This project will continue the development of a master curve of geomagnetic secular variation for western North America during the last 12,000 years. The curve is derived from the paleomagnetic study of suites of overlapping cores from small lakes in the western United States. The records from each lake are correlated on the basis of ash layers from various Cascade volcanoes. The research will involve the measurement and analysis of samples already collected from five lakes as well as the collection of samples from several additional sites. These samples will be used to verify and refine a proposed master curve of secular variation as well as to develop a curve of geomagnetic intensity variation. These curves will be compared to those developed from lava flows and archaeological features as well as from lakes in other parts of North America. As the curves are being developed, they will be used to solve geologic problems relating to the distribution of volcanic ash layers, the assessment of volcanic hazards, and the dating of archae ological sites. In addition, the relationship between rock magnetic properties and various palynological and sedimen tological indicators o f climate and environment will be studies. The PI is at the forefront of this important area of paleo magnetism. Funding at the revised level is recommended.
