The rocks of the Pennsylvanian and Permian Systems of the central Appalachians are a series of shales and fine- to coarse-grained sandstones, locally conglomeratic, arranged in repetitious sequences with thinner coals, clays, lacustrine and marine limestones, chert, and ironstone.

Isopachous and facies maps of arbitrarily selected thick units suggest two bodies of rocks, each with distinct orientations and distributions of swamp (organic) and lacustrine-marine (chemical) environments with respect to alluvial (deltaic) deposits. The earlier body, including the Pocahontas, New River, Kanawha, and Charleston, is a wedge of fine- to coarse-grained clastic rocks derived principally from older rocks of the Appalachians to the southeast. The sediments were deposited in a northeast-southwest–trending rapidly subsiding basin in western Virginia, southern West Virginia, and southeastern Kentucky. The coal-bearing facies thins rapidly to the northwest into massive marine (early) and deltaic (later) sandstones. The later body of rocks is divided into two groups distributed in a northerly deepening restricted basin of deposition. The lower group includes the Pottsville, Allegheny, and lower Conemaugh to the top of the Saltsburg Sandstone. Coarse- to fine-grained clastic sediments encroached on swamp, lacustrine, and marine environments in northeastern Kentucky, northern West Virginia, Maryland, Ohio, and Pennsylvania. The upper group includes the upper Conemaugh, Monongahela, and Dunkard, in ascending order. Fine (red)- to medium-grained clastic sediments of southwestern West Virginia and adjacent areas of Ohio and Kentucky encroached on swamp and lacustrine environments of northern West Virginia and contiguous areas of Maryland, Ohio, and Pennsylvania.