CENOZOIC TECTONICS OF THE HIGH ANDES OF WEST-CENTRAL ARGENTINA (30-36-DEGREES-S LATITUDE)

The structure of the Central Andes shows three distinctive segments ch aracterized by different geometries. These geometries are superimposed on the present large-scale plate tectonic setting characterized by di stinct subduction segments. The northern La Ramada segment is a thick- skinned fold and thrust belt formed by tectonic inversion of a Late Tr iassic rift. The central Aconcagua segment consists of a thin-skinned fold and thrust belt while the southern Malargue segment like the firs t one is a thick-skinned fold and thrust belt developed by tectonic in version of a Late Triassic-Early Jurassic rift system during late Ceno zoic times. The amount of shortening gradually decreases from north to south, as indicated by the crustal roots of the Central Andes. The di fferent geometries along the Principal Cordillera controlled the abrup t changes in the shortening among segments. The structure of Precordil lera and Sierras Pampeanas has also been considered in order to accoun t for the total shortening. In the La Ramada segment the main shorteni ng occurred in the Precordillera; in the Aconcagua segment in the Prin cipal Cordillera while in the Malargue segment the shortening is widel y distributed in a broader Principal Cordillera, because south of the flat-slab subduction segment the Precordillera and Sierras Pampeanas a re missing.