The North Patagonian Orogen: Meso-Cenozoic Evolution from the Andes to the Foreland Area

Abstract

In the last decades an important amount of studies have dealt with the Patagonian orogen. However, an holistic approach on the evolution of this sector has not been addressed yet. A review of recent advances in different geological aspects of the Patagonian orogen and its related broken foreland system, reveals a clear correlation between the geological evolution of both sectors. This enabled us to integrate them in an evolutionary model connecting tectonic events from the North Patagonian Andes to the broken foreland area throughout the Mesozoic to Cenozoic era. During the break-up of Western Gondwana, beginning in Jurassic times, several extensional basins developed in the Patagonian region. In late Early Cretaceous to Paleocene, a switch in the tectonic regime caused the uplift of the North Patagonian Andes and the initial fragmentation of the foreland area. Synchronously an eastward magmatic arc migration is documented at the retroarc area. At this moment, a series of mid-ocean ridges collided one after another against the patagonian margin. A causative relation among young lithosphere subduction, slab shallowing, orogenesis and eruption of anomalous orogenesis at the arc and retroarc region has been proposed. In concert to regional compression, synorogenic foreland rifting occurred transversaly to the main andean trend in the San Jorge Gulf Basin, describing an exeptional setting for this type of rifting mechanism. From Eocene to early Miocene westward definition of the magmatic arc, possibly related to roll-back, opened the highly attenuated Traiguen Basin, splitted the arc and forearc area. To the east, extensive intraplate magmatism began in the patagonian foreland collapsing the broken foreland orogen. During the Neogene, an acceleration of the convergence rate caused the renewal of Patogonian Andes orogenesis and reactivation the broken foreland system. Orogenesis along with Late Cenozoic global cooling triggered aridization in the foreland zone which had dramatic consequences for the patagonian fauna and flora.