CONTINUOUS LAKE-SEDIMENT RECORDS OF GLACIATION IN THE SIERRA-NEVADA BETWEEN 52,600 AND 12,500 C-14 YR BP

The chemistry of the carbonate-free clay-size fraction of Owens Lake s ediments supports the use of total organic carbon and magnetic suscept ibility as indicators of stadial-interstadial oscillations. Owens Lake records of total organic carbon, magnetic susceptibility, and chemica l composition of the carbonate-free, clay-size fraction indicate that Tioga glaciation began similar to 24,500 and ended by similar to 13,60 0 C-14 yr B.P. Many of the components of glacial rock flour (e.g., TiO 2, MnO, BaO) found in Owens Lake sediments achieved maximum values dur ing the Tioga glaciation when valley glaciers reached their greatest e xtent, Total organic carbon and SiO2 (amorphous) concentrations reache d minimum values during Tioga glaciation, resulting from decreases in productivity that accompanied the introduction of rock hour into the s urface waters of Owens Lake. At least 20 stadial-interstadial oscillat ions occurred in the Sierra Nevada between 52,600 and 14,000 C-14 yr B .P. Total organic carbon data from a Pyramid Lake sediment core also i ndicate oscillations in glacier activity between >39,500 and similar t o 13,600 C-14 yr B.P. Alpine glacier oscillations occurred on a freque ncy of less than or equal to 1900 yr in both basins, suggesting that m illennial-scale oscillations occurred in California and Nevada during most of the past 52,600 yr. (C) 1998 University of Washington.