Abstract The surface and near-surface geology of the Atlantic Coastal Plain from Cape Fear, North Carolina to Cape Canaveral, Florida, below 76 m (250 ft) in altitude, comprises Pliocene and Pleistocene fluvial marine, back-barrier, barrier, and shallow-shelf sand, silt, and clay. The fossil content of age-equivalent Pliocene and Pleistocene sediments decreases from the Cape Fear area southward into Georgia. In the Carolinas, fossils are common. Paleontological analyses and isotopic and chemical age determinations, combined with lithostratigraphic studies and geologic mapping, have resulted in the establishment of a regional time-stratigraphic framework. In Georgia, fossils are scarce. Most known fossil localities are in early late Pliocene sediments paleontologically dated between 3.5 and 2.8 Ma. Microfossil data suggest the presence of at least two other Pliocene units—late early Pliocene (4.2-4.0 Ma) and latest late Pliocene (2.4-1.8 Ma). Fossil data are insufficient to differentiate Pleistocene units, but there are distinctive changes in shell morphology and species abundance of foraminifera in sediments topographically above and topographically below 9 m (30 ft) in altitude. No isotopic or paleomagnetic data are available for Pliocene or Pleistocene sediments in Georgia. There has been no detailed geologic mapping. Regional mapping dates to the turn of the century. The fossil-poor nature of both onshore and offshore Pliocene and Pleistocene Coastal Plain sediments in the Georgia part of the Atlantic Coastal Plain may be due to any one or combination of the following: styles and rates of regional and/or local uplift; sediment load of the numerous rivers that drain this region; freshwater influence on estuarine and nearshore littoral environments; shoreline configuration relative to major ocean currents; dissolution as the result of weathering, and erosion.

Abstract The Atlantic Coastal Plain south of the glacial limit stretches 2,200 km from southeastern New York and northern New Jersey to the Florida Keys, and is as much as 320 km wide from the Piedmont to the continental slope (Figs. 1 and 2). It is divided into three subdivisions/belts that parallel the Atlantic Coast: the Upper (Inner), Middle, and Lower (Outer) Coastal Plains (Fig. 1). The subdivisions commonly are separated by escarpments and each subdivision has distinctive topography and surficial stratigraphy. The Upper Coastal Plain is underlain by Cretaceous and Tertiary sediments that unconformably onlap Mesozoic to Precambrian rocks of the Piedmont Section; it is not discussed here. It commonly is separated from the Middle Coastal Plain by an escarpment. This topographic boundary is the Orangeburg Scarp in North and South Carolina and northern Georgia, the Chippenham and Thornburg Scarps in Virginia, and unnamed scarps in most of Georgia and northern Florida. These ancient scarps are much eroded and dissected. The Middle and Lower Coastal Plains have a stair-stepped topography comprising discontinuous, somewhat dissected plains (called terraces) at various levels that are separated by scarps (Table 1). The scarps vary in height and commonly, particularly the older ones, are obscured by mass-wasting and eolian deposits. The terrace steps decrease in altitude seaward and toward major transverse streams. The coastwise terraces are believed to be former marine shore/nearshore platforms, but they merge into or are cut by fluvial terraces along the transverse rivers. The Middle