Paper No. 147-10
Presentation Time: 4:00 PM
THEY DON’T BUILD 'EM LIKE THEY USED TO; EXAMINING LIDAR OF MODIFIED COSTAL TERRACE SURFACES SHOWS THE CAROLINA BAY LANDFORM TO BE ROBUST WHEN THREATENED WITH ALTERATION BY GRADUALISTIC PROCESSES
Carolina bays exist in prodigious quantities on North America’s Atlantic Costal Plain. Research into the geomorphology of these enigmatic landforms is typically directed at easily recognized, hydraulically closed examples which show an affinity to undissected interfluves on the coastal terraces. There may seem to be little reason to identify less wholesome examples; yet, a holistic assessment shows that erosional and accretionary processes are struggling to annihilate existent bays. Here we present LiDAR digital elevation maps to elucidate bays succumbing to erosion during the dissection of costal terraces of Cenozoic and Mesozoic age, yet leaving intriguing vestiges in terrace remnants at elevations over 200 meters above sea level. We also discuss Carolina bays inundated by fluvial and estuarine deposits, only to delicately project their ovoid planforms to the surface. Sheets of dune sands and aeolian loess have overridden and blanketed clusters of bays, yet they continue to offer evidence of their presence. Such findings suggest that once created, a Carolina bay’s ovoid shape and orientation is deeply imprinted into the landscape, often revealing its presence despite the reworkings of host topography. While such processes apply to isolated bays, the findings are far more satisfying when demonstrated within a collection of co-aligned and identically shaped adjoining bays. Rather than being “wispy ephemeral” landforms, bay survival in hostile conditions supports a finding that they are very robust landforms. The temporal aspects of such alterations may provide constraints on the timing of bay creation. 14C dating had long ago evaluated the age of organic deposits in cored Carolina bay basins to be older than 50 ka, the limit of that technology. The age of bays based on their existence on Cape Fear River terraces sets a minimum date for bay formation at prior to the Illinoian glaciation - beyond the reach of OSL dating. Bays on a terrace remnant above the fall line in Virginia have been deemed by other workers to be far older, still. When attempting to date bay creation episodes, workers must discriminate between foundational rim deposits and those of subsequent gradualistic processes. Future research goals include application of 10Be/26Al isotopic burial dating techniques to the surfaces beneath these landforms.