Earth Planets Space, Vol. 61 (No. 1), pp. 191-204, 2009
Elise Sbarbori1, Lisa Tauxe1, Avto Goguitchaichvili2, Jaime Urrutia-Fucugauchi3, and Wendy A. Bohrson4
1Scripps Institution of Oceanography, La Jolla, CA 92093-0220
2LIMNA, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Campus Morelia, Michoacan, Mexico
3Laboratorio de Paleomagnetismo y Paleoambientes, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico City 04510 DF, Mexico
4Department of Geological Sciences, Central Washington University Ellensburg, WA 98926-7418
(Received November 1, 2007; Revised February 25, 2008; Accepted March 3, 2008; Online published January 23, 2009)
The direction and magnitude of the geomagnetic field vary both spatially and temporally and undergo significant departures from that of a geocentric axial dipole. In order to properly characterize persistent behaviors, time-averaged field models must be based on the highest quality data. Here we present full-vector paleomagnetic data for volcanic units exposed in the southeast quadrant of the island of Socorro, Mexico. We carried out a joint expedition between the Scripps Institution of Oceanography and the Universidad Nacional Autónoma México to Isla Socorro in January of 2005 during which we collected oriented paleomagnetic samples from 21 sites, representing as many as 10 different volcanic units (the oldest of which is ∼540 ka). We subjected over 100 specimens to the most up-to-date paleointensity methods, and included the standard reliability checks. In an earlier study, Bohrson et al. (1996) proposed a series of widespread eruptive events, based on similarities of argon/argon dates. Paleointensity from specimens that conform to the strictest acceptance criteria are available from both the (unoriented) original sample collection and our fully oriented (but as yet undated) new collection. Correlation between the two collections is however problematic. The time-averaged direction from Socorro is consistent with that expected from a geocentric axial dipole, and the time-averaged intensity is 30.0±7.1 μT, equivalent to a virtual axial dipole moment (VADM) of 67.6±16.0 ZAm2.
Key words: Paleomagnetism, paleointensity, Socorro, Bruhnes, IZZI method.