Bedrock Geology of Western Story County, Iowa

In Story County the glacial drift rests directly upon both Pennsylvanian and Mississippian rocks. The Pennsylvanian, as now known from outcrops and well borings, is limited to the Cherokee group. The Mississippian rocks known to directly underlie the drift are assigned to the following formations, in descending order, the St. Louis, Warsaw, Keokuk, Gilmore City, and the Hampton. Although it is highly probably that the Burlington formation, stratigraphically between the Keokuk and the Gilmore City, also underlies the drift, no evidence of it has as yet been recognized. The St. Louis and the Warsaw are the only exposed Mississippian formations