UNIVERSITY OF CINCINNATI DATE: May 8, 2003 I, Stephanie R. Fuentes , hereby submit this as part of the requirements for the degree of: Master of Science in: Geology It is entitled: Faunal Distribution across the Ordovician-Silurian boundary in Ohio and Ontario Approved by: Carlton E. Brett Arnold I. Miller Thomas Algeo Steven M. Holland FAUNAL DISTRIBUTION ACROSS THE ORDOVICIAN-SILURIAN BOUNDARY IN OHIO AND ONTARIO 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 Stephanie R. Fuentes B.A., SUNY Geneseo, 2001 Committee Chairs: Dr. Carlton E. Brett, Dr. Arnold I. Miller ABSTRACT The Late Ordovician mass extinction is one of the most extensive faunal events in earth history. However, there have been few local analyses on the faunal turnover at this boundary. In addition, it has been suggested that this boundary does not exhibit marked ecologic change. The purpose of this study is to compare faunal distribution from the Upper Ordovician to the Lower Silurian in terms of faunal turnover, ecologic structure, and genus richness. Samples were collected from strata that represent comparable depositional environments, including the Drakes and Brassfield Formations of Ohio, and the Georgian Bay and Cabot Head Formations of Ontario. Multivariate techniques suggest a change in the composition and abundance ratios of taxa across the boundary in the study region. There is no evidence of significant ecologic restructuring across the Ordovician-Silurian boundary and the distribution of some rarefied samples suggests slightly elevated richness in the Silurian. ii iii ACKNOWLEDGEMENTS I would like to thank my advisors, Carl Brett and Arnie Miller, for their continued encouragement, guidance, and support throughout this project. Their assistance in the field and the lab, as well as their review of this manuscript, provided me with motivation, insight, and ability, without which this research could not have been completed. I would also like to thank committee members Tom Algeo and Steve Holland for their significant contributions to this project. I am very grateful to those who assisted me in the field, including Susie Taha-McLaughlin, Eric Wysong, Alex Bartholomew, Pat McLaughlin, and Mike DeSantis. I am especially grateful to Brian Nicklen for his hard labor, support, and good company in Ontario. I would also like to thank James Bonelli for his continued assistance with statistical analysis. Thanks to my fellow grad students for their encouragement and friendship throughout this program, and also to the department as a whole for providing an intellectually stimulating, cordial working environment. Thanks to my family for their love and guidance throughout my education, particularly during the past two years of my Master’s. This research was funded by the University of Cincinnati Geology Department and the American Museum of Natural History Theodore Roosevelt Memorial Fund. iv TABLE OF CONTENTS Page ABSTRACT………………………………………………………………………………ii ACKNOWLEDGEMENTS……………………………………………………………...iv LIST OF FIGURES……………………………………………………………………...2 LIST OF TABLES……………………………………………………………………….5 LIST OF APPENDICES………………………………………………………………...6 INTRODUCTION………………………………………………………………………..7 GLOBAL LATE ORDOVICIAN MASS EXTINCTION………………………………12 STRATIGRAPHIC FRAMEWORK…………………………………………………...17 METHODS……………………………………………………………………………...38 Date collection………………………………………………………………….38 Date analysis…………………………………………………………………...40 RESULTS AND DISCUSSION……………………………………………………….45 Variations in faunal composition through space and time…………………45 Variations in abundance ratios of key taxa through space and time……..54 Variations in ecologic structure through space and time………………….78 Variations in genus richness through time………………………………….83 CONCLUSIONS……………………………………………………………………….86 REFERENCES…………………………………………………………………………88 APPENDIX I……………………………………………………………………………93 APPENDIX II………………………………………………………………………….122 1 LIST OF FIGURES Figure Page 1. Diagrammatic chart of the four sampled formations……………………….18 2. Map of the study area…………………………………………………………22 3. Stratigraphic column and outcrop photographs of the Drakes Formation, West Union, Ohio…...……………………………………………24 4. Stratigraphic column and photographs of the TST of the Drakes Formation, West Union, Ohio………………………………………………...25 5. Stratigraphic column and outcrop photographs of the Brassfield Formation, West Union, Ohio………………………………………………...27 6. Stratigraphic column and outcrop photographs of the Georgian Bay Formation, Oakville, Ontario………………………………………………….30 7. Photographs of EHST samples from the Georgian Bay Formation, Oakville, Ontario……………...