Carolina bays

[2][12][13] If the long axes of these Carolina bays, as measured by Johnson (1942), are projected westward, then they generally converge in the area of southeastern Indiana and southwestern Ohio.

[2] At the northern end of the distribution of Carolina bays, within the Delmarva Peninsula and New Jersey, the average orientation of the long axes abruptly shifts by about 112 degrees to N48°E.

[2] Plate 3 of Rasmussen and Slaughter,[4] which is reproduced as Figure 51 of Kacrovowski,[2] illustrates the disorganized nature of the orientations of the long axes of Carolina bays in Somerset, Wicomico, and Worcester counties, Maryland.

[2] Most Carolina bays consist of a few meters of sand and/or mud that rest on an unconformity above a harder substrate that does not show signs of deformation or other disturbance.

For example: Cores taken within several Carolina bays have revealed a stratigraphy of a few meters of sand and/or mud resting on a unconformity above a harder substrate.

Lake Mattamuskeet (Hyde County, North Carolina):[17] Cores from within this Carolina bay revealed a 0.3–1.2 m thick unit of sand and silty sand (lacustrine deposits and paleosols) that rests on an unconformity above an undisturbed unit of gray clay and sandy clay (with marine shells and burrows) of Pleistocene age.

Charcoal and wood from a western sand rim (closer to the bay) yielded radiocarbon ages of ~5,760 and 1,270 years before present (BP).

Organic sediment and charcoal from an eastern sand rim (farther from the bay) yielded radiocarbon ages ranging from ~7,750 to 2,780 years BP.

Duke's Pond (Tattnall County, Georgia):[15] A sediment sample from a sand rim at the margin of this Carolina has yielded an OSL age of ~23,600 years ago.

[14][20][16][30][22][31] Radiocarbon dates have been obtained from organic matter collected from the undisturbed sediments filling Carolina bays by Bliley and Burney,[18] Mixon and Pilkey,[32] Thom,[33] and Kaczorowski.

During times when the water table was below the bottom of a Carolina bay (e.g., possibly during glacial periods when sea level was 130 meters (400 ft) below present), organic matter could have been destroyed by oxidization and weathering.

There are some who suggest that the oldest radiocarbon date from a Carolina bay only indicates the time when the water table rose high enough for a permanent lake or swamp to exist within it.

Some bays are predominantly open water with large scattered pond cypress, while others are composed of thick, shrubby areas (pocosins), with vegetation growing on floating peat mats.

Species that thrive in the bays' habitats include birds, such as wood storks, herons, egrets, and other migratory waterfowl, mammals such as deer, black bears, raccoons, skunks, and opossums.

Some bays have been greatly modified by human activities including farming, highway building, and construction of housing developments and golf courses.

Most geologists today interpret the Carolina bays as relict geomorphological features that developed via various eolian and lacustrine processes.

[20][16][30] Recent work by the U.S. Geological Survey[14] has interpreted the Carolina bays as relict thermokarst lakes that have been modified by eolian and lacustrine processes.

This interpretation is consistent with the optically stimulated luminescence dates, which suggest that the Carolina bays are relict features that formed when the climate was colder, drier, and windier.

[13][14] Within the Atlantic Coast Plain, the orientation of the long axes of Carolina bays and the inferred direction of movement of adjacent sand dunes, where present, are generally oblique to each other.

In southern Georgia and northern Florida, the orientation is matched by an inferred west to east direction of movement of Pleistocene sand dunes.

In the Delmarva Peninsula, the 112 degree shift in the average trend of the long axes also corresponds with a shift in the average inferred direction of movement of Pleistocene parabolic sand dunes such that their direction of movement is also oblique to the long axes, as is the case in the rest of the Atlantic Coastal Plain.

The measurement of the long axes of 200 elliptical Grady / Citronelle ponds in southwestern Baldwin County, Alabama found a very distinct orientation tightly clustered about N25°W.

[42] Undrained depressions, circular to oval in shape and exhibiting a wide range of area and depth, are also a feature of the Gulf of Mexico coastal plain in Texas and southwest Louisiana.