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University of Cincinnati UNIVERSITY OF CINCINNATI DATE: May 29, 2003 I, , Jocelyn Anne Sessa hereby submit this as part of the requirements for the degree of: Master of Science in: The Department of Geology It is entitled: THE DYNAMICS OF RAPID, ASYNCHRONOUS BIOTIC TURNOVER IN THE MIDDLE DEVONIAN APPALACHIAN BASIN OF NEW YORK Approved by: Dr. Arnold I. Miller Dr. Carlton E. Brett Dr. David L. Meyer Dr. Gordon C. Baird THE DYNAMICS OF RAPID, ASYNCHRONOUS BIOTIC TURNOVER IN THE MIDDLE DEVONIAN APPALACHIAN BASIN OF NEW YORK A thesis submitted to the Division of Research and Advanced Studies Of the University of Cincinnati in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in the Department of Geology of the College of Arts and Sciences 2003 by Jocelyn Sessa B.A. State University of New York at Geneseo, 2000 Committee Co-Chairs: Dr. Carlton E. Brett and Arnold I. Miller ABSTRACT High resolution stratigraphic and paleoecological analyses of regional biotic turnovers can reveal much about their evolutionary and ecological processes. Biotic turnover in the Devonian of the Appalachian Basin was investigated to determine whether taxonomic replacement across a key boundary was: 1) abrupt or gradual; 2) synchronous across the basin. Analyses of abundance data that reveal a depth-controlled gradient persisted, with moderate variation, until just prior to the boundary. Two biotic assemblages occur above and below the boundary, while another occurs only above it. Turnover was asynchronous; certain assemblages appeared earlier than others. Above the boundary, a unique assemblage appeared abruptly, another assemblage appeared gradually, and a third remained unchanged. Taxonomic composition was controlled by sedimentologic/environmental variables; specific faunas occur in particular lithofacies. Many taxa were not facies restricted, and occurred in many environments, but their abundance varied significantly. Taxon abundance and paleoenvironmental context is therefore important for understanding biotic transitions. ii iii ACKNOWLEDGEMENTS I wish to sincerely thank my committee co-chairs, Dr. Arnie Miller and Dr. Carl Brett, for their support and guidance throughout my studies at UC. Arnie, you have given me the tools to think critically, pose interesting research questions, to balance work with everything else, and have provided a role model I can aspire to. Thanks also for bringing me into the PBDB, and exposing me to different ideas and research questions. Carl, thank you for all of the fun hours in the field and looking at specimens, be it in the car during thunderstorms or in the lab at night. Your unbridled enthusiasm and support of this project is sincerely appreciated. Thanks also for introducing me to SSETI and giving me the opportunity to be part of such an interesting and fun experience. Special thanks to my committee member Gordon Baird his hospitality on numerous occasions, for greatly assisting in fieldwork, and providing thoughtful comments on both research and music. Thanks to committee member Dave Meyer, whose thoughtful comments and general good nature are always appreciated. The Paleontological Research Institution in Ithaca New York, and specifically Paul Harnik, were invaluable in collecting samples and providing assistance during fieldwork. Evelyn Mohalski Pence, graphic designer, was extremely helpful with the drafting of figures. Fieldwork was aided greatly by the skills and time of Sue Taha-McLaughlin, Rich Krause, Alex Bartholomew, and James Bonelli, who all provided companionship during sampling. A. Bart at the Center for the Study of Dynamic Cyclo-Stratigraphy of the Siluro-Devonian Appalachian Basin of New York State provided unending hours of laughs and interesting discussion about the Hamilton Group. To my fellow students, thank you for your friendship, patience, listening, and support throughout my masters. You will be missed. iv To my parents and family, thank you all for your support and your encouragement to pursue my dreams. To James, I could not have made it through without you. Thanks for your friendship, compassion, and love – you are my sunshine. Funding for this research was granted through Sigma Xi, the American Museum of Natural History Theodore Roosevelt Fund, the Paleontological Society, the Geological Society of America, a University of Cincinnati Student Summer Research Grant, a University of Cincinnati Office of Sponsored Research matching grant for Sigma Xi awards, a University of Cincinnati Departmental Fellowship, and NASA Exobiology Grants awarded to Dr. A.I. Miller. v TABLE OF CONTENTS Page ABSTRACT…………………………………………………………………………..….ii ACKNOWLEDGEMENTS………………………………………………………………iv LIST OF FIGURES.………………………………………………………………………2 LIST OF TABLES………………………………………………………………………...3 LIST OF APPENDICES…………………………………………………………………..4 INTRODUCTION…………………………..