K-Ar ages of lavas from shield volcanoes in the Michoacan-Guanajuato volcanic field, Mexico

Abstract

We present new K-Ar ages for eight shield volcanoes and one stratovolcano in the Michoacan-Guanajuato Volcanic Field of central Mexico. The ages range from 0.06 Ma to 2.27 Ma. The volcanoes in the northern part of the study area are older than those in the south. Similar age relationships exist among smaller volcanoes; the cinder cones and maars in the north are also older than those in the south. The shield volcanoes and the cinder cones in the northern part of the Michoacan-Guanajuato Volcanic Field both span a similar time range. Our results suggest that the volcanic activity in the Michoacan-Guanajuato Volcanic Field migrated southward in the last 2 m.y ., probably in response to changes in plate motion, or in the geometry and location of the Wadati-Benioff zone.