| The Quaternary and upper Tertiary geologic framework for the coastal zone south of Charleston, South Carolina is presented. Approximately 1400 km of high-resolution shallow seismic profiles, 2.5 km of ground penetrating radar lines, 73 new vibracores (>150 total), 122 new amino acid analyses for Mulinia lateralis (A/I; 426 total for region), and topographic and bathymetric maps are used to delineate the geologic framework and relate coastal morphology to geologic controls. The study region, including Folly Island, Kiawah Island, Seabrook Island, and Edisto Island, extends from approximately 15-km inland to approximately 15-km offshore, comprising multiple emergent coastal deposits from +15 in MSL to a highly variable shoreface to −15 in MSL. Type sections for individual seismic reflectors are presented. Composite profiles across two major coastal compartments are compiled. This detailed, multi-tasked approach to delineating a geologic framework and influences on short- and long-term coastal development provides a fundamental base-line study to future studies along the coast.; Influences of the geologic framework on coastal evolution directly affect island size and position; inlet position, size and morphology; Quaternary geomorphology and evolution; tidal channel morphology and position; and shoreface development. Three dominant coastal barrier morphologies within three distinct compartments along the coast have formed within this mesotidally dominated coastal zone. Beneath each of these distinct compartments, a defined, mappable, shallow, heterogeneous geologic framework has forced the stratigraphic and geomorphologic development of this coast throughout the last 500 ka. The individual compartments, centered on Folly, Kiawah, and Edisto islands, began to appear during the late Tertiary. Since the early late-Pleistocene, these compartments have been reoccupied repeatedly. Island morphologies and inlet positions changed very little if at all from one sea level highstand to another.; Geomorphic, stratigraphic, and amino acid racemization studies indicate at least four distinct, post-“Talbot” sea level highstands. Amino acid racemization studies reveal the possibility of multiple chronologic zones, although all were not sampled as emergent systems. Parabolic kinetics for site (horizon)-averaged alloleucine/isoleucine (Mulinia) height ratios distinguish individual sequences: P5/P5+ (Stage 19?, +9 m), P5 (Stage 15?, +8 m), P4 (Stage 9, +7 m), P3 (Stage 7, +7 m), P2 (Substage 5e, +4.5 m), P2?? (Substage 5c, 3.5 m), P1 (Substage 5a, +1 m), H2 (Stage 1, −0.5 m), and H1 (Stage 1, 0 m). These subdivisions are consistent with geomorphic and stratigraphic data both on land and off shore. |
