AEOLIAN RECORD OF MEGADROUGHTS FROM A CONTINUOUS LAKE CORE RECORD IN THE GREAT PLAINS

Continuous, long-term hydroclimatic records in the United States Great Plains are scarce. Nonetheless, periods of dune mobilization suggest the occurrence of at least four significant droughts within the past 5000 years. The paleoclimate conditions associated with these droughts is not well known, however, because of the limited availability of records in this region. Whether these droughts were related to changes in annual average precipitation or variations in the seasonal distribution of precipitation remains an important and unresolved question. In this study, we address this question using a 12-meter-long sediment core from Blyburg Lake, NE. Situated in Dakota County, NE, the small oxbow lake lies within the Missouri River floodplain and captures sediment from a substantial portion of the Missouri River watershed during flood stages. Employing radiocarbon dating, X-ray fluorescence (XRF), grain size analysis, bulk density (BD), and loss on ignition (LOI), we developed proxy records of Missouri River flood intensities and regional aeolian events. Four intervals with persistently elevated levels of silicon (Si) and aluminum (Al) relative to titanium (Ti) and zirconium (Zr) were identified. Radiocarbon dates from two of the Si and Al peaks have ages consistent with dune mobilization events, suggesting the Si and Al peaks reflect with ag with are interpreted as indicative of an increase in Si-rich aeolian dust within the Missouri River Basin, potentially linked to dune activation driven by aridity. Importantly, these peaks in Si and Al align with documented events of Great Plains aeolian activity, as dated by optically stimulated luminescence (OSL). Integrating these new geochemical findings with existing records of mid-to-late Holocene "megadroughts," our investigation provides valuable insights. Future research on Blyburg Lake will focus on refining the radiocarbon-based age model to precisely reconstruct sediment accumulation rates and flood recurrence.