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Behavior of the James Lobe, South Dakota During Termination I Behavior of the James Lobe, South Dakota during Termination I A dissertation submitted to the Graduate School of the University of Cincinnati in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in the Department of Geology of the McMicken College of Arts and Sciences by Stephanie L. Heath MSc., University of Maine BSc., University of Maine July 18, 2019 Dissertation Committee: Dr. Thomas V. Lowell Dr. Aaron Diefendorf Dr. Aaron Putnam Dr. Dylan Ward i ABSTRACT The Laurentide Ice Sheet was the largest ice sheet of the last glacial period that terminated in an extensive terrestrial margin. This dissertation aims to assess the possible linkages between the behavior of the southern Laurentide margin and sea surface temperature in the adjacent North Atlantic Ocean. Toward this end, a new chronology for the westernmost lobe of the Southern Laurentide is developed and compared to the existing paradigm of southern Laurentide behavior during the last glacial period. Heath et al., (2018) address the question of whether the terrestrial lobes of the southern Laurentide Ice Sheet margin advanced during periods of decreased sea surface temperature in the North Atlantic. This study establishes the pattern of asynchronous behavior between eastern and western sectors of the southern Laurentide margin and identifies a chronologic gap in the western sector. This is the first comprehensive review of the southern Laurentide margin since Denton and Hughes (1981) and Mickelson and Colgan (2003). The results of Heath et al., (2018) also revealed the lack of chronologic data from the Lobe, South Dakota, the westernmost lobe of the southern Laurentide margin. To address this problem, surface exposure age dating is applied to James Lobe deposits within the Pierre Sublobe, a westward-flowing sublobe of the western James Lobe. A new geomorphic map of the Pierre Sublobe is produced to provide geologic context for 10Be surface exposure age dating efforts. Results of this study offer insights into possible problems associated with site selection in this region and yields some insight into the behavior of the James Lobe during Termination I. The history of the main trunk of the James Lobe is expanded upon using radiocarbon ages compiled from South Dakota Geological Survey reports. Three stratigraphic cross sections of the James Lobe are assembled to provide stratigraphic context for these radiocarbon ages Results of this study bear on the timing of maximum extent of the James Lobe, as well as advance and retreat patterns of the lobe during late-glacial time. The James Lobe is compared to the neighboring Des Moines Lobe in Iowa and the existing paradigm of surging and streaming is evaluated. ii Finally, the behavior of the James and Des Moines Lobes is compared to the rest of the southern Laurentide margin for three time slices to evaluate the asynchronous relationship established in Chapter 2 (Heath et al., 2018). Results of this study bear on differences between extent and timing of the lobes, and the mechanisms that may have controlled southern Laurentide margin position during the last glacial period and termination. This dissertation affords insight into the patterns of advance and retreat of the southern Laurentide Ice Sheet during the last glacial period and Termination. In reconstructing these behaviors and producing a new chronology for the westernmost Laurentide lobe, this work offers new perspective for the mechanisms that controlled southern Laurentide margin position during the Termination. iii iv Acknowledgements My Ph.D. program and research activities were funded by the Department of Geology at the University of Cincinnati and by the Comer Science and Education Foundation. I would like to extend my sincere thanks to my primary advisory Professor Tom Lowell for his invaluable instruction, patience and support through this process. I would like to thank my committee members, Dr. Dylan Ward, Dr. Aaron Diefendorf and Dr. Aaron Putnam for their expertise and thoughtful suggestions. I owe a great deal of gratitude to Dr. Brenda Hall for her continued support and to Jill Pelto, Peter Strand, Lizzie Orr, and Sarah Hammer for processing my samples. I am eternally grateful for UC’s Counseling and Psychological Services, who helped me to find a way forward during the most difficult moments of the last five years. Thank you to my family in Rhode Island and Maine for their love and support. I thank Lizzie Orr for her unwavering patience and friendship. I would like to thank the students, staff and faculty of the Department of Geology for their support and kindness. I dedicate this dissertation research to my husband Adam Heath, who held me up and believed in me when I needed it the most. v Table of Contents ABSTRACT....................................................................................................................................... ii Acknowledgements ........................................................................................................................... v Chapter 1: Introduction ................................................................................................................... 1 References .................................................................................................................................... 3 Chapter 2: Pattern of southern Laurentide Ice Sheet margin position changes during Heinrich Stadials 2 and 1 ABSTRACT ....................................................................................................................................... 4 1. Introduction ........................................................................................................................... 5 2. Data and methods .................................................................................................................. 6 2.1. Establishment of Heinrich Stadial timing ....................................................................... 6 2.2. Chronologic data of Laurentide Ice Sheet history .......................................................... 7 2.3. Analysis .......................................................................................................................... 9 3. Results of chronologic data compilation ............................................................................... 10 3.1. New England Region ..................................................................................................... 10 3.2. Finger Lakes Region ....................................................................................................... 11 3.3. Lake Huron-Erie Lobe .................................................................................................... 12 3.4. Lake Michigan Lobe ....................................................................................................... 14 3.4.1. Lake Michigan Lobe chronology ........................................................................ 14 3.4.2. Harvard Sublobe chronology ............................................................................... 16 3.5. Green Bay Lobe .............................................................................................................. 17 3.6. Chippewa Lobe ............................................................................................................... 19 3.7. Des Moines Lobe ............................................................................................................ 19 vi 4. Summary ................................................................................................................................ 21 5. Discussion .............................................................................................................................. 22 5.1. Did the terrestrial margin of the southern Laurentide Ice Sheet advance during cold phases of sea surface temperature (Heinrich Stadials 2 and 1) in the adjacent North Atlantic? ................................................................................................................................. 22 5.2. Comparison with other Northern Hemisphere ice sheets ............................................... 23 5.2.1. Cordilleran Ice Sheet ........................................................................................... 23 5.2.2. British-Irish and Scandinavian Ice Sheets ........................................................... 24 5.3. Hypothesis for differences in Heinrich Stadials ............................................................. 25 6. Conclusions .............................................................................................................................. 27 Acknowledgements ...................................................................................................................... 27 Tables ........................................................................................................................................... 28 Figures .......................................................................................................................................... 29 References ................................................................................................................................... 40 Chapter 3: Assessing the utility of surface exposure age dating of fluctuations of the James Lobe, South Dakota ABSTRACT ......................................................................................................................................
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