STRATIGRAPHY OF THE UPPER DEVONIAN OHIO SHALE IN SOUTHERN WEST VIRGINIA

Data from closely spaced wells are used to delineate the internal stratigraphy of the Ohio Shale in southern West Virginia. The Ohio Shale is a transgressive black shale that onlaps the underlying Java Formation. The interval thins to the east where the black shale of the Huron Member intertongues with, and feathers out in, gray silty shale. Thickness ranges from about 800 feet in the west to 200 in the east.

The basal unit is the Huron Member that consists of pyritic black shale and silty black shale interspersed with cross bedded gray silty shale. The frequency of intertonguing increases up section delineating at least 5 intervals/cycles in the lower Huron. An upper tongue is separated from the lower part of the Huron Member by a tongue of gray silty shale which thins to the west and eventually pinches out in the black shale of the Huron Member.

The upper unit is the Cleveland Member an eastward extension of the youngest major tongue of the Ohio Shale. In southwestern West Virginia it thins from 150 feet in the west to a feather edge where it pinches out between the Bedford Shale and the Chagrin Shale.

Deposition of the black shale occurred as sea level rose onlapping a very flat disconformity at the top of the Java Formation. Organic-rich sediments were deposited in relatively shallow water where circulation was restricted and anoxic conditions prevailed.