Post-Tectonic Landscape Evolution of Sedimentary Basins in Southeastern Arizona and Northern Chile by Matthew Cross Jungers A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Approved July 2014 by the Graduate Supervisory Committee: Arjun Heimsath, Chair Kelin Whipple Ramon Arrowsmith Enrique Vivoni Duane DeVecchio ARIZONA STATE UNIVERSITY August 2014 ABSTRACT Sedimentary basins are defined by extensional tectonics. Rugged mountain ranges stand in stark relief adjacent to muted structural basins filled with sediment. In simplest terms, this topography is the result of ranges uplifted along normal faults, and this uplift drives erosion within upland drainages, shedding sediment into subsiding basins. In southeastern Arizona's Basin and Range province extensional tectonics waned at approximately 3-5 Myr, and the region's structural basins began transitioning from internal to external drainage, forming the modern Gila River fluvial network. In the Atacama Desert of northern Chile, some basins of the Central Depression remain internally drained while others have integrated to the Pacific Ocean. In northern Chile, rates of landscape evolution are some of the slowest on Earth due to the region’s hyperarid climate. While the magnitude of upland erosion driven by extensional tectonics is largely recorded in the stratigraphy of the structural basins, the landscape's response to post-tectonic forcings is unknown. I employ the full suite of modern geomorphic tools provided by terrestrial cosmogenic nuclides – surface exposure dating, conventional burial dating, isochron burial dating, quantifying millennial-scale upland erosion rates using detrital TCN, quantifying paleo-erosion rates using multiple TCN such as 21 Ne/ 10 Be and 26 Al/ 10 Be, and assessing sediment recycling and complex exposure using multiple TCN – to quantify the rates of landscape evolution in southeastern Arizona and northern Chile during the Late Cenozoic. In Arizona, I also use modern remnants of the pre-incision landscape and digital terrain analyses to reconstruct the landscape, allowing the quantification of incision and erosion rates that supplement detrital TCN-derived erosion rates. A new chronology for key basin high stand remnants (Frye Mesa) and a flight of Gila River terraces in Safford basin provides i a record of incision rates from the Pliocene through the Quaternary, and I assess how significantly regional incision is driving erosion rates. Paired nuclide analyses in the Atacama Desert of northern Chile reveal complex exposure histories resulting from several rounds of transport and burial by fluvial systems. These results support a growing understanding that geomorphic processes in the Atacama Desert are more active than previously thought despite the region’s hyperarid climate. ii DEDICATION To Jeff Kellogg A man who understood rivers better than anybody… iii ACKNOWLEDGMENTS I could not have gotten to the starting line of this project without the guidance of my past mentors and friends David Dethier and Paul Bierman. They both played huge roles in helping me become the scientist that I am today, and they have never stopped encouraging me and offering advice. I am very happy that I can add Arjun Heimsath to that list of scientific mentors and friends that pushed me professionally and offered support at the right times. Each meeting with Arjun during my first year at Arizona State University, he encouraged me to think bigger and find something that truly inspired me. That is a lesson I will never forget. Then there was that time that he said I just had to check out these incredible surfaces near Safford, AZ… The rest of my committee has also helped along the way. Kelin Whipple always manages to ask the next hard question. Ramon Arrowsmith took me on a whirlwind tour of the greater Salt River basin in the summer of 2009, and really got me started thinking about ‘life after faulting’ in Arizona. Enrique Vivoni always had great insight and a kind word during the hard times when the elevators seemed like the only thing working properly in ISTB4. Phil Christensen remains as an honorary committee member and always helped me keep my dissertation in perspective. Duane DeVecchio was quick to step in and offer his eye to this project, and his enthusiasm and engaging questions were invigorating at the end. Ronald Amundson believed in me enough to bring me along to Chile in 2009 and subsequent field seasons. I do not know whether I am more inspired by Ron’s sharp intelligence or his remarkable humility and kindness. I truly value my collaborations with Ron. iv I got into this whole mess with Wendy Bohon and Matt Rossi, and we’re getting out of it at just about the same time. I couldn’t have asked for a better cadre. Roman DiBiase and Byron Adams provided an incredibly high standard to strive for from day one, and I’m lucky to call them colleagues and friends. The same goes for the rest of the broader Whipsath crew, with special appreciation for Erin DiMaggio, Marina Foster, Andy Darling, and Scott Robinson. I would still be stuck in some inefficient loop without Allen McNamara’s guidance in Numerical Methods. One of the best courses I have ever had the pleasure to take. Conversations and help in the field from Arizona Geological Survey geologists Phil Pearthree, Joe Cook, Ann Youberg, and Mike Conway were revitalizing and helped reassure me that all this hard work was worth it. Arizona is a special place, and southeastern Arizona is the crown jewel in my humble opinion. Greg Balco and Dave Shuster were great hosts during my time at the Berkeley Geochronology Center, and they remain great collaborators. I would like to thank the fraction of my friends and family who realize that getting a PhD is quite different from ‘still being in college’. Kolee has been my best and most reliable field assistant from my earliest trips to Safford, Sonoita, Winkelman, Klondyke, etc. She was always game to get out for the weekend and camp while I tried to get my head around this project, and she developed a keen eye for quartz. I love you more than anything, Kolee. Thank you for your unflagging support. v TABLE OF CONTENTS Page LIST OF TABLES ............................................................................................................................... x LIST OF FIGURES ........................................................................................................................... xi PREFACE........... ............................................................................................................................... xiii CHAPTER 1 INTRODUCTION........... ...................................................................................................... 1 Motivation........... .......................................................................................................... 1 Chapter Outline........... ................................................................................................ 4 References........... .......................................................................................................... 8 Figure Caption........... ................................................................................................. 10 Figure........... ................................................................................................................ 10 2 ACTIVE EROSION-DEPOSITION CYCLES IN THE HYPERARID ATACAMA DESERT OF NORTHERN CHILE........... ......................................................... 11 Abstract........... ............................................................................................................ 12 Introduction........... ..................................................................................................... 13 Methods....................................................................................................................... 17 Results and Discussion........... .................................................................................. 20 Conclusions........... ..................................................................................................... 27 Acknowledgements.......... ......................................................................................... 29 References........... ........................................................................................................ 30 Table........... ................................................................................................................. 34 Figure Captions........... ............................................................................................... 35 vi CHAPTER Page Figures........... .............................................................................................................. 38 3 COMPLEX EXPOSURE HISTORIES IN ALLUVIAL DEPOSITS OF THE ATACAMA DESERT, NORTHERN CHILE…………………………........ 45 Abstract........... ............................................................................................................ 45 Introduction and Motivation ................................................................................... 46 Background........... ...................................................................................................... 48 Methods....................................................................................................................... 55 Results........... .............................................................................................................