Model for Barrier Island-Tidal Inlet Stratigraphy: ABSTRACT

Abstract

A three-dimensional stratigraphic model for a tidal inlet-barrier island facies was constructed through examination of 37 vibracores and 10 auger drill holes on Capers and Dewees Islands, South Carolina. Two cycles of southerly inlet migration and subsequent abandonment resulted in beach ridge truncation on the northern ends of the barriers. The inefficiency of overextended migrating inlet channels caused shorter northerly oriented channels to breach the ebb-tidal delta. Inlet reorientation allowed a large wave-formed swash bar to migrate landward, attach to the barrier, and close the former inlet channel. Price Inlet formed during the onset of the Holocene transgression by submerging the ancestral Pliocene-Pleistocene End_Page 1002------------------------------ Santee River drainage system. Coarse, poorly sorted sand disconformably overlies Pleistocene estuarine clays and is capped by a dense clay plug. Beach ridges prograded seaward over the first inlet sequence. A second cycle of inlet migration truncated the northernmost part of the beach ridges and scoured into the inactive-fill clay plug of the earlier inlet deposit. The resultant stratigraphic framework consists of a stacked series of upward fining, active inlet-fill sands overlain by thicker inactive inlet-fill clay plugs. Migrating tidal inlets greatly alter barrier island stratigraphy. Reworked beach ridge sediments are incorporated into tidal inlet channels preserved on the updrift end of the barrier island. Fine-grained clay plugs form permeability barriers between adjacent barrier island sand bodies. Shoreline transgression will remove the uppermost barrier island deposits sealing the lower inlet-fill sequences between Pleistocene estuarine clays and continental shelf silts and clays. End_of_Article - Last_Page 1003------------