MAMMALIAN FAUNAL CHANGE DURING THE EARLY EOCENE CLIMATIC OPTIMUM (WASATCHIAN AND BRIDGERIAN) AT RAVEN RIDGE IN THE NORTHEASTERN UINTA BASIN, COLORADO AND UTAH by ALEXANDER R. DUTCHAK B.Sc., University of Alberta, 2002 M.Sc., University of Alberta, 2005 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Geological Sciences 2010 This thesis entitled: Mammalian faunal change during the Early Eocene Climatic Optimum (Wasatchian and Bridgerian) at Raven Ridge in the northeastern Uinta Basin, Colorado and Utah written by Alexander R. Dutchak has been approved for the Department of Geological Sciences ______________________________ Jaelyn J. Eberle (Supervisor) ______________________________ John Humphrey ______________________________ Mary Kraus ______________________________ Tom Marchitto ______________________________ Richard Stucky Date: ________________________ The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. ABSTRACT Dutchak, Alexander R. (Ph.D., Geological Sciences, Department of Geological Sciences) Mammalian faunal change during the Early Eocene Climatic Optimum (Wasatchian and Bridgerian) at Raven Ridge in the northeastern Uinta Basin, Colorado and Utah Thesis directed by Assistant Professor Jaelyn J. Eberle This project investigated patterns of mammalian faunal change at Raven Ridge, which straddles the Colorado-Utah border on the northeastern edge of the Uinta Basin and consists of intertonguing units of the fluvial Colton and lacustrine Green River Formations. Fossil vertebrate localities comprising >9,000 fossil mammal specimens from 62 genera in 34 families were identified and described. Included in this fauna are the index taxa Smilodectes, Omomys, Heptodon, and Lambdotherium, among others, which were used to biostratigraphically constrain the Raven Ridge strata as mid- Wasatchian (Wa3-5, ~53.5mya) through mid-Bridgerian (Br1b, ~48.5mya) in age. This time interval coincides with the Early Eocene Climatic Optimum (EECO), an extended interval of globally warm temperatures that is coincident with a large negative δ13C excursion. The onset, peak, and decline of the EECO at Raven Ridge were constrained by analyzing 197 sediment samples, collected from measured sections at Raven Ridge, for Total Organic Carbon (TOC) content and then chemostratigraphically correlating this data with established marine isotope curves. The Raven Ridge TOC data show a large negative carbon excursion that starts during the Wa6 biochron, peaks during the Wa7 biochron, and is followed by a positive excursion near the Wa-Br boundary. Results of the chemostratigraphic correlation are consistent with onset of the EECO at Raven Ridge iii occurring during the Wa6 biochron, the peak of the warm interval near the Wa-Br boundary, and the decline of the EECO during the Br1a and Br1b biochrons. Generic diversity of the mammalian fauna from Raven Ridge is relatively stable during the onset and peak of the EECO, with a sharp decline during the Br1b biochron. The relative abundance of arboreal taxa increases significantly during the EECO interval, which is consistent with the appearance of dense tropical forests in central North America during this period. This change in habitat structure is marked by an increase in abundance of omomyids primates and a decrease in abundance of terrestrial taxa such as Diacodexis and hyopsodontid ‘condylarths’. The results of this study show equivocal support of the hypothesized direct link between higher global temperatures and increased mammalian generic diversity during the Wa-Br transition, but are consistent with ecological restructuring associated with climate-driven habitat change. iv For all those who came before me, upon whose broad shoulders I stand, and for my wife, Melissa, with whom I look forward to sharing many new adventures. ACKNOWLDGMENTS Three people need to be mentioned as the primary influences on my career in paleontology. Firstly, my parents, whose unwavering support in all aspects of my life is a constant source of strength. Words are insufficient to adequately express my thanks for everything they have done for me. Secondly, my wife, Melissa, who bravely joined me on our Colorado adventure while leaving behind family, friends, and an established career. There isn’t a day that goes by when I don’t realize how lucky I am to have such an amazing woman by my side. I owe my advisor, Jaelyn Eberle, a debt of gratitude for providing me with the opportunity pursue my Ph.D. at the University of Colorado. Her thoughtful guidance and expertise in the field of mammalian paleontology have been excellent resources throughout the past five years. Similarly, my committee members have all gone out of their way to share their experience and provide guidance and feedback whenever called upon. In particular, John Humphrey provided his instruments, time, and expertise during some very long days and