Callovian (Jurassic) Ammonites from the United States and Alaska

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Callovian (Jurassic) Ammonites from the United States and Alaska Callovian (Jurassic) Ammonites from the United States and Alaska Part 1. Western Interior United States GEOLOGICAL SURVEY PROFESSIONAL PAPER 249-A Callovian (Jurassic) Ammonites from the United States and Alaska Part 1. Western Interior United States By RALPH W. IMLAY GEOLOGICAL SURVEY PROFESSIONAL PAPER 249-A Descriptions and illustrations of cephalopods of Late Jurassic age UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1953 UNITED STATES DEPARTMENT OF THE INTERIOR Oscar L. Chapman, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. CONTENTS Page Page Abstract -—--—---—-——————_—————__________.._____.„__.______ 1 Ecologic considerations—Continued Introduction --——————————————.._____________._„._.„___ 1 Conditions of deposition—— _.____.__———-——.——— 9 Biologic analysis ——————.——__——._____.___.._____„_„_____ 1 Conglomerate —...— ——————————_.., 9 Stratigraphic summary ———————._.__——____.____________ 4 Sand ——_———————————————— — 9 Faunal zones and correlations————..__————_.._——— 5 Marine siltstone and shale.—————-—_——— 10 Arcticoceras codyense zone..————.._______....——_„ 5 Limestone -——————_.-_————————.——— 10 Gowericeras costidensum zone____—._...„——_.——_——— 7 Other types of sediment———————————— 10 Gowericeras subitum zone————_-.........._..._„„........ 7 Ammonite distribution and associations—————— 11 Kepplerites tychonis zone.__————————_———. 7 Geographic distribution - - ———————————————— 14 Kepplerites mcleami zone.—————„___„..—.............. 7 Summary of results--------———————————————— 17 Comparisons with other faunas————____........„—....„.. 8 Systematic descriptions ———.—_.————————— 18 Ecologic considerations —————————_——.__..._.... 8 References ———————————————————— ———. 34 Sources of sediment———_——.._ _„__..—_———._.. 8 Index -.-—————————.———————-—-—--——— 37 ILLUSTRATIONS [Plates 1-24 follow index] PLATE 1. Xenocephalites and Lilloettia 2-4. Arcticoceras 5. Cosmoceras and Arcticoceras 6,7. Cadoceras 8, 9. Cadoceras and Cosmoceras 10-13. Cadoceras 14. Cosmoceras, Cadoceras, and Kepplerites 15-18. Kepplerites 19. Kepplerites and Grossouvria 20. Kepplerites 21,22. Gowericeras 23. Gowericeras and Procerites 24. Grossouvria and Procerites Page FIGURE 1. Index map showing Callovian localities in the western interior of the United States- 12 2. Lower Callovian paleogeography of the Boreal region ...——.__ - _____......——__._ 13 TABLES TABLE 1. Stratigraphic distribution of Callovian ammonite species in the western interior of the United States—.——. 6 2. Correlation of Jurassic formations in the western interior of the United States...——————————Pacing 8 3. Geographic distribution of the Callovian ammonities in the western interior of the United States ——Facing 12 GALLOVIAN (JURASSIC) AMMONITES FROM THE UNITED STATES AND ALASKA PART 1. WESTERN INTERIOR UNITED STATES By RALPH W. IMLAY ABSTRACT INTRODUCTION Early Late Jurassic ammonites have been obtained from the Rierdon formation of Montana and the lower part of the Studies of the Callovian ammonites of the western Sundance formation of Wyoming and South Dakota. These interior region were begun by the writer in the sum­ ammonites represent only the lower part of the Callovian mer of 1944 and were nearly completed the follovdng stage and correspond with the northwest European zones of year except for photographic work. The delay in Macrocephalites macrocephalus, Proplanulites koenigi and publication was beneficial in several ways: impor­ Sigaloceras calloviense. Possibly the highest ammonite-bearing beds are as young as the Cosmoceras jason zone, although tant collections and valuable field data were added most of the evidence is against such a correlation. in Montana and Wyoming, the Callovian ammorites Careful stratigraphic collecting has demonstrated the exist­ of Alaska were studied thoroughly, and a much bet­ ence of five ammonite zones and their positions with respect to ter understanding was obtained of comparable various lithologic units. The basal zone, characterized by faunas of Europe, Asia, and South America. In par­ Arcticoceras .codyense, has been identified at many localities in the basal oolitic beds of the Sundance formation in Wy­ ticular, the many months spent in the field measur­ oming and South Dakota and in the lowermost beds of the ing sections, tracing lithologic units, and collecting Rierdon formation in Montana. It is correlated with the fossils made possible definite conclusions concerning European zone of Macrocephalites macrocephalus on the basis faunal zones and stratigraphic correlations that of its stratigraphic position beneath beds containing abundant should be useful to mapping parties. Gowericeras and because it contains numerous Cadoceras that are not older than the Callovian. The immediately overlying Most of the fossils described herein have been col­ beds in central and nothwestern Montana have furnished a lected since 1938, but some were collected as early as densely ribbed ammonite, called Gowericeras costidensum. 