THE DIVERSION OF GLACIAL MELTWATER FROM THE EASTERN ST. LAWRENCE RIVER OUTLET INTO THE OHIO RIVER BASIN BY AN MIS 3 ADVANCE OF THE LAURENTIDE ICE SHEET: EVIDENCE FROM RAPIDLY AGGRADED OUTWASH AND SLACKWATER LAKE DEPOSITS IN THE LOWER OHIO RIVER VALLEY (Invited Presentation)

The Ohio River basin was the primary meltwater drainage outlet for the Lake Erie, Lake Huron, and Saginaw lobes of the Laurentide Ice Sheet when the ice sheet covered the eastern drainage outlet through the St. Lawrence River. Geologic and geomorphic mapping using sediment coring, geophysics, and AMS radiocarbon and luminescence dating show that landforms in the lower Ohio River valley are last glacial maximum landforms formed during marine oxygen isotope stage (MIS) 2, but deeper subsurface sediments are older. Two cores in the main Ohio River valley contained ~12 m of 38 ka outwash deposited during MIS 3. The rapid aggradation of outwash in the main Ohio River valley dammed the mouths of tributaries, which had much lower sediment loads, and slackwater lakes formed in the tributary valleys. AMS radiocarbon ages from slackwater lake deposits in 3 different tributaries ranged from ~37.5 ka to 42.5 ka, which are also MIS 3 ages. Additionally, the Roxana silt, a MIS 3 loess deposit, is ubiquitous in the valley. New research in the Mississippi and Wabash River valleys also confirm a MIS 3 ice advance and suggest the chronologies for Laurentide ice advance and retreat needs to be revised to include these new data.