CAROLINA BAYS: BORN IN THE LEE OF PLEISTOCENE EOLIAN BARCHAN SAND DUNES - A NEW MODEL FROM SCOTLAND COUNTY, NC

Carolina Bays, the well-known shallow elliptical depressions along the Atlantic seaboard, have been described by Glenn 1895, Prouty 1952, Kaczorowski 1976, Davias 2021, and others. Many of these studies advocate an impact (comet, meteorites, ejecta, glacier fragments) origin to the Bays, although numerous other models have also been put forth.

This study proposes that the Carolina Bays of Scotland County, NC are consequent features of eolian barchan sand dunes, part of a broad Pleistocene desert that developed during glacial sea level low stands on the sandy Carolina coastal peneplain. In the wind shadow leeward of the barchans, an elliptical area (the Bay) of finer grained sediments settled and accumulated due to wind velocity drop across the dune face. The orientation of the Bays and parent barchan dunes indicate an onshore wind field from the southeast. Differential compaction of the fine-grained Bay sediments was the initial cause of Bay subsidence. After dune migration ceased, finer sediments continued to accumulate behind the barchans. Further compaction, subsidence, diagenesis, soil formation and the establishment of vegetation indurated and anchored the fine-grained sediments within the nascent Carolina Bays. The Bay sediments thus were made resistant to the several interglacial marine incursions (Cooke’s terracing) which eroded and redistributed the surrounding unconsolidated desert sands. Typical remaining dune features include a sandy southeastern Bay lobe (the remnant barchan), peripheral sand rims (marine bars) and marine terrace headlands, formed by longshore currents, wave action, tides and other littoral marine processes. Hence, submarine and subaerial processes have removed most of the evidence of the barchans. However, one largely intact barchan dune, with up to 20 feet of current topographical relief, its adjacent Bay to the northwest, occurs in Scotland County and is presented. This dune has survived complete erosion due to its large size and location above the local erosional marine scarp. Further studies on this feature should validate this model for Bay formation. Vintage air photos and modern LiDAR imagery have proven excellent tools in identifying the Bays, remnant barchans and related sand bodies. The study results, the barchan dune model and modern analogs will be presented.