Paleoenvironments of Buried Alluvial Soils Representing Paleoindian-Age Landscapes in Draws on the High Plains of Western Kansas

Thick deposits of alluvium with multiple buried soils dating to the Pleistocene-Holocene transition are stored in dry valleys of low-order intermittent streams, or draws, on the High Plains of western Kansas. Late-Quaternary loess on the High Plains surface is a major source of silty alluvium, which accounts for the large volume of sediment in the draws. The soil-stratigraphic record preserved in the draws indicates aggradation punctuated by episodes of landscape stability and cumulic soil development beginning as early as ca. 13,300 ¹⁴C yr B.P. and continuing as late as ca 8,200 ¹⁴C yr B.P. Most of the radiocarbon ages determined on organic carbon from buried soils in the draws, however, range between ca. 11,000 and 9,000 ¹⁴C yr B.P. From an archaeological perspective, documenting the paleosol record preserved in the draws is important for interpreting the early record of human occupation in the region. Many of the buried soils in alluvial fills of draws represent Paleoindian-age landscapes that may harbor cultural deposits. This is underscored by the recent discovery of stratified, Early Paleoindian archaeological deposits at the Kanorado locality along Middle Beaver Creek, a draw in northwestern Kansas. At Kanorado, the remains of mammoth and camel that may represent pre-Clovis cultural deposits are buried in valley fill dating to ca. 12,300 ¹⁴C yr B.P. A thick, organic-rich buried soil (Kanorado Paleosol) above the mammoth/camel level contains stratified Clovis and Folsom-age cultural deposits. Paleoenvironmental data, especially δ¹³C values of soil organic matter, indicate significant bioclimatic change across the Pleistocene-Holocene boundary at Kanorado and other localities in the region, with increased aridity accompanied by a shift from tall-grass savanna to short-grass prairie and replacement of mammoth and camel with bison. This change affected the subsistence strategies of the earliest human inhabitants on the Central High Plains, as reflected in the archaeological record.