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Copyright by Tomas Neil Capaldi 2019 The Dissertation Committee for Tomas Neil Capaldi Certifies that this is the approved version of the following Dissertation: Stratigraphic response to Cordilleran Processes along the South Central Andean Margin Committee: Brian Horton, Supervisor Peter Flaig Mark Helper Ryan McKenzie Ronald Steel Daniel Stockli Stratigraphic response to Cordilleran Processes along the South Central Andean Margin by Tomas Neil Capaldi Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy The University of Texas at Austin AUGUST, 2019 Dedication This work is dedicated to the late Mavis Archer. She knew this was going to happen before any of us did. Acknowledgements There are many people to thank in inspiring and helping me through the challenging but rewarding years of my PhD. My drive to understand Earth's long and complicated history is thanks to Mike and the Creation Study group and their welcoming setting to deliberate Earth’s origin. I thank Sinan Akciz, Ray Ingersoll, Ed Rhodes, and An Yin for being supportive, imaginative mentors at UCLA, who pushed me to be the best scientist I could. Additionally, to all the 4th and 5th floor ESS grad students: Dallon Stang, Peter Haproff, Nate Brown, Kevin Coffey, Andrew Zuza, Robbin Zuza, Mike Lawson, Evan Wolf, John Merring, and Chris McGuirre and for all the roof top conversations, dark lab help, and tricking me into graduate school. My mapping partner Bill Pepper who got me through the Poleta summer. At Texas I was around some of the greatest people and minds who have built a community I am so lucky to be a part of. This includes thanking the Stratigraphy and Tectonics grad students Kelly Thomson, Emily Cooperdock, Cody Lee Colleps, Evan Ramos, Ben Smith, Jake Makis, Michelle Gevedon, Mike Prior, Nikki Seymour, Renas Koshnaw, Ben Cardenas, Spencer Semen, Nick Perez, Edgardo Pujols, Scott Eckley, Jasmin Mason, Cullen Kortyna, Carolyn Tewksbury-Christle, Peter Gold, Sam Robbins, Sol Cooperdock, Alissa Kotowski, Hima Gutipadi, and Adam Goldsmith, whose scientific debates at Double Dave’s and Crown shaped my PhD ideas. To the many excellent faculty, I interacted and taught with over all those summers, especially Mark Helper who has shown me how to me an effective teacher and leader. My committee members Ryan McKenzie, Danny Stockli, Peter Flaig, Ron Steel, and Mark Helper for letting me run wild with ideas but also for keeping me grounded and sane. I thank a thousand times over my academic sisters Meredith Bush, Kristina Butler, Amanda Calle, Sarah George, Gabby Gutierrez, Lily Jackson, and Chelsea Mackaman-Lofland for all the v help and conversations in Monday group meetings, at Growler, in Barbs, and on mountains. A special thanks to my advisor Brian Horton who gave me shot when no one else would, and showed me how to be a researcher, field geologist, writer, instructor, public speaker, but not a punker. I thank my family for all their love and always encouraging me to follow my passion. But none of this would have been possible without my better half Margo. She spent countless days helping me in the spooky sections, being a plasma whisperer, editing and reediting word docs, being my cheerleader, and traveling across the world with me. I will forever and always thank her for all her love. vi Abstract Stratigraphic response to Cordilleran Processes along the South Central Andean Margin Tomas Neil Capaldi, Ph.D. The University of Texas at Austin, 2019 Supervisor: Brian K. Horton Subduction zones along convergent plate margins are fundamental components of Earth systems that link mountain building, magmatism, lithospheric dynamics, surface processes, and climate-carbon cycles. Resolving the feedbacks and relationships among these components has been a longstanding challenge in Earth science with broad implications for understanding coupling among rheology, deformation, and erodibility. The sedimentary record within convergent systems provide a unique opportunity to understand long-lived Cordilleran processes between subduction, magmatism, erosion, sediment routing, and deposition. This dissertation investigates the Phanerozoic to present sedimentary record to address the dynamic interactions among Earth-surface processes and lithospheric processes throughout a complex tectonic history along the Andean Cordilleran margin of Argentina. Chapter 1 applies detrital zircon U-Th-Pb and Lu-Hf isotopic datasets as a powerful methods for evaluating long-term, regional geologic patterns and the processes of crustal addition, removal, and recycling to help resolve the onset of Andean subduction, and the vii relationships and feedbacks among upper-and lower-plate processes, and