THE CAROLINA BAYS

Optically Stimulated Luminescence (OSL) dating:



Over the last several years, Ivester et al. (2002, 2003, 2004a, 2004b, 2007) have dated the sand rims of numerous Carolina Bays using Optically Stimulated Luminescence (OSL) They found sand rims of many Carolina Bays to be as old as 80,000 to 100,000 BP. For example, Ivester et al. (2002) wrote about Flamingo Bay, a Carolina Bay:

In the upper Coastal Plain, dates from Flamingo Bay indicate the rim was active at 108.7 ± 10.9 ka BP and again at 40.3 ± 4.0 ka BP. The nearby Bay-40 had an actively forming sand rim at 77.9 ± 7.6 ka BP. Near the confluence of the Wateree and Congaree Rivers in the middle Coastal Plain, an eolian sand sheet was dated to 74.3 ± 7.1 ka BP.
About Carolina Bays in general, Ivester et al. (2004a) concluded:

Luminescence and radiocarbon dating of inland dunes and Carolina bay rims indicate activity during multiple phases over the past 100,000 years. Some bays have evolved through phases of activity and inactivity over tens of thousands of years, as evidenced both by multiple rims along a single bay and by multiple ages within single rims.
and

Both dunes and bays were active during the Wisconsin glaciation, with ages tending to fall between 15,000 and 40,000 years BP, and near the isotope stage 5/stage 4 boundary 70,000 to 80,000 years BP.
Based on OSL dating, Brooks et al. (1996, 2001), Grant et al. (1998), and Ivester et al. (2002, 2003, 2004b) argue that lacustrine and eolian processes have periodically modified the shape and size of the Carolina Bays during the last 100,000 to 120,000 years. For example, Ivester et al. (2003), using OSL dating, dated the nested, concentric sand rims, which are found in Big Bay, a Carolina Bay in South Carolina.

From the outside to the inside the age of the rim becomes progressively younger, i.e. 35,660±2600; 25,210±1900; 11,160±900; and 2,150±300 years BP. These dates demonstrate that Big Bay has shrunk over the last 36,000 years by 1.6 miles (1 km). Ivester et al. (2004a) also found these rims to be composed, not of impact ejecta, but rather "are composed of both shoreface and eolian deposits". Concerning the Carolina Bays, they concluded:

The optical dating results indicate that present-day bay morphology is not the result of a single event, catastrophic formation, but rather they have evolved through multiple phases of activity and inactivity over tens of thousands of years. This is evidenced both by multiple rims of differing ages along the same bay, and by multiple ages within single rims.

On the basis of 45 OSL dates from and sedimentological analyses of rims of Carolina Bays in Georgia and South Carolina, Ivester et al. (2007) concluded that their rims were actively modified between 12,000 to 50,000 BP; 60,000 to 80,000 BP; and 120,000 to 140,000 BP.