The southern Guadalajara volcanic chain, Jalisco, Mexico.

Abstract

The chain consists of eight small lava and cinder cones of Plio-Pleistocene age which follow a NW-SE trend through the southern portion of the city of Guadalajara. This chain and numerous other volcanic alignments in the western TMVB are related to a major continuing episode of crustal rifting, and provide valuable information concerning the upper crustal stress field at the time of eruption. Lava samples from the southern Guadalajara cones are olivine-bearing basaltic andesites of calc-alkaline character showing little compositional variation. Similar basaltic andesites occur at Colima, Paricutin, Jorullo and other volcanoes in the eastern TMVB, particularly those close to the Middle America Trench. Basaltic andesite is probably the most abundant magma type rising from upper mantle and lower crustal depths in the region.-J.M.H.