Abstract

Holocene beach-ridge development has produced a sequential constriction of many of Georgia's tidal inlets. Inlet constrictions were produced as marginal spits encroached on both sides of many of Georgia's inlets. The constriction of the inlets appeared to be a response to retreating shorelines, seasonal reversals in longshore sediment transport, localized flood channel deposition, and decreasing lagoonal tidal prisms caused by marsh deposition. While the inlets were contracting along their horizontal axes, they were expanding along their vertical axes. The slow retreat of the shoreline produced by the Holocene transgression was expressed by washover deposits in low-lying areas and bluff development in other areas. Sediment was transported away from the bluffs by longshore currents and was deposited in sand bodies on the margins of tidal inlets. Seasonally reversing longshore currents and flood-dominated channeling permitted accretion on both margins of many inlets. Reversing tidal currents produced sediment accumulations landward of the inlets and tidal deltas seaward of inlets. During the Holocene, the rising sea level produced expanding lagoonal tidal prisms and an increase in the volume of water exchanged through the inlet throats. The increased exchange through the inlet throats produced high velocity currents that eroded the floors of the cannel (at the inlet throats) and scoured deep troughs into the underlying Pleistocene, Pliocene, and Miocene deposits.

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