THE ORANGEBURG AND PARLOR SCARPS: SURFICIAL CONTACTS SEPARATING THE EOCENE, PLIOCENE, AND PLEISTOCENE SEDIMENTS IN ALLENDALE, SOUTH CAROLINA

Detailed 1:24,000 –scale geologic mapping has defined the areal and three-dimensional distribution of preserved Eocene, Pliocene, and Pleistocene depositional systems adjacent to the Savannah River in South Carolina. Mapping was conducted on the basis of surface exposures; observations of cuttings from power-auger and hand-auger holes; and on geomorphic expression, elevation, and soil types. The Cenozoic units are bound by a number of erosional scarps. In the Allendale area, the Orangeburg scarp toes at +60 m and the Parlor scarp toes at +42.5 m. The Orangeburg scarp was formed by a sea level high stand associated with the Pliocene Duplin Formation deposits. The Parlor scarp was formed by a subsequent, lower high stand associated with the early Pleistocene Marietta unit deposits. The geomorphic and stratigraphic expression of both scarps is modified by several factors. Those factors are: the river-dominated nature of the sediments from the Savannah River; the post-depositional erosion by the Savannah, Salkehatchie, and Coosawhatchie river drainages; and eolian erosion from Carolina Bay formation.