Pre-Illinoian Glacier

The term refers to glacial advances during the Pleistocene Ice Age that preceded the advance of the Illinoian glacier. In the classic subdivision of the Pleistocene in North America, four glacial advances occurred. From oldest to youngest: Nebraskan, Kansan, Illinoian, and Wisconsinan. Deposits from the pre-Illinoian advances, Nebraskan and Kansan, are poorly preserved in a limited area near Cincinnati. Because of the lack of evidence to assign these sediments to either Nebraskan or Kansan, they are referred to as “pre-Illinoian.”

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