Temporal growth of the Puna Plateau and its bearing on the post-Salta Rift system subsidence of the Andean foreland basin at 25°30′S

The Puna Plateau, a high-elevation portion of the central Andean Plateau, possesses some of the thickest crust on Earth, and its structural growth should be reflected in the adjacent foreland basin (present-day Eastern Cordillera and Santa Bárbara system) as a flexural response to crustal thickening via contractional deformation. The Cretaceous-Cenozoic stratigraphy preserved within the Eastern Cordillera and Santa Bárbara system also records the influence of the Cretaceous Salta Rift system, which heavily influenced depositional patterns in the region, particularly during postrift thermal subsidence. The Eastern Cordillera and Santa Bárbara system were significantly modified by Neogene inversion of Salta Rift basins, which subdivide the foreland basin and localize depocenters. Here, we examine results of two-dimensional kinematic models of basin formation and fill that proxy the thermal and mechanical behavior of the Salta rifting, and superimpose upon this rifting event two different scenarios for the temporal growth of the Puna Plateau-one with crustal thickening predominantly in the Eocene, and another with progressive crustal thickening beginning in the early Miocene. The two models attempt to forecast the combined effects of inherited rift history and growth of the Puna Plateau on the development of accommodation within the adjacent foreland basin. A Neogene (Miocene-age) Puna Plateau scenario creates a coeval foredeep within the Salta Rift system, but its magnitude and wavelength are influenced by crustal thickening in the Eastern Cordillera and Santa Bárbara system. In contrast, a Paleogene (Eocene-age) growth scenario for the Puna Plateau results in a substantial amount of coeval flexural accommodation in the adjacent Eastern Cordillera that extends across most of the Salta Rift system, which is broken up by subsequent loading in the Eastern Cordillera and Santa Bárbara system. Thermal subsidence associated with thinned or delaminated mantle lithosphere in the Late Cretaceous also contributes to accommodation and is most prominent during periods of tectonic quiescence. Our modeling results show that: (1) Neogene topographic growth of the Puna Plateau produces a basin subsidence history that is consistent with the geologic record, (2) the Salta Rift system was not buried deeply prior to Neogene exhumation, (3) the eastward advance of the flexural foreland can be related to crustal thickening and elevation gain of the Puna Plateau and Eastern Cordillera at ca. 15 Ma, and (4) interpretations of foreland subsidence history across the Eastern Cordillera may need to consider the influence of thinned mantle lithosphere during Late Cretaceous Salta rifting, which continues to create some accommodation in the region through subtle thermal subsidence.