 1) which that and (3) the adult body whorl remains strongly author suggested belonged to the variant pseudo- ribbed instead of becoming smooth. lamb erti. The specimen in question from the Saviukviayak The moderately ribbed variant from Alaska also River probably belongs to Arcticoceras rather than resembles A. ishmae (Keyserling) (1846, p. 331, pi. Pseudocadoceras, but its certain generic identifica­ 20, figs. 8-10; Sokolov, 1912, p. 17, 49, pi. 1, fig. 1; tion will have to await the discovery of larger speci­ Spath, 1932, pi. 15, figs. 7a, b) from Petchora-Land mens. The specimens from Ignek Mesa, however, as well as ammonites from northern Canada that are large enough for their assignment to Arctico­ are assigned to that species by Frebold (1961, pi. ceras to be certain. 10, fig. 3, pi. 13, figs, la, b, pi. 15, figs. 3a, b). These identifications, plus the reassignment to In summation, the specimens of Arcticoceras de­ Arkelloceras of ammonites formerly identified as scribed herein show the same rib characteristics and Reineckeia (Reineckeites) (Imlay, 1955, p. 91, pi. 18 BAJOCIAN AND BATHONIAN AMMONITES FROM NORTHERN ALASKA

13, figs. 1-7), show that the Callovian is poorly rep­ Moore, R. C., ed., Treatise on invertebrate paleontology, resented in northern Alaska. The only positive evi­ Part L, Mollusca 4, Cephalopoda, Ammonoidea: New dence consists of one worn Cadoceras found as float York and Lawrence, Kans., Geol. Soc. America and Univ. Kansas Press, p. L80-L437. (USGS Mesozoic loc. 30136) near the Aichilik Buckman, S. S., 1887-1907, Monograph of the ammonites of River in extreme northeastern Alaska. the Inferior Oolite Series: London, Palaeontographical Figured specimens. USNM 180732, 108781. Soc., 456 p., 103 pis. (1887-1894); Supplement, 262 p., Occurrences. Kingak Shale at USGS Mesozoic 24 pis. (1898-1907). loc. 29877 on Ignek Mesa. The genus is probably Callomon, J. H., 1959, The ammonite zones of the Middle Jurassic beds of East Greenland: Geol. Mag., v. 96, no. present at Mesozoic loc. 22745 on the Saviukviayak 6, p. 505-513, pis. 17, 18. River. Dagis, A. A., and Dagis, A. S., 1967, Stratigrafiya Toarskikh otlozheniy Vilyuyskoy sineklizy [Stratigraphy of Toarsk Family PERISPHINCTIDAE Steinmann, 1890 Genus CHOFFATIA Siemeradzki, 1898 deposits from the Vilyuysk syncline], in Saks, V. N., ed., Problemy paleontologicheskogo obosnovaniya detal'- Choffatia? sp. noy stratigrafii Mezozoya Sibiri i Dal'nego Vostoka Plate 2, figure 10; plate 4, figures 9, 11 [Problems of paleontological criteria for the detailed One internal mold shows parts of three corroded Mesozoic stratigraphy of Siberia and the Far East] : septate whorls of a perisphinctid ammonite. The Leningrad, Akad. Nauk SSSR, Sibirskoye Otdel., Inst. Geologii i Geofiziki, p. 41-60, pis. 1, 2. outermost whorl is represented only by a small frag­ Detterman, R. L., and Hartsock, J. K., 1966, Geology of the ment, but its umbilical imprint is preserved slightly Iniskin-Tuxedni region, Alaska: U.S. Geol. Survey Prof. below the middle of the next smaller whorl. That Paper 512, 78 p., 6 pis., 7 figs. whorl is