PLAYA LAKE RESPONSE TO RAPID CLIMATE CHANGES DURING THE LATE-PLEISTOCENE AND HOLOCENE ON THE HIGH PLAINS OF KANSAS

Rapid climate changes (RCCs), such as the Younger Dryas, can have dramatic impacts on ecosystem form and function. Ephemeral playa lakes are particularly sensitive to climate change and are continually evolving in response to changing precipitation patterns, wind regimes, and plant community dynamics. These geographically-isolated depressions and associated lunettes (dune-like accumulations that form downwind of larger playas) preserve an extensive record of climate change on the High Plains.

The purpose of this project was to reconstruct paleoenvironment throughout the history of playa-lunette evolution in order to identify RCCs and assess their impact on playa-lunette form and function. To accomplish this, two playa-lunette systems on the High Plains of western Kansas were cored and sampled. Samples were analyzed for particle size distribution, color, magnetic susceptibility, and stable carbon isotopes (δ¹³C). Numerical age control was provided by AMS radiocarbon dating of buried soils and luminescence dating of sedimentary units. Initial results suggest that lunettes preserve an extended history of environmental change, from before 40 ka, while at least the last 10,000 years are preserved within playa basin fills. Particle size, color, and susceptibility data indicate that lunette stratigraphy is complex, with three to four well-developed buried soils and several incipient buried soils (Entisols). In contrast, playa basin stratigraphy is much less complex with only one to two buried soils separated by thick, clay-rich, sedimentary units. Values of δ¹³C reveal that several RCCs impacted playa-lunette evolution. Nearly every period of the Blytt-Sernander sequence, as well as Marine Isotope Stage 3 and other global and regional climate change events, are represented within lunettes. Throughout playa-lunette evolution, reconstructed mean July temperature fluctuated from nearly 3 ^oC cooler to more than 3 ^oC warmer than present day. RCCs caused substantial changes in regional plant community composition, which had major impacts on landscape stability and erosion/deposition events within playa-lunette systems.