T242 Dynamics of the Laurentide Ice Sheet

Wednesday, 13 October 2021
1:30 PM - 5:30 PM
Portland Ballroom 253 (Hybrid Room)

REEXAMINING THE DEGLACIATION OF THE HURON ERIE LOBE THROUGH SUBGLACIAL MELTWATER-DERIVED LANDFORMS IN INDIANA, USA

Paper number: T242-4
Program: Technical Sessions
Time: 2:15 PM – 2:30 PM

Authors

Abstract

Our current understanding surrounding deglaciation of the Huron-Erie Lobe (HEL) of the Laurentide Ice Sheet in Indiana is changing due to the discovery of meltwater-derived landforms thought to be a new variation of tunnel channels. These landforms are called parallel tunnel channels (PTCs) and consist of discontinuous, semi-parallel pairs of depressions separated by a continuous central ridge. The PTCs have been observed cross-cutting multiple recessional moraines and transitioning to standard tunnel channels and proglacial channels in the down-ice direction. Geophysical surveys and water well logs reveal that the depressions are erosional features cut into New Holland till, are filled with lacustrine muds, and are occasionally floored with sand and gravel. Due to the morphology and stratigraphy of the depressions, the PTCs are interpreted to be subglacial, meltwater-derived, erosional landforms. A subglacial origin for the PTCs has significant implications for the deglaciation of the HEL. First, because the PTCs cross-cut recessional moraines, those moraines must be palimpsest and therefore did not form during the final retreat of the HEL. Instead, the recessional moraines were overtopped during a readvance prior to the formation of the PTCs. Second, the down-ice relationship between PTCs, standard tunnel channels, and proglacial channels suggests these may have formed synchronously. If true, this would represent a partially preserved subglacial drainage network with meltwater being transported from subglacial interior, submarginal, and proglacial positions, respectively. To preserve both the recessional moraines after a readvance and this subglacial drainage network, the HEL likely underwent widespread stagnation rather than active retreat during the final stages of deglaciation. This interpretation significantly differs from our current understanding of HEL deglaciation and calls for a reevaluation of HEL dynamics and deglacial chronology.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-370115

© Copyright 2021 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.