HYDROSTRATIGRAPHIC UNITS DELINEATED FROM A DEEP COREHOLE IN ORANGEBURG, SOUTH CAROLINA

Ten hydrostratigraphic units are delineated from a deep (1,138 feet) corehole in Orangeburg, South Carolina. The basal, unnamed confining unit consists of indurated, clayey, feldspathic and quartzose sand beds and kaolin-rich clay beds of the Cape Fear Fm. The McQueen Branch aquifer overlies the confining unit and consists of unconsolidated, fine to very coarse, micaceous, quartzose sand of the Cape Fear and Cane Acre Fms. Pumping tests indicate a transmissivity of about 27,000 ft²/day (feet squared per day). The McQueen Branch confining unit consists of calcareous, carbonaceous, silty clay beds of the Tar Heel, Bladen, and Donoho Creek Fms. The Crouch Branch aquifer overlies the confining unit and consists of unconsolidated, fine to very coarse, micaceous, quartzose sand and interbedded sand and clay of the Donoho Creek and Steel Creek Fms. Pumping tests indicate a transmissivity of about 11,000 ft²/day. The Crouch Branch confining unit consists of feldspathic, clayey sand and sandy clay beds of the Steel Creek and Sawdust Landing Fms, and carbonaceous, silty clay of the Rhems Fm. The Gordon aquifer consists of unconsolidated, fine to very coarse, quartzose sand and thin clayey sand and sandy clay beds of the Congaree Fm. Pumping tests indicate a transmissivity of about 3,000 ft²/day. The Gordon confining unit consists of glauconitic, sandy marl of the Santee Limestone. The Middle Floridan aquifer consists of indurated, moldic, shelly limestone and marl of the Santee Limestone, and interbedded sand and clayey sand of the Tinker Creek and Harleyville Fms. The Middle Floridan confining unit consists of carbonaceous, sandy, silty, clay beds of the Ashley Fm. (?). The surficial aquifer consists of unconsolidated, fine to very coarse, clayey sand of the Ashley Fm (?). Two hydrogeologic cross sections illustrate the lateral continuity of these units to the west and south. Representative core samples of each unit are presented.