Primeras edades u-pb en circones detríticos del Grupo Neuquén en el extremo oriental de la Cuenca Neuquina (Paso Córdoba, Río Negro)

Abstract

This work provides new U-Pb detrital zircon ages of the eastern synorogenic Upper Cretaceous deposits of the Neuquén Basin at Paso Córdoba, Río Negro, Argentina. The Neuquén Basin is a large depocenter developed during the Late Triassic to Paleogene along the southwestern margin of Gondwana (30-40°S). It originated by continental-scale rifting processes resulting in the break-up of the Pangea supercontinent. It records a thick Mesozoic sedimentary succession more than 7,000 m thick including marine and non-marine sedimentary rocks. Important geodynamic changes occurred during the latest Mesozoic with the accelerated westward movement of the South American plate following its separation from the African plate, and the continuation of subduction processes along its western margin, most notably the convergence between the Nazca-Farallón and the South American plates. This new compressive tectonic setting triggered the foreland basin deposition of the Neuquén Group. The non-marine Neuquén Group shows an important regional distribution and is characterized as the first foreland basin deposits linked with the early uplift of the Andean orogen at ca. 100 Ma. The Neuquén Group contains an important fossil record and is a reservoir rock in some depocenters of the basin. For this reason, it has been a well-studied unit in both the southern and central parts of the basin. Regionally, this stratigraphic unit is covered by Maastrichtian to Paleocene marine facies of the Malargüe Group.