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EDIACARAN-CAMBRIAN STRATIGRAPHY and PALEONTOLOGY of WESTERN NEVADA and EASTERN CALIFORNIA DISSERTATION Presented in Partial Fulf

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EDIACARAN-CAMBRIAN STRATIGRAPHY and PALEONTOLOGY of WESTERN NEVADA and EASTERN CALIFORNIA DISSERTATION Presented in Partial Fulf EDIACARAN-CAMBRIAN STRATIGRAPHY AND PALEONTOLOGY OF WESTERN NEVADA AND EASTERN CALIFORNIA DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Soo Yeun Ahn Graduate Program in Geological Sciences The Ohio State University 2010 Dissertation Committee: Dr. Loren E. Babcock, Advisor Dr. William I. Ausich Dr. Matthew R. Saltzman Dr. Steven K. Lower ABSTRACT The Ediacaran-Cambrian transition was an important time span from both geologic and biologic perspectives. It was a time of dramatic evolutionary changes such as the diversification of early metazoans, the development of resistant skeletons in many taxa, and the escalation of prey-predator systems. In North America, the transition is well recorded in terminal Neoproterozoic to Cambrian strata of Esmeralda County, Nevada, and adjacent Inyo County, California. Strata recording this transition are the Deep Spring Formation (Ediacaran-Cambrian), and the Campito, Poleta, and Harkless formations (Cambrian). For many years the Deep Spring, Poleta, and Harkless formations were informally divided into mappable members. New, formal names are proposed for the members of these formations. In ascending order the new members are the Dunfee, Montezuma, and Gold Point members of the Deep Spring Formation; the Lida, Indian Springs, and Clayton members of the Poleta Formation; and the Weepah and Alkali members of the Harkless Formation. Two formal members of the Campito Formation, the Andrews Mountain Quartzite and the Montenegro Member, have long been recognized. The Deep Spring Formation and succeeding formations have the transition from a microorganism-dominated record to the more diverse and complex record of the Phanerozoic. Stromatolites are common in the Dunfee Member of the Deep Spring Formation, and fossilized microbial mats (―wrinkle structures‖) are present in siltstone ii layers of the Montezuma Member. Microbial mats or microbially stabilized substrates are inferred to be responsible for the fine preservation of Ediacaran trace fossils as well as sedimentary structures. In Cambrian strata, microbial related structures are mostly wrinkle structures and gas escape structures. Trace fossils have a trend toward increasing diversity, complexity, and abundance across the Ediacaran-Cambrian transition, although behavioral patterns are conserved. These changes parallel faunal changes across the same interval of strata. Trace fossils in the Ediacaran part of the Deep Spring Formation include Bergaueria, Palaeophycus, Planolites, and other simple resting, dwelling, and perhaps foraging traces. A new genus and species of trace fossil, Nevadichnos planum, is described from the Montezuma Member of the Deep Spring Formation. Cambrian trace fossils of the Nevada-California succession include Bergaueria, Monomorphichnus, Palaeophycus, Planolites, Rusophycus, and Treptichnus pedum. Although the morphologies of Cambrian tracemakers may have been different in the Cambrian than in the Ediacaran, the basic behavioral patterns of feeding and dwelling were already developed in the Ediacaran. Chalcopyrite and limonite commonly occur within burrows, especially in Planolites. Precipitation of these minerals is probably related to decay processes associated with biofilm development in burrows. iii ACKNOWLEDGMENTS I am very grateful for Loren Babcock‘s advice and guidance throughout my work and dissertation preparation. I thank William Ausich, Matthew Saltzman, and Steven Lower for helpful discussion and assistance with my work. I thank Margaret Rees, J. Stewart and Mary Hollingsworth, Adam English and Stephen Leslie for assistance with collecting of samples and providing stratigraphic advice. I also thank my friends in the School of Earth Sciences, and my family for their support during my work. I would like to acknowledge specially Alexa Sedlacek, Kate Tierney, and Alyssa Bancroft for all their support. Funding was provided through the Friends of Orton Hall Fund, the National Science Foundation (grants EAR-0073089, 0106883, awarded to Loren Babcock), and the Babcock Research Fund (School of Earth Sciences). iv VITA 2002................................................................B.S. Geology, Kyungpook National University, Korea 2004................................................................M.S. Geology, Kyungpook National University, Korea 2005 to present ..............................................Graduate Teaching Associate, School of Earth Sciences, The Ohio State University PUBLICATIONS Ahn, S. Y. and Lee. S. J., 2003. Meso-Neoproterozoic bacterial microfossils from the Sukhya