Michael Davias of Cintos.org presented another astonishing Carolina Bay poster at the October, 2013, Denver meeting of the Geological Society of America. My apologies to bay fans for not posting this earlier. Here is the direct download from GSA.
I speculate that the robustly repetitive Carolina bays may have been generated between 780 ka and 140 ka during a catastrophic mass-transport and deposition of high purity quartz particles, materialized as a surficial blanket of sand, spread chaotically over an antecedent terrain. The bays may be imperfections generated within the blanket while the sand was in a state of liquefaction, and preserved at lockup as a densely compacted stratum.
Davias, from the 2013 poster
CAROLINA BAYS AND AEOLIAN DUNES: PLAYING NICE IN THE SANDBOX?The juxtaposition and interplay between elliptical Carolina bay basins and accompanying aeolian dune structures has been previously recognized across the USA’s Atlantic Coastal Plain. Recent advances in 3D terrain visualization using LiDAR (Light Detection And Ranging) remote sensing technology allows for new insight into the nature of the bays’ enigmatic elliptical circumferential rims and their spatial relationships with unambiguous aeolian sheets. In support of a survey to discover and elucidate the full geographic range of Carolina bay landforms, 500,000 km2 of hsv-hinted (hue-saturation-value) Digital Elevation Maps have been produced using publically accessible LiDAR data. Using examples from the survey’s geospatial database of over 40,000 bays, I share some observations about bay-dune relationships that appear pervasively in the data. Instances of “secondary rims” are seen, where robust wave-like repetitions of bay rim structures are found rippling away from a Carolina bay’s primary rim. Also of interest are bay planforms that have remained intact while the surrounding landscape has been resurfaced with extensive parabolic and longitudinal dune topography, differentiated from others where classic aeolian landforms have encroached into bay basins; intriguingly, cases exist where both outcomes are seen in close proximity. An established hypothesis holds that bay basins and their closed rims were generated by glacial-era katabatic winds passing perpendicular to the bay’s major axis, yet inspection of classic wind-blown dunes in the vicinity of bays document long-term resultant sand drift directions which fail to correlate, perhaps suggesting entirely independent mechanisms were responsible for their presence in these topographies. Detailed examination of these spatial relationships may illuminate Carolina bay geomorphology research and guide future OSL dating and chemical analysis activities to relevant locales.