AEOLIAN RESPONSE TO LATE QUATERNARY DROUGHT, WHITE RIVER BADLANDS, SOUTH DAKOTA, NORTHERN GREAT PLAINS

The goal of this study is to determine the timing of the latest episode of regional dune migration in the White River Badlands (WRB), South Dakota. Our previous studies of alluvial pediments in the Badlands National Park (BNP) indicate that pediments experienced an episode of fluvial incision initiated no later than 1,000 AD, which we interpret as a geomorphologic response to a regional drought that is possibly coincident with the Medieval Climatic Anomaly (MCA). The MCA, which occurred approximately 900 to 1200 AD, is evident from records of dune activity from the central and western Great Plains, including the Nebraska Sand Hills which are located approximately 60 km to the south of our study area. If our interpretation is correct, we anticipate other geomorphic systems, including dune fields, will show evidence of activity during this period.

Dune fields in the WRB are located south of the BNP on approximately 400 km2 of dissected strath terraces north of the White River. Aeolian features include sand sheets, parabolic dunes, and aeolian cliff-top dunes (ACT). A typical strath table has some mix of stabilized sand sheets and parabolic dunes on the tabletop, and in many instances active ACT dunes are located on cliff edges. Using 14C from paleosols in the ACTs, Rawling (2003) identified periods of surface stability and soil formation at ca. 3600, ca. 2500 and ca. 1400 radiocarbon years before present (RCYBP), which he interpreted as periods of relatively moderate humid climatic conditions. A similar record of soil formation was found by Burkhart (2008 and 2014) in the paleosols preserved in WRB sod tables. Both Rawling and Burkhart indicate that drier conditions in the WRB began sometime after ca. 1300.

Here we report the preliminary results from sand dune sampling on private land in the Buffalo Gap National Grasslands. We collected sand samples for optically stimulated luminescence (OSL) dating from the crests of parabolic dunes found on tabletops. Samples were collected from depths of 1 m and 2 m below the ground surface to identify the last episode of dune migration. If the timing of dune migration is correlative to incision of the alluvial pediments, we will begin to build a Late Quaternary chronology for erosion, sedimentation, and drought for this section of the Northern Great Plains.