CHANGES IN TULARE LAKE LEVELS FOR THE PAST 35,000 YEARS FROM THE UPPER EIGHT METERS OF THE TL05-4 CORES

Physical and chemical changes in the lithology of deposited sediment can act as proxies for past lake levels and, hence, climate change, particularly when terminal lake basins are studied. Ever since the MIS 2 glacial maximum one such lake, Tulare Lake, CA, has been the terminus of four of the largest rivers from the southern Sierra Nevada Mountains and hydrologic modeling has shown that its surface elevation is a good gauge of Sierran stream discharge. Here we extend the relative paleolake-level record of Tulare Lake from the TL05-4 cores based on geochemical and geophysical proxies back to ~35 ky. Proxy data from these cores include magnetic susceptibility, grain size, total inorganic and organic carbon, and carbon-nitrogen ratios. These data co-vary to some extent and, based on comparisons with earlier trench sample based lake-level records, reflect relative lake level. The earliest part of the record shows a sharp increase in lake level, likely associated with the creation of a small fan dam around 30 kyr BP. Lake level steadily decreased during the Tioga Glaciation (~30-19 kyr BP). This decrease is likely caused by decreased summer precipitation and winter precipitation that has been sequestered in the snowpack. Following the Tioga Glaciation, large amounts of runoff from the melting glaciers filled the lake and increase significantly the sill height of the fan dam (19-14 kyr BP) to more or less present elevations. After this, Tulare Lake levels varied in conjunction primarily due to changes in sea surface temperatures. Further work including additional radiocarbon dating will test these initial conclusions.