Paleomagnetism of the Rocks of Ascension Island

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Valentine EAR-0003411 A dearth of paleomagnetic data from volcanic rocks hampers our understanding of temporal variations of the geomagnetic field, including field reversals, during the last 5 My. Although a number of increasingly sophisticated models for the geodynamo and the reversal process have been proposed in recent years, such models are being tested with a severely limited knowledge of the nature of field variation. One of the greatest problems with regard to paleosecular variation (PSV), time-averaged field (TAF), and reversal modeling is a geographical bias in the paleomagnetic data set. Most of the current data come from sites in the northern hemisphere, and a more uniform distribution of paleomagnetic sites for the last 5 My is critical to improving our understanding. Preliminary paleomagnetic study of Ascension Island rocks by the PI has shown that Ascension Island has the potential to provide quality PSV, TAF, and reversal data. This study will perform a detailed paleomagnetic study of Ascension Island rocks in conjunction with precision 40Ar/39Ar dating and mineralogical analyses, producing high-quality PSV and TAF data. It also has the potential to reveal reversals recorded in the volcanic flows of Ascension Island. In addition, magnetic mineralogy work, including identification of any post-emplacement alteration of mineralogy, and precision radiometric dating of the rocks will certainly help to better define the geologic history of this hot spot island on the flank of the Mid-Atlantic Ridge. The project will significantly involve undergraduate students, who will participate in exciting, cutting-edge of research.