CONICET | Buscador de Institutos y Recursos Humanos

The subduction of seismic oceanic ridges can result in the formation of slab windows, which can affect not only the retroarc volcanism and heat flow, but also the exhumation and topographic evolution of the upper plate. Southern Patagonia, in southernmost South America, is an active and world class example, related to the subduction of the South Chilean seismic oceanic ridge since the middle-late Miocene to Present day. How the subduction of the ridge and formation of the slab window have influenced the evolution of the Patagonian landscape, exhumation and topography is still under debate. While some works have proposed orogenic deformation affecting mostly the Pacific margin and hinterland areas or an inherited early Miocene tectonic relief generated previous to the slab window formation, others have prefered epirogenesis hypotheses as dynamic uplift or isostatic rebound by lithospheric thinning associated with the changes in the asthenospheric or lithospheric mantle. In this work, we analyzed the landscape evolution at medium- (orogen scale) and long-wavelengths (embracing the whole southern Patagonia across, from coast to coast) using a landscape numerical model (FastScape). This data processing is coupled to an optimization scheme, suitable for non-linear inverse problems (Neighbourhood Algorithm). The goodness (fit to data) of our landscape evolution models was evaluated using: i) cooling ages and ii) maximum elevations in order to provide constraints on the uplift rates, erosion efficiency and effective elastic thickness. With the best values, we compared two forward models which represent medium versus long wavelength processes. Our results indicate that a long-wavelength uplift geometry (including dynamic uplift and/or lithospheric rebound by thinning), involving areas from the Andes to Atlantic coast, was needed from 12 My to Present day to reproduce not only the youngest cooling ages but also Present-day topography.

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