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Sedimentation, Pedogenesis, and Paleoclimate Conditions in the Paleocene San Juan Basin, New Mexico, U.S.A

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University of New Mexico UNM Digital Repository Earth and Planetary Sciences ETDs Electronic Theses and Dissertations 7-1-2016 Sedimentation, pedogenesis, and paleoclimate conditions in the Paleocene San Juan Basin, New Mexico, U.S.A. Kevin Hobbs Follow this and additional works at: https://digitalrepository.unm.edu/eps_etds Recommended Citation Hobbs, Kevin. "Sedimentation, pedogenesis, and paleoclimate conditions in the Paleocene San Juan Basin, New Mexico, U.S.A.." (2016). https://digitalrepository.unm.edu/eps_etds/104 This Dissertation is brought to you for free and open access by the Electronic Theses and Dissertations at UNM Digital Repository. It has been accepted for inclusion in Earth and Planetary Sciences ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. Kevin Michael Hobbs Candidate Earth and Planetary Sciences Department This dissertation is approved, and it is acceptable in quality and form for publication: Approved by the Dissertation Committee: Dr. Peter Fawcett, Chairperson Dr. Leslie McFadden Dr. Gary Weissmann Dr. Thomas Williamson i SEDIMENTATION, PEDOGENESIS, AND PALEOCLIMATE CONDITIONS IN THE PALEOCENE SAN JUAN BASIN, NEW MEXICO, U.S.A. by KEVIN MICHAEL HOBBS B.S., Geology, The University of the South, 2006 M.S., Geological Sciences, The University of Idaho, 2010 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Earth and Planetary Sciences The University of New Mexico Albuquerque, New Mexico July 2016 ii ACKNOWLEDMENTS I thank the following persons for professional help in the form of discussions, critique of ideas, or suggestions during the research and writing of this dissertation: From the Earth and Planetary Sciences Department: Viorel Atudorei, Adrian Brearley, Ben Burnett, Jeff Carritt, Laura Crossey, Magdalena Donahue, Maya Elrick, John Geissmann, Nick George, Karl Karlstrom, Bekah Levine, Grant Meyer, Corrinne Myers, Lyman Persico, Jane Selverstone, Zach Sharp, Mike Spilde. From the University of the South: Karen Kuers, Nicole Nunley, Bran Potter, Steve Shaver, Sarah Sherwood, Ken Smith, Scott Torreano. From farther afield: Tim Gallagher, Judy Parrish, Leighton Reid, Tom Williams. I thank committee member Tom Williamson of the New Mexico Museum of Natural History and Science for introducing me to many of the San Juan Basin field sites described herein and for his patience in my slow acquisition of the basin’s complexities. I thank my UNM EPS committee members Peter Fawcett, Les McFadden, and Gary Weissmann for suggestions, discussion, and critique of ideas that helped to improve this work. I thank my family: Rachel Hobbs for her support, love, and encouragement during a program of study that seemed to have no end and for reminding me that it did; Labrador retriever Cocoa for her companionship and devotion during field work; and Rio Grande rathound Scruffy for providing constant good cheer, excitement, and humor. Funding for these studies came from the University of New Mexico Graduate and Professional Student Association, the Colorado Scientific Society, and the Earth and Planetary Sciences Department. iii SEDIMENTATION, PEDOGENESIS, AND PALEOCLIMATE CONDITIONS IN THE PALEOCENE SAN JUAN BASIN, NEW MEXICO, U.S.A. by Kevin Michael Hobbs B.S., Geology, The University of the South, 2006 M.S., Geological Sciences, The University of Idaho, 2010 Ph.D., Earth and Planetary Sciences, The University of New Mexico, 2016 ABSTRACT This dissertation follows the hybrid format as defined by the Office of Graduate Studies at the University of New Mexico. The three chapters herein were prepared as manuscripts to be submitted for publication to peer-reviewed journals in the field of Earth sciences. Chapter 1 will be submitted to New Mexico Geology. Chapter 2 will be submitted to Geology. Chapter 3 will be submitted to the Geological Society of America Bulletin. The main theme of these works is an exploration of paleoenvironmental conditions recorded in the Paleocene siliciclastic sediments of the San Juan Basin, northwestern New Mexico. Chapter 1 is an investigation of the lithologic and stratigraphic properties of Cretaceous and Paleogene terrestrial siliciclastic rock units in the San Juan Basin. I used petrography, stratigraphy, and geochemistry to show that marked changes occurred in sedimentation styles, sedimentary sources, and regional landscape evolution in the study area during the Laramide Orogeny and that these changes caused observable trends in San Juan Basin rocks. Chapter 2 explores the enigmatic silcretes of the Nacimiento Formation. My work shows that these silcretes represent a product of silica diagenesis that cannot be explained using currently accepted iv models of silcrete genesis and that significant accumulation of volcanic ash occurred in the Paleocene San Juan Basin. Chapter 3 is an exploration of the paleosols preserved in the Nacimiento Formation. This work shows that widely used methods of estimating paleoclimate conditions based upon the geochemical composition of paleosols will produce inaccurate estimates in many realistic sedimentary basin environments. The major properties of Nacimiento Formation paleosols appear to be controlled by non- climate factors. I show that the evolution of a fluvial system can explain the observed trends. v Table of Contents ACKNOWLEDMENTS .................................................................................................... iii ABSTRACT ....................................................................................................................... iv EPIGRAPH ........................................................................................................................ ix Chapter 1 ............................................................................................................................. 1 Ojo Alamo Sandstone: New interpretations of its sedimentologic and tectonic significance ......................................................................................................................... 1 ABSTRACT .................................................................................................................... 1 INTRODUCTION ........................................................................................................... 2 Geologic Setting .......................................................................................................... 5 Previous Work ............................................................................................................. 6 METHODS...................................................................................................................... 9 RESULTS...................................................................................................................... 10 The Ojo Alamo Sandstone ......................................................................................... 10 Descriptions of Ojo Alamo Sandstone Facies ........................................................... 11 Sedimentary Architecture .......................................................................................... 15 Sandstone Petrography .............................................................................................. 15 Geochemical Analyses .............................................................................................. 17 INTERPRETATIONS ................................................................................................... 17 Changing Sediment Sources Across K-Pg Boundary................................................ 17 Regional Landscape Evolution Recorded in SJB K-Pg Deposits.............................. 20 Avulsion and Preservation During Ojo Alamo Sandstone Deposition...................... 22 CONCLUSIONS ........................................................................................................... 27 REFERENCES CITED ................................................................................................. 30 FIGURES ...................................................................................................................... 42 TABLES ........................................................................................................................ 61 Chapter 2 ........................................................................................................................... 64 Pyroclastic silcretes in the Paleocene Nacimiento Formation, New Mexico: a new genetic origin for silcretes ................................................................................................. 64 ABSTRACT .................................................................................................................. 64 INTRODUCTION ......................................................................................................... 65 THE NACIMIENTO FORMATION ............................................................................ 67 METHODS.................................................................................................................... 69 vi RESULTS...................................................................................................................... 70 DISCUSSION ............................................................................................................... 72 Volcanic Origin for NFm Silcretes ............................................................................ 72 NFm Silcrete
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