subovate near its adoral end, has a whorl Donovan, D. T., 1953, The Jurassic and Cretaceous strati­ height of 31 mm, a whorl thickness of 24 mm, and graphy and paleontology of Traill 0, East Greenland: an umbilical width of 39 mm. Its primary ribs trend Medd. Gr0nland, v. Ill, no. 4, 150 p., 25 pis., 14 figs. radially, are widely spaced, are swollen near the Efimova, A. F., Kinasov, V. P., Parakestov, K. V., Polubatko, umbilicus, and fade out ventrally below the middle I. V., Repin, Yu. S., and Dagis, A. S., 1968, Polevoy atlas Yurskoy fauny i flory Severe-Vostoka SSSR [Field of the flanks. Its secondary ribs are faint, closely atlas of Jurassic fauna and flora from northeast spaced, arise near the middle of the flanks, incline USSR] : Magadan, Knigoizdat, 382 p., 114 pis., 12 figs. slightly forward, cross the venter transversely Frebold, Hans, 1957, The Jurassic Fernie group in the where they become slightly stronger, and outnum­ Canadian Rocky Mountains and foothills: Canada Geol. ber the primary ribs about 6 to 1. The next smaller Survey Mem. 287, 197 p., 44 pis., 5 figs. whorl, as exposed in the umbilicus, has weak broad 1958, Fauna, age and correlation of the Jurassic rather widely spaced primary ribs. Corrosion ac­ rocks of Prince Patrick Island: Canada Geol. Survey counts in part for the weakness of the primary ribs. Bull. 41, 69 p., 18 pis. 1 fig. This species is assigned to Choffatia rather than 1960, The Jurassic faunas of the Canadian Arctic Lower Jurassic and lowermost Middle Jurassic ammon­ to Procerites because of its fairly evolute coiling ites: Canada Geol. Survey Bull. 59, 33 p., 15 pis., 8 figs. and because its primary ribs are widely spaced and 1961, The Jurassic faunas of the Canadian Arctic are swollen near the umbilicus. Its rib pattern is Middle and Upper Jurassic ammonites: Canada Geol. essentially the same as in Choffatia sakuntata Spath Survey Bull. 74, 43 p., 21 pis., 3 figs. (1931, p. 351, pi. 68, figs. 4a, b) from India except 1964a, Illustrations of Canadian fossils Jurassic of for having shorter and less sharply defined primary western and Arctic Canada: Canada Geol. Survey Paper ribs. C. balinensis (Neumayr) (Waagen, 1875, p. 63-4, 107 p., 51 pis. 163, pi. 45, figs. 2a, b; Spath, 1931, p. 348, pi. 48, 1964b, The Jurassic faunas of the Canadian Arctic Cadoceratinae: Canada Geol. Survey Bull. 119, 27 p., figs. 5a, b) is also similar but has even sharper pri­ 20 pis., 1 fig. mary ribs. These differences may in part reflect the Frebold, Hans, Mountjoy, E. W., and Templeman-Kluit, poor preservation of the Alaskan specimen. D. J., 1967, New occurrences of Jurassic rocks and fos­ Figured specimen. USNM 180733. sils in central and northern Yukon Territory: Canada Occurrence. Kingak Shale at USGS Mesozoic Geol. Survey Paper 67-12, 35 p., 3 pis., 2 figs. loc. 30075 in association with Arcticoceras. Grantz, Arthur, Thomas, Herman, Stern, T. W., and Sheffey, N. B., 1963, Potassium-argon and lead-alpha ages for stratigraphically bracketed plutonic rocks in the Tal- REFERENCES CITED keetna Mountains, Alaska: U.S. Geol. Survey Prof. Arkell, W. J., 1950-58, Monograph of the English Bathonian Paper 475-B, p. B56-B59. ammonites: London, Palaeontographical Soc., 8 v., 33 Haughton, Samuel, 1858, [Geological notes and illustrations pis., 83 figs. in M'Clintock's reminiscences of Arctic ice travel]: Arkell, W. J., and others, 1957, Mesozoic Ammonidea, in Royal Dublin Soc., Jour., v. 1, p. 183-250, illus., map. REFERENCES CITED 19

