FIGURE 6.3 Late Quaternary fluctuations in sea level. Solid line is the generalized sea level curve (from Curray, 1965); dashed line is detailed curve (from Curray, 1960, 1961). Tree ring and Uranium/Thorium dates give greater age than the radiocarbon ages for these curves. Recent studies (Fairbanks, 1989; Bard, 1990) indicate the glacial maximum was 21,000 (230TH/234U) yearsBP with a sea level lowering of 121 ± 5 m.
And the original:
Your graph is probably a rolling 1000-year average or something like it. If you could view it year-by-year, it would be a lot more erratic.
One would assume there was/is some smoothing of chart lines along the way, but it doesn't even come close to explaining the elephant in the room and that is: Give or take a few feet, the last time sea levels were as high as they are now was ~120,000 years ago. ~70,000 years ago, sea levels were ~200 - 250 feet LOWER than they are today.
Now, if one assumes, based on THIS study, that South Carolina, and by extension surrounding areas experienced no appreciable uplift in the intervening years, where does that leave us as far as explaining the bay's formation by sea level fluctuations? To this layman, it doesn't seem possible.
I did some looking around to see if the La Palma "mega" tsunami could have generated enough havoc to be associated with the bays; doesn't appear so. Liquifaction caused by earthquake(s) that may have run the length of the Appalachians might be a possibility, but do we know if anything like that ever occurred???
One other point: You seem to have a habit of avoiding or possibly putting off some of my more interesting questions. I know we all get busy or otherwise distracted at times but it gets frustrating asking questions several times before hitting pay dirt. No offense.
FGS