Paleomagnetic constraints on the volcanic history of Iztaccihuatl

Abstract

The directions of remanent magnetization of 24 lava flows from Iztaccihuatl ali show normal magnetic polarity suggesting that the present edifice of the volcano was formed during the Brunhes Chron. This relative youth of the mountain has been substantiated by recent K-Ar dating. Analysis of the dispersion of VGP positions yields an estimate of the angular standard deviation due to secular variation of 14.2°. This value is similar to that predicted at the latitude of Iztaccihuatl by recent models of secular variation and to average paleosecular variation determined from globally distributed lava flows. Agreement of the amount of dispersion with that expected indicates that extrusion of lavas from this volcano probably occurred over a time interval long enough to have obtained a representative sample of secular variation, i.e., volcanism extended over a time interval shorter than the Bruhnes Chron but longer than or comparable to the time scale of secular variation. The average Iztaccihuatl VGP is statistically indistinguishable from the geographic pole.