Flow Structures in the Berea Sandstone and Bedford Shale of Central Ohio

Abstract

The structures in the Berea sandstone and the Bedford shale described in the past as "concretionary" or "disturbed" layers are shown to result from contemporaneous mass movements on the free surface of deposition. The top of the disturbed rock was generally truncated by erosion before the overlying undisturbed beds were laid down. Lateral movements are evident in many instances and at many levels in the formations. These movements and others in which lateral movement is not readily apparent are interpreted as surface flows and slides. The causes of subaqueous flows are reviewed in an attempt to find the reason for the flows. The conclusion is reached that they may have started spontaneously in the soft sediment as it accumulated under the conditions which obtained. Important causes of such flows include an increasing weight of sediment, a slight surface slope, and occasional beds or seams of clay which flowed readily and also acted as a lubricant between sand layers, permitting them to slide past one another.