A LATE QUATERNARY HYDROCLIMATIC AND VEGETATION RECONSTRUCTION IN THE EASTERN SIERRA NEVADA: PRELIMINARY RESULTS

Understanding Quaternary climatic controls on vegetation change and hydrologic variability in the Sierra Nevada (CA) is an urgent topic of study, because the High Sierra snowpack is a primary source of drinking water for dense population centers downstream, not to mention its role in sustaining a 40 billion dollar per year sector of the USA’s agricultural industry. Well-dated paleoenvironmental records from lakes may hold the key for unlocking the hydroclimatic history of the Sierra Nevada. However, relatively few lake sediment cores are available from Sierra Nevada region, in part because tephra layers from numerous episodes of deglacial and Holocene volcanism makes collecting long cores in the region especially difficult. Here, we present preliminary results from ~9.5-meter sediment core collected from Convict Lake, a small, deep, and hydrologically open glacial lake basin located in the Sherwin Range. While only ~30 miles southeast of the Mono Basin and its volcanic craters, Convict Lake’s strata appear to be less impacted by thick and coarse tephra layers. Preliminary facies analysis suggests that depositional environments have changed at the core site considerably in the late Quaternary, with sediment composition variably reflecting the influence of deep limnological processes, mass wasting from margin coincident topography, and glacial advance. Convict Lake sediments contain abundant plant macrofossils, and radiocarbon dating is being applied to these materials to develop a robust age-depth model. Pollen analysis and bulk geochemistry (total organic carbon, total carbonate, and stable isotopes of carbon and nitrogen) will be used to reconstruct changes in vegetation and lake level, in order to ascertain the influence of global climatic changes on the basin.