Although the Bay Rims date from the Pleistocene-holocene boundary, the bays themselves do not.
How can this possibly be? You'll probably need to go slow here with this ol' East Texas country boy. But, I have an open mind however, so I'm trainable.
They are contemporaneous with the fluviomarine terraces upon which they occur, and therefore, were not all formed at once, but sequentially; as sea level dropped and each new terrace was exposed, new bays were formed.
You're suggesting the bays were laid down over a period of hundreds, maybe thousands of years? Some within others? And different sizes; many overlapping? But the rims are all the same age??? I understand and appreciate your familiarity with the bays, but you'll forgive my skepticism?
You recall those 100 pound hailstones mentioned in the Bible(and possibly elsewhere)? To be honest, that seems as plausible as anything else I've read so far. And that's my story and I'm stickin' to it ;^)
FGS
Back about '97 or '98 I read a paper (unfortunately, I've forgotten the author and journal, but I could probably hunt it up eventually) on bay rims in South Carolina. The researcher dated them to the P-H boundary (perhaps by Optical Stimulation Luminescense?). Formation of rims is pretty easy to understand. 12,000 to 10,000 years ago, most of North America was both colder and windier than it is now. There were still trees in South Carolina, but they would have been more thinly spread than today, sort of like a Savannah. Bays, being depressional areas, were wetter than the surrounding higher areas, and would have supported much denser stands of trees. These denser stands of trees acted like windbreaks; when wind slows down, it drops much of its aeolian load, and indeed, the thickest portions of bay rims are along the southeastern edges of bays, which would have been in the lee of prevailing winter winds. (This is similar to snow drifts forming on the lee side of a hedge or fence). The woody vegetation in bays was (and is) different from that of the surrounding upland areas, too; deciduous evergreens like Red Bay, Loblolly Bay, Sweet Bay, Dahoon, Ti-Ti, etc, while the vegetation on the uplands was dominantly oak-hickory...trees that would lose their leaves during the winter. The Bays were very effective windbreaks.
As for the ages of bays themselves, I think that was from a paper by Ray Daniels and Ehrling Gamble circa 1967. The copies weren't mine, they belonged to one of my colleagues, so it would take me some effort to track them down.
"....You're suggesting the bays were laid down over a period of hundreds, maybe thousands of years? Some within others? And different sizes; many overlapping? But the rims are all the same age??? I understand and appreciate your familiarity with the bays, but you'll forgive my skepticism?..."
I am indeed. And I think I have a good theory to explain it. I'm reluctant to post it all here, partially because it would require a lot of drawings and illustrations, and partially because I'm mulling over the possiblity of going back to school for my PhD in geomorphology, and I don't want someone else to steal my research idea out from under me. However, if you are ever in my area and would like to meet me in person, I'll be glad to talk your ear off about it. :)