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Book Chapter

Ice advances and retreats, inlets and outlets, sediments and strandlines of the western Lake Superior basin

By
Howard C. Hobbs
Howard C. Hobbs
Minnesota Geological Survey, 2642 University Avenue W., St. Paul, Minnesota 55114-1032, USA
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;
Andy Breckenridge
Andy Breckenridge
Department of Natural Sciences, University of Wisconsin–Superior, Belknap and Catlin, Superior, Wisconsin 54880, USA
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Published:
January 01, 2011

ABSTRACT

This field guide examines the evidence for multiple readvances of the Superior lobe, as well as the morphological and sediment record of glacial lakes in the western Lake Superior basin. During each readvance of the Superior lobe, ice went a shorter distance, reached a lower elevation, and laid down a finer-grained till due to incorporation of proglacial lake sediment. There are three distinct tills, which are correlated to three readvance phases: the St. Croix/Automba, Split Rock, and Nickerson. A red clay typically caps the stratigraphy at lower elevations in the basin. This clay may be a fourth till associated with a late readvance, perhaps equivalent to the Marquette phase in eastern Lake Superior. Alternatively, the red clay may be lacustrine. At issue are the potential hydraulic connections between glacial Lake Agassiz and the Atlantic Ocean during, and after, the Younger Dryas, because a readvance would fill the western Superior basin with ice and prohibit eastern Lake Agassiz drainage. Additional stops highlight the strandline and sediment record of the youngest glacial lake phase (glacial Lake Duluth), including the inspection of Lake Superior sediment cores that are archived at the National Lacustrine Core Repository in Minneapolis. The goals of the selected stops are to underscore the current understanding of the late glacial history of the western Superior basin and to provide new insights to spark discussion.

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GSA Field Guide

Archean to Anthropocene: Field Guides to the Geology of the Mid-Continent of North America

James D. Miller
James D. Miller
Department of Geological Sciences and Precambrian Research Center University of Minnesota-Duluth Duluth, Minnesota 55812 USA
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;
George J. Hudak
George J. Hudak
Precambrian Research Center Natural Resources Research Institute 5013 Miller Trunk Highway Duluth, Minnesota 55811 USA
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;
Chad Wittkop
Chad Wittkop
Department of Chemistry and Geology Minnesota State University Mankato, Minnesota 56001 USA
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;
Patrick I. McLaughlin
Patrick I. McLaughlin
Wisconsin Geological and Natural History Survey Madison, Wisconsin 53705 USA
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Geological Society of America
Volume
24
ISBN electronic:
9780813756240
Publication date:
January 01, 2011

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