The state of South Carolina has an area of 30,989 square miles, of which 494 square miles are water. More than 20,000 square miles, or about two-thirds of the area of the state, is in the Coastal Plain. It varies in width from about 120 miles to 150 miles, and in elevation from sea-level to nearly 600 feet above sea-level. The rest of the state is in the Piedmont and the Blue Ridge Province.
The sedimentary rocks of the Coastal Plain have a feather edge along the Fall Line and increase in thickness toward the coast. In the southeastern part of the state at Parris Island, they are about 3,500 feet thick, and in the northeastern part near Conway, they are about 1,400 feet thick. A deep well near Charleston was still in Upper Cretaceous (Black Creek) at 2,007 feet. The Coastal Plain sedimentary rocks overlie the basement complex and range in age from Cretaceous to Recent, although it has been reported that rocks of Triassic age were penetrated in water wells near Florence where the Black Creek formation of the Upper Cretaceous is at the surface. The rocks are probably 90 per cent marine in origin: poorly consolidated sands, shales, marls, and shell marls in a few places indurated into fairly hard local limestones. The younger formations overlap on the Cretaceous, representing broad advances and regressions of the seas.
Several deep wells have been drilled, but there is as yet no commercial production of oil and gas. Reports of