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The role of permafrost on the morphology of an MIS 3 moraine from the southern Laurentide ice sheet

Elizabeth G. Ceperley, Shaun A. Marcott, J. Elmo Rawling, Lucas K. Zoet and Susan R. H. Zimmerman
The role of permafrost on the morphology of an MIS 3 moraine from the southern Laurentide ice sheet
Geology (Boulder) (March 2019) 47 (5): 440-444


The Laurentide Ice Sheet (LIS) represents the single largest contributor to global sea level during the late Pleistocene glacial-interglacial cycle. Fluctuations of global sea level prior to the Last Glacial Maximum (LGM; 26-19 ka) are well documented, but the terrestrial extent of the LIS prior to the LGM is uncertain. In central Wisconsin, United States, three north-south-trending end moraines of the LIS are preserved. The two eastward moraines are constrained to the LGM through radiocarbon and surface exposure dating methods, while the westward moraine is constrained only by relative dating techniques and is estimated to be up to >125 ka. Here, we report surface exposure ages from this westward moraine (the Arnott moraine) and demonstrate that the LIS reached an equivalent extent to its LGM position at ca. 35 ka, during Marine Isotope Stage (MIS) 3. These new age constraints for the Arnott moraine are significantly younger than prior estimates, which were based on sediment weathering and low-relief moraine morphology. To address this dichotomy between the relatively young exposure dates and the low relief, we applied a landscape diffusion model to the Arnott moraine and found that during permafrost conditions, intense erosion can act to efficiently and quickly smooth the moraine surface. This study connects the LIS as a potential source for sea-level lowering during MIS 3 while simultaneously demonstrating the inherent uncertainty associated with relative dating techniques if nonlinear erosional conditions are not accounted for in periglacial terrains.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 47
Serial Issue: 5
Title: The role of permafrost on the morphology of an MIS 3 moraine from the southern Laurentide ice sheet
Affiliation: University of Wisconsin at Madison, Department of Geoscience, Madison, WI, United States
Pages: 440-444
Published: 20190321
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 31
Accession Number: 2019-032137
Categories: Quaternary geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2019172
Illustration Description: illus. incl. geol. sketch map
N44°10'00" - N44°34'60", W89°40'00" - W89°19'60"
Secondary Affiliation: Lawrence Livermore National Laboratory, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201917
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