Abstract

MARTINO, Roberto D; GUERESCHI, Alina B  and  CARIGNANO, Claudio C. Infuence of the pre-Andean tectonics on the Andean tectonics: the case of the Sierra Chica fault, Sierras Pampeanas of Córdoba, Argentina. Rev. Asoc. Geol. Argent. [online]. 2012, vol.69, n.2, pp.163-178. ISSN 0004-4822.

The Sierra Chica fault is one of the most important Tertiary reverse faults of the Sierras Pampeanas of Córdoba. The Andean fragile deformation would have been partially controlled by previous structures as the regional foliation of the late Proterozoic-Cambrian metamorphic basement. Another important control is given by the Cretaceous extensional tectonics that produced the opening of the Atlantic Ocean. The present-day trace of the fault shows straight tracts of high angle (~50-60°) linked with Cretaceous deposits, which are interpreted as reactivation of previous normal faults, and curved tracts of low angle (~30°) that do not associate in particular with any specific deposit, which would be new reverse faults originated by the Tertiary tectonics. A series of ancient shear belts, oblique to the main direction, named the Carapé, Quebrada Honda and Soconcho lineaments, produce the segmentation of the Sierra Chica fault in three large thrust sheets. During the Tertiary compression, these lineaments were reactivated as dextral slip faults, which acted as lateral ramps while the thrust sheets moved towards NNW (~N 330°). The west-directed convex form would be due to the effect of the low angle inverse faulting together with the expansion of the frontal part of the thrust sheet. The present-day geobarometric difference (~5000 m) between the blocks exhumed at both sides of the Sierra Chica fault, at the latitude of Alta Gracia (31º 36 ' S), would still refect the effects of the Cretaceous extensional tectonics that were not compensated by the Tertiary inversion.

Keywords : Faulting; Gneisses; Geobarometry; Cretaceous; Tertiary.

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