OPPORTUNITIES IN DEVELOPING LONG LAKE SEDIMENT RECORDS OF QUATERNARY HYDROCLIMATE IN THE EASTERN SIERRA NEVADA (CA)

Lake basins of the Eastern Sierra Nevada are ideally located to record ancient climatic signals that may be important for understanding the future of California’s water supply. Yet limnogeological research in the Eastern Sierras remains a challenge. The shallow stratigraphies of many extant lakes in the region contain relatively thick beds of volcanic ash, which makes sampling by traditional coring techniques exceptionally difficult. Volcanic eruptions have disrupted large swaths of the subsurface at Mono Lake, the largest and arguably one of the most important lacustrine archives of Pleistocene environmental change in the western United States. In smaller glacial lakes like June and Convict Lakes, mass movements along steep basin walls produce gravity flows that erode and punctuate otherwise high-resolution Holocene stratal records. Consequently, recovering unaltered and complete stratigraphic sequences, as well as establishing accurate chronologies of sediment accumulation, requires a multi-faceted approach that leverages sampling technologies that are not yet widespread in the limnogeological community. The use of UWITEC percussion piston coring and low frequency CHIRP seismic profiling has shed new light on the stratigraphy of deepwater areas of Mono, June, and Convict Lakes. Preliminary results indicate the presence of finely laminated muds rich in biogenic components, which hold great promise for generating records of hydroclimate and ecological processes with annual to decadal temporal resolution. Geochronology of lake muds relies heavily on radiocarbon, using both traditional materials (plant fragments, charcoal) and pollen purified by flow cytometry. The application of sub-mm resolution core scanning for magnetic susceptibility, spectral reflectance (color), and elemental chemistry, as well as new techniques in thin section analysis, allows the composition of individual laminations to be determined, and will advance our understanding of the hydroclimate filter influencing sedimentation and stratal development at each site.