GEOLOGIC MAPPING OF THE CENTRAL PORTION OF THE MYRTLE BEACH 7.5-MINUTE QUADRANGLE: EDMAP 2002

The focus of this USGS-funded EDMAP study is to refine and provide a more detailed geologic map of a portion of the South Carolina lower Coastal Plain along the mid-Atlantic East Coast. This project refines smaller-scale (larger region) geologic studies, particularly the 1:250,000 geologic maps produced by McCartan et al. (1983) and Owens (1990). A contemporaneous study to the north and adjacent to this study area is currently being conducted (Kuykendall et al., 2003). Surficial geologic units in this area are underlain by Cretaceous and Tertiary strata that dip to the south, and represent regionally extensive Pleistocene and Holocene barrier islands and shelf deposits. In this area, the Pleistocene Myrtle Beach and Jaluco barriers represent former high stands of sea level and are the dominant ridges on the landscape. Lithostratigraphically, the materials beneath these landforms have been mapped as the Socastee Formation.

The findings of this study were based upon high-resolution topographic data, soil survey information, existing borehole data, fourteen new hand augers, five new vibracores, offshore rock samples and data from the USGS-SC Coastal Erosion Study. Using high-resolution topographic maps in conjunction with quadrangle-scale soil map of the study area, the boundaries between the Jaluco Formation and the Socastee Formation were identified. Indicating a stratigraphic and temporal distinction within the previously defined Socastee Formation, this study showed that the depositional environments, soils, and geomorphology of the study area provide enough support to map the Jaluco barrier system as the Jaluco Formation instead of the Socastee. The results of this study will aid other geologic research that is currently being performed, and aid the community of the Myrtle Beach area to understand the geology of the area, and therefore be able to plan the community better.