DOLINES AND CAROLINA BAYS ON THE DOUGHERTY PLAIN; AN UNCONVENTIONAL HYPOTHESIS FOR A CONJOINT GEOMORPHOLOGY

A Carolina bay survey has measured ~25,000 gentle depressions conforming to an egg-shaped 'baySouth' planform located along the coastal plains from mid-South Carolina clockwise through the Gulf Coast region. Their orientations rotate from NW-SE to N-S, respectively. They are prominent on low relief landscapes, a description that applies to the Dougherty Plain topographic province within the Apalachicola-Chattahoochee-Flint River Basin. Numerous doline/karst depressions are present within the undated (post Miocene) surficial sediments which mantle the plain. While some dolines host vernal ponds as hydraulically closed basins, many have penetrated down into the Upper Floridan Aquifer within the underlying Eocene Ocala limestone strata and function as sinks. New LiDAR-quality elevation data offers better discrimination between depressions conforming robustly to the baySouth planform shape/orientation and the more randomly shaped and randomly oriented dolines.

An unconventional hypothesis is offered for the depositional mechanism of the Quaternary member of the Dougherty Plain’s residuum, informed by the work of Daniels, Wheeler and Gamble from the 1970's. In their extensive studies, Carolina bays are asserted to be topological artifacts created during the final stages of deposition of the Coastal Plains strata they are formed within. Their analysis regarding the nature of that deposition was tested against many gradualistic processes but left unsettled. Here, a catastrophic deposition of regolith is invoked to bury an antecedent Dougherty plain and its mature dendritic drainage, effectively repaving the low relief province and instantiating a deranged drainage pattern. Such a geomorphological history may explain the existence of buried hydrological flow paths that allow ground water to mobilize and trigger linear-sequences of dolines. Also explained would be the existence of highly incised streams, where antecedent channels are recaptured by the evolving deranged pattern. Carolina bays could metamorphose over time into karst landforms through the solutioning of limestone substrate by focused percolation of collected and perched waters. The hypothesis is falsified if cosmogenic nuclide 10Be/26Al dating of Post-Miocene sediment stratigraphic contacts disallows emplacement circa 800 ka.