AN ABSTRACT OF THE DISSERTATION OF Brendan T. Reilly for the degree of Doctor of Philosophy in Ocean, Earth, and Atmospheric Sciences presented on June 8, 2018. Title: Deciphering Quaternary Geomagnetic, Glacial, and Depositional Histories Using Paleomagnetism in Tandem with Other Chronostratigraphic and Sedimentological Approaches Abstract approved: ______________________________________________________ Joseph S. Stoner Stratigraphy and chronology are essential to sedimentological study of Earth system histories. And, stratigraphy and chronology are often challenging and interesting problems themselves. The Quaternary (2.588 Ma - present) experienced paleoenvironmental and paleo-geomagnetic variability well outside the range of the recent instrumental record, providing the opportunity to place recent observations in a more complete perspective. This dissertation presents three studies that combine paleomagnetism in concert with radiocarbon, stratigraphic correlation, and/or age-depth modeling to develop stratigraphy and assign chronology. This in turn, helps to better understand the evolution of these glacial, geomagnetic, and depositional systems. The first study investigates the glacial history of the Petermann Glacier, a major outlet glacier of the Greenland Ice Sheet, over the last ~7 ka. Petermann Glacier has been remarkably stable for as long as there have been historical observations apart from two anomalously large calving events of its floating ice tongue over the last decade. This is unique when compared with many other large marine terminating Greenland outlet glaciers. Yet, our geologic evidence clearly show the Petermann Ice Tongue was not present for much of the time recorded in the sediments of Petermann Fjord. While radiocarbon and paleomagnetic methods could not constrain the sediment’s chronology alone, due to large reservoir issues and uncertain regional paleomagnetic templates, using the two methods in tandem we determine the paleoenvironmental conditions that were required to maintain the stable ice tongue of the Late Holocene. Specifically, a stable ice tongue only formed around 2-2.5 ka after sea ice conditions intensified, limiting Ekman transport of warm modified Atlantic Waters into the fjord, and surface air temperatures were within ~2o C of preindustrial conditions, slowing the subglacial run-off driven circulation of the fjord. The second study investigates the geomagnetic history of Western North America from ~35-15 ka. While the Holocene has been the focus of most studies about past directional changes of the geomagnetic field, the Late Pleistocene spans a greater range of field intensity variations that have a largely unknow relationship with field morphology. Yet, late Pleistocene sediments that could be used to investigate these questions, particularly from terrestrial archives of Western North America, are notoriously difficult to date. This makes comparison of millennial scale directional variations, like other studies have done for the Holocene, difficult. Using new data from Fish Lake, Utah and existing data from Bessette Creek, British Columbia, and Bear Lake on the Utah and Idaho Border, we construct a composite stacked record to define these variations and we account for radiocarbon and magnetic uncertainties in the stack’s chronology. We demonstrate that this PSV template can provide new insight to longstanding chronostratigraphic debates, such as the implications of various proposed chronologies of the sediments in the Wilson Creek Formation at Mono Lake, California on the outcrop’s chronostratigraphy and radiometric age estimates. The third study investigates the depositional history of the Bengal Fan over the last ~1.25 Ma. Regionally extensive hemipelagic deposits with good reversal magnetostratigraphy offer constraints on the evolution of the fan’s channel levee system through climate and sea-level transitions of the Pleistocene. Yet, it has been challenging to assign ages to the turbiditic sediments of the fan due to the absence of reliable chronostratigraphic markers. To address this issue, we model sediment accumulation rates at seven drill sites, incorporating all available age control points and integrating seismic observations to establish the stratigraphic relationships of paleo-channel-levee systems. The model results are stacked to create a composite regional signal for the Lower Bengal Fan, which, in the additional context of other regional archives, suggests growth of the spatial extent of the Bengal Fan channel-levee system along with increases in glacial-interglacial sea level amplitude. ©Copyright by Brendan T. Reilly June 8, 2018 All