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Subsidence of the Ediacaran Johnnie Formation, Cumulative Offset Along the Lavic Lake Fault, and Geomorphic Surface Development Along The

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Subsidence of the Ediacaran Johnnie Formation, Cumulative Offset Along the Lavic Lake Fault, and Geomorphic Surface Development Along The Tectonics in Nevada and Southern California: Subsidence of the Ediacaran Johnnie Formation, Cumulative Offset Along the Lavic Lake Fault, and Geomorphic Surface Development Along the Southern San Andreas Fault Thesis by Rebecca Amber Witkosky In Partial Fulfillment of the Requirements for the degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2019 (Defended 12 October 2018) ii 2019 Rebecca Amber Witkosky iii ACKNOWLEDGEMENTS The material that I present in this thesis is based upon work supported by the National Science Foundation Graduate Research Fellowship Program (under grant 1144469). Mako thermal hyperspectral airborne imagery was acquired under the auspices of the Aerospace Corporation’s Independent Research and Development program. I thank my colleagues at The Aerospace Corporation: Dave Tratt, Kerry Buckland, Dave Lynch, Tamara Volquarts, Paul Adams, and Pat Johnson, for providing me with a cornucopia of data, as well as fruitful collaboration and discussion throughout my years as a graduate student. I thank the interns who have helped me during my time at Caltech: Gillian Ferguson, Maggie Andersen, and Jack Nguyen. I thank the Marine Corps Air Ground Combat Center in Twentynine Palms, California, for allowing us access to the military base for geological research; that was really fun and interesting. I thank Ginny Short, Manager of the Thousand Palms Oasis Preserve, for granting access to field sites in the Coachella Valley. Additional acknowledgements are formally included at the end of each chapter, specific to help provided for the individual projects. Thank you to everyone who supported me and helped me with field work, performing the research, preparing the manuscripts, and anything else that I might have not explicitly remembered in this moment. In my experience, the Acknowledgements section of a graduate student’s thesis can often be the most enjoyable, and inspiring part to read. It is like crafting an acceptance speech for an absolutely fabulous award! So, I wanted to make mine special (i.e., way too long and drawn out), and to do that, I wanted to have fun writing this, and hopefully also make it fun for you, the reader. Thank you, Reader, for honoring me by taking the time to acknowledge and review my effort. iv There are many people who I would like to thank on a more personal level. My PhD thesis advisors: Joann Stock, thank you so much for helping me earn my PhD; Brian Wernicke, thank you for helping me improve my writing; Jean-Philippe Avouac, thank you for charmingly advising my oral exam project on the Franz Josef Glacier in New Zealand; Bethany Ehlmann, George Rossman, and John Grotiznger, thank you all for working on my thesis advisory committee, and especially for the thoughtful reviews of my work that you provided. All of the Caltech professors and teaching assistants who taught the graduate courses that I completed and learned a lot from. My mentors who helped me arrive and thrive at Caltech: Doug Yule (CSUN/Caltech), Jamshid Hassanzadeh (Caltech/CSUN), Dick Heermance (CSUN), and Kate Scharer (USGS). My fellow Caltech Arms pitsters: Sean Mullin (good community and eats), and Florian Hofmann (good pranks). My friends that I made as a graduate student in the Division of Geological and Planetary Sciences: Elle Chimiak (Hey Girl!), Leah Sabbeth (the Scandinavian swimmer), Heather Steele, Frank Sousa (many pumpkin spices), Jason Price (a true Alpine geologist), Lisa Christiansen, Julie Lee, Janet Harvey, and Ted Present (deep and abundant laughter). All of the many Caltech administrative personnel who handled and assisted in various matters throughout my time here. My friends at the Caltech Center for Diversity: Erin-Kate Escobar, Taso Dimitriadis, and Monique Thomas, thank you for supporting me and helping me discover others and myself. I probably learned some of the most important lessons in my life, and got to see some of the most interesting speakers and presentations during my time at Caltech through events made possible by the Diversity Center. I highly encourage everyone to attend these events, because they celebrate, uplift and raise voices of those who have been systematically oppressed throughout history. You will learn something special about others and yourself, to v be sure! I learned how to recognize the marginalization of people of color, and how to acknowledge the privilege I experience as a white, able-bodied person. I also learned about the great Leslie Feinberg, and how ze once said “…the most powerful way for peoples who face different oppressions to understand each other is by fighting back shoulder to shoulder.” That is how I plan to live my life from now on, in solidarity with others who have struggled to be accepted by society. Thank