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

Abstract

Presents K-Ar ages for eight shield volcanoes and one stratovolcano in the Michoacan-Guanajuato Volcanic Field. 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. 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. -Authors