An Integrated Study of Paleointensity during Mesozoic and Tertiary using Dated Basalt, Submarine Basaltic Glass, and Single Plagioclase Crystals

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ZhaoEAR-0207389The record of the intensity of Earth's magnetic field during the past (paleointensity) carries important information about the geodynamo and probably about the state of Earth's interior that is not contained in the record of paleodirection. Firm conclusions regarding long-term paleointensity variation and its role in mantle dynamics require averages of many more data than are currently available. For this reason, the investigators propose to carry out new determinations of Earth's field during Mesozoic and Tertiary time using dated rock materials from Siberia, Kazakhstan, China, the Faroe Islands, and Ontong Java and Kerguelen plateaus. The principal objectives of this study are focused on three important geophysical problems which are currently debated: (1) to obtain reliable paleointensities to test the hypothesis that there was an extended period of low field intensity in the Mesozoic and, if so, to better define its onset and termination; (2) to determine mid-Cretaceous paleointensities to test the recent suggestion that the field strength was unusually high during the Cretaceous Normal Superchron (CNS); and (3) to obtain mean paleointensity values during the Tertiary period of high reversal frequency for comparison with those for the mid-Cretaceous period of low reversal frequency to see whether there is a correlation between reversal rate and geomagnetic field strength. The rock units the investigators have targeted for sampling and those they currently have available have high potential of providing valuable paleointensity data to address these questions of fundamental importance in geophysics. The opportunity to compare paleointensity results from these different geologic materials is a strong secondary motivation for this research.