Foraminifera from the Pierre Shale (Upper Cretaceous) at Red Bird, Wyoming GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-C Foraminifera from the Pierre Shale (Upper Cretaceous) at Red Bird, Wyoming By JAMES F. MELLO STRATIGRAPHY, PALEONTOLOGY, AND SEDIMENTATION OF A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE GEOLOGICAL SURVEY PROFESSIONAL PAPER 393-C Sixty-one foraminiferal taxa are described from the complete section of the Pierre Shale at Red Bird, Wyo. UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY William T. Pecora, Director Library of Congress catalog-card No. 70-610218 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1 (paper cover) CONTENTS Page Page Abstract_ _ _______________________________________ Cl Vertical distribution and biostratigraphy_____________ C7 Introduction.______________________________________ 1 Problems in the study of Foraminifera of western interior Acknowledgments__ _ __________________________ 1 United States.___________________________________ 7 Environmental interpretations__-_-_-_----____-_-___ 1 Stratigraphic positions of the samples.________________ 14 Interpretations based on regional geology._________ 1 Sample preparation.________________________________ 15 Interpretations based on Foramimfera__--_________ 4 Systematic paleontology.____________________________ 15 Interpretations based on macrofossils____________ 5 References cited____________________________________ 50 Comparison of foraminiferal faunas between the strati- Index _____________________________________________ 53 graphic units.____________________________________ ILLUSTRATIONS [Plates 1-7 follow Index] PLATE 1. Alabamina, Ammobaculites, Ammobaculoides?, Anomalinoides, Astacolus, Bathysiphon, Bulimina, and ?Buliminella. 2. Caucasina, Cibicides, Dentalina, Dorothia, Eouvigerina, Fissurina, Globigerinelloides, and Glomospira. 3. Frondicularia, Gaudryina, Glomospirella, and Gyroidina. 4. Haplophragmoides, Lagenammina, and Pseudobolivina?. 5. Heterohelix, Lagena, Lenliculina, Marginulina, Oolina, Pseudoclavulina?, Reophax, Saccammina, and Saracenaria. 6. Neobulimina, Silicosigmoilina, Spiroplectammina, and Trochammina. 7. Nodosaria, Stilostomella, Textularia, Trochammina, Verneuilinoides, and incertae sedis. Page FIGTJKE 1. Graphs showing changes in foraminiferal faunal size and gross composition, bathymetry based on macrof ossils, and strandline position during deposition of the Pierre Shale at Red Bird, Wyo ______________________ C2 2. Chart showing ranges and relative abundances of foraminiferal species which have restricted local ranges, are typically represented by numerous specimens, and are morphologically distinctive.______________________ 11 3. Chart showing ranges of foraminiferal species in the Pierre Shale at Red Bird, Wyo., and their composite ranges from elsewhere in the Cretaceous interior seaway.___________________________________________________ 12 4. Outline drawings of Spiroplectammina sp. 1 and of a topotype of S. semicomplanata_ _ _ ________________________ 44 TABLES Page TABLE 1. Summary of foraminiferal ratios and faunal-sample relationships____--_-_--__-_---------_- C4 2. Sizes and comparisons of macrofossil collections.___-_____________-____-_--__-_---_------- 6 3. Ranges and relative abundances of foraminiferal species._____-___-_-__--_--__-----------_- 8 4. Percentage of samples in each stratigraphic unit in which each species of Foraminifera is found. 11 5. Stratigraphic positions of the samples..------------------------------------------------- 14 rn STRATIGRAPHY, PALEONTOLOGY, AND SEDIMENTATION OF A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE FORAMINIFERA FROM THE PIERRE SHALE (UPPER CRETACEOUS) AT RED BIRD, WYOMING By JAMES F. MELLO ABSTRACT ACKNOWLEDGMENTS Foraminifera were recovered from 75 samples taken from Considerable help received from William A. Cobban, the complete section of the Pierre Shale exposed at Red Bird, James R. Gill, and Robert E. Burkholder, U.S. Geo­ Wyo. Arenaceous Foraminifera are dominanit in most samples, both in number of species and number of specimens, but some logical Survey, is gratefully acknowledged. Elinor samples contained calcareous benthonic and planfctonic speci­ Stromberg, U.S. Geological Survey, made the draw­ mens, and many samples yielded internal molds of presumably ings of Foraminifera. Thanks are also due Cobban and calcareous species. Patterns of distribution of identifiable fora- Norman F. Sohl, U.S. Geological Survey, and Dr. miniferal taxa show no convincing relationship with regional John H. Wall, Research Council of Alberta, who depositional history, macrofossil occurrences, or Holocene dis­ tributional patterns. Most foraminiferal