Geología de la caldera de San Marcos, Chihuahua

Abstract

The lithostratigraphic units of the San Marcos caldera are described in this article. The caldera is a silicic volcanic system of Eocene (?) age, located in the eastern foothills of the Sierra Madre Occidental, about 30 km NW of the city of Chihuahua. Volcanic activity began with plinian eruptions that led to the collapse of the San Marcos caldera, which had an estimated diameter of 20 km and a mínimum vertical displacement of 250 m. The plinian eruptions continued after collapse, filling the depression with the rhyodacitic Victorino Ignimbrite. Resurgent (?) doming of the floor of the caldera probably took place shortly after the emplacement of the Victorino Ignimbrite. Between the resurgent dome and the walls of the caldera a moat zone was formed, in which conglomerates, sandstones, and thin ignimbrites of the clastic member of the Cumbres Formation accumulated... In order to continue, download the full paper in PDF.