Berryville Clay Member of the Coosawhatchie Formation of Hawthorne Group here named in southeast GA. Offshore, on the continental shelf, the Berryville constitutes the entire Coosawhatchie, and at its type section near Berry Landing was previously referred to the Coosawhatchie Clay Member of the Hawthorne Formation (Ernissee, Abbott, and Huddlestun, 1977; Abbott and Andrews, 1979). Unit extends from Jasper Co., SC, along the coastal area and continental shelf of GA, to northeastern FL. Consists principally of yellowish gray to light olive gray, thin-bedded to laminated, silty phosphatic, calcareous in some areas, variably siliceous clay. Minor lithologies include quartz sand and silt. Dominant minerals are smectite in the type area and palygorskite offshore. Disconformably or paraconformably overlies the Marks Head Formation or gradationally overlies the Tybee Phosphorite Member (new name) in GA, but paraconformably overlies the Cooper Formation on the shelf. Grades laterally westward into the overlying Ebenezer Member (new name). The Berryville is at least 9 ft (2.7 m) thick at the type locality, but contacts are not exposed. Greatest known thickness in type area is 54 ft. A maximum thickness of 175 ft (53 m) is recorded offshore. Age is middle Miocene (early Serravallian) based on Foraminifera.

Source: GNU records (USGS DDS-6; Reston GNULEX).