THE RIVER RAISIN FLOODWAY AS A SOURCE OF SAND TO THE LAKE WARREN SHORELINE
Recent field investigations of another, unusual, feature on the ALE lake plain in SW Monroe County, MI – the Ottawa Lake basin – led to a regional evaluation of the sources and relative timing of the supply of large volumes of sediment to the ALE system. As a working hypothesis that will guide upcoming field studies, the River Raisin Floodway appears to have channeled large volumes of sediment and water, presumably as glacial outwash derived primarily from the southern flank of the Saginaw Lobe. Upstream to the west, and at the margin where higher-elevation shorelines rework glacial deposits, the main stem of the Raisin and its largest tributary, Black Creek, show evidence of several episodes of braided-river and fan or fan-delta deposition. Downstream near Dundee, MI, the River Raisin valley shows evidence of the catastrophic breaching of the Warren shoreline as a geomorphic dam, and possible smaller, lateral flood drainage which appears to have interacted with the lagoon behind the Warren shoreline. The River Raisin Floodway lies north of a subtle topographic lineation that may separate a smaller glacial lobe extending from the Huron Lobe from the main body of the Erie Lobe in the modern valley of the Maumee River. In this model, sand delivered to the Lake Warren shoreface was carried by littoral transport to the S-SW to build the Oak Openings Ridge.