Cretaceous Deltaic Facies in Southwestern Coastal Plain of South Carolina

W. C. Fallaw, Van Price, P. A. Thayer

Cored wells within a 750-km² area in Aiken and Barnwell Counties, South Carolina, provide detailed data for facies mapping. The Cretaceous section is approximately 200 m thick in the center of the area. Facies studies are in progress for three Cretaceous units: the Middendorf and Black Creek Formations and a time-equivalent of the Peedee Formation.

Four facies occur: (1) upper delta plain--yellow, orange, and tan poorly to moderately sorted sands and thin clays; (2) distributary--tan and gray poorly to well-sorted sands and pebbly sands, some containing abundant muscovite, lignite, and/or feldspar, and thin clays; (3) interdistributary bay--white, gray, or variegated clays; and (4) delta front-prodelta--dark, poorly sorted, micaceous, lignitic sands interbedded with dark clays containing fine sand and silt laminae.

The lower Middendorf contains upper delta-plain deposits in the northwest and distributary sands; bay clays dominate elsewhere. The upper Middendorf consists of clays or sands with interbedded clays that formed in a bay environment over most of the area and in a delta-front-prodelta environment in the east.

The lower Black Creek contains upper delta-plain deposits in the northwest and distributary deposits elsewhere. Delta-front-prodelta environments were in the east and south. The upper Black Creek consists of bay clays in the northwest and delta-front-prodeltaic sands and clays elsewhere.

The lower Peedee equivalent consists mostly of distributary sands, with delta-front-prodeltaic sands and clays occurring in the southeast. The upper part consists mostly of bay clays.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.