Western Washington University Western CEDAR WWU Graduate School Collection WWU Graduate and Undergraduate Scholarship Fall 1990 Danian (Paleocene) Molluscan Paleoecology in the Aftermath of the Cretaceous-Tertiary Extinctions, East-Central Texas Benjamin R. Farrell Western Washington University Follow this and additional works at: https://cedar.wwu.edu/wwuet Part of the Geology Commons Recommended Citation Farrell, Benjamin R., "Danian (Paleocene) Molluscan Paleoecology in the Aftermath of the Cretaceous-Tertiary Extinctions, East- Central Texas" (1990). WWU Graduate School Collection. 809. https://cedar.wwu.edu/wwuet/809 This Masters Thesis is brought to you for free and open access by the WWU Graduate and Undergraduate Scholarship at Western CEDAR. It has been accepted for inclusion in WWU Graduate School Collection by an authorized administrator of Western CEDAR. For more information, please contact [email protected]. DANIAN (PALEOGENE) MOLLUSCAN PALEOECOLOGY IN THE AFTERMATH OF THE CRETACEOUS-TERTIARY EXTINCTIONS, EAST-CENTRAL TEXAS by Benjamin R. Farrell Accepted in Partial Completion of the Requirements for the Degree of Master of Science Dean of Graduate School/^ Advisory Committee Master^s Thesis In presenting this thesis in partial fulfillment of the requirements for a master's of science degree at Western Washington University, I agree that the Library shall make its copy freely available for inspection. I further agree that extensive copying of this thesis is allowable only for scholarly purposes. It is understood, however, that copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without my written permission. Signature Date feJ:>r<^Ajry / MASTER'S THESIS In presenting this thesis in partial fulfillment of the requirements for a master's degree at Western Washington University, I grant to Western Washington University the non-exclusive royalty-free right to archive, reproduce, distribute, and display the thesis in any and all forms, including electronic format, via any digital library mechanisms maintained by WWU. I represent and warrant this is my original work and does not infringe or violate any rights of others. I warrant that I have obtained written permissions from the owner of any third party copyrighted material included in these files. I acknowledge that I retain ownership rights to the copyright of this work, including but not limited to the right to use all or part of this work in future works, such as articles or books. Library users are granted permission for individual, research and non-commercial reproduction of this work for educational purposes only. Any further digital posting of this document requires specific permission from the author. Any copying or publication of this thesis for commercial purposes, or for financial gain, is not allowed without my written permission. Name: Signature: Date: DANIAN (PALEOGENE) MOLLUSCAN PALEOECOLOGY IN THE AFTERMATH OF THE CRETACEOUS-TERTIARY EXTINCTIONS, EAST-CENTRAL TEXAS A Thesis Presented to The Faculty of Western Washington University In Partial Fulfillment of the Requirements for the Degree Master of Science by Benjamin R, Farrell December 1990 ABSTRACT Danian shelf sediments from the Brazos River region of east-central Texas span approximately the first two million years after the Cretaceous-Tertiary (K-T) extinctions with only minor changes in lithofacies. Study of these virtually continuous stratigraphic sections reveals the nature and timing of the molluscan faunal rebound in the wake of the K- T extinction event. Diverse Late Maastrichtian molluscan faunas were dominated by epifaunal suspension-feeders, primarily oysters. Immediately above the K-T extinction horizon, low-diversity molluscan assemblages were characterized by a bloom in the abundance of the pelagic herbivore family Litiopidae, which were rapidly replaced by a low diversity assemblage dominated by a deposit-feeding bivalve of the family Nuculanidae (Upshaw, 1989; Hansen and Upshaw, 1990). This low diversity assemblage persisted for approximately 300,000 years after the K-T extinctions and may have been caused by the low productivity of the hypothesized "Strangelove" ocean of Hsu (1986). Diversity rapidly increased to nearly pre-extinction levels within the Globigerina pseudohulloides zone (Plb), roughly 300,000 years after the K-T extinctions. Coinciding with this diversity increase was a change in the composition of the fauna from a roughly even mixture of Cretaceous, Paleocene, and undescribed species to a fauna composed primarily of Paleocene species. The relative proportions of IV deposit-feeders and suspension-feeders also return to roughly Late Cretaceous levels within this biozone. Above the base of the G. pseudobulloides zone (Plb), the