80 Recent Advances in Glacial Geology, Geomorphology, and Chronology

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.

Monday, 20 October 2025
8:00 AM - 12:00 PM
HBGCC, 213AB

Subglacial hydrology insights from eskers developed atop soft beds of the Laurentide ice sheet

Paper number: 80-13
Program: Technical Sessions
Time: 11:30 AM – 11:45 AM

Authors

Abstract

Glacial landforms offer a valuable record of past ice sheets’ history and dynamics. Eskers, composed of sediment deposited by water flowing through subglacial channels, record paleo subglacial hydrologic and sediment transport conditions. Despite decades of study, debates persist about their formation mechanisms, particularly the differences between eskers formed over soft and hard beds. To address this complexity, we analyzed eskers formed over soft beds along the southern margin of the Laurentide Ice Sheet (LIS) in the Lake Superior region. To calculate the basal effective pressure gradient during esker formation along the subglacial channel, we developed a new method using grain size estimates from a 20 m tall esker exposure (Cable Esker). The sedimentology of the Cable Esker reveals a non-monotonic pattern in channel boundary shear stress, ranging from 10 to 300 Pa. Additionally, the basal effective pressure gradient fluctuates between -9 to -70 Pa m-1. Negative basal effective pressure gradients indicate esker formation in channels close to the glacier terminus, suggesting lower water pressure than previously assumed. This, coupled with dynamic water level fluctuations within the esker channel, supports the theory of esker formation near the ice margin.

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

doi: 10.1130/abs/2025AM-412741

© 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.