Landscape and drainage evolution during the Cenozoic in the Salinas Grandes Basin, Andean Plateau of NW Argentina

Abstract

Endorheic basins are distinctive features of the modern Andean plateau. These basins record thick Neogene-to-Modern evaporite successions that are considered as the onset of internal drainage and aridity. Some isolated older (Paleogene) evaporites and intermontane depocenters have been also described across the Argentine Puna, suggesting that some degree of hydrological isolation would have pre-dated the main Miocene-Pliocene plateau uplift. Evaporites beds, however, are not conclusive evidence for endorheism, given that their formation depends not only on the tectonically-driven paleo-drainage, but also on other sensitive variables as climate, and salinity of the sources. Here, we discuss the paleo-drainage evolution across the eastern Puna plateau at 23°-24° S, combining landscape numerical modeling with seismic stratigraphy. Seismic observations suggest an intermontane configuration as early as the late Paleogene, and relief formation to the east and west basin margins. Using different combinations of precipitation rates, our landscape models allowed us to reproduce the modern elevations observed in the study region as well as published thermochronological data. Our results suggest that endorheism would have started in the Paleogene, and would have dominated most (>70%) of the Cenozoic basin history. Models show the recurrence of endorheism, interrupted by intermittent phases of drainage connectivity (exorheism) to the east (foreland) in the upper half Eocene and the early Miocene. According to these results, the formation of closed basins in the Puna region would have pre-dated the main Miocene-Pliocene uplift stage of the Andean plateau.