LATE QUATERNARY OSTRACOD STRATIGRAPHY AND PALEOECOLOGY FROM MONO LAKE, CALIFORNIA

Located on the eastern side of California's Sierra Nevada, Mono Lake contains a proxy-rich sedimentary archive of hydroclimate and ecological change for a region of great importance to California’s water supply. An ostracod-based paleoecological record was developed from an ~11 m long sediment core recovered from 18 m water depth in Mono Lake’s western embayment. The core chronology, which spans ~16.6-4.3 cal ka BP, was established using radiocarbon dating and correlation to well-dated tephras from a nearby core. Ostracods were counted (n=300) from screen-washed samples (n=191) and identified to the species level using light and scanning electron microscopy. Adults and juveniles from seven different species were identified: Limnocythere staplini, Limnocythere ceriotuberosa, Limnocytheresappaensis, Candona patzcuaro, Fabaeformiscandona caudata, Potamocypris sp., and Eucypris meadensis. Ostracods were abundant and diverse during the late Pleistocene. It included the presence of C. patzcuaro and F. caudata. These ostracods are consistent with fluctuating deep-lake environments during the deglacial. In the Holocene, total ostracod abundances decline, and the assemblage is defined by Potamocypris sp. and E. meadensis, likely controlled by lower lake-level elevations, expansion of marsh or nearshore spring discharge environments, and variable chemical conditions and substrates. These changes highlight the sensitivity of Mono Lake and its benthos to hydroclimatic and limnological changes during the late Pleistocene and Early-Mid Holocene.