Tectónica de la sierra Cuesta El Infierno y su posible relación con fallas reactivadas cerca del levantamiento de Plomosas, Chihuahua, México

Abstract

Geologic and structural mapping of volcanic rocks in sierra Cuesta El Infierno, located on the western flank of the Plomosas uplift, allowed us to divide the Paleogene volcanic section into two succesions. The volcanic rocks unconformably overlie sedimentary rocks of the Chihuahua fold belt. The lower volcanic succession (felsic ash flow tuffs and epiclastic continental deposits) is separated from the upper volcanic succession (andesitic lava flows with interlayered rhyolitic ash flow tuff) by a small angular unconformity. The volcanic successions are exposed in northern and southern structural domains of the SCI, which are separated by an inferred basement fault (N70°W) with a complex history. The basement fault acted since middle to late Paleogene as a transfer zone that accommodated the deformation of fault systems with different trends in the areas located north and south of its trace. The basement fault also controlled the distribution of some of the ash flow tuffs, the eruption of the lava flows, and the local Basin and Range strain pattern during the Cenozoic. A SSE-plunging syncline with a N20°W trend associated with a system of listric normal faults parallel to the fold axis and a small roll-over anticline occur in rocks of the lower volcanic succession in the northern structural domain. The syncline is interpreted as a fault bend fold. In the southern domain of the study area, we recognize an accommodation zone between two antithetic listric faults that consists of a N45°W-trending antiform.