Continuous Lake-Sediment Records of Glaciation in the Sierra Nevada between 52,600 and 12,500 14C yr B.P.

The chemistry of the carbonate-free clay-size fraction of Owens Lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial-interstadial oscillations, Owens Lake records of total organic carbon, magnetic susceptibility, and chemical composition of the carbonate-free, clay-size fraction indicate that Tioga glaciation began ~24,500 and ended by ~13,600 14C yr B.P. Many of the components of glacial rock flour (e.g., TiO2 , MnO, BaO) found in Owens Lake sediments achieved maximum values during the Tioga glaciation when valley glaciers reached their greatest extent. Total organic carbon and Si02 (amorphous) concentrations reached minimum values during Tioga glaciation, resulting from decreases in productivity that accompanied the introduction of rock flour into the surface waters of Owens Lake. At least 20 stadial-interstadial oscillations occurred in the Sierra Nevada between 52,600 and 14,000 14C yr B.P. Total organic carbon data from a Pyramid Lake sediment core also indicate oscillations in glacier activity between \u3e39,500 and ~13,600 14C yr B.P. Alpine glacier oscillations occurred on a frequency ofbasins, suggesting that millennial-scale oscillations occurred in California and Nevada during most of the past 52,600 yr