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A CHEMOSTRATIGRAPHIC AND DETRITAL ZIRCON GEOCHRONOLOGICAL ANALYSIS OF UPPER CRETACEOUS STRATA: APPLICATIONS FOR DATING AND CORRELATING STRATA BY EDWARD MOREHOUSE Submitted to the graduate degree program in Geology and the Graduate Faculty of the University of Kansas in partial fulfillment of the requirements for the degree of Master of Arts. __________________________ Chairperson: Luis González __________________________ Mike Blum __________________________ Andreas Möller Date Defended: May 5 2015 The Thesis Committee for EDWARD MOREHOUSE certifies that this is the approved version of the following thesis: A CHEMOSTRATIGRAPHIC AND DETRITAL ZIRCON GEOCHRONOLOGICAL ANALYSIS OF UPPER CRETACEOUS STRATA: APPLICATIONS FOR DATING AND CORRELATING STRATA ______________________ Chairperson: Luis González Date approved: May 13 2015 ii ABSTRACT Rates of sedimentation, length of hiatus, temporal relationships and absolute age of strata are all difficult to determine in clastic non-marine and shallow marine environments due to their erosive and rapidly fluctuating depositional nature. High energy environmental conditions, erosion, and diagenesis make preservation of common chronological markers unlikely. Lack of chronological information results in the interpretation of sedimentation rates, length of hiatus/erosion, and genetic relationships based on chronological information obtained from strata bracketing the section of interest. Temporal relationships between strata and sequence stratigraphic interpretation can also be based on lithostratigraphic correlation to other dated sections. However, this can be highly unreliable when the lithological data is discontinuous, complex, or appearing homogeneous (e.g. shales or amalgamated sandstones). To provide chronostratigraphic control, this study demonstrates the utility of using high resolution organic 13 carbon (δ C OM) stable isotope chemostratigraphy to better understand the timing of fluvial and shallow marine siliciclastic successions from a 200m thick section of Mid-Campanian Mesaverde Group strata. Because recognizable changes in the carbon cycle can occur in the 10’s to 100’s of the years, organic carbon chemostratigraphy has the potential to precisely date individual strata at a resolution greater than is achievable with 87Sr/86Sr techniques. Constraining the organic carbon isotopic data using detrital zircon geochronology allows better understanding of the relative and absolute timing of major periods of deposition, as well as the temporal relationships between strata. The studied rock units include: The Grassy highstand sequence set and Desert lowstand sequence set of the Desert Member of the Blackhawk Formation, the Castlegate Sandstone, and the Buck Tongue of the Mancos Shale. iii Detrital zircon (U/Pb) radiometric and chemostratigraphic studies conducted east of Green River, Utah, reveal that the top of the Grassy highstand sequence set was deposited sometime between 76.9–77.2 ± 0.1 Ma. The Desert lowstand sequence set was deposited sometime between 76.2–76.9 ± 0.4 Ma. The lower Castlegate Sandstone was deposited sometime between 75.8–76.2 ± 0.4 Ma. The Buck Tongue of the Mancos Shale was deposited sometime between 75.2–75.8 ± 0.4 Ma. The Sego Sandstone was deposited at 73.3 ± 1.3 Ma. Duration of unconformities during lowstand incisional events is estimated to be 100–200 kyr based on global eustatic curves for the Campanian. iv ACKNOWLEDGEMENTS I am greatly indebted to Dr. Luis González for backing this project. This project would not have succeeded without his mentorship, encouragement, and financial support. This project would also not have been possible without Dr. Mike Blum. He has shared much of his time and expertise, provided access to the ExxonMobil Sego #2 core, and shared the detrital zircon dates. I am thankful to Dr. Diane Kamola for helping me in the field, and for taking time to share ideas. I also wish to thank my committee member, Dr. Andreas Möller for his encouragement, guidance in writing, and expertise. I would like to thank Greg Cane and the University of Kansas Keck Paleoenvironmental and Environmental Stable Isotope Laboratory for the chemostratigraphic analyses and support during 2014-2015. I am very thankful for KUEA support from the Roscoe G. Jackson III Graduate Research in Geology Scholarship, the Alice Mitchel Jackson Award, the Department of Geology at the University of Kansas, and my parents for their financial support. Field work would have taken several weeks without the hard work of Tucker Steen, Ty Tenpenny, and Matt Green, I am very grateful for their time. I am also deeply appreciative for the guidance in writing and the various expertise provided by Adam Jackson, Dr. Steve Hasiotis, Jeff Oalmann and Raymond Morehouse. Most of all, I thank my wife Jaylyn for supporting me through it all. I could not have done it without her love and encouragement. I would also like to thank my sons Briggs, Finn, and Max for being there for me even though I was gone so much. They gave me the motivation to finish strong. v Table of Contents ABSTRACT ..................................................................................................................................................... iii ACKNOWLEDGEMENTS ................................................................................................................................. v INTRODUCTION ............................................................................................................................................. 1 Geologic Setting ............................................................................................................................................ 3 Stratigraphy ................................................................................................................................................... 4 Prior Chronostratigraphic Work ................................................................................................................ 5 Sequence Stratigraphy .............................................................................................................................. 6 Alternative Interpretations ................................................................................................................... 7 High Resolution Chemostratigraphy and Detrital Zircon Geochronology .................................................... 8 METHODS .................................................................................................................................................... 12 Outcrop Studies ....................................................................................................................................... 12 Detrital Zircon Dating .............................................................................................................................. 13 Chemostratigraphy ................................................................................................................................. 14 RESULTS ...................................................................................................................................................... 16 ExxonMobil Sego #2 Research Core ........................................................................................................ 16 Stratigraphy ......................................................................................................................................... 16 Organic Carbon Chemostratigraphy ................................................................................................... 17 TOC and % Carbonate ......................................................................................................................... 18 Thompson Canyon ................................................................................................................................... 19 Stratigraphy ......................................................................................................................................... 19 Organic Carbon Chemostratigraphy ................................................................................................... 19 TOC and % Carbonate ......................................................................................................................... 20 Blaze Canyon ........................................................................................................................................... 21 Stratigraphy ......................................................................................................................................... 21 Chemostratigraphy ............................................................................................................................. 21 TOC and % Carbonate ......................................................................................................................... 22 Tusher Canyon ......................................................................................................................................... 22 Detrital Zircon Dating .............................................................................................................................. 23 Detrital Zircon MDAs ............................................................................................................................... 23 Grassy LSF of the Desert Member of the Blackhawk Formation ......................................................... 23 vi Desert FLV of