SURFICIAL GEOLOGY OF THE CHILLICOTHE, OHIO REGION

The Ohio Department of Natural Resources, Division of Geological Survey currently is conducting detailed mapping of the surficial geology of the Chillicothe, Ohio region at 1:24,000 scale. The area surrounding Chillicothe has a uniquely diverse geologic setting. This location, being near the terminus of both the Illinoian and Wisconsinan ice advances, displays dramatic changes in the landscape over short distances. Surficial deposits of Illinoian and Wisconsinan till, outwash, and loess dominate much of the area surrounding Chillicothe. Well-defined kames, eskers, and outwash terraces also are present in the mapping area. The Scioto River, one of the most prominent features in the area, sits atop a buried valley. Prior to glaciation, the ancient Teays River flowed in a northward direction. As Pre-Illinoian glacial ice advanced southward, it blocked the Teays northward drainage, creating Lake Tight. As water levels rose, the lake breached lower-elevation topography, causing a new southward-flowing Deep Stage drainage. During the Deep Stage, sections of the original Teays valley were abandoned and left hanging more than 100 feet above the modern drainage. Subsequently, as ice advanced and retreated over the area, the main valley was infilled with glacial debris consisting mostly of outwash. During mapping, a large exposure of laminated silt and clay was discovered in the upper reaches of a valley west of the Scioto River. Given the elevation and nature of the sediments they were possibly deposited as part of Lake Tight. It is possible that additional Lake Tight deposits are present in similar valleys across the region. Additional exposures like this could lead to a better understanding of the extent of Lake Tight. Surficial geology and bedrock topography maps currently being produced will aid in further understanding the glacial history of the Chillicothe region.