HR: 0800h
AN: C41A-0057    [Abstracts]
TI: Late Wisconsin Permafrost Conditions Evidenced by Patterned Ground in the Saginaw Lowlands, Eastern-Central Lower Michigan
AU: * May, C L
EM: maychri1@msu.edu
AF: Michigan State University, Department of Geological Sciences, 206 Natural Sciences Building, East Lansing, MI 48824, United States
AU: Kendall, A D
EM: kendal30@msu.edu
AF: Michigan State University, Department of Geological Sciences, 206 Natural Sciences Building, East Lansing, MI 48824, United States
AU: Lusch, D P
EM: lusch@msu.edu
AF: Michigan State University, Department of Geography, 118 Geography Building, East Lansing, MI 48824, United States
AU: Schaetzl, R J
EM: soils@msu.edu
AF: Michigan State University, Department of Geography, 118 Geography Building, East Lansing, MI 48824, United States
AU: Van Dam, R L
EM: rvd@msu.edu
AF: Michigan State University, Department of Geological Sciences, 206 Natural Sciences Building, East Lansing, MI 48824, United States
AU: Stanley, K E
EM: loess@msu.edu
AF: Michigan State University, Department of Geography, 118 Geography Building, East Lansing, MI 48824, United States
AU: Archer, J K
EM: archerj1@msu.edu
AF: Michigan State University, Department of Geography, 118 Geography Building, East Lansing, MI 48824, United States
AB: Permafrost associated with the Laurentide ice sheet has never been positively identified in the state of Michigan, in contrast to surrounding states and Canada. This study examined patterned ground in the Saginaw Lowlands of eastern-central lower Michigan to see if freeze-thaw processes in a permafrost environment had led to its formation. The area of the patterned ground is constrained by two glacial lake strands, Lake Warren and Lake Elkton-Lundy, limiting the age of the patterned ground to approximately 14.3-14.8 thousand radiocarbon years BP. Aerial photo analysis revealed a widespread area (>1020 km²) of elongate polygons in a reticulate mesh, individually measuring between 150 and 160m along the long axis and 60-90m along the short axis. Surface electrical resistivity (ER) tomography and invasive soil studies were conducted at a small sampling of mapped patterned ground locations. Polygon centers typically stood about 1 meter higher in elevation than corresponding inter-polygon swales, and often exhibited a sandy covering above the silty clay loam till below. A bowl-shaped sandy loam deposit in one polygon edge/suture was determined to be a thermokarst channel infilling following the trace of a former ice wedge. The subtle morphology and sedimentological characteristics of the patterned ground in the Saginaw Lowlands suggest that thermokarst erosion, rather than ice-wedge replacement, was the dominant geomorphic process associated with the degradation of the Late-Wisconsin permafrost in the study area.
DE: 0702 Permafrost (0475)
DE: 0710 Periglacial processes
DE: 0720 Glaciers
DE: 0744 Rivers (0483, 1856)
DE: 1824 Geomorphology: general (1625)
SC: Cryosphere [C]
MN: 2007 Fall Meeting