North Inlet-Winyah Bay Reserve, South Carolina

North Inlet-Winyah Bay Reserve, South Carolina

Geology

North Inlet waters drain a very large marsh located between Debidue Beach and North Islands and the mainland. The mainland consists of Pleistocene Storm Beach Terrain with ridges oriented in a northeasterly-southwesterly direction. These ridges intersect the Atlantic ocean at the north end of Debidue Beach. These superficial mainland features are underlain by a complex sequence of older coastal plain sediments, a sequence which is poorly understood in the immediate area at the present time.

Debidue Beach and North Island represent part of the Holocene Barrier Beach System. This system has migrated southwest in recent times, with principal evidence here being the major spit along the northern entrance to Winyah Bay, and the smaller spit migration land forms along the northern border of North Inlet.

North Inlet drains numerous tidal creeks, and two of these extend back though the marsh to lie in close proximity to the Pleistocene mainland. The creeks are very shallow in depth, never exceeding 30 feet below sea level, commonly showing floors which are occupied by sand bars. The marsh areas are underlain by silts and clays, which extend to an unknown depth below the surface. Relief is generally flat; the western third of the peninsula has the most relief with bluffs adjacent to Winyah Bay as high as 15 meters. Geologically, Winyah Bay represents a drowned river basin and receives water from an extensive drainage basin.

Soil Types

Most of the salt marsh soils in North Inlet and Winyah Bay are classified as "Bohicket silty clay loam". These poorly drained soils have a high sulfur content and are flooded twice daily by the tides. Former rice field marshes along Winyah Bay are edged with "Levy silty clay loam" soils. Marsh islands in Winyah Bay created by dredging activity include Bohicket silty clay loam soils and areas of "Udorthents, loamy" in places where fossilized shell material has been piled up.