80-5 Revisiting the Origins of Megaflood Bedforms in Rapidly Draining Glacial Lake Basins: Insights from Camas Prairie (Glacial Lake Missoula) and Christmas Dunes (Glacial Lake Duluth)

Session: Recent Advances in Glacial Geology, Geomorphology, and Chronology

Presenting Author:

Phillip Larson

Authors:

Larson, Phillip Herman¹, Rowen, Jayda Kaylee², Breckenridge, Andy³, Fischer, Abigail⁴, Seong, Yeong Bae⁵, Wickert, Andrew David⁶, Olson, Leah⁷, Hurner, Neil⁸, England, Henry⁹, Hilgendorf, Zach¹⁰

(1) EARTH Systems Laboratory, Minnesota State University, Mankato, MN, USA, (2) EARTH Systems Laboratory, Minnesota State University, Mankato, MN, USA, (3) University of Wisconsin-Superior, Duluth, MN, USA, (4) EARTH Systems Laboratory, Minnesota State University, Mankato, MN, USA, (5) Geography Education, Korea University, Seoul, Korea (The Republic of), (6) Earth & Environmental Sciences, University of Minnesota, Minneapolis, MN, USA, (7) EARTH Systems Laboratory, Minnesota State University, Mankato, MN, USA, (8) EARTH Systems Laboratory, Minnesota State University, Mankato, MN, USA, (9) EARTH Systems Laboratory, Minnesota State University, Mankato, MN, USA, (10) University of Wisconsin-Eau Claire, Eau Claire, WI, USA,

Abstract:

Top-down drainage-integration processes play a critical role in shaping and reorganizing fluvial networks, yet they have long been overshadowed in both scientific and pedagogical discourse by less efficient and less probable mechanisms. This has led to a persistent legacy of conceptual ambiguity. Over the past two decades, renewed interest in drainage integration—particularly in the context of both terrestrial and Martian landscapes—has driven a long-overdue paradigm shift. Modern perspectives emphasize spillover-driven integration in both non-glacial and glacial contexts, linking processes in non-glaciated settings with glacial lake outburst floods (GLOFs) driven by spillover or natural dam failure. They are pointed to as key mechanisms for integrating hydrologically closed/constrained basins and creating new hydrogeomorphic systems.

Despite considerable recent attention towards downstream landscapes following integration, the geomorphic evolution within breached basins remains underexplored. Yet, these upstream landscapes preserve critical geomorphic and sedimentary evidence of the erosional magnitude, sediment transfer dynamics, and timing of these events. Among the most enigmatic landforms are megaflood bedforms—morphochronologic and depositional markers that record the magnitude and dynamics of prior events. These landforms have long been recognized in regions such as the Channeled Scablands and Camas Prairie in the northwestern USA, and the Chuja–Katun River system in south Siberia—both associated with catastrophic glacial lake outburst floods. Despite this, a lack of modern methodological analysis and comparison of forms in different landscapes, particularly within the drained basins, leaves prior hypotheses and characterizations inadequately tested.

Here, we present initial findings from high-resolution topographic analysis (LiDAR), ground-penetrating radar surveys, and cosmogenic nuclide dating in the Camas Prairie (Glacial Lake Missoula) of Montana and the recently identified Christmas Dunes (Glacial Lake Duluth) within the Lake Superior basin. These comparative case studies offer new insights into the genesis, preservation, and variability of megaflood bedforms, providing a framework for reevaluating the geomorphic legacy of drainage events in glacial lake basins.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7546

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