Structure and tectonic evolution of the South Patagonian fold and thrust belt: Coupling between subduction dynamics, climate and tectonic deformation

Abstract

We present an appraisal of structural domains in the SPA (Southern Patagonian Andes),recognizing a thick-skinned BD (Basement domain) and a hybrid thick- and thin-skinnedtectonic systems in the FTB (fold and thrust belt). Distribution and width of structuraldomains, Andean shortening and sedimentary thickness are compared with exhumationpatterns from thermochronological studies to assess the influence of erosion on the internal1dynamics of mountain building. Along the northern third of the SPA the FTB is verynarrow, and the orogen?s width is dominated by BD, in agreement with focused glacialerosion leading to exhumation of deep structural levels. A southward increase in width andshortening of the FTB along the southern segment coincides with a thicker sedimentarycover and erosion focused on the retroarc. These findings show that SPA orogenconfiguration is dominated by a combination of climatic drivers, erosion efficiency andvariations in the stratigraphic column under strain. A change from thrusting dominatedorogenic growth towards erosion dominated regional exhumation occurred during theMiocene, although the exact timing is still under discussion. It is here proposed that a lateMiocene post-contractional neutral tectonic regime can be defined in the retroarc, indicatedby the development of a transport surface and sediment bypass towards the ocean basins.