ABSTRACT

The Coffee Group of Upper Cretaceous age within the Desha Basin is composed of two major lithologies; a light to dark marlstone and a series of white, fine to medium grained siltstones and sands. There are two source areas for the sands; the Sharkey platform to the south and the southern Appalachian Mountains to the east. The presence of hydrocarbons have been described at the outcrop and in subsurface cuttings and cores. Depositional environments in the shallow shelf consist of lagoons, barrier island bars, offshore bars and surge channel deposits. Southwest regional dip of approximately 40 ft/mi (7.5 m/km) is reflected on all upper Cretaceous horizons. Cross sections, isopachous and structure maps of various sand intervals depict depositional environments and the regional geology. Entrapment of oil is postulated in up dip portions of these shallow shelf sands similar to fields in southern Arkansas.