RUI: Paleomagnetic Study of the Matuyama-Brunhes Reversal from Dated Lava Sequences on Tahiti, French Polynesia

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9627927 Hoffman The PI proposes to continue his studies of the earth's most recent magnetic polarity reversal, Matuyama-Brunhes (M-B) in lavas in Tahiti, and to integrate this record into a global model of the M-B reversal process using available data sets from other lava flows and reliable sedimentary sequences worldwide. The study of geomagnetic field reversals is rapidly evolving in its degree of sophistication with recent successful 3D computer-assisted simulations of the dynamo process. These advances make essential an understanding of actual field behavior at Earth's surface obtained from the paleomagnetic record. Available data of the Matuyama-Brunhes reversal obtained from lavas from 4 sites about the globe and recent 40Ar/39Ar age determinations on these lavas support not a singular process in which the virtual geomagnetic pole (VGP) migrates along a south-to-north geographic track, but rather a more complicated process involving a series of dynamo events and long-standing field configurations. The PI requests funding to continue his effort over the next two years to (1) sample several parallel sections recording the reversal, (2) develop further a composite chronological picture of the reversal process as experienced on Tahiti, (3) perform paleointensity determinations on these rocks whenever possible using a newly-modified multispecimen technique, and (4) construct a global model for the Matuyama-Brunhes reversal process using available data from sediments. This RUI will continue to involve a number of undergraduate physics majors at California Polytechnic.