the timescales of Cordilleran evolution. A large Phanerozoic compilation of new and published zircon data provides new insights into how changes in the subducted lower-plate are fundamental drivers to magmatism composition, spatial patterns, and deformation. This chapter will be submitted to Geosphere with coauthors Ryan McKenzie, Brian Horton, Chelsea Mackaman-Lofland, and Daniel Stockli. Chapter 2 integrates field measurements with a large detrital geochronology datasets to establish a lithostratigraphic and chronostratigraphic record of Neogene Andean flat-slab subduction. Coeval cycles of upward coarsening stratigraphic trends, erosional unroofing, deformation, and magmatic high flux events provides new evidence of upper- plate Cordilleran feedbacks driven by changes in subduction regime. This chapter will be submitted to Tectonics with coauthors Brian Horton, Chelsea Mackaman-Lofland, Ryan McKenzie, Daniel Stockli, Gustavo Ortiz, and Patricia Alvarado. Chapter 3 uses detrital zircon from modern river sands to understand how landscapes respond to variation in bedrock erosion, structural setting, drainage network, and transport processes. This chapter provides new tools and geologic understandings to arm future researchers attempting to studying sedimentary provenance in convergent margins settings. This chapter was published in Earth and Planetary Science Letters in December, 2017 with coauthors Brian Horton, Ryan McKenzie, Daniel Stockli, and Margo Odlum. viii Table of Contents List of Tables ................................................................................................................... xiv List of Figures ....................................................................................................................xv CHAPTER 1: CORDILLERAN MAGMATISM AND GEODYNAMIC EVOLUTION OF THE WESTERN SOUTH AMERICAN PLATE MARGIN ..........1 ABSTRACT................................................................................................................1 INTRODUCTION ......................................................................................................2 GEOLOGIC FRAMEWORK .....................................................................................6 METHODOLOGIES ................................................................................................11 PHANEROZOIC MAGMATISM AND ASSOCIATED TECTONIC HISTORY ...........................................................................................................14 Cambrian-Ordovician Collision ....................................................................17 Carboniferous Ocean-Continent Convergence .............................................18 Permian-Triassic Subduction and Back-arc Extension .................................24 Jurassic to Present Continental Arc ..............................................................25 DISCUSSION ...........................................................................................................30 Andean Arc Tempo .......................................................................................30 Radiogenic Isotopic Trends ..........................................................................34 Subduction Angle..........................................................................................39 Plate Velocity ................................................................................................42 Andean Geodynamic processes ....................................................................43 CONCLUSIONS ......................................................................................................49 ix CHAPTER 2: NEOGENE RETROARC FORELAND BASIN EVOLUTION, SEDIMENT ROUTING, AND MAGMATISM IN RESPONSE TO FLAT-SLAB SUBDUCTION, WESTERN ARGENTINA ...............................................................52 ABSTRACT..............................................................................................................52 INTRODUCTION ....................................................................................................53 GEOLOGIC FRAMEWORK ...................................................................................57 ANDEAN RETROARC BASIN STRATIGRAPHY ...............................................61 Calingasta Hinterland Basin .........................................................................64 Basal Volcaniclastic and Volcanic unit C1 ..........................................64 Braided Fluvial Deposits in units C2, C3, and C4 ...............................65 Internally to externally drained basin: Unit C5....................................65 Precordillera Wedge-top Basins ...................................................................68