molluscan assemblages were characterized by increased stability. Diversity and trophic proportions of these assemblages persisted at nearly pre-extinction levels for the remainder of the studied interval, a period of at least 1.6 million years. In contrast to the large amount of faunal turnover apparent in the earliest Paleocene, molluscan assemblages within and above the G. pseudobulloides (Plb) biozone are characterized by increased species longevity in the studied sections. Some faunal constituents were affected more permanently by the K-T extinctions. Epifaunal soft-bottom suspension- feeders such as oysters were a prominent component in local Late Cretaceous faunas, but they never regained their former levels of diversity and abundance in the studied Paleocene stratigraphic sections. Infaunal burrowing carnivorore- scavengers such as Naticidae and various opistobranchs became much more abundant in the Paleocene than they were in the Cretaceous. V ACKNOWLEDGEMENTS Special thanks goes to my committee members Dr. Thor Hansen, Dr. Chris Suczek, and Dr. Dave Schneider for their considerable help and advice. Dr. Tom Waller and Mr. Warren Blow provided me with access to systematic collections at the United States National Museum. Dr. Norm Sohl of the U.S.G.S. kindly helped identify some of my mollusks. Dr. Warren Allmon verified identifications for mollusks of the family Turritellidae. Planktonic foraminiferal biostratigraphy for the Danian stratigraphic sections was worked out by Dr. Gerta Keller. Dr. Erie Kauffman, Richard Farrand, and Banks Upshaw III shared data. Financial assistance for this project was provided by Sigma Xi Grants-in-Aid-of-Research, a Geological Society of America Student Research Award, and a Western Washington University Geology Departmental Grant. Many people in Bellingham have made my stay here enjoyable. I'd particularly like to thank Dr. Russ Burmester and Gary Hurban for a fantastic, adventurous summer of field-mapping in the Idaho wilderness. The boys of 1420 Ellis St. provided me with an entertaining temporary home during the end of this drawn-out process. This thesis was substantially improved through numerous discussions with Banks Upshaw. Administrative assistants Patty Combs and Vicki Critchlow helpfully answered my many questions and VI steered me past the school-bureaucracy. Lastly, I'd like to thank my family and friends for encouraging me during the course of this project. Thanks! vii TABLE OF CONTENTS ABSTRACT..................................................iv ACKNOWLEDGEMENTS......................................... vi LIST OF FIGURES...........................................xi LIST OF TABLES..........................................xiii INTRODUCTION...............................................1 REGIONAL GEOLOGY...........................................9 The Cretaceous-Tertiary Contact..................... 13 Outcrop Stratigraphy.................................15 Brazos-2........................................16 Cottonmouth Creek.............................. 20 Darting Minnow Creek............................21 Frost Bluff.....................................21 Ravine..........................................21 Tehuacana Creek.................................22 Lithostratigraphic and Biostratigraphic Correlations.........................................22 Sedimentation Rates..................................26 METHODS...................................................29 Sample Collection and Processing.................... 29 Grain-size Analysis..................................31 Analytical Methods...................................31 Cluster Analysis................................32 Diversity.......................................36 RESULTS................................................... 38 viii Cluster Analysis.................................... 38 Taxonomic Composition............................... 45 Assemblage A................................... 45 Assemblage B................................... 45 Assemblage C................................... 49 Assemblage D................................... 49 Assemblage E................................... 52 Taphonomy of the Assemblages........................ 54 Sediment Grain-size Distribution.................... 55 Species Ranges...................................... 58 Brazos River localities........................ 58 Ravine Locality................................ 61 Diversity........................................... 63 Species Richness............................... 63 Species Range-richness......................... 64 Shannon-Weaver Diversity....................... 67 Rarefaction Analysis........................... 69 Life-habits of the Fauna............................ 71