Self-reversal in Titanomaghemite: Implications for the Magnetization of Oceanic Crust

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TardunoEAR-0230230Self-reversal of natural remanent magnetization, the remarkable ability of some rocks to acquire a magnetization in a direction antiparallel to that of the Earth's geomagnetic field, is thought to be rare; it has been established only in a few igneous rocks bearing hemoilmenite. The investigators have have found two pervasive, nearly antipodalcomponents of magnetization (revealed through detailed demagnetization studies) from pillow basalts in which hemoilmenite is absent. Laboratory thermoremanent magnetization experiments suggest that the componentisolated at lower temperatures represents a partial self-reversal of the primary magnetization. This self-reversed magnetization is carried by titanomaghemite formed by low temperature oxidation. Because maghemitization of ocean crust is ubiquitous, partial self-reversals may play an important role in controlling changes in marine magnetic anomaly amplitudes with age.the investigators propose to investigate the extent and mechanism of self-reversal carried by titanomaghemite in oceanic basalt recovered by the Deep Sea Drilling Project and the Ocean Drilling Program. Through astudy of sites having ages ranging from recent to 170 Ma, they hope to constrain the time scales of acquisition of self-reversed magnetizations. Techniques to be applied will include paleomagnetism, rock magnetism, x-ray diffraction, microprobe, scanning electron microscopy and transmitted electron microscopy. The work proposed will support a Ph.D. thesis and the studies of several undergraduate students at theUniversity of Rochester.--