Folded duplex structure at the mountain front of the Principal Cordillera, Atuel river, Mendoza province.

Abstract

The aim of this study is to attain a structural reconstruction of the outcrops at the high valley of Atuel river, southwest of Mendoza province, Argentina. This area form parts of the mountain front of the Principal Cordillera that was builted by means of thrust systems. In the studied region, between the Blanco and La Manga streams, near El Sosneado locality, the stratigraphic sequence is composed by Mesozoic rocks of Auquilco Formation up to Malargüe Formation. This sedimentary pile is affected by thrust systems that appear to detach the Auquilco Formation (gypsum) whose attitude in the study area is moderately dipping to the east. This detachment is directed to the foreland, with fault systems and associated folds developed above it. These fault systems seem to be connected with roof decollements located into Huitrín and Diamante Formations, thus achieving duplex geometries. The frontal portion of this duplex, outcroping at the western side of the La Manga stream, shows a inverted section of the Mesozoic strata. This suggests that it is a structure with the characteristics of a folded antiformal stack. A basement-driven tectonic wedge propagating into the foreland with backthrusts at the front, located underneath the studied area, is accountable for the final tilting of the described structures.