Western Washington University Western CEDAR WWU Graduate School Collection WWU Graduate and Undergraduate Scholarship Summer 2016 Depositional Environments and Provenance of Early Paleogene Strata in the Huerfano Basin: Implications for Uplift of the Wet Mountains, Colorado, USA Dirk M. Rasmussen Western Washington University, [email protected] Follow this and additional works at: https://cedar.wwu.edu/wwuet Part of the Geology Commons Recommended Citation Rasmussen, Dirk M., "Depositional Environments and Provenance of Early Paleogene Strata in the Huerfano Basin: Implications for Uplift of the Wet Mountains, Colorado, USA" (2016). WWU Graduate School Collection. 536. https://cedar.wwu.edu/wwuet/536 This Masters Thesis is brought to you for free and open access by the WWU Graduate and Undergraduate Scholarship at Western CEDAR. It has been accepted for inclusion in WWU Graduate School Collection by an authorized administrator of Western CEDAR. For more information, please contact [email protected]. DEPOSITIONAL ENVIRONMENTS AND PROVENANCE OF EARLY PALEOGENE STRATA IN THE HUERFANO BASIN: IMPLICATIONS FOR UPLIFT OF THE WET MOUNTAINS, COLORADO, USA By Dirk M. Rasmussen Accepted in Partial Completion of the Requirements for the Degree Master of Science Kathleen L. Kitto, Dean of the Graduate School ADVISORY COMMITTEE Chair, Dr. Brady Foreman Dr. Bernard Housen Dr. Katie Snell MASTER’S THESIS In presenting this thesis in partial fulfillment of the requirements for a master’s degree at Western Washington University, I grant to Western Washington University the non-exclusive royalty-free right to archive, reproduce, distribute, and display the thesis in any and all forms, including electronic format, via any digital library mechanisms maintained by WWU. I represent and warrant this is my original work, and does not infringe or violate any rights of others. I warrant that I have obtained written permissions from the owner of any third party copyrighted material included in these files. I acknowledge that I retain ownership rights to the copyright of this work, including but not limited to the right to use all or part of this work in future works, such as articles or books. Library users are granted permission for individual, research and non-commercial reproduction of this work for educational purposes only. Any further digital posting of this document requires specific permission from the author. Any copying or publication of this thesis for commercial purposes, or for financial gain, is not allowed without my written permission. Dirk M. Rasmussen 27 May 2016 DEPOSITIONAL ENVIRONMENTS AND PROVENANCE OF EARLY PALEOGENE STRATA IN THE HUERFANO BASIN: IMPLICATIONS FOR UPLIFT OF THE WET MOUNTAINS, COLORADO, USA A Thesis Presented to The Faculty of Western Washington University In Partial Fulfillment of the Requirements for the Degree Master of Science By Dirk M. Rasmussen May 2016 ABSTRACT Sedimentary basins throughout the Western Interior of North America preserve a record of Late Cretaceous through latest Eocene sedimentation derived from flanking Laramide uplifts. In northern and western basins, the strata contain a well-documented proxy history of Laramide- style exhumation and climatic conditions within the region. However, the tectonic and climatic histories of more southerly basins, such as the Huerfano Basin studied herein, are comparatively underdeveloped despite being key in understanding the spatiotemporal evolution of Laramide tectonism and regional climatic gradients. This study addresses this issue and presents the first detailed lithofacies analysis and provenance analysis of the Poison Canyon, Cuchara, and Huerfano formations in the Huerfano Basin (south-central, Colorado, U.S.A.). We interpret a suite of alluvial sub-environments within these formations whose upsection variability and broad depositional patterns are similar to those observed in other early Paleogene successions in Laramide basins. Specifically, these features include deposition of organic-rich strata during the Paleocene; Eocene strata dominated by red-bed formation; and an anomalously coarse-grained intervening fluvial unit. The major difference in the Huerfano Basin compared to other Laramide basins is the exceptionally coarse-grained nature of all the units, which is likely related to its proximal position to Laramide ranges. Overall, the patterns are consistent with the widespread climatic shift between the wet, cooler Paleocene, and the drier, warmer, potentially more seasonal Eocene climate. As part of our provenance analysis, we characterized petrographic compositions of sand-bodies (N = 31 thin sections) and U–Pb detrital zircon age spectra (N = 848 age determinations) from fluvial sandstones within each of the three formations. The results indicate a new unroofing and source history for the sediment within the basin that contradicts previous hypotheses. Diagnostic zircon peaks at 516-517 Ma, 1423-1430 Ma, and 1678-1687 Ma show that sediment delivered to the Huerfano Basin did not originate in the San Luis Highlands or incipient Sangre de Cristo Mountains, but that the Precambrian crystalline core and associated Cambrian plutons of the Wet Mountains were exposed by the time Laramide deposition initiated in the basin. There are no provenance shifts upsection, indicating a largely stable or lithologically uniform sediment source from the Paleocene through at least ~51 Ma. This suggests the major changes in deposition are more likely related to tectonic and climatic conditions rather than lithologic controls on stratigraphic patterns. iv ACKNOWLEDGEMENTS This manuscript benefited from discussions with B. Housen, K. Snell, C. Siddoway, and H. Fricke. We thank M. Pecha and M. Ibanez-Mejia (MIT) for assistance at the University of Arizona LaserChron Facility. Thank you to B. Paulson for technical assistance at WWU while conducting lab work. WWU graduate students R. Morris, L. Heywood, and O. Anderson are thanked for their assistance improving petrographic results in this study. We thank WWU undergraduate students C. Curd, S. Holt, L. Gipson, and D. Burns for their assistance in the lab. The WWU Research-Writing Studio and L. Weiso are recognized for their aid in improving this manuscript. Funding was generously provided from the RMAG Foster Memorial Scholarship, AAPG Grants-in-Aid, GSA Graduate Research Grant, Colorado Scientific Society Grant, and internal research grants from Western Washington University. Thank you to Wolf Springs Ranch (Tom Redmond, Paulette Shapland, and ranch staff) for generously granting land access to conduct this research. Thank you B. Donovan for assistance completing fieldwork and continuous encouragement. v TABLE OF CONTENTS ABSTRACT .................................................................................................................................. iv ACKNOWLEDGEMENTS ......................................................................................................... v LIST OF FIGURES AND TABLES .......................................................................................... vii INTRODUCTION ........................................................................................................................ 1 GEOLOGIC SETTING ............................................................................................................... 3 Hinterland Geologic Setting ...................................................................................................... 4 Early Paleogene Deposition ....................................................................................................... 5 METHODS .................................................................................................................................... 9 Lithofacies Analysis ................................................................................................................... 9 Cobble Censuses and Sandstone Petrography ........................................................................ 10 Detrital Zircon Analysis ........................................................................................................... 11 RESULTS .................................................................................................................................... 12 Lithofacies Associations .......................................................................................................... 12 Poison Canyon Formation Coarse-grained Lithofacies .................................................. 13 Interpretations ................................................................................................................. 14 Poison Canyon Formation Fine-grained Lithofacies ....................................................... 16 Interpretations ................................................................................................................. 17 Cuchara Formation Coarse-grained Lithofacies ............................................................. 18 Interpretations ................................................................................................................. 19 Cuchara Formation Fine-grained Lithofacies .................................................................. 19 Interpretations ................................................................................................................. 20 Huerfano Formation Summary ......................................................................................... 21 Petrographic