Imlay, R. W., 1955, Characteristic Jurassic mollusks from the Jackson-Harmsworth Expedition during 1894-96; northern Alaska: U.S. Geol. Survey Prof. Paper 274-D, Geol. Soc. [London] Quart. Jour., v. 53, p. 477-519, pis. p. 69-96, pis. 8-13, 1 fig. 37-41. 1962a, Jurassic (Bathonian or early Callovian) am­ Patton, W. W., Jr., and Tailleur, I. L., 1964, Geology of the monites from Alaska and Montana: U.S. Geol. Survey Killik-Itkillik region, Alaska: U.S. Geol. Survey Prof. Prof. Paper 374-C, 32 p., 8 pis., 7 figs. Paper 303-G, p. 409-500, pis. 50-51, figs. 66-91. 1962b, Late Bajocian ammonites from the Cook Inlet Sokolov, D. N., 1912, Zur Ammonitenfauna des Petschora- region, Alaska: U.S. Geol. Survey Prof. Paper 418-A, schen Jura: Com. geol. St. Petersbourg Mem. new ser., 15 p., 5 pis., 4 figs. Livr. 76, p. 1-65, 3 pis., 11 figs. 1964, Middle Bajocian ammonites from the Cook Spath, L. F., 1927-33, Revision of the Jurassic cephalopod Inlet region, Alaska: U.S. Geol. Survey Prof. Paper fauna of Kachh (Cutch) : India Geol. Survey, Palaeonto- 418-B, 61 p., 29 pis., 5 figs. logia Indica, new ser., v. 9, 6 pts., 945 p., 130 pis. Imlay, R. W., and Detterman, R. L., 1973, Jurassic paleo- 1932, The invertebrate faunas of the Bathonian- biogeography of Alaska: U.S. Geol. Survey Prof. Paper Callovian deposits of Jameson. Land (East Greenland): 801, 32 p., 15 figs. Medd. Gr0nland, v. 87, no. 7, 158 p., 26 pis., 14 figs. Kalacheva, E. D., and Sey, I. L, 1970, Tugurites novyy Waagen, W. H., 1873-75, Jurassic fauna of Kutch. The pozdneaalenskiy Severotikhookeanskiy rod [Tugurites Cephalopoda: India Geol. Survey, Palaeontologia Indica, a new late Aalenian genus from the North Pacific vol. 1, pt. 1, p. 1-22, pis. 1-4 (1873) ; Pt. 2, p. 23-76, Ocean]: Akad. Nauk SSSR Doklady, v. 193, no. 2, p. pis. 5-14 (1875) ; Pt. 3, p. 77-106, pis. 15-24 (1875) ; 449-452, pi. 1. Pt. 4, p. 107-247, pis. 25-40 (1875). Kellum, L. B., Daviess, S. N., and Swinney, C. M., [1945?], Westermann, G. E. G., 1964, The ammonite fauna of the Geology and oil possibilities of the southwestern part Kialagvik Formation at Wide Bay, Alaska Peninsula of the Wide Bay anticline, Alaska: U.S. Geol. Survey Part I, Lower Bajocian (Aalenian) : Bulls. Am. Pale­ 17 p., 9 pis. ontology, v. 47, no. 216, p. 327-503, pis. 44-76, 37 figs. Keyserling, Alexander, 1846, Wissenschaftliche Beobach- 1969, The ammonite fauna of the Kialagvik Forma­ tungen auf einer Reise in das Petschora-Land im Jahre tion at Wide Bay, Alaska Peninsula Part 2. Sonninia 1843: St. Petersburg, Carl Krey, 465 p. sowerbyi Zone (Bajocian) : Bulls. Am. Paleontology, v. Madsen, Victor, 1904, On Jurassic fossils from East Green­ 57, no. 255, 226 p., 47 pis., 56 figs. land : Medd. Gr0nland, v. 29, no. 6, p. 157-210, pis. 6-10. White, C. A., 1889, On invertebrate fossils from the Pacific Neumayr, Melchior, 1885, Die geographische Verbreitung coast: U.S. Geol. Survey Bull. 51, 102 p. der Jura-formation: K. Akad. Wiss., Wien, Denkschr. Whitfield, R. P., 1906, Notes on some Jurassic fossils from Math.