OVERVIEW OF THE STRATIGRAPHY OF THE PERMO-PENNSYLVANIAN DUNKARD GROUP, APPALACHIAN BASIN

Dunkard Group strata, the youngest in the central Appalachian Basin are preserved in the northeast-southwest trending Pittsburgh-Huntington Synclinorium and are bounded by erosion on all sides. The maximum preserved sections of approximately 1,200 feet occur beneath the highest hills along the synclinorium axis in northwest West Virginia and southwest Pennsylvania. The Dunkard Group is named from exposures along Dunkard Creek, a tributary of the Monongahela River which flows west-to-east in the border area of West Virginia and Pennsylvania. The Dunkard Group included all of the strata above the top of the Waynesburg coal and was first divided into the Washington and Greene Formations. Later the lower part of the Washington Formation was designated the Waynesburg Formation and the base moved to the base of the Waynesburg coal. A plethora of names assigned to stratigraphic units by various state and federal investigators has lead to some confusion across state lines. One example is the identity and possible miscorrelation of the Jollytown A, Hundred, Jollytown, and Tenmile coal beds. Historically, lack of exposures has made resolution of these correlation issues difficult. Today logs of core holes penetrating the Dunkard Group enroute to minable coal beds below the Dunkard have clarified these relations.

The Dunkard Group is comprised of interbedded gray, green, and red shale, gray, green and red claystone and mudstone, nonmarine limestone, immature, fine grained sandstones, siltstones, and thin, impure coals. There are no known marine beds in the Dunkard Group, although the brackish form Lingula has been found in shale associated with the Washington coal bed in eastern Ohio and nearby areas of West Virginia. Calcareous material is common in siliciclastic facies both as nodules and in disseminated form. The coals are economically unimportant with the local exception of the Washington coal and the Waynesburg coal where the Waynesburg Formation is in usage. The Dunkard Group thins from south to north. The limestones and coals thin out and disappear to the south, where the Dunkard is dominated by sandstone, red shale, and red claystone and mudstone.