The structure of the Chaٌarcillo Basin: An example of tectonic inversion in the Atacama region, northern Chile

The Chañarcillo Basin is an Early Cretaceous extensional basin in northern Chile (27–29°S). The folding style of the syn-rift successions along the eastern side of the basin reveals an architecture consisting of a NNE-trending anticline “Tierra Amarilla Anticlinorium”, associated with the inversion of the Elisa de Bordos Fault. A set of balanced cross sections and palinspastic restorations across the basin show that a partially inverted “domino-style” half-graben as the structural framework is most appropriate for reproducing the deformation observed at the surface. This inverted system provides a 9–14 km shortening in the basin. The ages of the synorogenic deposits preserved next to the frontal limb of the “Tierra Amarilla Anticlinorium” suggest that basin inversion occurred close to the “K–T” boundary (“K–T” phase of Andean deformation). We propose that tectonic inversion is the fundamental deformation mechanism, and that it emphasizes the regional importance of inherent Mesozoic extensional systems in the evolution of the northern Chilean Andes.