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Barrier Island Sequence District

Atlantic Plain Major Division

Coastal Plain Province

Sea Island Section

Barrier Island Sequence District

Pleistocene sea levels advanced and retreated several times over the Barrier Island Sequence District to form a step-like progression of decreasing altitudes towards the sea. These former, higher sea levels existed as barrier island-salt marsh environments similar to the present coast. The former sea levels left shoreline deposit complexes parallel to the present coastline at characteristic elevations: Wicomico, 160-95 feet; Penholoway, 70-76 feet; Talbot, 40-46 feet; Pamlico, 25 feet; Princess Anne, 13 feet; Silver Bluff, 5 feet; Holocene, the present mean sea level. 

There has been slight to moderate dissection of these former levels allowing marshes to exist in poorly drained low areas. Generally, dissection is further advanced toward the western portion of the district. Relief varies from 50 to 75 feet on the east side of Trail Ridge to just a few feet near marshes and along the coast. Maximum elevations are approximately 160 feet on Trail Ridge. 

The western boundary is at the western base of Trail Ridge as far north as the Altamaha River, where the ridge becomes obscure. North of the Altamaha River the western boundary is the base of the Orangeburg Escarpment which approximates the 150 foot elevation.

Source: William Z. Clark, Jr. and Arnold C. Zisa, Physiographic Map of Georgia (Atlanta: Georgia Department of Natural Resources, 1976).