you all for making my experience at Caltech so memorable and providing me with support through times of struggle. I am sorry if I forgot anyone, please don’t be offended! Academic research has helped me find discipline and balance in my life. In earning the PhD, I have also earned self-respect, self-esteem, and patience through the thousands of labor hours that go into writing a thesis. Although this is certainly not a requirement for everyone, I feel like for myself personally, the culmination of this experience has given me the ability to not only pass my oral exam and thesis defense as a student, but more importantly, to pass in life as an empathetic and real human being. I have also realized that a typical grad student’s experience can perhaps be summarized quite briefly, in the following manner. I am about to spill the tea on how it often plays out, and you could say, here, that *the category is* PhD annual progression realness: The First year fear (of not passing your oral exam, or the dreaded “quals”); the Second year slump (classes mean little, but you still have to take a bunch!); the Third year throes (struggling to find meaning, discipline, and direction); the Fourth year freedom (no more social obligations, can finally devote 100% of your time to research!); and finally, the Fifth year finale (time to wrap it up and quick, because by now you know how fast a year goes by). From reading other students’ theses, I discovered that students always seem to thank their favorite vices, so for me it is vi decaffeinated coffee, sugar-free soda, and non-alcoholic beer(; For others who read this and might be struggling, I like to offer this piece of advice that I heard recently: some people like to say that things will get better, but since that is not always the case, perhaps a better outlook is to believe that things will get different. My final thanks go to my closest loved ones. My blood family: my mom (Anita), dad (Mitchell), stepdad (Sammy), Scarlett, Samantha, Megan, Cyrus, Sasha, and Kai. I love you all so much, and I miss you all the time! My chosen family: Chris, Joy, Brianna, Cassie, and Sasha the dog. I know that the past few years I have been such a doubting Thomassina, but now that I have finally unlocked this epic achievement (woot!), we will all get to spend more time together, just like Nostradama predicted. Thank you Mom, for always encouraging me to return to school and pursue higher education. I would also like to thank Goddexx, whoever, whatever, and wherever she might be ⚧ vii ABSTRACT While we know the ages and tectonic histories of many critical geologic events in the history of the Earth, there are still questions regarding the timing of key events and structures that have and continue to influence life on this planet. This thesis includes three separate studies in Nevada and southern California: two potential new methods for measuring/organizing geologic time, and also an analysis of the long-term displacement along an active fault in the eastern California shear zone. In Chapter II, we used tectonic subsidence modeling to find that the Shuram carbon isotopic excursion in the Ediacaran Johnnie Formation likely occurred from 585-579 Ma, and that incision of the Rainstorm Member shelf occurred during the 579 Ma Gaskiers glaciation. The pre-Shuram-excursion chemostratigraphic carbon isotope profiles from the Khufai Formation in Oman and the type locality of the Johnnie Formation in Nevada are both generally positive and therefore possibly correlative. In Chapter III, we determined the cumulative tectonic offset along the Lavic Lake fault, an active structure that ruptured with >5 m of coseismic slip in the 1999 Mw 7.1 Hector Mine earthquake. We calculated a net slip of 960 +70/-40 m, based on the slip vector formed by a vertically separated lithologic contact and a horizontally separated older cross fault. The net slip we calculated is significantly less than a previous estimate that was based on an offset magnetic gradient, a disparity that may be explained by considering off-fault deformation, as well as the unknown depth and nature of the source of the magnetic contrast. In Chapter IV, we explored using a new method for the relative dating of Quaternary geomorphic surfaces, which is based on the positive correlation between increased spectral contrast in thermal hyperspectral airborne imagery and surface age. With field data, we found that desert varnish scores, desert pavement scores, and vegetation spacing estimates also viii correlate positively with surface age, implying that these factors could contribute to the increased spectral contrast in airborne remote sensing spectra. Additionally, the general increase in the band depth of airborne spectra at 9.16 μm could be due to increasing clay mineral abundance in progressively heavier desert varnish coatings on older surfaces. The positive correlation observed in this study between surface age and spectral contrast in airborne spectra can perhaps be used to develop a method for relative dating of varnished geomorphic surfaces elsewhere.
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