Mesozoic Tectonics of the Maria Fold and Thrust Belt and Mccoy Basin : an Examination of Polyphase Deformation and Synorogenic Response Anthony C
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University of New Mexico UNM Digital Repository Earth and Planetary Sciences ETDs Electronic Theses and Dissertations 8-27-2009 Mesozoic tectonics of the Maria fold and thrust belt and McCoy basin : an examination of polyphase deformation and synorogenic response Anthony C. Salem Follow this and additional works at: https://digitalrepository.unm.edu/eps_etds Recommended Citation Salem, Anthony C.. "Mesozoic tectonics of the Maria fold and thrust belt and McCoy basin : an examination of polyphase deformation and synorogenic response." (2009). https://digitalrepository.unm.edu/eps_etds/75 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]. MESOZOIC TECTONICS OF THE MARIA FOLD AND THRUST BELT AND MCCOY BASIN, SOUTHEASTERN CALIFORNIA: AN EXAMINATION OF POLYPHASE DEFORMATION AND SYNOROGENIC RESPONSE BY ANTHONY CHRISTOPHER SALEM B.S., Arizona State University, 1999 M.S.., Geological Sciences, Arizona State University, 2005 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Earth & Planetary Sciences The University of New Mexico Albuquerque, New Mexico August, 2009 ©2009, Anthony C. Salem iii DEDICATION For Audrey, my best friend, chief advisor, drill sergeant, sounding board, editor extraordinaire, GIS wizard, partner in crime and great love. Without her love and support, life and this work would have been a lonely endeavor. iv ACKNOWLEDGMENTS All the work that goes into conducting research and writing a dissertation may be indeed done by one person, but is actually the result of the efforts and support of many people who should be acknowledged. First of all, I would like to thank Karl Karlstrom, my dissertation advisor. Through his interactive and engaging style of advisement, his broad manner of thinking about geology, especially the disciplines of structural geology and tectonics, his seemingly never-ending supply of energy, enthusiasm and ideas and his high expectations, he challenged me to become a better geoscientist and encouraged me to bring out as much as I could about the geology of this interesting part of the Cordillera. He has been a great mentor and good friend. I would also like to thank Steve Reynolds from Arizona State University, who introduced me to the geology of the Maria Fold and Thrust Belt and was advisor for my master’s thesis. I would not have made it this far without his initial encouragement and continued guidance and support throughout my studies. Thanks to the support of the rest of my dissertation committee: Yemane Asmerom and Lou Scuderi, and Tom Hoisch from Northern Arizona University, for their support, guidance and discussions. Thanks to Barry Kues for serving as outside examiner for my comprehensive exams. Special thanks to Jeff Geier and Bryan MacFarlane, for their many hours of help in the field, discussion and idea exchanges, map compilation and friendship. Special thanks also to Laurie Crossey for her kindness, warmth, help in the field and excellent photography. Thanks to Hope Johnston, Mark Tyra, David Haddad, Ryan Crow, Magdalena Sandoval and Austin Zinnser for their help in the field. Matt Heizler, Lisa Peters and Josh Feldman assisted greatly with Ar-Ar geochronology; Matt in particular deserves special thanks for all his help with obtaining and reporting Ar-Ar hornblende and biotite ages for this study. George Gehrels and the rest of Arizona LaserChron lab crew at the University of Arizona Tucson deserve thanks for making available the Laser Ablation ICP-MS facility at UA and assisting me with all stages of data collection and analyses in obtaining and reporting U-Pb zircon ages. This dissertation benefited from discussions with Paul Stone, Carl Jacobson, Dick Tosdal and Jon Spencer about the geology of the Maria Fold and Thrust Belt and McCoy Basin. Thanks to the Department of Earth & Planetary Sciences at UNM for giving me a place to work and providing financial support for my time here. Cindy Jaramillo and the rest of the office staff in the department never receive enough gratitude for helping me and my colleagues navigate the UNM bureaucracy. Finally, thanks go to my friends and family, especially my parents, Jim and Phyllis Salem, my sisters Shelley Pajak, Dana Salem-Silva and Theresa Thornburgh, my brother Marc Salem, my stepdaughter Rebecca Hamilton and my stepson Ali Al-Ali for all their love, support and patience during these past four years. Financial support provided by the National Science Foundation (NSF GK-12 EMRGE program grant EHR-0538396 