Geology and groundwater resources of western Crawford County, Pennsylvania

Western Crawford County is in northwestern Pennsylvania. The project area is 15 to 20 miles south of Lake Erie and is bordered on the west by Ohio. Drift of Pleistocene age (Wisconsinan Age) covers most of the area, which is a maturely dissected plateau. The drift in the upland area is mostly till, which ranges in thickness from 0 to 25 feet. In the large stream valleys and deep buried valleys the drift is as much as 500 feet thick. The bedrock was mapped in detail and consists of rocks of Devonian, Mississippian, and Pennsylvanian age. Devonian rocks underlie the entire area and form the bedrock surface in most of the northern one third of the area and in the deep bedrock valleys. Mississippian formations underlie the uplands in the southern two thirds of the area; these are capped by thin remnants of Pennsylvanian rocks and knobs near the south edge of the area.