species are rare and reviewed the manuscript. occur sporadically, and most of the rest are long ranging, either locally or regionally. No biostratigraphic subdivisions are ENVIRONMENTAL INTERPRETATIONS proposed. INTERPRETATIONS BASED ON REGIONAL GEOLOGY Of the 61 identified taxa, 46 are assigned positively or pro­ visionally to previously named species, one species is described In general lithologic character, the Pierre Shale at as new, and 14 taxa 'bear informal species nomenclature. The Red Bird "* * * consists of dark- to light-gray- species Haplophragmoides excavata Cushman and Waters is weathering noncalcareous clayey to silty shale that is emended to include five morphologic subgroups. entirely of marine origin" (Gill and Cobban, 1966, p. Al). During deposition at Red Bird, the nearest INTRODUCTION strandlines were to the west and northwest. According The discovery of a well-exposed complete section to Gill and Cobban (1966, p. AST), the strandline was of the Pierre Shale at Red Bird, Niobrara County, about 185-205 miles west of Red Bird during Gammon Wyo., by U.S. Geological Survey geologists and its time, 135-160 miles to the west during Mitten time, subsequent intensive investigation (Gill and Cobban, and probably no more than 60 miles away during 1966; Sohl, 1967) provided a theoretically ideal frame­ deposition of the Red Bird Silty Member (see fig. 1). work for the study of Foraminifera. Careful strati- Immediately after deposition of the Red Bird Silty graphic work was done, and fine zonation based on Member, the strandline moved about 110 miles west of mollusks was established. This created an excellent Red Bird, during which time the lower third of the opportunity for relating the Foraminifera from the lower unnamed member was deposited. While the Pierre Shale to widely recognized fossil zones and middle third of the lower unnamed member was being regionally important stratigraphic units. deposited at Red Bird, uplift and erosion took place Despite the promise of these initial conditions, the to the west, accompanied by a probable regression of results of this study were less than expected. The the strandline nearer to Red Bird. Renewed transgres­ Foraminifera are monotonous in general faunal char­ sion shifted the strandline to a point 150 miles west acter. Nearly all recovered faunas are arenaceous and of Red Bird during deposition of the upper third of not very diverse, and most species are long ranging. the lower unnamed member, the Kara Bentonitic Mem­ All three factors limit the usefulness of these Foram­ ber, and the basal part of the upper unnamed member. inifera for zonation and environmental interpretation. During deposition of the upper unnamed member, If the character of foraminiferal faunas at Red Bird the strandline shifted eastward and southeastward reflects the faunal character predominating in the and was as close as 60 miles north of Red Bird during Pierre Shale of other areas, the data and conclusions deposition of the upper third of the unit. The strand- presented here may be of wider use than presently line was probably never nearer than 40 miles from expected. Red Bird, and it was usually 100 or more miles away. Cl C2 DESCRIPTIVE STUDY OF A CLASSIC REFERENCE LOCALITY OF THE PIERRE SHALE MEMBER AND NUMBERED .Gammon Ferruginous Member Red Bird Silty Member 46 36 37 38 39 41 43 45 47 48 49 50 51 52 20 25 30 35 R R MM RM RM M R RM EM RM RM RM RS S M EM R RM R EM EM R RMRMR? LS LS ML MS SAMPLE NUMBER <=> "" 50- o _ -L-1 I U L I I 35 40 SAMPLE RED BIRD, WYO. <2 150 FIGURE 1. Changes in foraminiferal faunal size and gross composition, bathymetry based on FORAMINIFERA AT RED BIRD, WYOMING C3 UNIT OF MEASURED SECTION Kara Bentonitic Member Lower unnamed shale member 62 65 70 76 64j 69/ 71 72 75 77 78 Bathymetric changes, based on macrofossil lists given in Gill and Cobban (1966). Bathymet­ ric interpretations are by Erie Kauffman, U.S. National Mu­ seum (written commun., 1968). See Gill and Cobban (1966) EXPLANATION for numbered units Interpreted depth range of num bered unit of measured section Generalized bathymetric curve Dashed where inferred EXPLANATION Total number of foraminiferal Letter symbols beneath sample species number indicate presence of: O R, Radiolaria Number of planktonic species M . molds of calcareous Foraminifera L , linguloid brachiopod fragments A S, inferred seed or spore cases Number of B calcareous benthonic species Changes in size and composition of the foraminiferal fauna. See table 5 for sample numbers 45 50 75 RM M RM RM M RM R RM R R M R? L M ML ML MS AND FOSSILS Changes in approximate percent­ age of arenaceous Foraminifera in the foraminiferal fauna, de­ termined by assuming median absolute