-naturh. Kl., v. 50, p. 57-144, 1 pi. Franz Josef Land, brought back by a member of the Newton, E. T., and Teal, J. J. H., 1897, Notes on a collection Ziegler Exploring Expedition: Am. Mus. Nat. History of rocks and fossils from Franz Josef Land, made by Bull., v. 22, p. 131-134, pis. 18, 19. INDEX [Italic page numbers indicate major references and descriptions 1

Page Page Page Choffatia ______1,2,18 I balinensis ------18 Aalenian (lower Bajocian) _----_-____- 5 sakuntata __--_-_----_-_.______-- 18 Ignek Mesa ______------_------17, 18 Age of collection localities __-_------_- 9, 10 sp -___----______-__.- 8, IS; pi. 2; pi. 4 collection localities ______9, 10 Aichilik River ______2, 7 Classificatory analysis ______1 most complete Middle Jurassic collection locality ______10 Cobbanites ----_-__-_--____---__-__-___ 7 succession ------3, 4, 5, 7 crinoid of Pliensbachian age ____-- 5 Collection localities --______------9 ignekensis, Cranoccphalites -..._ 3, 5, 8, 15; pi. 2 evidence for Callovian ----___----_ 18 Correlation with European, East Inoceramus ambiguus ______-----___.. 3, 5 Aleutian Range batholith ______5 Greenland, Canadian, and lucifer ------3, 4, 5, 11, 12, 17 Amaltheus ------_----_-_-______5, 10 southern Alaska faunas ___ 5, 14 Interruptions in normal sequences __-_- 3 (Amaltheus) whiteavesi. Ammonites __ 11 Cranoccphalites ______.. 1, 2, 4, 5, 7, 14, 15, 16 Introduction ____-___-__------1 ambiguus, Inoceramus --___-_____.-__. 3, 5 pompcckji -______-...._-.______15 ishmae. Ammonites ------16 Ammonites ishmae ______16 pompcckji zone .___-----_------__ 7 Arcticoceras ------3, 7, iff, 17; pi. 3 maclintocki ______10 vulgaris --.______-__--._-- 16 Macroccphalites ------16 (Amaltheus) whiteavesi ______n sp -__-.______3,8 Itkillik River, Middle Jurassic outcrops _ 2 Arcticoceras _--_-__-______1, 2, 7, 16, 17, 18 crassifalcata, Canavarefla __._ 5, 8, 11, 12; pi. 1 ishmae ______... 3, 7, 16, 17; pi. 3 Cyclicoceras ______2 kochi ______17 kochi zone -__-_--_--______7 Jasper Park in Alberta pseudolambcrti -__-_----______17 sp ------_--__---_.._ 16 Disconformities ______---__-- 3, 4 K sp. juv ----_----_-______8, 17; pi. 3 Duplication of sequences ______4 arcticus, Arctocephalites __-____.-- 8, 16; pi. 4 Katakturuk Canyon ___ ------5,10,12 Arctocephalites -.-______1, 2, 3, 4, 7, 14, 16 E collection locality -_----..--_-_----- 9 arcticus ___.----______8, 16; pi. 4 partial sequence of Kingak Shale -- 4 callomoni ______16 Eagle Creek _____..______-..._ 9,10 Katakturuk River ___---__-----_------9 elegans ______3, 5, 7, 8, iff; pi. 4 elegans, Arctocephalites ____ 3, 5, 7, 8, 16; pi. 4 Kaviak Creek, collection localities ----- 9 nudus zone ______7 Arkelloceras ______---__...._____ 14, 15 crinoids ______-_-__--_--- 5 pilaeformis ______16 Enjcitoides ______1,2,3,5,12,14 Kekiktuk River, co'.lection locality __._ 9 sp _. ._ --..