Abstract

The Devonian black shale in Kentucky is separated into two basins by the Cincinnati arch; the Illinois basin (New Albany Shale) on the west, and the Appalachian basin (Ohio Shale) on the east. Inter-basinal correlations were made using closely spaced, chemically characterized cores. Five intervals: one biostratigraphic, one geochemical and three lithologic were traceable across the Cincinnati arch. Most of the New Albany Shale correlates with the lower part of the Huron Member of the Ohio Shale; only the uppermost 1 to 2 m correlates with the Cleveland Member of the Ohio.

The Devonian black shale can be divided into three “types”. The Middle Devonian Duffin-Blocher type is characterized by high organic carbon to sulfur ratio, intermediate trace element concentrations and the presence of carbonates. This interval represents a significantly different environment from the overlying shales and was followed by a major hiatus of non-deposition and/or erosion. The Late Devonian Huron type is characterized by intermediate concentrations of organic carbon, low organic carbon to sulfur ratios (similar to that of the modern Black Sea) and low trace element concentrations. This shale type was deposited in a stagnant euxinic basin. The third is the organic rich Cleveland type, which is characterized by high organic carbon to sulfur ratios, high transition trace element concentrations which correlate with organic carbon, and the presence of phosphate nodules. This shale type was deposited during an upwelling regime.