nights on the mass spec in Golden, and Richard Stucky shared his considerable expertise regarding mammalian faunal change during the Early Eocene Climatic Optimum while also showing me around the Wind River Basin. The Wind River camps with the Denver Museum crew were an immense amount of fun and I enjoyed getting to know the dozens of DMNS volunteers, Paul Rosen and the many Teen Science Scholars, and other specialists in the field including Brenda Chinnery-Allgeier, Deb Anderson, Amy Chew, and Henry Fricke. I owe apologies to my field assistants (Ben Burger, Laura Wilson, Sean Bryan, Ryan Nell, and Will Gelnaw) who helped measure section and collect fossils at Raven vi Ridge. Many of the days were obscenely hot and we were often set upon by countless insects. Hopefully the gorgeous scenery and random camp visits by pronghorn, elk, coyotes, golden eagles, and sheep (yes, woolly sheep are wandering about in northeastern Utah) helped distract them from the monotony of the Jacob staff. I hope they will remember the incredible views of storms on Dinosaur National Monument and the excellent food provided by the Bedrock Depot in Dinosaur, CO, and forget about my ill- fated attempts to cook for them. I was also lucky enough to spend time in the field with Gregg Gunnell and Bill Bartels at some of their South Pass, Wyoming sites. I thank them for sharing their time and expertise with me, and I thank Andrea Bair for introducing us in the first place. The laser ablation portion of this project would not have been possible without the generous assistance of Thure Cerling at the University of Utah and Ben Passey of Johns Hopkins University. Lindsay Mackenzie was kind enough to take time out from her studies at the University of Montana to drive down to Salt Lake City and act as my lab assistant for a week, and Don DeBlieux (and Beasie) housed us for the week. Naomi Levin and Ashley Ballantyne were kind enough to allow me to run some laser ablation test samples while they were collaborating on a separate project and their generosity in this aspect is greatly appreciated. Mimi Katz shared her marine geochemical dataset for the chemostratigraphic portion of this study, and for that she is thanked profusely. Dena Smith provided a great deal of statistical expertise and insight that was invaluable near the end of my degree while writing up the faunal analysis chapter of this project. Her energy and enthusiasm for my project is greatly appreciated. vii Toni Culver provided unflinching support for both me and my project from the first day I arrived right through to the end. Her willingness to go out of her way to help me in any way possible is gratefully acknowledged. Mary Dawson and Amy Henrici of the Carnegie Museum of Natural History were extremely helpful in providing me with their specimen data for the Powder Wash locality. My educational experience at CU was greatly enhanced by several outstanding instructors who helped me become a confident and competent geologist. These professors include Lang Farmer, Alexis Templeton, Mary Kraus, Tom Marchitto, Joe Smyth, and Karl Mueller. I also owe thanks to David Armstrong, Ned Friedman, and particularly Bert Covert for their time and efforts in EBIO and Anthropology classes. My graduate school experience was not completed in a vacuum. My fellow graduate students were sources of staunch support and valuable critiques throughout my time at CU. Ben Burger taught me a great deal about mammalian paleontology, both in the field and in the lab. He is a trusted friend and someone with whom I look forward to associating for many years to come. Laura Wilson has been a pillar of strength and an outstanding officemate, field assistant, and friend. I will miss our discussions regarding life, the universe, paleontology, and everything. I also thank Erin Leckey, Ian Sweeney, Sean Bryan, Walter Szeliga, Karen Lloyd, Nate Bradley, Lyndsay Ball, Wendy Schultz, and John Hankla for all that they, and in many cases their families, did for me during my stay. Financial support for this project was provided by the William H. Burt Fund from the CU Museum, a Shell Petroleum student research grant, The Evolving Earth Foundation, a Beverly Sears grant from the CU Graduate School, travel grants from the viii Department of Geological Sciences, the United Government of Graduate Students, and the Society of Vertebrate Paleontology, and the Graham L. Anderson Postgraduate Scholarship from Shawnigan Lake School. Finally, this project would not have been possible without the efforts of Peter Robinson and Kentaro Doi. Dr. Robinson identified and catalogued over half of the Raven Ridge specimens, and was the driving force behind the UCM’s collecting efforts in the Raven Ridge area. Peter also provided an immense amount of insight into previous work at Raven Ridge and was always willing to help when I came around with questions.