Quaternary geology of the Atlantic Coastal Plain
Donald J. Colquhoun, Gerald H. Johnson, Pamela C. Peebles, Paul F. Huddlestun, Thomas Scott, 1991. "Quaternary geology of the Atlantic Coastal Plain", Quaternary Nonglacial Geology, Roger B. Morrison
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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.