EPISODIC REACTIVATION OF QUATERNARY AEOLIAN DEPOSITS, WHITE RIVER BADLANDS, SOUTH DAKOTA, NORTHERN GREAT PLAINS

Here we report 23 optically stimulated luminescence (OSL) ages from Quaternary aeolian deposits collected from tables in the White River Badlands (WRB) south of Badlands National Park, approximately 60 km north of the Nebraska Sand Hills. The tables located north of the White River are interfluves of the White River, Cheyenne River, and White River tributaries. Quaternary fluvial and aeolian deposits rest unconformably on the Oligocene and Miocene strata of the White River and Arikaree Groups. Above the unconformity, Quaternary strata include terrace deposits of reworked Tertiary strata, Red Dog Loess, aeolian sand, and aeolian cliff-top deposits. The Red Dog Loess ranges from 20 m thick at its type locality 40 km southwest of the study area to 2 m or less in the study area. Aeolian sands range in thickness on the tables from a few meters to as much as 60 m. In some places, the aeolian sand is not present and aeolian clifftop deposits rest on the Red Dog Loess.

The dunes on the tables have been described as sand-limited hairpin parabolic dune and blowout complexes. Because of regional incision of the White River and its tributaries, it is likely that sediment from the river valleys is no longer supplied to the tables. Evidence from cliff-top dune deposits suggests dissection occurred at least 3.6 ka.

Analysis of aerial photos and digital elevation models suggests at least two episodes of aeolian sedimentation on the table surfaces. An older episode of blowouts and dune formation is evident based on low relief and low elevation parabolic dunes and blowouts. OSL results from dune crest samples from low relief dunes indicate activity from Late Pleistocene to middle Holocene, ending by approximately 6000 a. Analysis of aerial photographs and topographic maps show clear evidence of reactivation of these older dune forms. Younger dunes are generally steeper and higher relief. OSL analyses of samples from high relief dune crests indicate reactivation occurred at 600 a and ended at approximately 250 a. This event dates to the Little Ice Age and the timing is similar to other dunes from the western edge of the Great Plains in Colorado and Kansas. Analysis of aerial photographs from the 1930s and 1940s indicate no significant reactivation of WRB dunes during the Dust Bowl.