______8 hoivelli ---_..______- 2, 5, 7, 8, 14; pi. 3 kcllumi, Oppclia (Liroxyitcs) ------14 Arkelloceras __.-__-______1,2,3,6,7,14,15 sp --.______.___. 8 Kepplcrites ------7 elegans __----.______--______14, 15 European ammonite zone correlates __ 5, 6, 7 Killik River, Middle Jurassic outcrops . - 2 madearni ______8, 14, 15; pi. 1 Evolutionary lineage ______2 Kimmeridgian ______3 tozeri -_--_-__-____-_-______14, 15 Kingak Shale Sec in text under species sp. juv -----_-__------__-___ 8, 15; pi. 1 occurrence and locality descriptions. fallax, Oppclia (Oxycerites) ._---._ 14 kochi, Arcticoceras ------17 B Faults ___-----__..-__._. 3 Faunal settings ____--__.--. ._-____ 7 balinensis, Choffatia __. Fire Creek, collection localities __--_-.- 9, 10 belophora, Canavarella _ Folding, contorted beds _____-_-__------3 Leioccras --_-_--__--_---_------7 Biologic analysis ______Fortress Creek, collection locality ______9 opalinum ------5 Boreal realm ammonites Leioceratinae ------1 Brooks Range ______G Liroxyitcs ------2,14 Buchia fischeriana _____ (Liroxyitcs), Oppclia ------1 Geographic distribution of Bajocian and (Liroxyitcs} kelhimi. Oppclia ------14 Bathonian ammonites in C northern Alaska __-_._____ 7 Lithologry, collection sites ------0 Middle Jurassic beds ____---_---..- 2, 3 Geographic location of collection Cache Creek ______.______-_- 9, 10 localities ______---_----_ 9 lucifer, Inoceramus ___-____.- 3,4,5,11,12,17 LudwigcUa rudis ------10 Cadoceras ______18 Graphoccras concavum zone ______6 Ludirigia maclintocki ------10 Cadoceratinae _-__---______1 Graphoceratidae ______-___----______-- 12 callomoni, Arctocephalites --____-_____ 16 Gravel Creek, collection locality __--__- 10 Camp 263 Creek, collection locality ____ 9 Greenland, ammonite sequence ------7, 16, 17 M Canada, faunal comparisons with _ 6, 7, 14, 16 fireu-ingki, Pseitdocadoceras ______17; pi. 3 Canavarella _---___-.--__-_---_ 1,2,4,5,7,12 madearni, Arkelloceras __.--_ 8, 14, 15; pi. 1 belophora ______12 H madintocki, Ammonites ------10 crassifalcata ______5, 8, 11, / '; pi. 1 Harpoccras ------10 sp ___----______-__-_-___ 8 Hammatoceratidae _-______------1,14 Ludu-igia ------10 Canning River ______14,15 Hammatoceratinae ------1 Pscudolioccras _-__-_ 3, 5, 7, 8, 10, 17; pi. 1 collection localities ______9,10,13 Harpoccras maclintocki ______10 wliitcarcsi, Pscudolioccras . crinoid of Pliensbachian age ______5 u-hitcnvcsi ------11 Macroccphalites ishmae ___---. extent and continuity of Middle Harpoceratinae ______-_--_____--_----- 1 Macrophylloccras ------Jurassic beds ______2,3,4 Hildoceratidae ______--______---- 1,10 Marsh Creek, collection locality Cardioccras (Scarburgiccras) sp ______3,5 Holcophylloccras ------7 Mixed faunas ______-_._---. Cardioceratidae ______1,2,15 Itou-clli, Enjcitoidcs ______2, 5, 7, 8, 14; pi. 3 Mount Weller _-_____------

21 22 INDEX

