Abstract

Regional subsurface correlation and study of three outcrops in northern West Virginia are combined with data available in the geologic literature to provide a regional overview of the paleogeographic and sedimentologic evolution of the Upper Devonian Catskill delta complex of the central Appalachian basin.

Approximately five major river systems dominated the Catskill coastal plain during the Upper Devonian. Debouchement of these rivers into the Catskill sea during the Frasnian and lower Famennian Stages produced lobate shorelines dominated by fluvial processes in the vicinity of the rivers and by tidal processes in large embayments located between the delta lobes. By upper Famennian time, each delta system had expanded to supply sand rich sediment to wave dominated fluvial-deltaic aprons encompassing 160 km of shoreline and extending 130 km inland. Subsequent transgression of the coastal plain in latest Devonian produced embayed shoreline configurations.

Isopach mapping of sandstones of the Preston fluvial-deltaic apron (late Famennian; northern West Virginia) indicates that changing patterns of river avulsion resulted in the formation of numerous individual sandstone belts that are interpreted to mark paleoshoreline trends. Overprinting by eustatic sea-level changes and variations in total river discharge associated with the ongoing Acadian Orogeny grouped these individual units into distinct sandstone bundles. The relative importance of eustacy over orogeny as the major destabilizing force on the position of Catskill shorelines is interpreted to have gradually increased throughout Upper Devonian.

Southward migration of the area of maximum rate of coastal plain extension, from southern New York (Frasnian) to southern West Virginia (latest Famennian), reflects the southward translation of the Acadian Orogeny during Upper Devonian.