On the Manifestation of Deformation and Evolution of Two Cenozoic Orogens
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AN ABSTRACT OF THE DISSERTATION OF Ellen A. Lamont for the degree of Doctor of Philosophy in Geology presented on May 25, 2021 Title: On the Manifestation of Deformation and Evolution of Two Cenozoic Orogens Abstract approved: _____________________________________________________ Andrew J. Meigs The word orogenesis is derived from the Greek words oros meaning mountains and genesis meaning creation and refers to the study of the complex processes involved in the growth and evolution of mountain ranges (orogens). Orogens develop where crustal deformation builds topography and forms landscapes. This dissertation explores the role of structural deformation in two Cenozoic orogens, the NW Himalaya and the Oregon Cascades - Cenozoic mountain belts that offer well preserved records of orogenic processes and deformation in the landscape. Chapter 1 introduces orogenesis, discusses the role of faulting in deformation, presents key unknowns, and lays out what to expect in subsequent chapters. Chapters 2 and 3 investigate the spatial and temporal evolution of the NW sub-Himalayan mountain belt from the Pliocene (~5 Ma) to the present in the context of a widely accepted model for orogenesis. These chapters characterize the spatial and temporal growth of the NW-Himalaya by integrating new geologic mapping, balanced cross-sections, detrital apatite (U-Th)/He analyses and thermal history modeling with published structural and stratigraphic data. Chapter 4 considers the role of faulting in the development of subsurface permeability and the localization of magmatism and geothermal resources in the Oregon Cascade arc-backarc region. This chapter combines new, high-resolution fault trace mapping, published estimates of regional stress, and new modeling to assess the likelihood, or tendency, for a fault to slip or dilate in the modern stress field. Chapter 5 highlights the main findings of each chapter and discusses the broader implications for the deformation and evolution of two Cenozoic mountain belts. © Copyright by Ellen A. Lamont May 25, 2021 All Rights Reserved On the Manifestation of Deformation and Evolution of Two Cenozoic Orogens by Ellen A. Lamont A DISSERTATION submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Presented May 25, 2021 Commencement June 2021 Doctor of Philosophy dissertation of Ellen A. Lamont presented on May 25, 2021 APPROVED: Major Professor, representing Geology Dean of the College of Earth, Ocean, and Atmospheric Science Dean of the Graduate School I understand that my dissertation will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my dissertation to any reader upon request. Ellen A. Lamont, Author ACKNOWLEDGEMENTS To my advisor, Andrew Meigs: it takes a special person to patiently and diligently nurture the growth of another person; to take their hopes and dreams and help them make it a reality. But it takes an exceptional personality to take on that responsibility with gusto, to selflessly mentor another for that person’s betterment alone, and to do it with an unwavering sense of loyalty. A simple thank you could never be enough to express the tremendous impact you have had on my life, not to mention the countless others before me and those yet to come. While my journey has been full of ups and downs, you have been my greatest cheerleader, mentor, friend, and colleague along the way. You have taught me how to be an excellent leader, role model and scientist, and I could only hope to one day be as equally ‘bullet proof’ as you. You have my most humble gratitude and upmost respect. Thank you for believing in me. I sincerely wish to thank the incredible support community I’ve developed over my tenure at OSU. To my committee members Jessica Creveling, Frank Sousa, Rob Harris, Eric Kirby, and my GCR Mike Olson: thank you for your patience, guidance, and support. I’m thankful for the opportunity to have worked with each of you. You have always been willing to set aside time to help me grow as a scientist. I’ve learned so much. To the STAG community: what an incredible journey we have all been on together these last 6-years. Given this crazy rollercoaster ride called graduate school, I never would have made it through without your ready shoulders to cry on, many laughs to share, brains for the picking, and friendships to be made. I especially want to thank the STAG ladies, Danielle Woodring, Israporn (Grace) Sethanant, Marina Marcelli, MacKenzie Mark-Mozer, Sami Cargill, and Katie Worms, plus JC and Nicole Rocco. You have all become the closest and most supportive group of friends I’ve ever had; I look forward to taking over the world with you. To the student