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A Thesis Entitled the Chronology of Glacial Landforms Near Mongo A Thesis entitled The Chronology of Glacial Landforms Near Mongo, Indiana – Evidence for the Early Retreat of the Saginaw Lobe by Thomas R. Valachovics Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Geology ___________________________________________ Timothy G. Fisher, PhD., Committee Chair ___________________________________________ James M. Martin-Hayden, PhD., Committee Member ___________________________________________ Jose Luis Antinao-Rojas, PhD., Committee Member ___________________________________________ Cyndee Gruden, PhD, Dean College of Graduate Studies The University of Toledo August 2019 Copyright 2019 Thomas R. Valachovics This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of The Chronology of Glacial Landforms Near Mongo, Indiana – Evidence for the Early Retreat of the Saginaw Lobe by Thomas R. Valachovics Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Geology The University of Toledo August 2019 The Saginaw Lobe of the Laurentide Ice Sheet occupied central Michigan and northern Indiana during the last glacial maximum. Evidence exists that the Saginaw Lobe retreated earlier than its neighboring lobes but attempts to constrain this retreat using radiocarbon dating methods has led to conflicting results. Optically stimulated luminescence dating (OSL) offers an alternative methodology to date deglacial deposits. The Pigeon River Meltwater Channel (PRMC) was formed by a large, erosional pulse of meltwater that exited the ice sheet and eroded through the deglaciated landscape previously occupied by the Saginaw Lobe. Sediments that partially fill the PRMC were dated using OSL. Minimum ages for the retreat of the Saginaw Lobe were acquired to test the hypothesis that the Mongo area is ice free by 23 ka. A better understanding of deglaciation of study area was gained through mapping of surficial landforms. Knowledge of the subsurface stratigraphy was gained through geoprobe coring, vibracoring, and ground penetrating radar (GPR). Tunnel channels that are crosscut by the PRMC and the Sturgis Moraine were found to be ice collapse features that formed when buried ice deposited within the tunnel channels melted out after being covered by younger deposits. iii Optically stimulated luminescence dating is used to determine when outwash was deposited within the PRMC. Four OSL ages record sediment deposition in the PRMC following retreat of the Saginaw Lobe: 15.7 ± 2.7 ka, 17.1 ± 3.0 ka, 23.3 ± 5.8 ka, and 23.4 ± 4.4 ka. OSL ages therefore suggest that meltwater flowed through the PRMC as early as 23.3 ± 5.8 ka. The maximum PRMC age of 23.3 ± 5.8 ka is used as a minimum age for the final retreat of the Saginaw Lobe from Indiana. Three former Huron-Erie Lobe ice margins were mapped in the study area and further constrain ice sheet retreat. The Huron-Erie Lobe acted as the source of meltwater and sediment in the PRMC. Additionally, OSL ages of: 10.9 ± 0.9 ka, and 12.5 ± 1.5 ka from the Mongo dunes and one OSL age of 10.6 ± 0.8 ka from the top of the outwash surface buried by dunes record eolian activity during the Younger Dryas. iv Acknowledgements I would like to begin by thanking my advisor Dr. Timothy Fisher for his guidance throughout this project from helping formulate a research question to editing my Thesis. I would also like to especially thank Dr. Jose Luis Antinao-Rojas and Dr. Henry Loope from the IGWS, who provided seemingly endless support including taking me on field trips, mobilizing the geoprobe, teaching me the methods and analysis for OSL, and loaning time on their OSL machine for my samples. I could not have done any of this without their support and the support of the IGWS. Additionally, I would like to thank Dr. Jose Luis Antinao-Rojas and Dr. Jamie Martin-Hayden for serving on my committee. Next, I would like to thank everyone who helped me collect field data: Drew Packman and Don Tripp from the IGWS; Alex Sodeman, Dustin Dehm, Brian Samsen, and Sarah McGuinness from the University of Toledo. Their time spent in the field was invaluable. I would like to thank Brittany Slate and Marissa Schorr from the IGWS for their assistance prepping OSL samples. Additionally, I would also like to thank Savanah Vaughn the manager of the Pigeon River Fish and Wildlife Area for allowing access to the PRFWA property and working with hunters to allow for safe and efficient field work. I would also like to thank Steven Murphy the machinist at the University of Toledo. Funding was provided by the University of Toledo GSA Graduate Research Award and the University of Toledo Department of Environmental Science. v Table of Contents Abstract .............................................................................................................................. iii Acknowledgements ..............................................................................................................v Table of Contents ............................................................................................................... vi List of Tables ................................................................................................................... ix List of Figures ......................................................................................................................x 1 Introduction ..........................................................................................................1 1.1 Introduction ........................................................................................................1 1.2 Study Area .........................................................................................................3 1.3 Background ........................................................................................................6 1.4 Deglacial Chronology of the Huron-Erie Lobe and Lake Michigan Lobe ........7 1.5 Saginaw Lobe...................................................................................................13 1.6 Hypothesis for Tunnel Channel Formation......................................................18 1.6.1 Incipient Tunnel Channel Model ......................................................19 1.6.2 Palimpsest Tunnel Channel Hypothesis............................................20 1.7 Objective and Hypothesis ................................................................................22 2 Methods ........................................................................................................23 2.1 Introduction .....................................................................................................23 2.2 Maps and Digital Elevation Model ..................................................................23 vi 2.3 Field Work .......................................................................................................24 2.4 Ground Penetrating Radar................................................................................25 2.5 Radiocarbon Dating ........................................................................................26 2.6 Optically Stimulated Luminescence ................................................................27 3 Results………….. ..................................................................................................30 3.1 Introduction .....................................................................................................30 3.2 Surficial Geology ............................................................................................30 3.2.1 Pigeon River Meltwater Channel ......................................................32 3.2.2 Huron-Erie Lobe Fans ......................................................................35 3.2.3 Sturgis Moraine and Fans .................................................................37 3.2.4 Tunnel Channels ..............................................................................39 3.2.5 Eskers ...............................................................................................44 3.2.6 Ice-Walled Lake Plains ....................................................................48 3.2.7 Mongo Dunes ...................................................................................48 3.2.8 Landform Relationships ...................................................................49 3.3 Sediment Cores ...............................................................................................51 3.4 Ground Penetrating Radar (GPR) ...................................................................57 3.5 Stratigraphy .....................................................................................................64 3.6 Radiocarbon Ages ............................................................................................68 3.7 Optically Stimulated Luminesce .....................................................................68 4 Discussion and Conclusions .................................................................................74 4.1 Introduction .....................................................................................................74 4.2 Stratigarphy .....................................................................................................74 vii 4.3 Geochronology ................................................................................................77
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