INVESTIGATION OF THE GEOLOGIC FRAMEWORK OF THE GRAND STRAND COAST IN SOUTH CAROLINA

The Grand Strand consists of a continuous arcuate shoreline extending from Winyah Bay to Little River, South Carolina. This northern coastal segment is dominated by mainland beaches which are attached to eroding Pleistocene headlands. A few small inlets or "swashes" dissect the coast in places. Pleistocene and Holocene age deposits generally form a relatively thin veneer of unconsolidated sediments that overlie late Tertiary or Cretaceous sedimentary units. These older indurated to semi-consolidated deposits are exposed as "hardgrounds" in the immediate shoreface zone. Wave erosion of Quaternary deposits along with the underlying older shelfal strata provides sand to this sediment-starved coastal segment. Therefore, knowledge of the geologic framework of the lower coastal plain and the inner shelf is extremely important in understanding the long and short-term coastal erosion rates that affect this region.

Sixteen borings have been drilled to a maximum depth of sixty feet along this stretch of coastline. The internal stratification, sediment texture, composition, and faunal assemblage have been analyzed to determine the age of the underlying stratal units as well as the facies relationships of the younger surficial deposits. Additional data has been derived from the interpretation of geophysical water well logs, borings from building foundations, as well as existing core data. This land-based data will be coupled with additional information obtained from offshore seismic surveys to develop a comprehensive model for the geologic framework. It is believed that the subsurface stratigraphy coupled with Pleistocene and recent sea level fluctuations have had a profound affect on the depositional history and modification of the present day coast.