Localized faulting in the Andean Patagonian foreland: long-term influence of lithospheric heterogeneities revealed by thermochronology and field data

The tectonic evolution of a key region in the Andean Patagonian foreland is analysed (42°–43° S). This region exposes the deepest structural level of Patagonia, preserving evidence of large-scale Paleozoic lithospheric and upper crustal mechanical heterogeneities. The geological record involves multiple extensional and contractional deformation events of the past 200 Myr. Based on new thermochronological data, including apatite fission-track and apatite (U–Th)/He analyses, with surface and subsurface analysis, this research proposes a unified model of tectonic evolution since the onset of the Andean margin. The results reveal a complex interplay of cooling and heating episodes associated with major tectonic phases, including a Late Triassic–Early Jurassic contraction (∼215–200 Ma), Jurassic–Early Cretaceous extension (∼200–143 Ma), two pre-Paleocene contractional phases (∼143–133 and ∼85–62 Ma), a Paleogene extension phase (∼62–20 Ma) and a Miocene contraction event (∼20–10 Ma). Deformation has been largely controlled by Paleozoic metamorphic inheritance and the reactivation of pre-existing structures, regardless of the prevailing tectonic regime. This has led to a lithospheric configuration that alternated between broken foreland systems during contractional events and wide-rift systems during extensional events. This research provides new insights into the long-term geodynamic evolution of intraplate settings in subduction zones with weak lithospheric conditions.