Analyses of paleomagnetic data generally assume that the earth's magnetic field, when averaged over several thousand years, conforms to that of a geocentric axial dipole. Nevertheless, long-term non-dipolar components have been found to be important. In fact, recent analyses suggest that during the Cenozoic, multipolar field components have varied so as to produce alternating "far-sided" and "near-sided" effects of significant magnitude. Understanding the nature and magnitude of these deviations from an axial dipole are important in plate tectonic reconstructions using paleomagnetic data, since such reconstructions generally assume that the deviations are small when compared to other uncertainties in the paleomagnetic data. The objective of the present recommended award is to assemble and compile the paleomagnetic data from a large number of piston core sites from the Pacific Ocean. These data were generated during a number of separate projects during the last fifteen years and form an ideal data set for examining both spatial and temporal aspects of the non-dipole field. Initial activity on this project will be to determine sediment ages using a consistent stratigraphy for the cores. Additionally, individual data points will be examined for both their consistency and potential source of error. Once this task is completed, the nondipole field will be examined in several areas of the Pacific Ocean basin. The principal investigator on this project is highly qualified to undertake the proposed study. Funding is highly recommended at $85,000 in FY87 for 18 months.
