Abstract

The discovery of high-level Illinoian outwash gravel in the Tuscarawas River valley near Port Washington, Ohio, proves that Illinoian ice existed in the headwaters of the present valley. The deposit lies 35 miles east of the outwash from the Illinoian drift in central Ohio. The gravel is 90 feet above the Wisconsin outwash terraces and was deposited in a bypass of the main Illinoian drainage channel so that it was protected from removal when Wisconsin outflowing water passed down the Tuscarawas Valley. A lower gravel terrace 30 feet above the Wisconsin level is considered late Illinoian. Evidence for identifying the gravel as Illinoian, conditions during that epoch, and a discussion of the related preglacial and Pleistocene physiographic history are presented. Evidence is given to show that the Atlantic-Gulf divide at Port Washington was incised in pre-Illinoian time instead of later. The existence of Illinoian ice as far south as Shreve, Ohio, the presence of the Illinoian gravel at Magnolia, Ohio, and the gravel at Port Washington, Ohio, make it possible to connect more accurately the Illinoian drift of the Scioto lobe in central Ohio with that of northwestern Pennsylvania. The existence of Illinoian ice across northeastern Ohio disproves statements that drainage of the upper Ohio basin during Illinoian time was through the Lake Erie basin.

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