Analysis and structural restoration of the Abanico Formation, Principal Cordillera of central Chile, between 33°40’ – 34°20’S (Maipo and Cachapoal river valleys)

Abstract

In the Principal Cordillera of central Chile there are few quantitative structural analyses that continuously and completely cross overthe western Principal Cordillera and, simultaneously, displays values of tectonic shortening with models of the geometry of structurestoward deeper levels. The knowledge of the percentage of tectonic shortening and the geometry of the surface structures would helpto understand the deformation that gave rise to the uplift and current configuration of the Principal Cordillera, and also, to establishhypotheses about the internal architecture of the Abanico extensional basin (Charrier et al., 2002). There are a large number ofstructural sections and the evaluation of the structures that compose them, by remote sensing methods and by the contribution ofnew data for specific zones, allow their integration into continuous sections that completely cover the area of the western PrincipalCordillera in the study region.In this publication, we present the preliminary results obtained for two structural models of 50 km long cross sections that encompassthe Principal Cordillera and extend from the eastern edge of the Central Depression to the El Diablo fault system, which separates theCenozoic sequences from the Mesozoic in this region. The first model is based on 3 sections oriented at 95° azimuth, within an eastweststrip between 33°47’ and 33°53’S, and the second model based on 3 sections oriented at 105° azimuth within the strip between34°12’ y 34°26’S.The orientation of the principal structures and the parameters that define them were obtained from the generated structural models,from the calculation of the minimum crustal shortening value and from the combination of these data with the location of seismichypocenters within the study area. Finally, high-angle deep structures were identified, which would constitute master faults that delimitthe compartments of the Abanico basin for depth levels up to 2500 m.