CORRELATION OF SIERRA NEVADA CONTINENTAL AND PACIFIC MARINE PALEOCLIMATE RECORDS OVER THE LAST GLACIAL CYCLE

Until recently, the only long-term and high-resolution marine paleoclimate records available to compare with records from most continental locations were benthic foraminiferal delta-18O time series. These reflected largely a combination of global ice volume and bottom water temperature. Comparison with continental records has produced many puzzling discrepancies (e.g., "asynchronous glaciation"). Within the past five years the quality of both the chronology for glaciation in the Sierra Nevada and the temperature history of Pacific Ocean water off the California coast has greatly improved, offering the opportunity for a new regional comparison. Cosmogenic 36Cl ages on moraine boulders are corroborated by glacial rock flour data from Owens Lake (J. Bischoff and K. Cummins). These show major glacial advances at 160-140 ka, ~70 ka, 50-45 ka, and 29-18 ka. These are matched by recently published alkenone temperatures from southern California showing episodes of cold sea surface temperature at 160-145 ka, ~110 ka, ~90 ka, ~70 ka, ~55 ka, and 30-20 ka. Not all cold episodes are matched by glacial advances, possibly because moraines resulting from them were overridden by subsequent, more extensive, advances. However, the close correspondence of the majority of cold phases with glacial advances demonstrates that local marine and continental paleoclimate records are generally synchronous. The apparent disagreement with the global ice volume record may be due to regional differences in climate history, or may simply be due to the long time constant required for response of the huge Pleistocene ice sheets.