Trends in the regional extent, stratigraphical distribution, and character of upper Paleozoic terrestrial rocks in the central Appalachian basin were influenced by depositional events associated with basin evolution. Most of these rocks originated as siliciclastic detritus eroded from tectonic highlands that were elevated by plate collision along the southeastern margin of the basin. Terrestrial sediments, indicated by northwestward-prograding delta lobes and fluvial systems, were deposited in a slowly subsiding foreland basin. Concurrently, marine deposition encroached from the northwest in a shallow epicontinental sea that covered an unstable cratonic shelf. Terrestrial progradation extended northwestward during periods of high rainfall and sufficient subsidence to accommodate a high influx of clastic sediments. Conversely, marine incursions extended farthest southeastward during periods of diminishing rainfall and low clastic influx. As the Appalachian basin evolved, terrestrial deposition gradually shifted northwestward and occupied the entire basin by Early Permian time. In addition, the standline or wedgeout of terrestrial coal-bearing deposits rotated from N 30°E in Early Mississippian time to N 65° E in Early Pennsylvanian time. -from Authors
