Abstract

We assess the role of inherited structures on the Meso-Cenozoic tectonic evolution of the main Andean Cordillera in central Chile (33 degrees 30 ' S-34 degrees S). Based on extensive field mapping, U-Pb geochronology and palinspastic restorations along the Yeso and Volcan river valleys, we propose a tectono-stratigraphic model for the evolution of a hybrid fold-and-thrust belt, originated from the inversion of Mesozoic extensional basins. With these results, we highlight the structural graben configuration of the Yeguas Muertas and Nieves Negras depocenters, as evidenced by synextensional deposition of the Rio Damas and Lo Valdes Formations, controlled by normal faulting. The uppermost Cretaceous evolution can be approached through the analysis of the Las Coloradas Unit (ULC), which overlies the volcanic rocks of the upper Colimapu Formation and can be correlated, north of 32 degrees S, with the Juncal Formation, and south of 35 degrees S, with the Plan Los Yeuques Formation. The contractional Neogene-Quaternary deformation in the fold-and-thrust belt domain studied in this work, accommodated 27-28 km of minimum crustal shortening. The Neogene-Quaternary deformation that generated the final uplift of the Andes, has a close relationship with preexisting inverted Mesozoic structures. These structures deform the volcano-sedimentary Abanico Formation, deposited since the late Eocene, based on new U-Pb detrital zircon data. We propose that the active seismicity observed in the eastern border of the Principal Cordillera, located to the east of Santiago, can be associated with major crustal faults, as the Estero de Yeguas Muertas-Banos Colina fault system and the Chacayes-Yesillo fault.