1885 in the Yellowstone National Park area. The Above, near the middle of the Rierdon formation, follow beds principal collectors were T. W. Stanton in 1911 and containing abundant Gowericeras and Cadoceras and charac­ 1921, A. J. Collier in 1921 and 1923, D. A. Andrews terized by the species Gowericeras subitum. These beds con­ taining Gowericeras are correlated with the northwest Euro­ and W. G. Pierce in 1935, J. B. Reeside, M. M. Kn*ch- pean zone of Proplanulites koenigi because of the abundance tel and S. W. Hobbs in 1938, C. F. Deiss and R. M. of Gowericeras and the highest occurrence of Procerites. The Garrells in 1940, Josiah Bridge in 1941, William Cob- overlying beds which contain Kepplerites tychonis, are corre­ ban in 1944 and 1946, R. W. Imlay from 1944 to lated with the lower part of the Sigaloceras calloviense zone 1951, Oscar Mueller in 1944 and 1946, and J. D. of Europe because the same species occurs in Alaska and East Greenland in association with Cosmoceras (Gulielmiceras). Love, Theodore Botinelly and George Pipiringo^ in The highest beds of the Rierdon formation in Montana con­ 1946. tain many Kepplerites, of which K. mclearni has been desig­ nated the zonal index. Correlation with the Sigaloceras cal­ BIOLOGIC ANALYSIS loviense zone of northwest Europe is indicated by the presence of Cosmoceras (Gulielmiceras) and C. (Gulielmites), by the The Callovian ammonites from the western in­ abundance of Kepplerites with flattened venters, and by the terior of the United States include 482 specimens occurrence of similar forms in Alaska in beds containing that are specifically identifiable. Among these the Gowericeras and Paracadoceras. The Callovian ammonites of the western interior sea show Macrocephalitidae is represented by 11, the Cardio- greater resemblances to those of East Greenland than to ceratidae by 230, the Cosmoceratidae by 221, and the those of southwestern Alaska. This probably reflects differ­ Perisphinctidae by 20. In the Cardioceratidae, Arcti­ ences in depth of water, as all available evidence shows that coceras comprises 20 percent and Cadoceras 28 per­ the sea in the area of southwestern Alaska was fairly deep cent of the total number of ammonites present. In and bordered mountainous shores, whereas the seas of the western interior and of Greenland were very shallow and the Cosmoceratidae, Kepplerites comprises 15 per­ bordered low shores. cent, Gowericeras 23 percent, and Cosmoceras 8 CALLOVIAN (JURASSIC) AMMONITES FROM THE UNITED STATES AND ALASKA percent of the total. In number of species the Macro- The genus is represented by the following species: cephalitidae is represented by 4, the Cardioceratidae A. ishmae (Keyserling), 1846, p. 331, pi. 20, figs. by 10, the Cosmoceratidae by 17, and the Perisphinc- 8-10; Sokolov, 1912, pp. 15, 49, pi. 1, fig. 1, pi. 3, tidae by 7. The ammonites are distributed among fig. 12, text. fig. 2; Spath, 1932, pi. 15, figs. 7a, b. A. kochi Spath, 1932, p. 53, pi. 12, fig. 1, pi. 13, figs. 10 genera and subgenera, and 37 species and varie­ 4, 5, pi. 14, figs. 1-3, pi. 15, figs. 1, 4-6. ties. Nineteen species and 1 variety are described A. michaelis Spath, 1932, p. 56, pi. 13, figs. 3a, b. as new, 5 have been described previously from west­ A. ishmae Madsen (not Keyserling), 1904, p. 191, pi. ern interior collections, 1 is identified with a common 8, fig. 7. boreal species, 1 is compared with a boreal species, A. codyense Imlay, 1948, p. 20, pi. 6, figs. 4, 6, 8. A. henryi (Meek and Hayden), 1865, p. 122. pi. 5, 1 is compared with a Mexican species, 2 are com­ figs. 9 a-c. pared with European species, and 7 are not named A. rierdonense Imlay. because they are poorly preserved. A. n. sp. ind. (see pi. 3, figs. 13, 15, 17). The Macrocephalitidae is represented by Lilloettia A, crassicostatum Imlay. and Xenocephalites. These have been found only in A. loveanum Imlay. the Kepplerites mclearni zone at the top of the Rier- Possibly the list should include Cadoceras sub- don formation in Montana. Lilloettia has been re­ patruum Nikitin (1885a, p. 58, pl.'ll (13), fig?. 58), ported previously from Alaska and British Columbia whose adult whorl greatly resembles that of the (Crickmay, 1930, pp. 60, 62). In Alaska Lilloettia is adult A. henryi (Meek and Hayden). Of the species associated with other ammonites that indicate corre­ listed, A. codyense and A. henryi lose their ribbing lation with the middle Callovian zones of Sigaloceras earliest; A. ishmae, A. kochi,
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