to L.J. Crossey and S. Collins, the Geological Society of America (GSA Student Research Grant, 2008 to Salem). K. Karlstrom and the Department of Earth Planetary Sciences at UNM aided in funding presented research. v MESOZOIC TECTONIC OF THE MARIA FOLD AND THRUST BELT AND MCCOY BASIN, SOUTHEASTERN CALIFORNIA: AN EXAMINATION OF POLYPHASE DEFORMATION AND SYNOROGENIC RESPONSE BY ANTHONY CHRISTOPHER SALEM ABSTRACT OF 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 August 2009 Mesozoic tectonics of the Maria Fold and Thrust Belt and McCoy Basin: An examination of polyphase deformation and synorogenic response by Anthony Christopher Salem B.S., Business, Arizona State University, 1999 M.S., Geological Sciences, Arizona State University, 2005 Ph.D., Earth and Planetary Sciences, University of New Mexico, 2009 ABSTRACT Here we summarize all current knowledge about the Maria Fold and Thrust Belt and McCoy Basin tectonic provinces of southeastern California. We also present new geologic mapping, structural analysis from macroscopic to microscopic scale, U-Pb zircon ages and Ar-Ar hornblende and biotite ages from key areas in the Maria Fold and Thrust Belt and McCoy Basin to resolve kinematics and timing of polyphase deformation events related to the Mesozoic Cordilleran Orogeny in southeastern California. The Maria Fold and Thrust Belt (MFTB) is an east-west trending belt of amphibolite grade metamorphic rocks characterized by largely south-vergent folds and ductile shear zones that place Jurassic and Proterozoic crystalline rocks over Paleozoic and Mesozoic sedimentary and volcanic rocks correlative to strata observed on the Colorado Plateau and in southeastern Arizona. Rocks in the MFTB have undergone polyphase ductile deformation and high grade metamorphism. The McCoy Basin trends subparallel with the MFTB and is defined by exposures of Jurassic-Cretaceous McCoy vii Mountains Formation, a > 7 km thick siliciclastic wedge of sandstone, siltstone and conglomerate. In contrast with the MFTB, rocks in the McCoy Basin have undergone primarily brittle deformation and have undergone low grade regional metamorphism. Important questions remain regarding the tectonic evolution of these two tectonic provinces, the relationship of these two provinces to each other and their relationship to the Cordillera at large. Resolving kinematics and timing of polyphase deformation in the MFTB and assessing synorogenic response in the McCoy Basin using established and new methods of structural geology and geochronology will resolve these questions and illuminate fundamental geologic processes related to orogenesis. This dissertation is divided into three chapters, with the goal of assessing kinematics and timing of deformation in the MFTB and McCoy Basin. A general encompassing hypothesis for investigations is that sedimentation and later deformation of rocks in the McCoy Basin can be directly linked to Mesozoic polyphase deformation in the MFTB. Structural analysis of key areas shows that there are three deformation events in the MFTB-McCoy Basin region. D1 is characterized by initially subrecumbent isoclinal folds and shear zones and a north-dipping foliation designated S1. D2 is characterized by mesoscopic and macroscopic southwest-facing isoclinal folds that refold S1 and shear zones that imbricate and severely attenuate Paleozoic and Mesozoic strata (to less than 1% of original stratigraphic thickness). Analysis of kinematic indicators including elongate mineral lineation, stretched pebbles and concretions and microstructural textures indicates that D1 and D2 represent two stages of a single progressive deformation event formed by top-to-the-southeast-directed reverse and dextral shear. A diorite deformed by D1/D2 yields an U-Pb zircon age of 86.3 ± 1.3 Ma, indicating that D1/D2 represents Late viii Cretaceous deformation. Published detrital zircon ages indicate that sedimentation in the McCoy Basin was coeval with middle crustal deformation in the MFTB. Kinematics of D1/D2 suggests that this event is related to the Sevier Orogeny and timing of deformation is consistent with other regional studies. The tectonic setting of the McCoy Basin is interpreted to have evolved from a broad Late Jurassic-Early Cretaceous rift valley to a Late Cretaceous retroarc foreland basin. The geometry of the early rift basin placed important structural controls on the geometric and spatial configurations of the Late Cretaceous MFTB and McCoy Basin. D3 is characterized by northeast-vergent folds and shear zones and is coeval with emplacement of Late Cretaceous (79-67 Ma) granites and pegmatites, which crosscut D1/D2 fabrics. Strain