A PALEOSOL-DERIVED ENVIRONMENTAL PERSPECTIVE ON MIS 3 IN THE CENTRAL GREAT PLAINS, USA

Late Quaternary loess mantles much of the Central Great Plains (CGP) and has emerged as a proven source of paleoenvironmental proxy data (e.g., Johnson et al., 2007; Muhs et al. 2008; Woodburn et al., 2015). In particular, soils formed during interstadials preserve environmental data spanning these periods of relative landscape stability. The MIS 3 interstadial has received little attention in the CGP, leaving a void in our paleoenvironmental record for that time interval. The Gilman Canyon Formation (GCF) soil, formed during MIS 3, provides a source of proxy data for reconstructing the paleoenvironment and for tracking environmental changes within MIS 3. The Russell County Landfill in central Kansas is the paratype location for this study, chosen for its well-preserved sections of the GCF and for its central location within the nonglaciogenic CGP loess plume. The GCF has previously been studied in Nebraska, proximal to the loess source – the White River Group Badlands of South Dakota; however, loess and paleosols in Kansas, geochemically linked to the same source, have differing characteristics, indicating a north to south change in prevailing environments. This Kansas-based study provides juxtaposition for the thicker and coarser-grained GCF in Nebraska

The GCF soil is cumulic due to consistent slow sedimentation rates that spanned most of MIS 3 – roughly 48ka to 28ka, based on AMS ¹⁴C ages. Stable carbon isotope data (δ¹³C) suggest that Kansas was likely a semi-arid environment dominated by warm season C₄ grasses and, given the more negative δ¹³C values in Nebraska, indicates a north to south trend of increased aridity (moisture stress). Accumulations of pedogenic clay in tandem with magnetic data show that soil weathering was occurring to a greater degree in Kansas than in Nebraska. Organic C and N levels in the GCF soil indicate fairly active soil communities. Combined, these initial data provide some of the first evidence of disparate environments between Kansas and Nebraska during MIS 3, resulting in a more informed perception of CGP climate during that time.