Kinematic Evolution of the Santa Bárbara System in the Foreland of the Central Andes of Northwestern Argentina (26°S)

Compared to the thin-skinned Subandean foreland fold-and-thrust belt of northern Argentina and Bolivia, the tectonically active morphotectonic province of the Santa Bárbara System in the Andean broken foreland of northwestern Argentina is characterized by a temporally and spatially disparate deformation style. Although there is no well-defined orogenic deformation front associated with the uplift of these basement-cored, reverse-fault bounded mountain ranges, there has been an overall eastward trend in Andean compressional deformation since the Miocene. While reactivation of basement anisotropies, such as early Paleozoic metamorphic fabrics and Cretaceous normal faults, has been proposed to have profoundly affected deformation processes in the Santa Bárbara System, other mechanisms involving Mesozoic and Cenozoic cover rocks may also have played an important role in orogenic deformation in this sector of the Andean foreland. We present structural field observations, interpretations of seismic reflection profiles, and kinematic modeling from the basins bordering the Candelaria Range in the southern sector of the Santa Bárbara System at 26°S. Our analysis features a 110-km-long structural cross section that images and links deep-seated structures with shallow neotectonic faults. We find that regional shortening has been facilitated by several faults associated with a regional detachment at a depth of 23 km, resulting in total horizontal shortening of about 17% (18.4 km). While the deep-seated first-order structures seem closely linked to seismogenic processes in the Andean foreland, shallow second-order structures within the sedimentary cover modify the intermontane landscapes and appear to be associated with aseismic creep.