Devonian paleocurrents of the Appalachian basin

The paleocurrent system of the Devonian clastics of the central and northern Appalachian basin is uniformly oriented to the west judging by the orientation of sole marks on interbedded siltstones and sandstones and by the available directional data from interbedded black and gray shales. Paleocurrent indicators are at right angles to isopach of total Devonian thickness, which decreases westward from 12,000 ft. in eastern Pennsylvania to a few hundred feet in west-central Ohio. This clastic wedge is largely of Upper Devonian age and includes alluvial and delta plain environments (in the east) as well as shelf (east-central), turbidite slope, and basin plain environments (west-central and west), the latter representing most of the black shales. Lithologies within the wedge are more continuous north-south parallel to depositional strike than east-west. The gradient of carbon isotopes, which shows more marine than terrestrial carbon in the western part of the basin, closely parallels the average paleocurrent direction of the basin. The methodology of paleocurrent studies in shaly basins based on both outcrops and oriented cores, is set forth as is the relationship between paleocurrents and gas potential.