ENVIRONMENTAL HISTORY PRESERVED IN A QUATERANRY SEQUENCE AT THE BARTON COUNTY LAND-FILL SITE, CENTRAL KANSAS

The Barton County land-fill site, in central Kansas, consists of a 10m-thick Late Quaternary sedimentary sequence situated on the bedrock divide between the Arkansas River valley to the south and Cheyenne Bottoms, a large dissolution feature to the north. Stratigraphy includes the Illinoian Loveland Formation (loess and eolian sand) with intercalated paleosols, Sangamon Soil of the last interglacial, Middle Wisconsinan Gilman Canyon Formation (loess and paleosols), Late Wisconsinan Peoria Formation (loess), Late Wisconsinan/Early Holocene Brady Soil, and Holocene Bignell Loess. Numerical age dating, consisting of an array of TL and radiocarbon ages, indicates the sequence represents the last 250-300k yrs. Paleoenvironments of the Gilman Canyon Formation and adjacent units were reconstructed using phytolith and stable isotope analyses. Soils expressed within the sequence are characterized by chloridoid phytoliths and relatively high (>-18‰) SOC-derived δ¹³C values, both of which indicate warm-season (C₄) grass dominance; periods lacking soil formation (loess and eolian sand deposition) indicate a cool-season environment (tree, shrubs, C₃ grasses). Magnetic susceptibility depicts pedogenic enhancement (elevated susceptibility and frequency dependence of susceptibility) particularly within the Gilman Canyon Formation pedocomplex and Sangamon Soil.