A DETAILED SURFICIAL GEOLOGIC MAP OF PORTIONS OF THE OCEAN FOREST AND HAND 7.5-MINUTE QUADRANGLES, MYRTLE BEACH, SOUTH CAROLINA

This paper presents a surficial geological map for portions of the Ocean Forest and Hand 7.5-minute quadrangles in northeastern-coastal South Carolina as part of the EDMAP 2005 mapping program. The region covered by the quadrangles is dominated by the modern marine system to the southeast and a series of Pleistocene beach ridges and terraces to the northeast, capped by more recent Carolina Bays, dunes and sinkholes. Building off previous studies we further subdivide the surficial geological units of this coastal area. Detailed subsurface stratigraphy is provided by continuous 2-D and 3-D ground penetrating radar surveys verified by shallow vibracores. The geomorphology is defined by approximately 0.3-m topographic contour data and 3-D real-time kinematic GPS, combined with high-resolution aerial photography in a geographic information system. Combining stratigraphy, geomorphology and constructional context to the geologic framework, the older maps have been refined to include previously undescribed coast-parallel barriers and lagoonal regions. The offshore section consists of a series of modern boulders, shell, sand, and mud bodies overlying a stepped series of Cretaceous, scattered Tertiary (?), and Pleistocene units, decreasing with age landward. The Myrtle Beach barrier system is revised, as are the lagoonal and barrier facies of the Socastee Formation. The GPR data to the north portion of the study area displays dipping beds to the west, possibly representing spit growth along the Jaluco barrier system. Data on the eastern side of the Atlantic intracoastal waterway (ICW) display signs of dipping beds towards the modern coast along the coast-parallel Pleistocene Myrtle Beach barriers.