Field Guide to Berea Sandstone Outcrops in the Black River Valley at Elyria, Ohio: Slumps, Slides, Mud Diapirs, and Associated Fracturing in Mississippian Delta Deposits

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Synsedimentary slumps of Berea Sandstone and diapirs of Cleveland and Bedford Shales are seen in complex delta-front facies at Elyria, Lorain County, OH. Analysis of orientations of fractures, bedding, and crossbeds helps interpret the history of deformation. In many instances, initial conjugate shears formed with least stress parallel to paleoflow, down the paleoslope. Some conjugate joints subsequently become normal and strike-slip faults. Some blocks of Berea show tilting and/or sliding to the extent of creating recumbent overturned drag folds in subjacent shales. Deformation of slide bases varies from brittle to plastic (fluidized). These features support the view that irregular thicknesses of Berea Sandstone are the result of deformation and are not fillings of deep valleys eroded in a Red Bedford delta. We suggest that the Berea represents rapid progradation of sands over formerly deep-water shales following rebound at the end of foreland-basin subsidence.


Author Institution: Department of Geology, Kent State University



The Ohio Journal of Science. v91, n1 (March, 1991), 35-48