Paleointensity of the Earth's Magnetic Field Using Basaltic Glass

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The principal cause of the severe limitations of paleointensity data sets is the extreme difficulty of obtaining reliable results. Not only are the measurements time consuming, but the success rate is relatively low, despite great care in sample selection. One requires, a material possessing a thermal remanence, that has not altered since its acquisition and does not alter during the experiments. Furthermore, the material should have cooled at a rate reproducible in the laboratory, and should be datable with a relative precision of a few percent. Basaltic glass has been recovered from hundreds of Deep Sea Drilling Program holes from anomalies of known age. Glass is quenched at formation and the rate of cooling can be well approximated in the laboratory. It can be inspected for alteration and shown that it does not readily alter during the Thellier experiment. Finally, basaltic glass derived from MORB appears to contain single domain low-Ti magnetite. Shards can be found that have sufficient moments to be readily measured with our equipment; such shards obtained from 0 and 2640 year eruptions of the East Pacific Rise have yielded excellent paleointensity data and similar quality data can be obtained from other basaltic glass regardless of age. The PI will carry out a paleointensity study of basaltic glasses.