Caracterización geológica y estructural de unidades cretácicos - cenozoicas aflorantes entre la región entre la localidad de Ingeniero Jacobacci y la reserva Anecón Grande, suroeste de Río Negro

Abstract

study aims to characterize the geological and structural evolution of the sector located between Ingeniero Jacobacci and the Anecón Grande area, approximately 80 km east of Ingeniero Jacobacci and near the town of Comallo, with emphasis on the Anecón Grande Volcanic Complex (CVAG), a unit previously assigned a Late Cretaceous-Paleogene age. The research focuses on reconstructing the magmatic and tectonic processes linked to the evolution of the northern Patagonian retroarc since the Late Cretaceous. The methodology combined fieldwork, petrographic analysis, 3D photogrammetric modeling, and U-Pb zircon geochronology. Field activities included detailed mapping and description of CVAG outcrops, construction of a stratigraphic profile, and systematic sampling for laboratory analyses. Petrographic examination of thin sections, together with U-Pb zircon dating (64.77 ± 0.23 Ma), allowed the establishment of a Paleocene age for the CVAG and the characterization of its lithological evolution. Geochronological and structural data indicate a geological evolution controlled by changes in subduction dynamics and by the reactivation of upper-crustal faults since the Late Cretaceous. These results support a tectonomagmatic evolutionary model for the northern Patagonian retroarc and highlight the Anecón Grande-Ingeniero Jacobacci area as a key sector for understanding the interaction between magmatism and deformation along the Andean margin.