GEOMORPHIC RESPONSES OF THE CAROLINA SANDHILLS (CHESTERFIELD COUNTY, SOUTH CAROLINA) TO QUATERNARY CLIMATE CHANGES

The Carolina Sandhills comprise a 15 to 60 km-wide region along the updip portion of the Atlantic Coastal Plain province from western Georgia to central North Carolina (USA). In Chesterfield County (South Carolina), the Sandhills form a relatively high dissected plateau bounded to the west by Paleozoic schist and to the east by the Orangeburg Scarp. Poorly indurated Cretaceous sand and mud beds (mapped as the Middendorf Formation) are capped by a deeply weathered unconformity marked by plinthite and reticulate mottling. Pedogenic features in the overlying Quaternary sand include soil lamellae and modest argillic horizons. Soil survey maps suggest that thick Quaternary sand overlies Cretaceous strata on the upper parts of slopes along E-W, but not N-S, interfluvial regions. The Quaternary sand, interpreted as vegetated eolian dunes and sand sheets derived from the underlying Cretaceous sand, has yielded OSL ages ranging from ca. 21 to 8 ka. A prominant N-S scarp on the Pee Dee-Lynches drainage divide consists of broad arcuate embayments incised by headwater streams. Quaternary climate changes have induced the following geomorphic responses in the area: (1) remobilization of Cretaceous sand into eolian dunes and sand sheets; (2) headward erosion of fluvial drainages into poorly indurated Cretaceous sand; and (3) pedogenic alteration of Quaternary sands.