Two replicate 30-m sediment cores from Owens Lake California have been recovered. Paleomagnetic data from older Owens Lake core suggest that a high-resolution paleomagnetic secular variation (PSV) recorded can be recovered from these cores. This record should completely overlap the Mono Lake PSV record which includes the Mono Lake excursion and a distinctive pattern of repeating waveforms after the excursion. A PSV record from Owens Lake for late Pleistocene time will be recovered and the validity of the Mono Lake record tested. Paleointensity studies on both the new Owens Lake cores and our stored samples from Mono Lake will also be carried out. The combined study of both lakes will provide an important cross-validation for the paleointensity records. Finally, the PI will use PSV correlations, radiocarbon dates, and rock magnetic data to asses the timing of paleoclimatic changes recorded in the sediments of Mono and Owens Lakes. This study will provide an important new higher-resolution view of PSV (both field vector and paleointensity) in western North America and will be linked with other ongoing studies to provide a broader picture of North American PSV for more than the last 30,000 years.