………………………………………………..31 8. Photographs of sedimentary structures in the Cabot Head Formation, Hamilton, Ontario………………………………………………………………33 9. Stratigraphic column and outcrop photographs of the Cabot Head Formation at Chedoke Creek, Hamilton, Ontario…………………………..34 10. Stratigraphic column and outcrop photographs of the Cabot Head Formation at Mountain Brow Drive, Hamilton, Ontario…………………….35 11. Stratigraphic column and outcrop photographs of the Cabot Head Formation at Jolly Cut, Hamilton, Ontario…………………………………..36 12. Cluster analysis dendrogram of presence/absence data per locality……49 2 LIST OF FIGURES (continued) Figure Page 13. Two-dimensional MDS ordination of presence/absence data per locality…………………………………………………………………………..50 14. Cluster analysis dendrogram of presence/absence data per sample…...52 15. Two-dimensional MDS ordination of presence/absence data per sample………………………………………………………………………….53 16. Cluster analysis dendrogram of abundance data per sample with slab-counted data scaled to point count coverage…………………………56 17. Two-dimensional MDS ordination of abundance data per sample with slab-counted data scaled to point count coverage……………………57 18. Cluster analysis dendrogram of abundance data per sample based on equal weight between point and slab counts……………………………59 19. Two-dimensional MDS ordination of abundance data per sample based on equal weight between point and slab counts……………………60 20. Histograms showing average percent abundance of key families per cluster…………………………………………………………………………...64 21. Two-dimensional MDS ordination of abundance data from samples of the Drakes Formation, West Union, Ohio………………………………..66 22. Two-dimensional MDS ordination of abundance data from samples of the Georgian Bay Formation, Oakville, Ontario…………………………69 23. Two-dimensional MDS ordination of abundance data from samples of the Brassfield Formation, West Union, Ohio…………………………….70 3 LIST OF FIGURES (continued) Figure Page 24. Two-dimensional MDS ordination of abundance data from samples of the Cabot Head Formation, Hamilton, Ontario………………………….72 25. Two-dimensional MDS ordination from Ordovician samples……………75 26. Two-dimensional MDS ordination from Silurian samples…………………………………………………………………………77 27. Two-dimensional MDS ordination of samples represented by trophic group…………………………………………………………………...79 28. Histograms showing average percent abundance of key trophic groups per formation…………………………………………………………..82 29. Graphs showings number of genera versus number of specimens for rarefied data……………………………………………………………………84 4 LIST OF TABLES Table Page 1. Common genera categorized by trophic group membership……………..42 2. Number and percent of shared genera between each formation………...46 3. ANOSIM results showing relationships between formations in terms of faunal composition per sample……………………………………………55 4. ANOSIM results showing relationships between formations based on abundance data with equal weight between point and slab counts…..61 5. ANOSIM results showing relationships of formations divided into systems tracts comparing regions within each period……………………..67 6. ANOSIM results showing relationships of formations based on trophic structure………………………………………………………………..80 7. Comparison of the number of genera versus the number of specimens for Ordovician samples, Silurian samples, and each sampled formation………………………………………………………………………..84 5 LIST OF APPENDICES Appendix Page I. Raw abundance data……………………………………………………...93 II. Locality register…………………………………………………………..122 6 INTRODUCTION As one of the “Big Five” Phanerozoic mass extinctions (Sepkoski, 1995), the global nature of the Late Ordovician event has been studied extensively (e.g. Sheehan, 2001; Sheehan and Coorough, 1990; Sheehan, 1988; Berry, et al., 1995;Tuckey and Anstey, 1992; Berry and Boucot, 1973; Rong and Harper, 1988; Cocks, 1988; Brenchley, 1988; among others). However, in comparison with other mass extinction boundaries, there is a relative lack of research documenting local faunal transitions across the Ordovician-Silurian boundary. Based on qualitative assessment, it has been argued that the Late Ordovician extinction did not result in significant ecologic restructuring on a global scale (Droser et al., 1995, 1997, 2000). However, this concept is difficult to test on a local level, because of the lack of environmentally comparable sections across the boundary. In this context, the purpose of this study is to compare community-level faunal patterns among comparable environments in the pre- extinction versus post-extinction strata across the Ordovician-Silurian boundary. Various studies (e.g. Jablonski, 1998) have shown that local faunal patterns do not necessarily correspond to global trends, and, therefore, alpha- level studies may be of great importance