Abstract Subtidal shoals composed of Pleistocene and early to middle Holocene deposits, on the north-central South Central inner shelf, have been modified by wave and tidal processes since being flooded during the Holocene sea-level rise. The shoals, which extend seaward up to 20 km, are composed of a wide variety of sediment types, including silt- to gravel-size terrigenous clastic sediments, abundant shell material, and peat. Typically, the shoals terminate on their seaward ends at abrupt dropoffs, with relief commonly exceeding 14 m over a distance of 0.5 km. Three skoals, located off the Santee/Pee Dee Delta, Cape Romain, and the entrance to Bulls Bay, were studied by means of vibracores, scuba observations, box cores, bottom-sediment samples, and extensive bottom fathometer profiles. The shoal complex seaward of the modern Santee/Pee Dee Delta is the largest of the three studied, most probably because (at a lower sea-level stand) the Santee and Pee Dee Rivers were joined, forming a large deltaic deposit. Shore-parallel scarps on the shoals correlate well with updip stratigraphic units and most probably give evidence of pauses during the most recent sea-level rise. The shoal seaward of the modern Cape Romain cuspate foreland contains stacked packages of progradational mid- to lower shoreface (barrier-island) deposits. This progradational, downdrift-trending shoreline sequence is backed by a 6- to 7-km-wide back-barrier region and was formed during a pause or a drop of the most recent sea-level rise. All evidence indicates that the present transgressive Cape Romain barrier islands have migrated landward en mass away from the submerged shoal. The Bulls Bay shoal, which probably originated as an abandoned delta lobe of the ancestral Santee River, shows the highest degree of modification and is characterized by abundant ridge topography and high shell content. The reworked ridges have lengths of 1 to 2 km and elevations of 2 to 4 m. Shoal surfaces show evidence of significant wave and current modifications, such as abundant bedforms and erosional scarps. Southwesterly-facing scarps were cut presumably by storms (hurricanes). However, bathymetry, sediment-distribution patterns, bed-forms and gross morphology of the shoals indicate thai northeasterly waves dominate normal shelf processes.

Abstract The sedimentary deposits of the Santee River deltam, South Carolina, consist of two primary facies: (1) a 13-m-thick Late Pleistocene-Holocene alluvial sequence composed of coarse-grained, fluvial, point-bar deposits; overlain by (2) a 7-m-thick fine-grained deltaic complex. During the Wisconsin low stand of sea level, the river incised a deep valley, which in response to the Holocene sea-level rise, aggraded with fluvial deposits. During active channel migration within the confines of the valley walls, multistage, stacked, point-bar and channel sands were deposited. A decrease in river gradient brought about by the continued rise in sea level resulted in widespread overbank deposition and eventual stabilization of the fluvial channels by 7,000-5,000 BP. Sea-level stabilization at about this same time period initiated constructional phases of delta formation. A stratigraphic model for delta evolution has been constructed through analysis of 63 vibracores, 45 power augers, 30 gouge augers, and 12 radiocarbon dates. The alluvial sediments comprising the valley fill unit are composed of pebbly, coarsegrained sand deposited as fluvial, multistage, stacked, point-bar and channel deposits capped by a widespread, fining- upward, sandy clay unit representing floodplain deposition. The overlying deltaic complex is a gently inclined, seaward–thickening sediment body consisting of a lower delta plain and delta front facies. The lower delta plain deposits are composed primarily of organic-rich muds deposited in freshwater swamp and open bay environments. In a seaward direction, these deposits interfinger with estuarine sands and muds deposited in back–barrier–related environments of the delta front. The present delta front is in a destructive phase as the shoreline is advancing landward beyond reworked, abandoned deltaic deposits in water depths of 5-10 m. The facies complex of the Santee River delta should provide some insight into the stratigraphic nature of medium-to small-sized deltas deposited in a mixed energy setting during a major transgression.

Abstract This one-day field trip is designed to examine the morphology and stratigraphy of a mesotidal tidal inlet, Price Inlet, and barrier island, Capers Island, located in the central portion of the South Carolina coast. The tidal range in the study area averages around 2 m (mesotidal; Davies, 1964) and waves average 50-60 cm in height. Dominant longshore sediment transport is from north to south, with 150,000-200,000 m3 of sand moving past any given point on the Capers Island beach each year (Kana, 1976, 1979). The field trip will be conducted at low tide, which will allow the participants to observe in detail intertidal features such as bedforms, swash bars, and inlet channels. Trenches dug through swash bars and beach berms will allow for detailed inspection of the internal sedimentary structures of these features. The main ebb channel of the inlet will be surveyed with a depth recorder and bottom samples will be collected along its length in order to demonstrate the effects of the tidal currents in shaping the inlet and its ebb-tidal delta. A 3 km walk along the front of the northern half of Capers Island, as well as a perpendicular transect across the island’s midsection, will expose the participants to all important aspects of the morphology of a typical regressive, mesotidal barrier island. A core taken in the middle of the island will be displayed in order to augment the description of the island’s Holocene stratigraphy. An oblique aerial photograph of the area to be visited is