Structural trends and fault systems in Eastern Interior Basin [U.S.]

The Eastern Interior basin is a structural basin cradled between the Ozark uplift and the Cincinnati arch-Nashville dome uplift. The two most conspicuous structural features indicated by an areal geology map are the La Salle anticline and the nearly separated lobe of the basin in Kentucky. A cross section indicates that the area acquired its basin character early and retained it through most of geologic history. A study of the folding and faulting within the basin reveals two different types of structure. One consists of a series of faults trending S. 20 degrees W. and paralleling lines of anticlinal folding. Cross sections show these faults to be normal diagonal shears and the folds to be similar to the granite ridge and related lines of folding in the Mid-Continent area. The other is the Shawneetown-Rough Creek fault zone and associated faults extending across the south end of the basin. Cross sections and data gleaned from the literature dealing with this and the Kentucky River fault zone, to which it appears closely related, show this to be an entirely different type of faulting from the system first described. On the basis of the evidence presented, the writers suggest an explanation and classification of this zone of faulting different from any that has been proposed in the past.