…………………………………………….5 GEOLOGIC SETTING AND STRATIGRAPHY….......…………………………………9 METHODS…..…..………………………………………………………………………19 RESULTS AND DISCUSSION…………………………………………………………23 Windom Samples…………………………………………………………….…23 Transitional Samples……………………………………………………..….…30 Tully Samples………………………………………………………………..…38 Summary of Results…………………………………………………………....46 Implications………………………………………………………………….…47 CONCLUSIONS…………………………………………………………………………52 REFERENCES…………………………………………………………………………...54 APPENDIX I……………………………………………………………………………..63 APPENDIX II………………….…………………………………………………………67 1 LIST OF FIGURES Figure Page 1. Map of the study interval in New York State.......……………………………….10 2. Schematic cross section of the eastern Appalachian Basin during uppermost Windom and Tully time………………………………………………………….11 3. General stratigraphic column of the study interval………………………………14 4. Detrended Correspondence Analysis of Windom samples and taxa…………….24 5. Abundance and occurrence graphs of key Windom taxa………………………..25 6. Abundance and occurrence graphs of key Highland Forest taxa………………..31 7. Detrended Correspondence Analysis Axis one scores plotted in stratigraphic order for Locality 10…..………..………………………………………………………35 8. Detrended Correspondence Analysis Axis one 5 point moving average scores plotted in stratigraphic order for Locality 10…………….………………………37 9. Detrended Correspondence Analysis for all samples and taxa…….…………….39 10. Abundance and occurrence graphs of key Tully taxa……………………………40 11. Summary figure with samples coded to Detrended Correspondence Analysis group …………………………………………………………………..41 12. Percent occurrence of the most common taxa within the studied interval………42 2 LIST OF TABLES Table Page 1. Percentage of taxa within systems tracts of the Windom……………………….29 2. Percentage of key taxa from the Emanuella-dominated assemblage that occur in non-boundary Hamilton samples……...…………………….…….…...33 3 LIST OF APPENDICES Appendix Page I. Locality register and sample positions………………………….……………….63 II. Middle Devonian uppermost Hamilton Group and Tully Formation field census raw data…………………………………………………………...…......67 4 INTRODUCTION Previous studies of ancient biotic transitions at regional scales have typically documented prolonged periods of relative compositional stability interspersed with relatively brief intervals of rapid biotic reorganization. In this context, many investigators have focused on delineating and calibrating the periods of stability (i.e., Boucot, 1983; Brett and Baird, 1995; Bennington and Bambach, 1996; Holterhoff, 1996; Pandolfi, 1996; Sheehan, 1996; Patzkowsky and Holland, 1997; Olszewski and Patzkowsky, 2001; Gardiner, 2001). However, comparatively less attention has focused on the equally important intervals of biotic change (see Ivany, 1996, 1999, for theoretical discussions of turnover and its implications). High resolution analyses of critical boundaries can lead to a greater understanding of how, and perhaps why, these transitions occur. Specifically, transitional patterns may be important in the diagnosis of interaction – or lack thereof - among species that compose assemblages, and the constraints placed upon organisms by their environments in response to physical changes. A detailed study of turnover events may also reveal the variables, be they biotic or abiotic, to which organisms respond most significantly on a regional scale. Causal mechanisms aside, it would also be useful to identify just how abrupt turnover intervals are. Do turnovers take place across single horizons, or are they more gradual, with a progressive breakdown of existing assemblages and piecemeal development of subsequent biotas? It is plausible that these different end members could relate to the degree of biotic interaction within ‘communities’. If species within communities are strongly tied to one another by biotic interactions (e.g. Elton, 1927), then turnover should appear abrupt, given the unitary nature of the community. Alternatively, if species are not tightly linked to one another (e.g. Gleason, 1926), then a more diffuse transition might be observed. Admittedly, these are not the 5 only possibilities, as abrupt turnover may simply be related to the shared environmental preferences of taxa that appear or disappear during a turnover event (sensu Miller, 1997). Thus, an understanding of each taxon’s environmental preferences would be helpful in teasing apart the processes responsible for biotic turnover, and necessitates the characterization of species abundance within various biofacies before, during, and after a turnover event. It is also important to determine whether turnover is synchronous across coeval environments within a given region. Faunas in dissimilar environments
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