Tunguska Formation of the Turukhansk Uplift, Russia. Geosciences Journal, 7: 227-236. Ahn, S. Y., and Babcock, L. E., 2009. Ediacaran-Cambrian transition reflected in trace fossils and sedimentary structures in Western Nevada - Eastern California. Geological Society of America Abstracts with Programs, vol. 41, no. 7, p. 293 Ahn, S. Y., Babcock, L. E., Rees, M. N., and Hollingsworth, J. S., 2009. Trace fossils from the Ediacaran-Cambrian transition in western Nevada: Behavioral holdovers from the terminal Neoproterozoic. Ninth North American Paleontological Convention Abstracts, p. 65-66. Babcock, L. E., Zhu, M. Y., and Ahn, S. Y., 2009. A possible sprigginid fossil from the Cambrian of China. Ninth North American Paleontological Convention Abstracts, p. 66-67. v Ahn, S. Y., Babcock, L.E., Rees, M. N., and Hollingsworth, J. S., 2008. Body and Trace Fossils from the Deep Spring Formation (Ediacaran), Western Nevada. Geological Society of America Abstracts with Programs, vol. 40, no. 6, p. 143 FIELD OF STUDY Major Field: Geological Sciences vi TABLE OF CONTENTS Abstracts ............................................................................................................................. ii Acknowledgments.............................................................................................................. iv Vita ...................................................................................................................................... v List of Figures .................................................................................................................... ix Chapters: 1. Introduction .................................................................................................................... 1 2. Ediacaran-Cambrian biostratigraphy of the southern Great Basin ................................. 9 3. Ediacaran-Cambrian Chemostratigraphy of the southern Great Basin ......................... 23 4. Ediacaran fossils and sedimentary structures from the Deep Spring Formation .......... 27 4. 1. Ediacaran fossils ................................................................................................... 27 4.2. Systematic paleontology: trace fossils from the Deep Spring Formation ............. 34 4.3. Sedimentary structures from the Deep Spring Formation ..................................... 37 5. Cambrian body fossils and trace fossils from the Deep Spring, Campito, Poleta, and Harkless formations ........................................................................................... 45 5.1. Paleontology of the Deep Spring Formation .......................................................... 47 5.1.1. Systematic paleontology: Cambrian trace fossils from the Deep Spring Formation ........................................................................................................ 47 vii 5.2. Paleontology of the Campito Formation .................................................................. 50 5.2.1. Systematic paleontology: body fossils from the Campito Formation .............. 51 5.2.2. Systematic paleontology: Trace fossils from the Campito Formation ............. 52 5.3. Paleontology of the Poleta Formation...................................................................... 55 5.3.1. Systematic paleontology: body fossils from the Poleta Formation ................. 56 5.3.2. Systematic paleontology: Trace fossils from the Poleta Formation ................ 59 5.4. Paleontology of the Harkless Formation.................................................................. 66 5.4.1. Trace fossils from the Harkless Formation ...................................................... 67 5.4.1.1. Planolites-Palaeophycus problem ............................................................. 67 5.4.1.2. Systematic paleontology: trace fossils from the Harkless Formation ....... 69 5.4.2. Sedimentary structures from the Harkless Formation ..................................... 80 6. Conclusions .................................................................................................................. 94 References ......................................................................................................................... 97 viii LIST OF FIGURES Figures 1. Locality map of the Ediacaran-Cambrian strata in western Nevada and eastern California ......................................................................................................... 7 2. Geologic time scale and a composite δ13C curve for the Cambrian system ................ 8 3. Regional correlation of the Ediacaran-Cambrian strata of the southern Great Basin 19 4. Generalized stratigraphic column of the Deep Spring Formation ............................. 20 5. Generalized stratigraphic column of the Poleta Formation ....................................... 21 6. Generalized stratigraphic column
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