NUMERICAL AGE ESTIMATES OF QUATERNARY STRATIGRAPHY EXPOSED ON TABLE EDGES IN BADLANDS NATIONAL PARK

Quaternary strata overlay the Tertiary White River Group in the Southern Unit of Badlands National Park and include fluvial silt, sand, and gravel, eolian sand, and eolian cliff-top deposits.  These strata also occur, but are less extensive, in the Northern Unit.  The lowest strata at Sheep Mountain Table and Hay Butte are laminated course-silt/very fine sand interbedded with gravel.  A thermal luminescence sample taken near the base of this deposit at Sheep Mountain Table yielded a minimum age estimate of 171,460 ± 23,810 yrs ago.  On the eastern side of Cuny Table the lowest strata are sand and gravels, which in one location fill a channel-shaped unconformity.  Above the fluvial strata are eolian sand and parabolic dunes exposed at two surface elevations (~950 and ~830 m).  The ~950 m elevation dunes are found on Cuny Table, and the ~830 m elevation dunes are more extensive and located on the interfluve between tributaries of the White River.  A section sampled on the ~830 m elevation contains at least seven buried A-C soils that span the Holocene from ~9600-800 ¹⁴C yrs BP.  Eolian cliff-top deposits containing buried soils are restricted to table edges and were sampled at seven sections.  These deposits typically have loam and sandy loam textures with dominantly very fine sand, 0.5-1% organic carbon, and 0.5-5% CaCO₃.  Occasionally, these eolian deposits contain coarse granule and fine pebble size particles.  The buried soils are weakly developed with A-C and A-AC-C profiles.  Late Holocene soil morphology and chronology correlate at ~ 1300, ~2500 and ~3700 ¹⁴C yrs BP.  The ~1300 ¹⁴C yr BP soil is cumulic.  Soils beneath the cliff-top deposits are early Holocene (~7900-10,000 ¹⁴C yrs BP) at higher elevation tables (~950 m), and late Holocene (~2900 ¹⁴C yrs BP) at lower elevation tables (~830 m).