Tectonic evolution of the North Patagonian Andes, from the exhumed crystalline rocks to the foreland basin

BECHIS, F.; YAGUPSKI, D.; ENCINAS, A.; THOMSON, S.; SANTONJA, C.; VALENCIA, V.; SURIANO, J.; OLAIZOLA, E.; RAMOS, V. A.

Santiago

Simposio; PRIMER SIMPOSIO DE TECTÓNICA SUDAMERICANA; 2016

Asociación de tectónica sudamericana

We present an ongoing integral and multidisciplinary study of the North Patagonian Andes at about 41°S. Our general goal is to analyze the main tectonic and climatic factors that controlled the late Cenozoic geodynamic evolution of this Andean segment. To achieve this, we are studying the structural architecture, age, and evolution of the deformation and exhumation within the fold and thrust belt by integrating previous and new structural, stratigraphic, sedimentologic, geochronologic and thermochronologic data. The North Patagonian fold and thrust belt at these latitudes shows a general thick-skinned structural style, with involved basement blocks comprised of highly exhumed Paleozoic to Cenozoic metamorphic and plutonic rocks. Local thin-skinned deformation is also present near the thrust front, where it affects the synorogenic deposits represented by the upper section of the Ñirihuau basin infill. We present new thermochronologic and structural data from the exhumed basement blocks, and U/Pb dating, structural observations, and sedimentary provenance data from the foreland basin. Our data are consistent with a relatively short stage of deformation and exhumation along the central and eastern sectors of the fold and thrust belt during the middle to late Miocene (~14 to 8 Ma). The temporal and spatial patterns of exhumation and deformation, and the geometry, location and evolution of the synorogenic depocenters suggest that the fold and thrust belt and its related foreland basin evolved under a relatively important control of climatic factors in this sector of the North Patagonian Andes