Sedimentary characteristics and unconformities in the Del Ratón, El Planchón and Del Salto Formations. Neopaleozoic lithostratigraphy and new units in the San Juan Precordillera, Argentina

Abstract

In the western Precordillera, and especially in the area around kilometre 114 of National Road 20, along the San Juan River valley, the Upper Paleozoic stratigraphic record is composed of the Del Ratón, El Planchón, Del Salto, La Escombrera and Quebrada de la Arena formations. Although most of these units have been studied for many years (Sessarego, 1983; Limarino & Cesari, 1992), consistent information on their stratigraphic arrangement, facies and processes of accumulation is still lacking. For instance, unreliable data about fossil remains identified as Devonian (Kerlleñevich, 1967), which have never been subsequently cited, have given rise to significant problems concerning the stratigraphic location of the El Planchón Fm and related units (Amenábar & di Pasquo, 2008).