Page Page Page O Pseudolioceras ______1, 2, 5, 10, 12, 15 Stratigraphic distribution of ammonites _ maclintocki ______3, 5, 7, 8, iO, 17; pi. 1 Stratigraphic summary of Middle Oecotraustes -- __ ---- __-_____-_--__ 7 maclintocki whiteavesi ______11 Jurassic beds in northern Okerokovik River, collection locality __ 10 whiteavesi ______2, 3, 5, 7, 8, 10, 11; pi. 1 Alaska ______-- opalinum, Leioceras ______5 stuebeli, Reineckeia (Reineckeites) ___ Oppelia --- _-- ______14 Pseudoperisphinctinae ___-----_- -____ 1 (Liroxyites) ______1 14 Tethyan realm ammonites ______7 kellumi ______R n. sp ______1, 14; pi. 1 Tigulpuk Creek, collection locality __ 9 (Oxycerites) ______7,14 Tithonian __-_-_.__--______-----_----_-- 3 fattax 14 Reineckeia (Reineckeites) ___-__-_---_ 15, 17 Tmetoceras ______1,2,5,7,10 Oppeliidae ______1, 14 (Reineekeites) stuebeli ______14 scissum ______-__---_-___--- 2 Oppeliinae ______1 (Reineckeites), Reineckeia ______15, 17 sp ______8, 10 Otoites sauzei zone ____--_-___--- 5, 6 stuebeli, Reineckeia ______Tmetoceratinae ______1 Oxfordian ______3,4 Repetition of faunules ______tozeri, Arkelloceras ------14, 15 (Oxycerites), Oppelia ______-_--__-- 7, 14 Richardson Mountains in Yukon Turgites ivhiteavesi ------11 6 fattax, Oppelia .--______-______14 Territory ______10 U Oxytoma jacksoni ______11 rudis, Ludwigella ______Unconformities, Callovian ______4 Callovian, only positive evidence for ______--______--_-_ 18 Pacific realm ammonites _-_-______-___ 7 Sadlerochit Mountains _--____-__--._ 9 late middle to late Bajocian age ___ 2, 4 Paleobiogeographic differentiation _____ 7 Sadlerochit River ______5, 13 middle Bajocian-Tithonian ______3 Paraeineckeia ______7 collection localities ____------_ 9 southern Alaska ______5 Pentaerinus subangularis alaska ______5 Sagavanirktok River, Middle Jurassic Perisphinctidae ______1, 18 outcrops _-___--___------_ 2 piaeformis, Arctocephalites ______16 Saviukviayak River, probable Middle vulgaris, Cranocephalites ______16 Plieatula ______5 Jurassic exposures __ 2, 10, 17, 18 W Pliensbachian ______5 (Scarburgiceras) sp., Cardioceras _____ 3, 5 Point Barrow-Cape Simpson area scissum, Tmetoceras ______2 whiteavesi, Ammonites (Amaltheus) __ 11 subsurface Middle Jurassic Seaway connections ______-__. 7 Harpoceras ______11 beds ______2 Shublik Island ______3,4,9 Pseudolioceras ____ 2,3, 5, 7, 8, 10, 11; pi. 1 pompeckji, Cranocephalites ______15 Siemiradzkia ______7 Pseudolioceras maclintocki ______11 Previously unrecorded genera ______2 Sonninia sowerbyi zone ______5, 7 Turgites ------___ 11 Procerites ______18 Stemmatoceras _____--_____-_------_-_ 6 Wide Bay, Alaska Peninsula ______6 Pseudocadoeeras ______2, 17 Stephanoceratidae _-_--__------_ 1, 14 grewingki ______17; pi. 3 Stratigraphic assignment of collection X pseudolamberti, Arcticoceras ______17 localities ______9 Xenocephalites ______7

* U.S. GOVERNMENT PRINTING OFFICE: 1975 0-211-319/35 PLATES 1-4

