A NEW FAUNA FROM THE COLORADO GROUP OF SOUTHERN MONTANA. By JoHN B. REESIDE, Jr. Feet. INTRODUCTION. Telegraph Creek formation......... 320-350 Sandstones and shales. This group of beds con­ This paper describes a small but interesting tains at places in the upper part a fauna like that fauna collected in 1921 by W. T. Thorn, jr., of the Eagle sandstone, but in the lower beds it Gail F. Moulton, T. W. Stanton, and K. C. contains Uintacrinus sp., Marsupites sp. (identi­ Heald in the Crow Indian Reservation in fied by Frank Springer), Inoceramus dejormis southern Montana. The locality is in sec. 36, Meek var., Ostrea cf. 0. congesta Conrad, Baculites sp., Puzosia (Latidorsella) n. sp., and Scaphites n. T. 6 S., R. 32 E ., Big Horn County, and is 2 sp. aff. S. geinitzi D'Orbigny. • miles east of the Soap Creek oil field. Niobrara formation (top formation of Colorado The stratigraphic section in the Soap Creek group)"........................................ 400 oil field was described briefly by Thorn and Bluish calcareous shale in upper and lower Moulton in a press notice issued by the United parts; dark shale in middle. In the upper part it contains Uintacrinus socialis Grinnell (identified States Geological Survey December 5, 1921, by Frank Springer), Yoldia sp., Inoceramus, large entitled "The Soap Creek oil field, Crow Indian thick-shelled species, Ostrea congesta Conrad, Reservation, Mont." It was described also in Lunatia concinna (Hall and Meek), Tessarolax cf. a later and more general paper.1 The youngest T. hitzi White, Baculites sp., Scaphites vermi- beds present near the oil field belong to the formis Meek and Hayden, and fish scales. In the middle part it contains Inoceramus aff. I. lamarcki Niobrara formation, but in the adjacent parts Parkinson, Inoceramus umbonatus Meek and Hay­ of the Crow Reservation to the east and north den, Inoceramus, large thick-shelled species, higher formations are present and are in part Pteria aff. P. nebrascensis (Evans and Shumard), included in the section given below. The part Anatina aff. A . subgracilis (Whitfield), Veniella of the section from the Cloverly formation to goniophora Meek, Cardium n. sp., Fusus sp., Volu­ toderma sp., Baculites aff. B. anceps Lamarck, the Niobrara formation, inclusive, is derived Baculites asper Morton, Scaphites vermiformis Meek frmn the publications mentioned above and and Hayden. In the lower part it contains from data kindly supplied by Mr. Thorn. The Inoceramus, large thick-shelled species, Ostrea thicknesses given for the Eagle sandstone and congesta Conrad, and the basal bed, a zone of large the Telegraph Creek formation apply especially yellow concretions, contains Yoldia sp., Nemodon to the vicinity of Pryor Creek, some 30 miles sp., Barbatia n. sp., Inoceramus jragilis (Hall and Meek)?, Inoceramus (Actinoceramus) n . sp., Veni­ north of the Soap Creek oil field. The included ella goniophora Meek, Callista tenuis (Hall and lists of fossils are based on the writer's deter­ Meek), Corbula cf. C. nematophora Meek, Denta­ minations. lium sp., Gyrodes aff. G. petrosa (Morton), Turri­ tella aff. T. whitei Stanton, Anchura sp. ,· Nautilus .Partial section of forma:tions exposed in the Crow Indian sp., Baculites sp., and Scaphites vermiformis Meek Reservat-ion, Mont. and Hayden. Feet. Carlile shale..... ............................... 425 :Eagle sandstone ............................ ... 200-250 This formation may be divided into a number of Sandstones and some shales; at base the massive units as follows: . Virgelle sandstone member. This formation con­ Dark shale with whitish septarian nodules con­ tains Scaphites hippocrepis (Dekay), Scaphites n. taining Inoceramus labiatus (Schlotheim), Ve­ sp. aff. S. aquisgranensis Schlueter, Inoceramus n,iella goniophora Meek, Corbula aff. C. nemato­ aff. I. lobatus Goldfuss, Placenticeras syrtale (Mor­ phora Meek, Pseudomelania? sp., Fusus sp., ton), Placenticeras meeki Boehm, Placenticeras Prionocyclus wyomingensis Meek. Thickness 50 planum Hyatt, Baculites ovatus Say, Baculites feet. as per Morton, Baculites n. sp. aff. B. anceps Zone of large yellowish · sandstone concretions. Lamarck, and many other fossils. Thickness 5 feet. Dark shale. Thickness 35 feet. 1 Thorn, W. T., jr., Oil and gas prospects-in and near the Crow Indian ·R eservation, Mont.: U . S. Geol. Survey Bull. 736, pp. 35-53, 1922 Shale with thin hard rusty red concretions and ·(Bull. 7313-B) layers containing Inoceramus fragilis Hall and 25 26 SHORTER CONTRJBUTIONS TO GENERAL GEOLOGY, 1923. Feet. region. It is therefore of interest to consider Meek, Inoceramus cf. I. lamarcki Parkinson, Veniella sp., Volutoderma? sp., Baculites gracilis some of the faunal zones recognizable in the Shumard, Scaphites warreni Meek and Hayden, Cretaceous deposits of this province. Prionotropisaff. P. woolgari (Mantell). Thickness A series of more or less widespread and more 30 feet. · or less distinctly defined faunal zones have Dark shale. Thickness 60 feet. Bluish calcareous shale containing in ita lower long been recognized in the Cretaceous de­ part the fauna described in this paper. Thick­ posits of the Western Interior. The lowest ness 100 feet. zone to be considered here is well characterized Dark shale and bentonite. Thic~ss 145 feet. only in the southern part of the province, where Frontier formation...... 