USING OSTRACODE DYNAMICS TO TRACK ECOSYSTEM RESPONSE TO CLIMATICALLY AND TECTONICALLY INDUCED LAKE-LEVEL FLUCTUATIONS IN FOSSIL BASIN, GREEN RIVER BASIN, WYOMING, USA A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Master of Science Andrew J. McFarland December, 2012 USING OSTRACODE DYNAMICS TO TRACK ECOSYSTEM RESPONSE TO CLIMATICALLY AND TECTONICALLY INDUCED LAKE-LEVEL FLUCTUATIONS IN FOSSIL BASIN, GREEN RIVER BASIN, WYOMING, USA Andrew J. McFarland Thesis Approved: Accepted: ______________________________ ______________________________ Advisor Dean of the College Dr. Lisa E. Park Dr. Chand K. Midha ______________________________ ______________________________ Faculty Reader Dean of the Graduate School Dr. John P. Szabo Dr. George R. Newkome ______________________________ ______________________________ Faculty Reader Date Dr. Francisco B. Moore ______________________________ Department Chair Dr. John P. Szabo ii ABSTRACT The Eocene Green River Formation (USA) contains one of the best known Konservat Lagerstätte in the fossil record. Whereas there have been many studies performed on the vertebrate fauna, particularly the fish, there have been relatively few studies done on the invertebrate fauna such as the ostracodes from this famous fossil deposit. Two species (Candona pagei and Hemicyprinotis watsonensis) were recovered from 16 intervals and three study sites from Fossil Basin, a sub-basin of the Greater Green River Basin. The two species represent differing ecological tolerances, both mud-dwelling and plant- dwelling. This formed the basis for a reconstruction of lake levels throughout the history of Fossil Lake. This in turn can be used to examine biotic response to climate change during the Paleocene-Eocene Thermal Maximum (PETM). Stratigraphic sections were measured at three sites and sampled for ostracodes. A 1 cm x 1 cm grid was used to quantify the number of ostracode valves in each sample. Lamination counts were also performed on samples collected in Smith Hollow Quarry (SHQ), which yielded the number of laminations per millimeter. This was compared throughout the section to assess how it changed throughout Fossil Lake’s history at SHQ. Taphonomic uniformity was quantified by comparing the number of whole valves in the samples of kerogen-poor versus kerogen-rich laminated micrites (kerogen-rich micrites are thought to have been deposited under deep, anoxic water conditions), and then compared to each other. Frequencies of occurrence and abundances of individuals per bed were also compared between the two types of micrites. The trophic structure of the iii lake was also assembled to attempt a better understanding of the community ecology of Fossil Lake. This study demonstrates the utility of ostracode species assemblages in tracking lake- level fluctuations throughout the history of Fossil Lake during a time of climate change. This has important implications and applications for studies of current climate change. iv ACKNOWLEDGEMENTS I would like to express my deepest thanks and gratitude to my thesis advisor, Dr. Lisa Park Boush, for all the help she has given me. Thanks for getting me interested in invertebrate paleontology, specifically ostracodes. Thank you also to my committee members, Dr. John Szabo and Dr. Francisco “Paco” Moore for their guidance during this process as well as in the classes I took with them. A large thank you to Elaine Butcher and Thomas Quick for their help and guidance; they are an invaluable asset to the department. A large thank you also goes to Arvid Aase from Fossil Butte National Monument for his hospitality and help navigating the back roads of Wyoming. I would like to thank Jerome Montgomery, quarry manager for the Green River Stone Company, for letting us use their quarry and for the guidance while we were there. I would like to thank my parents for their love and support throughout this process, from the beginning of my interest in dinosaurs, to a more refined interest in paleontology and geology in general. Thank you to my undergraduate professors, Dr. Lee Gray and Dr. Mark McNaught, who helped to broaden my interest in geology. Thanks also to Blossom Frank for her help in measuring sections in the field and cataloguing data in the lab at the University of Akron. Also thanks to Gary Motz for creating the template used to format this thesis. v TABLE OF CONTENTS Page LIST OF FIGURES ......................................................................................................... viii LIST OF TABLES ............................................................................................................. ix CHAPTER I. INTRODUCTION .........................................................................................................1 Paleocene-Eocene Thermal Maximum Climate Setting ................................................2 Geologic History ������������������������������������������������������������������������������������������������������������3 Fossil Basin ....................................................................................................................5 Green River Fauna .........................................................................................................6 II. METHODS ��������������������������������������������������������������������������������������������������������������������9 Sampling ������������������������������������������������������������������������������������������������������������������������9 Lamination Counts .........................................................................................................9 Taphonomic Analysis ...................................................................................................10 III. RESULTS .....................................................................................................................11 Diversity and Lake Level .............................................................................................11 Fossil Basin Stratigraphy .............................................................................................11 Road Hollow Section ...................................................................................................12 Smith Hollow Quarry Section ......................................................................................14 Bear River Gulch Section ............................................................................................16 Lamination Counts .......................................................................................................18 Ostracode Taphonomy .................................................................................................18 IV. DISCUSSION ..............................................................................................................22 vi Stratigraphy ..................................................................................................................22 Ostracode Diversity Dynamics and Lake Level Fluctuations ......................................23 Ecological Reconstruction ...........................................................................................26 Preservation ������������������������������������������������������������������������������������������������������������������26 Hydrodynamics and Relationship with the Greater Green River Basin ......................28 V. CONCLUSIONS..........................................................................................................30 REFERENCES ..................................................................................................................32 APPENDICES ...................................................................................................................37 APPENDIX A. ROCK DESCRIPTIONS ...................................................................38 APPENDIX B. OSTRACODE Data .......................................................................45 APPENDIX C. Lamination COUNTS ..................................................................56 vii LIST OF FIGURES Page Figure 1 Distribution of the Green River Formation within Fossil Basin, indicating the locations of the sites sampled for this study ......................................................4 2 Stratigraphic column of the Green River Fm as measured at Road Hollow, showing lithologies and locations of fish and ostracodes ......................................13 3 Stratigraphic column of the Green River Fm as measured at Smith Hollow Quarry, showing lithologies and locations of fish, plants and ostracodes .............15 4 Stratigraphic column of the Green River Fm as measured at Bear River Gulch, showing lithologies and locations of fish, plants and ostracodes ...............17 5 A. Frequency of occurrence chart for the number of beds with ostracodes as compared to the total number of occurrences for both kerogen-poor and kerogen-rich micrites. B. Abundance of individuals per bed for both kerogen-poor and kerogen-rich micrites. C. Number of beds with whole valves preserved for both kerogen-poor and kerogen-rich micrites. .....................19 6 Composite stratigraphic section of the Green River Formation exposed in Fossil Basin and comparing lamination counts/mm, ostracode species valve counts/cm2, and an interpretation of lake level throughout the lake’s history .......24 7 Paleoecological web displaying energy transfer from solar radiation at the