LATE PLEISTOCENE EOLIAN SEDIMENTATION, SOIL DEVELOPMENT AND CLIMATE CHANGE ON THE HIGH PLAINS OF SOUTHWESTERN KANSAS

In the Central Great Plains, loess-paleosol sequences have been shown to provide important archives of Late Pleistocene paleoenvironmental change. At least four stratigraphically superposed Quaternary-aged loesses have been documented in this region: the Loveland, Gilman Canyon, Peoria and Bignell loesses. This study presents stratigraphic, pedologic and stable isotope data from two cores (CMC1 and HP1A) that record Late Quaternary eolian sedimentation and soil formation on the High Plains of southwestern Kansas. These data allow for correlations with regional loess-paleosol sequences as well as inferring climatic change in this understudied part of the Central Great Plains.

The 20 m eolian succession includes 8 eolian units and intercalated soils developed in either sandy loam or loamy sand textured sediments. Soils have predominantly loam to silty clay loam textures and angular or subangular blocky structure. All soils have either Btk or Bk horizons and typically contain pedogenic carbonate in the form of discrete or coalescing carbonate nodules and fine threads. Most soils also contain discrete clay films on ped faces.

Three OSL ages (75.7±11.3, 76.1±13.5 and 76.8±13.1 ka) from the middle of the HP1A core indicate that units 4, 5, and 6 are coeval with the late Sangamon-Loveland complex. This chronology, together with the presence of multiple buried soils, confirms the episodic nature of eolian deposition during late MIS 5. Two OSL ages constrain the age of unit 3 to between 70.3±10.6 and 54.0±8.9 ka. Soil 3 may correlate to an unnamed paleosol that some studies have identified between the Sangamon soil and the Roxana Silt/Gilman Canyon Formation in the Mississippi River Valley and Central Kansas. An OSL age of 44.3±7.8 ka from soil 2 indicates that this soil likely represents the Gilman Canyon Formation pedocomplex.

δ¹³C and δ¹⁸O data from units 4-6 suggest a shift from warmer, wetter climates to colder, drier climates during late MIS 5. The seasonal distribution of precipitation may also have changed at this time. Isotope values increase in units 2 and 3 implying warmer and drier climates with perhaps more summer precipitation during MIS 3.