Depocentros Cenozoicos de los Andes Australes durante la apertura del Pasaje de Drake

Abstract

Cretaceous-Cenozoic interaction between the South America and Antarctica plates has been a major driver of kinematics in the Southernmost Andes, imprinting extensional and strike- slip deformation within the foreland in Tierra del Fuego. Late Cretaceous basin inversion and transpression along the Beagle channel was due to their left-lateral relative displacement. Orogen building continued during the Paleogene, together with progression of sedimentation in the associated Austral-Malvinas marine foreland basin system and depocenters migrations. The Eocene early opening of the Drake passage due to Antarctica separation, involved the combination of strike-slip and extensional tectonics, superposed to the previously consolidated orogen. A series of latest Paleocene–early Eocene fault-related extensional depocenters can be recognized in the Austral and Malvinas basins, which represent a direct indication of continental lithospheric stretching preceding the opening of embryonic basins in the West Scotia Sea. A middle-late Eocene compressional stage followed, characterized by rapid migration of the orogenic front and establishment of a widespread wedge-top depocenter. Since the Oligocene inception of oceanic spreading in the West Scotia Sea, strike-slip deformation has dominated, concentrated along the North Scotia ridge-Magallanes-Fagnano fault zone. As a result, late Cenozoic continental pull-apart basins are registered in a hinterland position. Coeval retroarc Miocene sedimentation includes an important continental volcaniclastic component and distributary system funneling sediments to deep marine basins. In this context, tectonic loading, dynamic subsidence, and transtension/pull-apart extension seems to be superposed; alternatively, they may be partitioned processes and geographically distributed. We present a synthesis of this history of changing tectonic regimes and depocenters migration in the southernmost Andes and the Austral basin from and discuss the implication of new detrital zircons provenance data.