227 Recent Advances in Glacial Geology, Geomorphology, and Chronology (Posters)

We invite papers on topics related to glacial systems, landforms, and chronology, especially work that has connections to (i) interpretations of past climates and/or (ii) surficial geology and resource extraction.

Tuesday, 21 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Revisiting Megaflood Landforms of Camas Prairie and the Drainage of Glacial Lake Missoula, Montana, USA.

Paper number: 227-5
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The floods of Glacial Lake Missoula (GLM), USA, are thought to be among the largest glacial lake outburst floods (GLOFs) in the geologic record. GLM drained up to ~100 times between ~18.7ka and ~13ka due to periodic dam failure. Despite the longevity of recognition of GLM’s floods, much of the work has focused on the landscapes (e.g. Channeled Scablands) beyond the former ice dam. However, abundant evidence exists within the GLM basin of both the lake’s existence and its catastrophic drainage. These landforms and sedimentary deposits can help constrain the timing and magnitude of GLM’s floods. In addition, the genesis of the landforms produced during these events have been inadequately studied with modern methods and remain poorly understood, especially in the context of rapidly draining lake basins. The Camas Prairie of northwestern Montana is an ideal case study that preserves abundant geomorphic and sedimentologic evidence of the drainage of GLM. These landforms (e.g. giant current ripples (GCRs), expansion bars, and erosional scablands) lack high-resolution data regarding the age, internal structure, and spatial variability, thereby inhibiting understanding of landform genesis. Understanding these landforms more comprehensively could provide implications for similar landforms found where GLOFs have occurred (e.g. Lake Superior basin and Altai Mountains). 

We revisit the Camas Prairie landforms by utilizing: 1) new LiDAR-derived DEMs to remap landforms, 2) ground penetrating radar (GPR) surveys to investigate internal sedimentary structures, flow regime, and sediment transport, and 3) cosmogenic nuclide 10Be exposure ages from quartz-rich metasedimentary boulders for depositional chronology. Mapping shows detailed morphology of landforms including ripple crest continuity, spatial variability, and bar margins, providing context for flood dynamics. GPR data indicates previous classification of some landforms as antidunes is incorrect, and these forms are akin to other GCRs in the basin that contain downflow dipping reflections and form under subcritical flow regimes. GPR suggests expansion bars are sediment-laden with gravels and contain downflow dipping reflections. 10Be exposure ages range from ~14ka to ~70ka, but exhibits distinct spatial distribution. We hypothesize this spatial distribution reflects prior exposure of Belt Supergroup rocks at the surface that were subsequently eroded and transported into the basin first, while those on top the expansion bars were not eroded and transported until flows had incised deeply into the Markle and Wilks Creek passes.  

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

doi: 10.1130/abs/2025AM-413872

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.