Dynamic topography control on Patagonian relief evolution as inferred from low temperature thermochronology

Abstract : We combine low-temperature thermochronology apatite (U-Th)/He data and semi-analytical modeling of dynamic topography to investigate the role of slab window and climate on cooling/heating history and relief evolution of the Patagonian Cordillera. In particular, we discuss a new thermochronological dataset consisting in 22 samples divided into four elevation transects. Sampling sites were chosen at the same distance from the trench (250-300 km), on the leeward eastern side of the orogen, for latitudes ranging between 45°S and 48°S to detect a potential northward migration of the thermal signal associated with the northward migration of the slab window. We show that history of heating and cooling for this region of the southern Andes compares well with the northward migration history of slab window. In particular, a phase of heating is recorded at 15-10 Ma to the south and at ≤5 Ma to the north, preceding by ∼5 Ma the opening of the slab window beneath Patagonia, followed by a phase of rapid cooling and denudation to the south, with values as high as 650 m/Myr between 5 and 3 Ma. We also show that present-day latitudinal topographic variations require a support by dynamic topography associated with slab window.