Multiple tectonic reactivations of the Cachi fault system at the eastern edge of the southern Luracatao valley, Calchaquíes valleys, northwestern Argentina

Abstract

The Luracatao valley (boundary between Calchaquí valleys and Puna) is flanked to the east by sierra de Cachi and cumbres de la Laguna mountain ranges, delimited by first-order structures called here as Cachi fault system, from east to west: eastern fault, central fault and western fault. These faults have N-S orientation dipping to the east. The eastern main fault corresponds to a normal cretaceous fault that bounded the Brealito-Molinos half-graben to the west. Central and western faults, interpreted as splays of the eastern fault, would have originated as cretaceous normal faults with multiple tectonic inversion-reactivation processes during the Andean orogeny. The basement heterogeneities have controlled the location of new structures during the Mesozoic and Cenozoic, through strong parallelism between the basement foliations and faults. In this study, we present new field data that help us to reconstruct this structures system evolution, which has been described in previous works as a unique master fault (Cachi fault) with a localized splay, and these document multiple reactivation stages from Eocene.