Pliocene to Holocene volcanic geology at the junction of Las Cruces, Chichinautzin and Ajusco ranges, southwest of Mexico City

Abstract

The geology of Mexico City's southern volcanic area is discussed on the basis of volcanological, stratigraphic and glacial criteria. Three different eruptive periods occurred from Late Pliocene to Holocene in the juncture between Las Cruces, Ajusco and Chichinautzin ranges. The oldest (Las Cruces) Eruptive Period is represented by the activity of Los Picachos polygenetic volcano with dacitic pyroclastic flows, lahars and lavas of Las Cruces Formation formed mostly during Late Pliocene-Early Pleistocene. During the Ajusco Eruptive Period (Middle Pleistocene), Ajusco volcano was formed by extrusion of several andesitic lava domes. The last stage is the Chichinautzin Eruptive Period of monogenetic volcanism, characterized by Strombolian-type activity during the Late Pleistocene-Holocene. -Authors