This award will support Professor Horst Worm and Professor Subir Banerjee of the University of Minnesota in collaboration with Prof. Jaime Urrutia-Fucugauchi of the Universidad Nacional Autonoma de Mexico (UNAM). The researchers intend to study the magnetic record in historic lava flows and to compare it with magnetic observatory data. Mexico is uniquely suited for this purpose because its active volcanic history has supplied numerous historic lava flows of varying composition and cooling history. Equally important, direct deter- minations of the geomagnetic field are available since 1791. The proposed research will consist of two phases. First, the variation of magnetic remanences in lava flows of different charac- teristics will be systematically studied in vertical and horizontal profiles. Additionally, magnetic properties and ore petrological characteristics will be determined. Results from the first phase of the study will provide an excellent basis for systematic paleointensity method studies. Thermal and non- thermal methods will be evaluated for their applicability, accuracy, and efficiency. Natural remanent magnetizations (NRM's) will be studied in the paleomagnetic laboratory at UNAM while magnetic hysteresis, anisotropy and other measurements as well as detailed intensity determinations will be performed at the University of Minnesota. In addition microprobe and scanning electron microscope work will involve Prof. Negendank in Germany, thus adding a multi- lateral dimension to this project. The proposed work will be the first stage in studying the paleointensity record all the way back to Permian times since when Mexico has retained an almost unique continuous volcanic record.
