Carolina Bay - Orientation

Orientation

As measured by Johnson (1942) and Kacrovowski (1977), the orientation of the long axes of Carolina bays systematically rotate northward along the Atlantic Coastal Plain from northern Georgia to northern Virginia; the average trend of the long axes of Carolina Bays varies from N16°W in eastcentral Georgia to N22°W in southern South Carolina, N39°W in northern South Carolina, N49°W in North Carolina, and N64°W in Virginia. Within this part of the Atlantic Coastal Plain, the orientation of the long axes of Carolina bays varies by 10 to 15 degrees (Johnson 1942, Kacrovowski, 1977, Carver and Brooks 1989). If the long axes of these Carolina bays, as measured by Johnson (1942), are projected westward, they converge, neither in the Great Lakes nor Canada, but in the area of southeastern Indiana and southwestern Ohio.

At the northern end of the distribution of Carolina bays within the Delmarva Peninsula, the average orientation of the long axes abruptly shifts by about 112 degrees to N48°E. Further north, the orientation of the long axes becomes, at best, distinctly bimodal, and exhibits two greatly divergent directions and, at worst, completely random and lacking any preferred direction (Kacrovowski, 1977). Plate 3 of Rasmussen and Slaughter (1955), which is reproduced as Figure 51 of Kacrovowski (1977), illustrates the disorganized nature of the orientations of the long axes of Carolina bays within the northernmost part of their distribution within Somerset, Wicomico, and Worcester counties, Maryland.

At the southern end of their distribution, the Carolina bays in southern Georgia and northern Florida are approximately circular in shape. In this area, they have a weak northerly orientation (Kacrovowski, 1977). The Carolina bays in southern Mississippi and Alabama are elliptical to roughly circular in shape. The measurement of the long axes of 200 elliptical Grady / Citronelle ponds found a very distinct orientation tightly clustered about N25°W in southwestern Baldwin County, Alabama (Otvos 1976).

Within the Atlantic Coast Plain, the measured orientation of the long axes of Carolina bays and the Pleistocene direction of movement of adjacent sand dunes, where present, are generally perpendicular to each other. In southern Georgia and northern Florida, the northerly orientation is matched by a westerly orientation of the direction of Pleistocene movement of sand dunes (Markewich and Markewich 1994). Northward from northern Georgia to Virginia, the average orientation of direction of Pleistocene movement of parabolic sand dunes systematically shifts along with the average orientation of the long axes of Carolina bays as to always lie approximately perpendicular to them. In The Delmarva Peninsula, the 112 degrees shift in the average trend of the long axes is also accompanied by a corresponding shift in the average direction of Pleistocene movement of parabolic sand dunes such that their direction of movement is also perpendicular to the long axes, as is the case in the rest of the Atlantic Coastal Plain (Carver and Brooks 1989).