SOUTHERLY PREVAILING PALEOWINDS RECORDED BY LATE PLEISTOCENE EOLIAN SAND DUNES IN THE LOWER MISSISSIPPI VALLEY

Knowledge of Quaternary paleoclimate is crucial to understanding the potential for future climate change, and eolian dunes can provide high quality paleo-wind direction information useful in paleoclimate reconstruction. Fields of late Pleistocene eolian sand dunes are present along fluvial terraces of the Mississippi River in a belt extending from southeast Missouri, through eastern Arkansas and Louisiana. OSL ages from these dunes range from 19 to 38 ka. They are most extensively developed on the 25 ka Ash Hill terrace in the Western Lowlands west of Crowleys Ridge in eastern Arkansas. These dunes have been described previously as NW-trending longitudinal and NE-trending transverse dunes and as having formed during northwesterly prevailing winds. However, field inspection and examination of recently available LiDAR reveal that these dune fields are comprised of NW-trending transverse dunes with NE lee slopes and parabolic dunes (up to 6 km long) with elongated NE-trending arms that record southerly and southwesterly prevailing winds. Internal dune cross-bedding also indicates southerly and southwesterly winds. Some parabolic dune arms have been reworked into en echelon transverse dunes, suggesting a late Pleistocene shift from southerly to southwesterly wind direction and a reduction in vegetation cover. Southerly wind directions recorded in these dune fields should be used to constrain general atmospheric circulation models for late Pleistocene climate.