Pleistocene-Recent stratigraphy, evolution, and development of the Apalachicola coast, Florida

Pleistocene sediments, which thicken to the southwest, have been deposited on an uneven Miocene surface of variable age. The thickest section consists of two superimposed sequences of clastic sediments grading upward from coarse to fine and representing two major late Pleistocene sea-level fluctuations. Radiocarbon dates and stratigraphy indicate that the upper probably represents a mid-Wisconsin, and the lower a Sangamon transgression of the sea. Thickest Recent sediments occupy the old Apalachicola River valley, cut during the last lowering of sea level, filled with sediments, and inundated by the Recent rise in sea level. A high stand near present sea level, between 24,000 and 40,000 yr B.P., probably corresponds to Silver Bluff shoreline of Florida and Georgia. Sea level was 10 to 15 feet below present between 4,000 and 4,500 years ago.