QUATERNARY AEOLIAN CHRONOLOGY, WHITE RIVER BADLANDS, SOUTH DAKOTA, NORTHERN GREAT PLAINS

The goal of this study is to determine a chronology of regional dune activity in the White River Badlands (WRB), South Dakota. Dune fields in the WRB are located south of the Badlands National Park on approximately 400 km2 of tables north and south of the White River. Aeolian features include sand sheets, parabolic dunes, and aeolian cliff-top dunes (ACT) previously reported by Rawling et al., 2003. A typical table has some mix of stabilized sand sheets and parabolic dunes on the tabletop, and in many instances, active ACT dunes located on cliff edges. The aeolian sequence, deposited unconformably on the White River Group Brule Fm, consists of 5 to 10 m of loess, fluvial sands and gravels of the Red Dog Loess, overlain by as much as 30 m of aeolian sand and ACT deposits. With the exception of local blowouts, the aeolian sands/tabletop dunes are stabilized by vegetation. Unlike the Red Dog Loess, the aeolian sands do not contain fluvial deposits.

Previously, Rawling (Burkhart et al., 2008) reported 14C and optical luminescence results from the Red Dog Loess and the base of the aeolian deposits. Those results indicate variable age for the regional deposition of the Red Dog Loess but Late Pleistocene (Peoria Loess equivalent) on tabletops in the study area. Optical luminescence results from the base and middle of the aeolian sand suggest periods of dune activity between 21 ka and 12 ka (Burkhart et al.). In this study, samples were collected from the crests of parabolic dunes at depths of 1 m and 2 m below ground surface to determine the youngest episodes of activity. Optically stimulated luminescence results of five samples taken at 1 m depth clustered at 7000 ca and 400 ca. Disparity in ages could result from a partial reactivation of the dune field at 400 ca. Alternatively, the results may indicate a single activation event at approximately 7000 ca. In this interpretation, the 400-year cluster is the result of bioturbation at three of the 1 m depth samples.

Results suggest a Quaternary chronology of aeolian activity that begins with the Late Pleistocene fluvial and aeolian deposition of the Red Dog Loess. No later than 21 ka, aeolian sands were deposited over the Red Dog Loess. Results of this study show the most recent activation of the stabilized parabolic dunes at 7000 ca and 400 ca.