Contact photographs of the plates in this report are available, at cost, from U.S. Geological Survey Library, Federal Center, Denver, Colorado 80225. PLATE 1 [Figures natural size unless otherwise indicated] FIGURES 1-5,7. Pseudolioceras maclintocki (Haughton) (p. 10). 1. Hypotype, USNM 192130 from USGS Mesozoic loc. 21023. 2. Hypotype, USNM 192129 from USGS Mesozoic loc. 22595. 3. Hypotype, USNM 192127 from USGS Mesozoic loc. 24035. 4. Rubber imprint of external mold of hypotype, USNM 192126 from USGS Mesozoic loc. 21023. 5. Hypotype, USNM 192125 from USGS Mesozoic loc. 29152. 7. Hypotype, USNM 192128 from USGS Mesozoic loc. 21023. 6,8-14. Canavarella crassifalcata Imlay, n. sp. (p. 12). 6. Paratype, USNM 192136 from USGS Mesozoic loc. 29153. 8,9. Lateral view and suture line (X 3) drawn at whorl height of 8 mm. Paratype, USNM 192138 from USGS Mesozoic loc. 29884. 10. Paratype, USNM 192135 from USGS Mesozoic loc. 29153. 11. Holotype, USNM 192134 from USGS Mesozoic Iocs. 29154 and 29156. Shows nearly half a whorl of body chamber. Note that the two parts of the holotype were collected at two localities. 12. Rubber imprint of external mold of paratype, USNM 192137 from USGS Mesozoic loc. 30267. 13. Paratype, USNM 192139 from USGS Mesozoic loc. 29154. 14. Paratypes, USNM 192140 from USGS Mesozoic loc. 30268. Shows that falcate ribbing develops at a small size. 15. Oppelia (Liroxyites) n. sp. undet. (p. 14). Adult body whorl of specimen USNM 192142 from USGS Mesozoic loc. 29435. 16-18. Pseudolioceras whiteavesi (White) (p. 11). 16. Rubber imprint of external mold (X 2). Hypotype USNM 192131 from USGS Mesozoic loc. 29147. 17. Small pyritic hypotype, USNM 192133-from USGS Mesozoic loc. 21023. 18. Internal mold (X 2). Hypotype, USNM 192132 from USGS Mesozoic loc. 10307. Note sharp raised umbilical edge in figures 16-18. 19,20. Arkellocerast sp. juv. (p. 15). Rubber imprint of external mold (X 2) of specimen, USNM 192149 from USGS Mesozoic loc. 22591. 21-26. Arkelloceras cf. A. maclearni Frebold (p. 14). 21. Rubber imprint of external mold, specimen USNM 192147 from USGS Mesozoic loc. 29141. 22. Specimen, USNM 192148 from USGS Mesozoic loc. 24033. Shows prominent lateral tubercles at an early growth stage. 23. Specimen, USNM 192144 from USGS Mesozoic loc. 21024. 24. Specimen, USNM 192145 from USGS Mesozoic loc. 22597. Shows ventral tubercles or swellings. 25. Specimen, USNM 192146 from USGS Mesozoic loc. 22597. 26. Specimen, USNM 192143 from USGS Mesozoic loc. 24033. Two-fifths of outer whorl is nonseptate. GEOLOGICAL SURVEY PROFESSIONAL PAPER 854 PLATE 1

PSEUDOLIOCERAS, CANAVARELLA, OPPELIA (LIROXYITES), ARKELLOCERAS?, AND ARKELLOCERAS PLATE 2 [All figures except suture line are natural size] FIGURES 1-9,11,12. Cranocephalites ignekensis Imlay, n. sp. (p. 15). 1,8. Complete adult body chamber and final suture line (X 2) of finely ribbed holotype, USNM 192151 from USGS Mesozoic loc. 28817. 2. Finely ribbed paratype, USNM 192155 from USGS Mesozoic loc. 28817. 3. Finely ribbed paratype, USNM 192154 from USGS Mesozoic loc. 29435. 4. Finely ribbed paratype, USNM 192153 from USGS Mesozoic loc. 29143. 5. Moderately ribbed adult body chamber of paratype, USNM 192156 from USGS Mesozoic loc. 28817. 6. Rubber imprint of external mold of moderately ribbed paratype, USNM 192157 from USGS Mesozoic loc. 28817. 7. Rubber imprint of external mold of moderately ribbed paratype, USNM 192152 from USGS Mesozoic loc. 28817. This specimen occurs on same slab as the finely ribbed holotype. 