Cenozoic contractional tectonics in the Fuegian Andes, southernmost South America: a model for the transference of orogenic shortening to the foreland

Authors

  • P.J. TORRES-CARBONELL Centro Austral de Investigaciones Científicas (CADIC-CONICET). Bernardo A. Houssay 200, 9410 Ushuaia, Tierra del Fuego, Argentina.
  • L.V. DIMIERI Instituto Geológico del Sur (INGEOSUR-CONICET), Departamento de Geología, Universidad Nacional del SurSan Juan 670, 8000 Bahía Blanca, Buenos Aires, Argentina.

Keywords:

Central belt, Thrust-fold belt, Shortening transference, Crustal duplex, Cenozoic, Fuegian Andes

Abstract

The Fuegian thrust-fold belt has been subjected to significant shortening during the Cenozoic. Although contemporaneous shortening and uplift was also recognized in the Fuegian Andes central belt (hinterland), previous studies stated that most of that deformation developed out-of-sequence with the thrust-fold belt and hence did not contribute to its shortening. Therefore, no suitable geometric and kinematic model has been proposed for the mechanism that links deformation in both domains. Here we address the style and timing of the younger (Late Cretaceous-Paleogene) structures of the central belt and the structural evolution of the thrust-fold belt, based on published and own data. We reinterpret the style of the central belt structures, proposing a new model in which basement thrusting in the central belt caused all the shortening in the foreland cover. We postulate that the basement was involved in a regional-scale duplex whose roof thrust was the décollement of the thin-skinned thrust-fold belt. Therefore, the total slip transferred through the roof thrust accounted for the shortening in the cover rocks. The basement duplex incorporated the underthrust crust from the footwall of the orogenic wedge through forward propagation, in sequence with the thrust-fold belt, from the Late Cretaceous to the Miocene.

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