Architecture, Kinematics, and Tectonic Evolution of the Principal Cordillera of the Andes in Central Chile (∼33.5°S): Insights From Detrital Zircon U‐Pb Geochronology and Seismotectonics Implications

Abstract

AbstractWe assess the role of inherited structures on the Meso‐Cenozoic tectonic evolution of the main Andean Cordillera in central Chile (33°30′S‐34°S). Based on extensive field mapping, U‐Pb geochronology and palinspastic restorations along the Yeso and Volcán 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 Río Damas and Lo Valdés 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°S, with the Juncal Formation, and south of 35°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‐Baños Colina fault system and the Chacayes‐Yesillo fault.