COASTAL PLAIN HISTORY AS REVEALED BY HIGH RESOLUTION TOPOGRAPHIC SURVEYS, HORRY COUNTY, SOUTH CAROLINA

The close relation between topographic expression and the history of formation of the Coastal Plain has been known and used by researchers for nearly a century. Topographic expression is usually the first aspect of a region that is used in researching the history of coastal plain formation. Where subsurface data is acquired, the generalities of the sequence of formation discerned from the topography are usually expanded into greater detail.

Both the topography and subsurface of Plio-Pleistocene deposits in Horry County, South Carolina, have been studied using high resolution topographic maps and a variety of subsurface techniques. High resolution topography has revealed the fine details of many past depositional environments typical of coastal zone accretion. Additionally, the topography often implies a sequence of formation. Where subsurface data has been obtained, the sequence stratigraphy corroborates the order of deposits suggested by the topography. High resolution topographic expression appears to be a faithful proxy for depositional sequence and sequence stratigraphy in this section of the lower Coastal Plain.

The record in Horry County, South Carolina, is dominated by a series of seaward building beach-dune ridge deposits and associated inlets, lagoons and marshes. Due to uplift on the Cape Fear Arch, this portion of the coast has become sediment starved during late Pleistocene high sea level stands. The late Pleistocene record is one of eroding older sediments and redistributing them to form newer coastal features. Although the generalities of this history have been known for decades, the high resolution topography adds details to the diversity of features preserved from all ages, expands the complexity of short term events associated with each high stand and establishes a logical sequence of sedimentary events within this portion of the Coastal Plain.