LANDSCAPE EVOLUTION AND SURFICIAL GEOLOGY OF A SIGNIFICANT PLEISTOCENE BARRIER SEQUENCE: HORRY, GEORGETOWN, AND PORTIONS OF BERKELEY, CHARLESTON, FLORENCE, MARION AND WILLIAMSBURG COUNTIES, SOUTH CAROLINA (USA)

The emergent Pleistocene marine features in northeastern South Carolina continue to provide a important resource for understanding significant interglacial cycles along the U.S. Southeast coastline. Compressed more in an offshore-onshore direction, the coastal ridges are stacked more closely together than the impressive features to the south in central coastal South Carolina, leading to rapid changes in landscape expression and geochronology, and less with lithostratigraphy. Understanding these deposits requires a more robust and continuous methods of stratigraphic sampling than standard sampling methodologies. One of the largest problems in Coastal Plain studies is the attention to either the stratigraphy or the geomorphology but not both, and one is often negated in the presence of the other. Herein, we provide a detailed map of primary (constructive) geomorphic features and a standard nomenclature to assist in site location and local geomorphic convergences between ridge systems that may cause mixing of geochronologic information. Over the last twenty years, we have focused our attention to the stacked nature of these deposits, their cross-cutting relationships, and clearly discernable geochronology where possible. Several hundred line kilometers of high- and low-frequency ground-penetrating radar, high-resolution vibracores, and various geochronological methods have allowed us to better reconstruct this region and provide a clear scientific approach to analyzing the landscape (outside 1:24,000 mapping programs). This type of research provides a strong surficial geologic framework for understanding and physical modelling of long-term isostatic adjustments due to glacial advance and retreat, denudation of inland areas, accumulation of offshore materials, and hydroisostatic adjustment.