Abstract

Contemporaneous normal faults in Late Mississippian sandstone are approximately parallel with structural strike and are downthrown in the direction of dip. Dip of the faults decreases from 70 degrees to 40 degrees with depth. Throw of the faults decreases upward from a maximum of less than 60 feet. Part of the sequence is thicker on the downthrown block of each fault than on the upthrown block, and the faults are buried beneath younger, unfaulted beds. Faulting was initiated by downdip mass flow of hydroplastic clay and unconsolidated sand on an unstable initial slope. Normal gravity-slide faulting at the updip edge of the moving mass produced an irregular surface that permitted accumulation of greater thickness of sand in the depressed blocks.

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