PRE-WISCONSINAN GLACIAL ADVANCES ACROSS THE DEEP STAGE VALLEY IN THE CINCINNATI, OHIO AREA

The age and significance of fluvial erosion deeper than recent, known as the Deep Stage, are problematic. Here we report new insights into the stratigraphy infilling the Deep Stage valley near Cincinnati. Over 90 deep boreholes have been drilled across a 2-km width of the Deep Stage valley in western Boone County, Kentucky. These borings provide evidence for at least five pre-Wisconsinan glacial advances of the southern Laurentide ice margin that reached northern Kentucky. The advances are generally characterized by clayey till sheets separated by dense outwash sand and gravel layers or by clayey alluvium and/or lacustrine layers. Simple index classification tests (grain size distribution and Atterberg limits) distinguish separate tills in the buried valley. Using these index tests, the uppermost till (Unit 1) can be distinguished based on grain size and plasticity. Two other groups (Units 2-3 and Units 4-5) can be distinguished based on plasticity. Based on stratigraphic relationships and on limited available index test data for uplands tills, Units 4 and 5 are documented in the uplands, suggesting that the portion of the now-buried Deep Stage valley west of Boone County, Kentucky was in place at the time of the initial Laurentide ice invasion to the southern glacial limit.