Estratigrafía de las rocas volcánicas de la región entre Sierra de Gamón y Laguna de Santiaguillo, Estado de Durango

Abstract

A sequence of volcanic rocks over 1,800 m thick, unconformably lies over Upper Cretaceous sediments or lower Tertiary molasse, between Sierra de Gamón and Laguna de Santiaguillo.

The basal portion of the sequence consists of andesitic flows of late Eocene-early Oligocene age, unconformably covered by ignimbrites and tuffs, erupted during successive explosive events of the Chupaderos and Río Chico calderas. The section was divided into six lithostratigraphic units that rango in age (K-Ar) from 31.8 to 28.6 Ma and is covered in turn by the Sierra de Gamón rhyolites.

Associated to the basin-and-range faulting (12 Ma), alkaline basaltic dikes fed the Metates Formation that covered the stratigraphic section. Reactivation of faulting was accompanied by the extrusión of Quaternary basalts. These rocks are interfingered or covered by talus, lake deposits or Recent alluvium.