HYDROCLIMATE AND PRECIPITATION CHANGES OF THE LAST 30,000 YEARS AT FISH LAKE, UTAH

Geologic proxy records across the southwestern United States (the Southwest) reveal a paleoenvironmental history featuring several abrupt and transitional climate events. However, our current understanding of southwestern climate regimes remains poorly resolved, especially prior to deglaciation. Fish Lake located in Utah, provides an opportunity to investigate paleohydrological and environmental change over longer timescales over which there have been major changes in insolation, greenhouse gas concentrations, and ice sheet dynamics. Fish Lake, located at 2700 m asl on the boundary between the Colorado Plateau and the Great Basin, provides a continuous sediment record with sufficient temporal resolution to investigate hydrologic response over periods of rapid climate change including the Younger Dryas-Holocene transition as well as DO and Heinrich events. Fish Lake is situated near the boundary of the modern limit of the North American Monsoon making it sensitive to shifts in precipitation source between the winter westerlies and the summer monsoon. Here, we present an organic geochemical analysis of the last 30 ka investigating precipitation-evaporation balance (P-E) and temperature variations from the Fish Lake Plateau. Branched glycerol dialkyl glycerol tetraether (brGDGT) data reveal abrupt decreases (increases) in relative temperature coincident with glacial advancement (retreat) on the Fish Lake Plateau, followed by stabilizing temperatures during the Holocene. Ongoing work includes leaf wax n-alkanes d²H (long chain) to document changes in P-E and potential mechanisms influencing precipitation over time.