410 it contains Exogyra columbella Meek and Chiefly dark shale with bentonite but with a zone of thin coarse sandstones near the top. Gryphaea newberryi Stanton as its guide fossils. Shark teeth the only fossils observed. This zone includes the Graneros shale of the Mowry shale.... • . 200-300 central Great Plains, the basal part of the Hard bluish-white sha1e with layers of hard dark Mancos shale of New Mexico, Colorado, and shale. Contains abundant :fish remains but ~ew Utah, and the Thermopolis shale of the north. other fossili. Thermopolis shale.. 550-800 At many places, especially in the north, it is Dark marine shale with streaks and lenses of nearly barren of fossils, and those present are light-colored sandstone containing Inoceramus not sufficiently restricted to serve as guide labiatus (Schlotheim), Pteria aff. P. nebrascensis fossils. (Meek and Hayden), Ostrea sp., Entolium sp., Mo­ Above this zone occurs a zone with an diola n. sp., Gyrodes aff. G. depressa Meek, fish and turtle remains. Middle part of formation of dark abrindance of Inoceramus labiatus (Schlotheim). clay and bentonite;lowerpartofdarkmarineshale. In the central Great Plains region this zone is Cloverly formation. ... 320-425 contained in the Greenhorn limestone, and An upper member of sandy shale and thin-bed- very few other fossils than the guide fossil ded rusty sandstone that may represent the have been found in it. In western Colorado Dakota sandstone of Upper Cretaceous age. A middle member consisting of variegated shale and the adjacent region it is well marked in where exposed along the Big Horn Mountains and the lower part of the Mancos shale. It occurs containing Unio sp. and Viviparusf sp. and a in southern and central Wyoming in the basal member of thick coarse-grained conglom­ Frontier formation and in northern Montana eratic sandstone. These divisions may repre- . in the lower part of the Colorado shale. sent the Fuson shale and Lakota sandstone, of Above this zone of Inoceramus labiatuslies a Lower Cretaceous age. zone which contains as its more prominent and THE FAUNA AND ITS RELATIONS. restricted species Scaphites warreni Meek and The collection described in this paper con­ Hayden, several species each of Prionotropis, tains five species of ammonites referred to and Prionocyclus, Inoceramus fragilis Hall and three genera, two species of Inoceramus, an Meek, Inoceramus dimidius White, and Ostrea ostreid, and a gastropod. lugubris Conrad. It very rarely co~tains The species are as follows: Inoceramus labiatus (Schlotheim). This zone V ascoceras thomi Reeside, n. sp. is perhaps the most sharply defined and most Vascoceras moultoni Reeside, n. sp. widely .recognized of the series. It comprises Vascoceras stantoni Reeside, n. sp. the entire Carlile shale of the central Great Vascoceras sp. undeterminable. Plains and Black Hills regions, part of the Pseudotissotia (Choffaticeras) sp.? Helicoceras pariense White? Mancos shale of western Colorado and adjacent Inoceramus labiatus (Schlotheim). regions, the Carlile shale of Wyoming, and part Inoceramus sp. undetermined. of the Colorado formation of Montana. Ostrea or Exogyra sp. Above the zone of Scaphites warreni comes a Gastropod, undetermined. zone which contains Uintacrinus socialis Grin­ This fauna is known from only this one nell, Inoceramus umbonatus Meek and Hayden, locality in the Western Interior province of Inoceramus deformis Meek, and, especially in North America, and consequently its correla­ the north, Scaphites ventricosus Meek and tion must rest in large part on its position with Hayden and Scaphites vermiformis Meek and relation to other faunal zones in the same Hayden. A very abundant and locally re­ stratigraphic section and in the adjacent stricted form of this zone is Ostrea congesta A NEW FAUN A FROM THE COLORADO GROUP OF SOUTHER.N MONTANA. 27 Conrad. Inoceramus labiatus is reported in the correlated with at least the upper part of the literature as occurring here also, but it has not Greenhorn limestone of the central Great been found in numerous recent collections, and Plains, though the occurrence of Inoceramus its earlier assignment to the fauna of this zone labiatus in beds some 800