9. Fragment of inner whorl of moderately ribbed paratype, USNM 192158 from USGS Mesozoic loc. 29855. 11. Rubber imprint of external mold of coarsely ribbed paratype, USNM 192160 from USGS Mesozoic loc. 29435. 12. Rubber imprint of coarsely ribbed paratype, USNM 192159 from USGS Mesozoic loc. 29143. 10. Choffatlat sp. (p. 18). Internal mold of specimen, USNM 180733 from USGS Mesozoic loc. 30075. See other views on plate 4, figures 9, 11. GEOLOGICAL SURVEY PROFESSIONAL PAPER 854 PLATE 2 v>,

CRANOCEPHALITES AND CHOFFATIA? PLATE 3 [All figures are natural size] FIGURES 1,2. Arcticoceras sp. juv. (p. 17). Immature specimens, USNM 180732 from USGS Mesozoic loc. 29877. 3,4. Arcticocerasl sp. juv. (p. 17). Rubber imprint of external mold of specimen formerly described as Pseudocadoceras grewingki (Pompeckj) by Imlay (1955, p. 90, pi. 12, fig. 1). USNM 108781 from USGS Mesozoic loc. 22745. 5,6,10. Erydtoides cf. E. howelli (White) (p. 14). 5, 6. Ventral and lateral views of specimen, USNM 192141 from USGS Mesozoic loc. 29153. 10. Laterally crushed specimen, USNM 180730 from USGS Mesozoic loc. 29150. 7-9,11-22. Arcticoceras ishmae (Keyserling) (p. 16). All specimens from USGS Mesozoic loc. 30075 unless indicated otherwise. 7, 8. Lateral and ventral views of septate finely ribbed hypotype, USNM 192164. 9. Ventral view of finely ribbed body chamber. Hypotype, USNM 192167. 11. Laterally crushed finely ribbed hypotype, USNM 192165. 12. Immature finely ribbed hypotype, USNM 192166. 13. Moderately ribbed hypotype, USNM 192170. 14. Moderately ribbed hypotype, USNM 192168. 15. Moderately ribbed inner whorls. Hypotype, USNM 192172. 16. Moderately ribbed inner whorls. Hypotype, USNM 192171. 17,18. Moderately ribbed, lateral and ventral views of hypotype, USNM 192169. 19. Coarsely ribbed venter of hypotype, USNM 192173. 20. Coarsely ribbed laterally crushed hypotype, USNM 192174. 21. Coarsely ribbed laterally crushed hypotype, USNM 192175. 22. Coarsely ribbed, worn hypotype, USNM 192176 from USGS Mesozoic loc. 21023. GEOLOGICAL SURVEY PROFESSIONAL PAPER 854 PLATE 3

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ARCTICOCERAS, ARCTICOCERAS?, AND ERYCITOIDES PLATE 4 [All figures are natural size] FIGURES 1-8. Arctocephalites cf. A. elegans Spath (p. 16). 1-3. Ventral and lateral views of adult specimen, USNM 192160 from USGS Mesozoic lac. 29145. Note smoothness of body chamber. 4, 5. Adult smooth body chamber of specimen, USNM 192161 from USGS Mesozoic loc. 29143. 6-8. Rubber imprint of ribbed inner whorl and ventral view of smooth outer whorl of same specimen, USNM 192162 from USGS Mesozoic loc. 29435. 9,11. Choffatiat sp. (p. 18). Lateral and ventral views of septate whorls. Specimen, USNM 180733 from USGS Mesozoic loc. 30075. Other view shown on plate 2, figure 10. 10. Arctocephalites cf. A. arcticus (Newton and Teall) (p. 16). Rubber imprint of laterally crushed specimen, USNM 192163 from USGS Mesozoic loc. 29146. GEOLOGICAL SURVEY PROFESSIONAL PAPER 854 PLATE 4

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ARCTOCEPHALITES AND CHOFFATIA?