Chronologies and mechanisms of last glacial loess deposition in the Central Lowlands of North America

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This project will advance understanding of windblown silt (loess) deposition during the last glaciation across Midwestern North American landscapes. Loess deposits are a vital ingredient to the region's rich agricultural soil and, with embedded fossil snails and ancient soils, are important paleoclimate archives. However, Midwestern loess remains poorly dated and disconnected from other climate and glacial records, limiting our understanding of the timing and drivers of loess deposition. New radiocarbon chronologies will relate deposition rate variations to past changes in sediment sources, climate, and ice lobe fluctuations in the Great Lakes region from ~ 25,000 to 18,000 years ago. This research will improve understanding of regional paleoclimate records and atmospheric dust budgets during this last glacial period. An interactive module on the Pleistocene Illinois landscape for an after-school enrichment program, STEAM (Science, Technology, Engineering, Arts, and Math), will introduce these important deposits to local students. New, high resolution radiocarbon chronologies of loess, coupled with U-Pb zircon dating and trace elemental analyses of loess and glacial tills will provide detailed sediment sourcing history. Stable oxygen and carbon isotope analyses of snail shells, along with species assemblages and stable oxygen isotope forward modeling, will aid determinations of the climatic context of changing loess deposition rates. Comparing these deposition rates with the timing of regional ice lobe fluctuations will permit better understanding of the relationships among glacier movement, climate, glacial sediment supply, and downwind loess deposition.