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Cores from more than 75 near-outcrop localities in Kentucky have been studied to determine the thickness and extent of shale containing more than 8% organic carbon by weight. Detailed microstratigraphy of the Upper Devonian sequence is made possible by the completeness of cores, the spacing of holes, and the recognition of key lithostratigraphic and biostratigraphic markers associated with radioactivity profiles of the sequence.

Episodic and localized subsidence of the arch along the west flank of the Appalachian basin is demonstrated by erratic thickness changes in the lowermost units of the Ohio Shale. These units include equivalents of the Blocher, Morgan Trail, and Camp Run Members of the New Albany Shale to the west. The syndepositional movement appears to have been most intense along the Irvine-Paint Creek and Kentucky River fault zones. These zones also had an influence on the preserved distribution of the Silurian and Middle Devonian units immediately underlying the shale.

Earlier studies indicated that most formal members of the New Albany Shale of the Illinois basin diminish or disappear where traced across the Cincinnati arch eastward into the lower part of the Ohio Shale. This study documents the details.

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