Late pleistocene paleowind directions, Atlantic Coastal Plain, U.S.A

Abstract

Parabolic dunes, transverse dunes and fields of irregular dunes are common along the left banks, the north or east sides, of streams of the Atlantic Coastal Plain from Georgia to Delaware and probably beyond. Similar dunes occur in the Appalachian Piedmont, but are less common. The features have been eroded, to some extent, and are normally recognizable on topographic maps only as areas of irregular topography with wet and dry depressions. The larger parabolic dunes can be recognized on aerial photographs and satellite images because the associated soils are poor and the vegetative cover relatively sparse. The dunes are of eolian origin and late Pleistocene in age. It is thought that most of the dunes are late Wisconsin in age and contemporary with the Carolina Bays. A small sample of paleowind directions based on average directions of parabolic dune axes indicates that late Wisconsin winds in Georgia were westerly and grain sizes suggest that the winds were stronger than present-day coastal winds of the area. Paleowind directions shift progressively toward the south across the Carolinas and are southwesterly in North Carolina. They change abruptly to the northwest in the Delmarva Peninsula. Following the theory that Carolina Bays are former lakes that are elongated perpendicular to the effective wind direction, the fact that paleowind directions derived from Carolina Bay orientations are virtually identical to those from parabolic dune orientations, strongly supports the wind orientation theory of Carolina Bay origin and confirms the validity of the small sample of directions obtained from parabolic dunes. By analogy with dunes of the eastern shore of Lake Michigan and the Atlantic and Pacific Coasts, the Atlantic Coast Plain dunes do not necessarily indicate arid conditions. The sediment load of some streams may have been sandier than at present and streams with sandy, braided channels may have been common.