The Ancient Configuration of the Southern Central Andes and Paleogeographic Reconstruction of the Late Cretaceous Foreland Basin at 34°40’S

Abstract

The early stages of Andean construction have been barely recognized due to a long history of tectonic superposition during the growth of the orogen. In this work, we present a multi-method approach integrating sedimentological, geochronological, structural, and provenance analyses to reconstruct the architecture of the Late Cretaceous foreland basin at 34°40’S. We identified a new depocenter located in an inner position of the Late Cretaceous foreland basin, a strategic location to understand the sedimentation dynamics near the topographic front of the orogen. Two sandstone samples from the basal and upper sections of the Diamante Formation were collected for detrital zircons dating, which yielded maximum depositional ages between 98 Ma and 91 Ma. The provenance analyses based on U-Pb zircons ages indicated a main source area located to the west, in the incipient orogenic belt, with a complementary contribution from basement rocks, located to the east. Moreover, growth strata documented in these deposits were compared with structural kinematic models, which suggest that some of these deposits are associated with inherited structures, reactivated during the tectonic inversion of the extensional Jurassic Atuel depocenter. Our paleogeographic model comprises an Andean Cordillera flanked by a hinterland basin to the west and a foreland basin to the east, with a deformational front positioned further east compared to previous models.