Magnetic Intensities of Ocean-Floor Basalts: Electron Microscopy, Rock and Paleomagnetic Studies

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VanderVooEAR-0207257magnetic anomalies generated by ocean-floor rocks have led to sea-floor spreading models and plate tectonics. The magnetism resides in titanomagnetite in fresh basalts, but the titanomagnetite oxidizes to titanomaghemite over geological time. Whether this titanomaghemite carries a magnetization that faithfully reflects the ancient magnetic field, is still an unanswered question. The investigators plan to study the degradation of the magnetic signal as a function of age. In particular, the intensity of the magnetization of the basalts (and, concomitantly, the peak values of the anomalies) appears to show a gradual degradation up to some 20 million years ago, beyond which the intensity gradually increases for Early Tertiary and Cretaceous times. The researchers will be studying the rates and effects of oxidation, the magnetic intensity of unaltered and oxidized rocks, and the idea that perhaps older basalts may have a natural remanent magnetization that consists of two anti-parallel components, which were acquired during successive normal and reversed polarity intervals. The methods to be employed include paleomagnetic and rock magnetic techniques and electron microscopy of the oxides. This project will show whether the causes for magnetic degradation warrant a re-evaluation of the details of the global polarity time scale, or whether magnetic intensity variations are a function of the global geomagnetic field. The latter possibility would create new insights into the origins of the geomagnetic field that are currently the subject of much debate.