services staff – Lori Hartline and Robert Allan: the two of you are the heart of graduate student success. Thank you for always keeping our best interest at the forefront of all you do. Most important of all, a major shout out goes to my natural and elected family for always having my back. Thanks for insisting that I go to college, encouraging me to explore the world, and to strive to greater things. Thank you for providing me with every opportunity within your power and for the sacrifices made on my behalf. I hope I’ve made you proud. Dan, you are the reason I started this journey; I am eternally grateful. Siddarth ji, thanks for being the reason I finished. Cheers to the future. I love all of you dearly. The work for Chapters 2 and 3 is made possible by the generous support of the USIEF Fulbright-Nehru Research Fellowship in collaboration with the Wadia Institute of Himalayan Geology, Dehradun, India; the GSA - Awards for Geochronology Student Research (AGeS2) Program in collaboration with the CU-TRaIL group at the University of Colorado-Boulder; and the German Academic Exchange Service (DAAD) – Short-term Research Fellowship Program in collaboration with the Low-Temperature Thermochronology Group at the University of Potsdam, Germany. These projects are further funded by National Science Foundation (EAR- 1759200 and EAR-1759353), the Ryoichi Sasakawa Young Leaders (SLYFF) Fellowship fund, the GSA Graduate Student Research Grant Program, and the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University. Thank you Aravind A, Perumal, and the Wadia directors for facilitating my research activities. Support for Chapter 4 comes from the U.S. Department of Energy (DE-EEO006727) as part of a larger collaboration between Oregon State University, the University of Utah, and the Lawrence Berkeley National Laboratory. CONTRIBUTION OF AUTHORS 1 Aravind Anilkumar, doctoral candidate in Geology at the Wadia Institute of Himalayan Geology, Department of Structure & Tectonics assisted with field logistics, digital and field mapping, data and sample collection for work presented in Chapters 2 and 3. 2 Rebecca Flowers, professor of Geology at the University of Colorado-Boulder, Department of Geological Sciences co-trained me in the apatite (U-Th)/He dating technique, through the NSF-GSA AGeS grant program. Dr. Flowers also assisted with data analysis and interpretation and related methods written content central to Chapters 2 and 3. 3 Jayangondaperumal, Scientist-E at the Wadia Institute of Himalayan Geology, Department of Structure and Tectonics generously hosted me at the institution for a period of 9-months while conducting field research for Chapters 2 and 3 through a Fulbright-Nehru Research Fellowship. Dr. Perumal provided data resources and access to lab facilities, participated in regular research discussions, and reviewed relevant written content. 4 Andrew Meigs, academic advisor and professor at Oregon State University, College of Earth, Ocean, and Atmospheric Sciences was pivotal to all aspects of presented research from experimental design, project funding, field research and sample/data collection, data analysis and interpretation, and writing of all chapters. 5 James Metcalf, research associate and CU-TRaIL lab manager at the University of Colorado-Boulder, Department of Geological Sciences co-trained me in apatite (U-Th)/He dating, through the NSF-GSA AGeS grant program, central to Chapters 2 and 3. 6 Edward Sobel, applied professor of geology at the University of Potsdam, Institut für Geowissenschaften trained me in the multi-step process of heavy mineral separation as well as the application of low temperature thermochronology methods through the DAAD Short-Term Research Fellowship program. Dr. Sobel further assisted in data analysis and interpretation central to Chapters 2 and 3. 7 Francis Sousa, assistant professor (senior research) at Oregon State University, College of Earth, Ocean, and Atmospheric Sciences was pivotal to the success of Chapters 2 and 3. Dr. Sousa assisted in field mapping and sample collection, instructed me in the use of the thermochronology modeling software, QTQt, assisted with data and model interpretation, participated in regular research discussions, and was involved in the writing of methods and data analyses components of Chapters 2 and 3. 8 Danielle Wooding, former master’s student at Oregon State University, College of Earth, Ocean, and Atmospheric Sciences assisted with field mapping and sample collection for samples presented in Chapter 2 and participated in regular science discussions. TABLE OF CONTENTS Page 1. Introduction...……………………………………………………………………… 1 1.1 Orogenesis – The Making of Mountains ...……………………………….. 2 1.2 Synopsis of Research …………………………………………………….