Rights Reserved Deciphering Quaternary Geomagnetic, Glacial, and Depositional Histories Using Paleomagnetism in Tandem with Other Chronostratigraphic and Sedimentological Approaches by Brendan T. Reilly A DISSERTATION submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Presented June 8, 2018 Commencement June 2018 Doctor of Philosophy dissertation of Brendan T. Reilly presented on June 8, 2018 APPROVED: _____________________________________________________________________ Major Professor, representing Ocean, Earth, and Atmospheric Sciences _____________________________________________________________________ Dean of the College of Earth, Ocean, and Atmospheric Sciences _____________________________________________________________________ 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. _____________________________________________________________________ Brendan T. Reilly, Author ACKNOWLEDGEMENTS I have benefited greatly from being surrounded by positive and supportive people through graduate school. Thanks for celebrating successes and helping me through failures. My committee members Alan Mix, Anders Carlson, and Anthony Koppers taught three of my all-time favorite classes. Alan and Anders also provided the opportunity to participate in field studies of the Greenland Ice Sheet, which transformed the way I thought about past glacial activity. I am very grateful to their continued support and time. I also thank Francisca Belart for agreeing to serve as my GCR so close to my defense date. I am grateful to Leslie and Mark Workman and the Oregon ARCS Foundation for their generous support and interest in my research. Thanks to the ‘Quat Tea(m)’ and my other friends in the department and beyond for making it easy to love OSU and Corvallis. My adventure buddies in Greenland—Gaylen Sinclair, Anna Glueder, Jorie Clark, Chris Holm. The people I love to play music with—Scott Klasek, Andy Menky, and Suzette Savoie. My official and unofficial lab mates--Katherine Solada, Ben Frieberg, Leah Zeigler, Sarah Strano, Fenna Bergmann, Julie Velle, Torsten Haberzettl, and Doug Steen. My department collaborators who have challenged my perspectives—Mo and Paul Walczak, Andrea Balbas, Kelsey Winsor. The core lab—Maziet Cheseby and Cara Fritz—and all the people that helped me navigate CEOAS, particularly Lori Hartline. The professors that taught and mentored me. All the graduate students that have come and gone. What a community! I hope we will look for shells on warm sunny beaches, play sold out shows at Squirrel’s Tavern, and solve Earth’s mysteries for many years to come. I learned the most while at sea and want to thank everyone involved with NBP1203, HLY1302, IODP Expedition 354, OD1507, OC1706B, and RR1718. These are experiences I will always treasure. Amy Leventer, Scott Ishman, Bruce Huber, Julia Wellner, Gene Domack, Mike McCormick, Kara Vadman, Natalie Elking, Lloyd Keigwin, Neal Driscoll, Ning Zhao, Chris Maio, Chis Moser, Marti Jeglinski, Jenna Hill, Shannon Klotsko, Tom Cronin, Rachel Marcuson, Mark Abbott, Matt Finkenbinder, Aubrey Hillman, Laure Meynadier, Peter Selkin, Jairo Savain, Christian France-Lanord, Volkhard Spiess, Tilmann Schwenk, Adam Klauss, Mike Weber, Petra Dekens, Valier Galy, Trevor Williams, Jarrett Cruz, Lindsey Fox, JJ Bahk, Alan Baxter, Hendrik Lantzach, Yasmina Martos, Camilo Ponton, Anne Jennings, Martin Jakobsson, Liz Ceperly, Shaun Marcott, Larry Mayer, Laurence Dyke, Summer Praetorius, Jainghui Du, Heather Bervid, Coquille Rex, Masako Tominaga, Mitch Lyle, Anne Trehu, Rebecca Fowler, Ashley Long, Alexis Wright, Emily Schottenfels and many, many more—I thank you all for your mentorship, collaborations, and support. I loved learning new things with each and every one of you. Most importantly, I have been very lucky to have incredible advisers. Stefanie Brachfeld took me on as a graduate student when I was just starting in geology. Stefanie revealed a world of paleomagnetism, paleoceanography, and glaciomarine systems that captured my imagination. I wouldn’t be here without her. Rob Hatfield was my second, unofficial adviser at OSU. We had a lot of adventures together and discussed a lot of fun ideas (some of which we’ve actually done!) I am lucky to have him as a mentor and a friend. I will forever be grateful to Joe Stoner. Joe is my role model of a good scientist—he gets excited about his projects, he keeps an open mind on controversial subjects, he always supports his mentees, and he enables a balanced life for those around him. He has supported almost every idea I have had and provided more opportunities that I ever could have expected. Thanks for pushing me to think