The Inner Forearc of the Central Andes (21°-23°S): Structural Styles, Age of Uplift and its Relation with Basement Weakness Zones (Spanish Presentation)

Authors: Fernando Martínez (presenter), Cristopher López, Rodrigo González, Belén Muñoz, Universidad Católica del Norte (Chile); Mauricio Parra, University of São Paulo (Brazil)

Presentation is in Spanish.

At 21º-23ºS the inner forearc of the Central Andes in northern Chile consist of two intermontane basins: The Salar de Atacama and Salar de Punta Negra basins. Both are bounded by the Chilean Precordillera (or Domeyko Cordillera) and the current volcanic arc and lie covered almost enterely by Pliocene salars, thus hindering a direct observation of their internal structural anatomy. For more than 20 years the structure and timig of deformation of this region have been an enigma to solve due to lack of subsurface geological information. In order to solve it, we integrated near of 38.000 km of 2D seismic data, field data, U-Pb ages of Cenozoic synorogenic deposits and apatite fission track data (AFT) from Paleozoic basement granitic rocks. The results show the existence of large doubly-verging basement-involved structures related to inverted Permian to Jurassic basement half-grabens and kilometric-scale reverse faults. The inverted structures consist of inversion anticlines linked to reactivated master normal faults, while that the reverse faults consist of moderate to high angle structures along which, basement-cored anticlines were developed. The basal synorogenic successions over the inversion anticlines report U-Pb ages ranking between 80-90 Ma, thus indicating a late Cretaceous age for the tectonic inversion. Samples from the basement-cored anticlines report Eocene to Miocene AFT ages suggesting a rapid exhumation of the basement rocks by reverse faulting. The last is superimposed to the tectonic inversion, and, is mostly controlled to changes in the tectono-thermal conditions of the upper crust from the eastward migration of the current volcanic arc.

Bio:

Fernando Martínez, Universidad Católica del Norte (Chile)

Fernando earned a PhD from the Universidad Católica del Norte, Chile, where he currently works as associate professor and main researcher at Andean tectonics. With 22 years of experience, he has previously worked as structural and regional geologist at PDVSA, Universidad de Oriente, Venezuela and assistant professor of University of Chile.

Fernando is a member of Sociedad Geológical Chilena, Asociación Geológica Argentina, Asociación Geológica Colombiana, Sociedad Venezolana de Ingenieros Geofísicos, among others.