DO EXTREME FLOOD DEPOSITS IN WABASH AND GRAND RIVER VALLEYS, INDIANA AND MICHIGAN, RELATE TO UPSTREAM SUBGLACIAL FLOODS?

Growing evidence is suggesting that SW subglacial meltwater flooding possibly associated with ice streaming in the glaciated Lake Ontario and eastern Lake Erie basins about 13.5 (16.1 cal) ka BP led to recession of the ice margin in the Mackinaw Interstadial or Phase about 13.3 ka. This suggestion raises questions whether the earlier Erie Interstadial or Phase, a retreat from full glaciation of the Great Lake basins, and Lake Leverett, were also induced by antecedent meltwater flooding and ice streaming. These processes would have occurred throughout the Lake Erie basin and may have played a role in forming the well-known ‘glacial grooves’ in the bedrock arch exposed on Kelley’s Island in western Lake Erie. The eroded Wabash and Grand River valleys of Indiana and Michigan were possible outlets and conduits for these flows, and sand and gravel sediments have been recognized in places as deposits of extreme floods (Fraser and Bleuer 1988, GSA Special Paper 229: 111-125 and Kehew 1993, Quaternary Research 39: 36-44). The ages of these sediments are unknown, yet dated constraints on extreme floods are needed to advance possible linkages among glacial and glacially-influenced features of the southern Laurentide Ice Sheet. We draw attention to these questions and urge the community of sedimentary geochronologists to address the unknown ages of the deposits of extreme flooding, possibly by applications of optically stimulated luminescence dating.