HR: 0800h
AN: GP31B-02    [Abstracts]
TI: Analysis of the Magnetic Susceptibility Anisotropy of the Cantera Ignimbrite, San Luis Potosé­ Volcanic field, Mexico
AU: * Caballero, C
EM: cecilia@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Lab. Paleomagnetismo, Instituto de Geofisica, Ciudad Universitaria, Col. Coyoacan, Del. Coyoacan, MEXICO, DF 04150, Mexico
AU: Torres-Hernandez, J
EM: jtorres@uaslp.mx
AF: Universidad Nacional Autonoma de Mexico, Posgrado en Ciencias de la Tierra, Ciudad Universitaria, Col. Coyoacan, Del. Coyoacan, MEXICO, DF 04150, Mexico
AU: Alva-Valdivia, L M
EM: lalva@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Lab. Paleomagnetismo, Instituto de Geofisica, Ciudad Universitaria, Col. Coyoacan, Del. Coyoacan, MEXICO, DF 04150, Mexico
AB: Anisotropy of Magnetic Susceptibility (AMS) results from a group of 17 - 18 sites (286 - 312 specimens) from the Cantera Ignimbrite - of Oligocene age and part of the San Luis Potosí Volcanic Filed (SLPVF), México - are presented and analysed in order to help to determine the source and flow directions. In each site a flow direction is inferred based on AMS results. As the Cantera Ignimbrite is generally dipping, AMS was structural corrected. So two sets of geographical and paleo-geographical (structural corrected) inferred-flow directions were obtained. Both sets are analysed trying to define if the source of the ignimbrite is related to a calderic (concentric structure) or to the NW-SE faulting and jointing. Geographical AMS results mostly give SW flow directions, the southernmost sites give to SSE. Meanwhile structural corrected results give a wider range of flow directions, a group of them to NW and another northerly group mostly to NE. AMS was measured in a KLY2 appliance, Jelinek and other statistics and density distributions were performed, giving all very similar results in each site. Mean susceptibilities range from 147 to 27200 x10^-6 SI (average = 5713 x10^-6 SI). Anisotropy degree (P_j) range from 1.011 to 1.055 with two sites of 1.134-1.254 (P_j average = 1.046). Shape is mostly oblate ranging the T-factor from 0.843 to 0.409 and only one site mainly prolate: T of -0.277 (T average = 0.550).
DE: 1518 Magnetic fabrics and anisotropy
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly