OSTRACODE-BASED PALEOLAKE LEVEL RECORD FROM PLUVIAL LAKE CHEWAUCAN, SUMMER LAKE, OREGON, TIED CHRONOLOGICALLY TO SPECIFIC FEATURES OF THE ~32 KA MONO LAKE EXCURSION

A detailed, high resolution record of relative lake-level was acquired between ~37ka and 32 ka based on ostracode faunal analysis. Samples were taken every 2 cm (~30 yr) from core BB3-I taken from the depocenter of Summer Lake, Oregon in the Fall of 2010. The time period sampled includes the 32 ka Mono Lake Excursion recovered in this core and correlated via tephrochronology and bulk organic carbon dating with the same excursion found in similarly high resolution sedimentary records from Pyramid Lake, NV and Mono Lake, CA. Several species of ostracodes are known to have lived in Pleistocene Lake Chewaucan for much of its history (past 250 ka). Because ostracodes are sensitive to changes in both temperature and salinity, past analyses of these organisms led to estimates of relative lake level which have been shown to be consistent with other lake-level indicators. In the present case, a more continuous record will allow for rapid changes in lake-level to be observed through the varying ostracode abundances based on the identification of trends in water chemistry and changes in the physical environment. The lake remained a closed basin throughout history suggesting that such lake-level records should be consistent with regional environment and climate. The new, more detailed record is tied to the paleomagnetic vector record of the Mono Lake Excursion which should allow us to test the regional implications of the new Summer Lake lake-level record at perhaps century-scale resolution by comparing it to existing and future records of climate from elsewhere in the Great Basin and potentially with paleoclimate records taken from marine cores that also contain the Mono Lake excursion.