HR: 17:50h
AN: GP44A-07    [Abstracts]
TI: Paleomagnetic behavior of volcanic rocks from Isla Socorro, Mexico
AU: * Sbarbori, E
EM: esbarbori@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0220, United States
AU: Tauxe, L
EM: ltauxe@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0220, United States
AU: Fucugauchi, J U
EM: juf@geofisica.unam.mx
AF: Univ Natl Autonoma Mexico, Instituto de Geofisica UNAM Ciudad Universitaria, Mexico City, FDM 04510, Mexico
AU: Gogichaishvili, A
EM: avto@tonatiuh.igeofcu.unam.mx
AF: Univ Natl Autonoma Mexico, Instituto de Geofisica UNAM Ciudad Universitaria, Mexico City, FDM 04510, Mexico
AU: Bohrson, W A
EM: bohrson@geology.cwu.edu
AF: Central Washington University, Dept of Geological Sciences 400 E University Ave. MS 7418, Ellensburg, WA 98926, United States
AB: Isla Socorro, Mexico is located in the eastern Pacific Ocean on the Mathematician Ridge, an abandoned spreading center that ceased activity ~3.5 Ma when activity shifted to the East Pacific Rise. Silicic volcanism continues to the present day. A lack of vegetation in the southeastern portion of the island has resulted in extensive erosion, exposing in steep-sided canyons a sequence of volcanic units the oldest of which are ~540ka. We carried out a joint expedition between the Scripps Institution of Oceanography and the Universidad Nacional Autonoma Mexico to Isla Socorro in January of 2005. We collected oriented paleomagnetic samples from 21 sites from as many as 10 different volcanic units. We subjected over 100 specimens to an "IZZI" type (Tauxe and Staudigel, 2004) paleointensity experiment in which in-field and zero-field first steps were alternated to detect high-temperature tails. We also included the standard pTRM checks. Although some specimens worked extremely well, we observed non-ideal behavior in many specimens. We categorized this ‘misbehavior' into four general groups reflecting contamination by non-single-domain magnetic carriers and alteration during the experiment. 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. Comparison of the two sample sets allows us to tie dates unambiguously from the dated collection to the new fully oriented data set. Bohrson, W. A., M. R. Reid, et al. (1996). "Prolonged History of Silicic Peralkaline Volcanism in the Eastern Pacific Ocean." Journal of Geophysical Research-Solid Earth 101(B5): 11457-11474. Tauxe, L. and H. Staudigel (2004). "Strength of the geomagnetic field in the Cretaceous Normal Superchron: New data from submarine basaltic glass of the Troodos Ophiolite." Geochem. Geophys. Geosyst. 5(2): Q02H06, doi:10.1029/2003GC000635.
DE: 1521 Paleointensity
DE: 1540 Rock and mineral magnetism
DE: 1599 General or miscellaneous
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly