RUI: Paleomagnetic Study of Transitional Fields Recorded Throughout the Cenozoic by Australasian Lavas

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Hoffman0230347The most remarkable feature of Earth's magnetic field is its ability to reverse polarity, and much of our knowledge of this phenomenon has come from the paleomagnetic record found in rocks. The goal of this project is to locate, sample and analyze transitional field behavior recorded in Australasia by hotspot-erupted lavas that comprise the Great Dividing Range of Eastern Australia and New Zealand's South Island volcanoes. These volcanics are known to span the past 70 Ma, that is, the entire Cenozoic period, and thus offer an unprecedented opportunity to investigate aspects of Earth's reversing geodynamo from a single regional site over considerable geologic time. In particular, the investigators plan to test the claim that an inordinate number of transitional virtual geomagnetic poles (VGPs) associated with several available paleomagnetic reversal records are found near Australia. This observation has prompted an intriguing possibility, namely, that a concentration of magnetic flux emanating from Earth's fluid outer core below Australasia has largely dominated the field structure during many past reversals, and further, that this flux feature is a consequence of long-standing physical conditions of the lowermost mantle. Because the volcanics of Australia and New Zealand are almost directly above the claimed flux concentration, the project is designed to test this hypothesis. It is anticipated that results from this project will shed light on whether the lower mantle has had such a pronounced effect on the transitioning field over much, or all, of the Cenozoic period, and if so, whether any observable variation, or drift, of the flux feature has occurred since the end of the Mesozoic. In addition, an attempt will be made to determine both paleointensity over this span of time as well as precise radiometric ages of the lava sections. The project will be assisted by undergraduate physics majors working on their senior projects (a mandatory requirement for graduation at Cal Poly State University), exposing them to many aspects of original basic research. Dr Gary Acton of Texas A& M University and Professor Brad Singer of the University of Wisconsin will collaborate on this research.--