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Paper No. 58-1
Presentation Time: 8:00 AM-12:00 PM
ANALYSIS OF EROSIONAL FEATURES IN THE NORTHWEST CORNER OF THE OTTAWA LAKE BASIN, MONROE COUNTY, MICHIGAN
The Ottawa Lake basin, located east of the town of Ottawa Lake, Michigan, sits between the shorelines of Lake Whittlesey, Lake Arkona, and Lake Warren of Ancestral Lake Erie (ALE). The basin of Ottawa Lake is approximately 7 km by 6 km and is comprised of a series of smaller basins. The average relief is ~5 m with the deepest basin 7 m below the surrounding land surface and often hosts an ephemeral lake. The Ottawa lake basin is atypical of regional lakes associated with deglaciation. Previous studies conducted in the Ottawa Lake basin identified some erosional characteristics of the lake margin. Karst landforms including dolines and subterranean water flow were identified in the region as early as 1900. To better understand the processes responsible for this landscape, geophysical techniques were used to characterize erosional lineations that trend NW–SE in the northwest corner of the basin. Three main hypotheses have been proposed for the how the Ottawa Lake bains may have formed: 1) scouring by high-pressure subglacial water, 2) glacial meltwater flow, and 3) karst processes. Further geophysical, stratigraphic, and geomorphic investigations are necessary to develop a more detailed model of processes that could have created the basin.
Two sites across lineations, OTL1 and OTL2, near the northwest corner of the Ottawa Lake basin show evidence of scouring in the subsurface. These sites were investigated using Schlumberger vertical electrical resistivity soundings. At site OTL 1 a boundary was observed between scoured areas and the land surface not affected by erosion. At site OTL 2 there was consistent depth to bedrock, with no indication of subsurface erosion. These data support all three proposed models. Further research within the basin is necessary to better differentiate karstic features from subsurface erosional features, and to constrain the timing and morphology of this regionally unusual geomorphic feature.