The structure of the Chañarcillo Basin: An example of tectonic inversion in the Atacama region, northern Chile F. Martínez a , C. Arriagada a, b, * , M. Peña a , I. Del Real a , K. Deckart a a Departamento de Geología, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile b Centro de Excelencia en Geotermia de Los Andes (CEGA-FONDAP), Universidad de Chile, Plaza Ercilla 803, Santiago, Chile article info Article history: Received 19 December 2011 Accepted 4 July 2012 Keywords: Chañarcillo Basin “Tierra Amarilla Anticlinorium” Inversion anticline Tectonic inversion “KeT” Andean deformation phase Palabras clave: Cuenca Chañarcillo “Anticlinorium de Tierra Amarilla” anticlinal de inversión inversión tectónica fase de deformación andina “KeT” abstract The Chañarcillo Basin is an Early Cretaceous extensional basin in northern Chile (27e29  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 9e14 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 “KeT” boundary (“KeT” phase of Andean deformation). We propose that tectonic inversion is the fundamental defor- mation mechanism, and that it emphasizes the regional importance of inherent Mesozoic extensional systems in the evolution of the northern Chilean Andes. Ó 2012 Elsevier Ltd. All rights reserved. resumen La Cuenca Chañarcillo, es una cuenca originalmente extensional de edad cretácica temprana ubicada en la region norte de Chile (27e29  S). Las series sin-rift de su extremo oriental, se encuentran envueltas en un anticlinal de orientación NNE, el “Anticlinorium de Tierra Amarilla”, que ha sido asociado con la inversion de la falla Elisa de Bordos. Las diversas secciones balanceadas y restauradas, construidas a través de la cuenca muestran como un arreglo structural de hemi-grabenes en “domino” parcialmente invertidos, constituye el escenario mas favorable para reproducir la deformación de superficie. Este arreglo estructural, aporta un acortamiento para la cuenca, que varía entre 9 km a 14 km. Por otro lado, los depósitos synorogénicos preservados cerca del limbo frontal del “Anticlinorium de Tierra Amarilla”, permiten interpretar que la inversion ocurriría cerca del límite de deformación andina “KeT”. Consid- erando lo anterior, se propone a la inversion tectónica como un mecanismo de deformación dominante, resaltando la importancia de los sistemas extensionales mesozoicos en la evolución de los Andes del norte de Chile. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The tectonic evolution of the Central Andes was dominated by different episodes of crustal stretching and shortening, which derived from complex geodynamic processes related to the oceanic plate subduction beneath the western South American continental margin from the Early Jurassic to present (Daziel et al., 1987; Mpodozis and Ramos, 1990; Aguirre-Urreta, 1993; Scheuber et al., 1994; Mpodozis and Allmendinger, 1993; Ramos, 2010). A wide- spread extension related to the Late PermianeEarly Triassic conti- nental fragmentation of southwest Gondwana allowed the formation of rift systems. The continuous kinematics of the retreating subduction, coeval with the break-up of PangeaeGondwana originated a progressive stretching of the upper crust, establishing a magmatic arc with extensional backarc basins on the eastern side, which are charac- terized by half-graben architectures along the continental margin. * Corresponding author. Departamento de Geología, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Plaza Ercilla 803, Santiago, Chile. E-mail address: cearriag@cec.uchile.cl (C. Arriagada). Contents lists available at SciVerse ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames 0895-9811/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jsames.2012.07.001 Journal of South American Earth Sciences 42 (2013) 1e16