SUPPLEMENTING A TULARE LAKE, CA LATE PLEISTOCENE TO HOLOCENE LAKE-LEVEL RECORD USING GEOCHEMICAL AND GEOPHYSICAL PROXIES FROM CORE SEDIMENTS

Geochemical and geophysical proxies from Tulare Lake cores in the San Joaquin Valley of California are shown to reliably reflect lake-level changes and extend the record back to 18,000 cal yr B.P. Previous outcrop and trench-based mapping studies indicated several high- and lowstand events throughout the Holocene, events that have proven to be consistent with other lake records from SW coastal U.S. The new record reported on here employs carbon/nitrogen, total organic carbon, grain size, and magnetic susceptibility proxies sampled at cm intervals to provide a significantly higher resolution record. These proxies systematically vary as predicted with previously suggested lake level changes. For example, the transition from deep lake to marsh conditions centered at 3.0 cal kyr B.P. was associated with a drop of C/N ratio from 40 to 5, and an increase in TIC% from 0% to 2%, The new record also extends further back in time well into the late-Pleistocene. Our results indicate that core-based proxies can be used to supplement outcrop and trench-based studies to collectively form an accurate and nearly continuous record of Tulare Lake levels for the past 18,000 years. Since historic and reconstructed lake-level histories indicate that the surface elevation of Tulare Lake is primarily controlled by Sierran stream runoff, our comprehensive lake-level history will be integral in forecasting future changes in southern San Joaquin Valley water supply due to anticipated global warming.