Andean deformation and basin evolution during changes in subduction zone geometry (29–33°S)


Understanding the surface, crustal, and tectonic processes controlling deformation and crustal evolution along subduction margins remains an outstanding challenge in Earth science, with implications for characterizing Earth systems, resource potential, and natural hazard assessment. The southern Central Andes of Chile and Argentina define type examples of deformation, arc magmatism, and basin evolution during long-lived subduction, and provide unique opportunities to study the overriding plate response to changing plate margin conditions and tectonic regimes. This dissertation presents new geo- and thermochronological assessments of sediment provenance, basin accumulation, and deformational timing at ~29–33°S that provide critical insight into retroarc deformational patterns and subsidence mechanisms over the past ~200 Myr. Mesozoic to mid-Cenozoic deposits recorded the unroofing of basin margins and sediment contributions from the Andean magmatic arc during Late Triassic to Early Cretaceous extension, thermal subsidence, and possible slab rollback, followed by initial shortening and sediment derivation from western sources during the Late Cretaceous. Newly dated volcanic and sedimentary deposits in the retroarc hinterland provide evidence for a late Paleogene episode of intra-arc and proximal retroarc extension preceding Negoene growth of the modern Andes. Geochronological and thermochronological data for thrust sheets and Neogene foreland basin fill indicate Andean shortening initiated with the inversion of the intra-arc basin system, followed by sequential eastward migration of the fold-thrust belt–foreland basin system along a regionally connected, hybrid thin- and thick-skinned decollement. Finally, new structural interpretations and flexural thermo-kinematic model results quantify the influence of inherited structures, precursor stratigraphic architectures, thrust belt critical taper, and non-flexural geodynamic processes during Neogene construction of the modern Andes


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