Abstract

The lower and middle Mississippian strata of Ohio, known as the Waverly series, consist of five formations, from older to younger: the Bedford shale, the Berea sandstone, the Sunbury shale, the Cuyahoga formation, and the Logan formation. They were laid down in the great shallow basin known as the Appalachian geosyncline. The floor of the basin rose and sank from time to time so that shore conditions with mud, sand, and conglomerate might prevail at any place, to be succeeded by deeper water and limestone formation. Sometimes it was dry, and again deltas spread across it. This resulted in a succession of deposits, varying in character as the condition surrounding their deposition changed.

The Black Hand sandstone and conglomerate member of the Cuyahoga formation of Ohio has been one of the perplexing problems of the Waverly series. This conglomeratic sandstone, correlated with the Big Injun sandstone of southeastern Ohio, forms the scenic cliffs and deep gorges of Old Man's Cave, the Rock House, Ash Cave, Cantwell Cliff, Conkle's Hollow, and Cedar Falls, in the Hocking County region.

The conglomerate facies of this sandstone occurs in elongate masses, from Vinton County at the south into Richland and Ashland counties to the north, a distance of more than 100 miles. The individual conglomerate lobes trend slightly west of north. The character of the sediments, which are marine, and the dip of the bedding planes suggest deposition in shallow water in rather strong currents with scouring action. All the evidence indicates that the currents came from the south; the true bedding planes dip 3°–15° and range in direction from N. to NE. to E. to NW.

The pebbles of the conglomerate, which are quartz, are a quarter of an inch to more than 2 inches long. They are well rounded, indicating that they have been reworked several times. The source of this quartz is believed to be to the north and northeast. When traced horizontally from the conglomeratic masses, the Black Hand member thins and contains more shale, and the sandstones are finer and do not exhibit the strong cross-bedding and evidence of scouring action. The change in facies is accounted for by the explanation that the area, during the deposition of the Black Hand member, was a shallow interior sea in which bars, spits, beaches, and deltas were developed. What appears to be a bar was built on the west side of the area. Quiet lagoons were present in which finer sands and muds accumulated. The thickness of the Black Hand (Big Injun) conglomerate suggests that the area was sinking during the accumulation of the Black Hand conglomerates. The variation in thickness of the Black Hand and the irregular contour of its top suggest a dis-conformity with the Berne conglomerate member above, at the base of the Logan.

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