Late-Quaternary Landscape Response to Environmental Change in South-Central Kansas

Abstract

The central Great Plains is an excellent place to study late-Quaternary geomorphic responses to climatic fluctuations because the landscape is easily disturbed and deposits contain abundant paleoenvironmental information. Although much research has already been conducted, studies are needed that correlate a variety of geomorphic responses to environmental change at specific sites. This paper presents a paleoenvironmental and geomorphic reconstruction for the Great Bend Sand Prairie, a mosaic of sand sheets and dune fields in south-central Kansas. Results indicate that two stratigraphic units dominate the upland geology. Late-Wisconsin deposits consist of poorly sorted sand, silt, and clay that probably accumulated in a low-energy fluvial environment. Eolian deposition of loess also occurred, but most silt was integrated with the alluvium. Intact deposits of loess are widely scattered. All sediments contain well developed soils, indicating extended surface stability. Macrofossil and isotopic (δ13C) evidence suggest a mesic environment. Where eolian sedimentation did occur, northwest winds were responsible for mobilization. Although late-Wisconsin strata crop out intermittently, eolian sand is the common surficial deposit. Radiocarbon dating indicates that most dunes are Holocene landforms. In comparison to late-Wisconsin deposits, dune sands are well sorted, δ13C values infer a relatively warm climate, and the orientation of parabolic dunes indicate mobilizing southwesterly winds. Dunes usually contain one or two weakly developed buried soils, indicating episodic mobilization of eolian sand in the latest Holocene. Surface soils are generally poorly developed, suggesting that dunes can easily be mobilized if vegetation is reduced, perhaps due to C02 warming.