QUATERNARY EOLIAN SYSTEMS AND CAROLINA BAYS OF THE U.S. ATLANTIC COASTAL PLAIN PROVINCE

Inland vegetated (stabilized) eolian dunes and sand sheets of Quaternary age are present throughout much of the U.S. Atlantic Coastal Plain. These locations include: (1) river valleys; (2) interfluvial upland areas of the northern coastal plain; (3) the Carolina Sandhills region; and (4) adjacent to low relief elliptical depressions named Carolina Bays. Most of these eolian sediments are composed of fine to medium sand, although silt is common in the northern coastal plain and coarse sand is common in the Carolina Sandhills region. The eolian dunes are parabolic in upland areas of the northern coastal plain and in river valleys, linear in the Carolina Sandhills region, and arcuate adjacent to Carolina Bays. Some eolian dunes show cross-cutting relations with Carolina Bays, such that some Carolina Bays are inset into eolian dunes and other Carolina Bays are overlain by eolian dunes. 89 previously published optically stimulated luminescence (OSL) ages from these various eolian sands range from ~92–5 ka, and 61 of these OSL ages occur within or near the interval of the last glacial maximum (LGM). These OSL ages suggests that eolian sediment mobilization occurred episodically at any given site, and that the eolian sands are relict features that have subsequently been stabilized and degraded by vegetation and pedogenic processes. Parabolic dune orientations suggest that the winds that mobilized the sand blew from the northwest in Maryland and Delaware, and from the west in North Carolina, South Carolina, and Georgia. Eolian sand mobilization would have required conditions of stronger wind velocity (at least 4–6 m/sec), and would have been facilitated by LGM conditions of lower air temperature and humidity, and reduced vegetation cover. Stratigraphic relations of eolian dunes and Carolina Bays, as well as generally coincident OSL ages, suggest that the Carolina Bays are relict features that formed episodically during the same time interval as the various eolian sands. This interpretation of Carolina Bays as relict features that formed under a colder and windier climate suggest that they may be relict thermokarst lakes (which develop via thaw and collapse of frozen ground with subsequent lacustrine and eolian modification), and thus their distribution may provide information about the former distribution of frozen ground.