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.

Abstract The foothills of the central Andes of northwestern Argentina hinder the interpretation of the complex structural rift system developed during late Mesozoic extension. Andean compressive deformation inverted the Salta rift system, resulting in a series of complex structures with trends oblique to the main Andes. The Lomas de Olmedo basin, a failed branch of the rift system located east of the Andean orogenic front, was selected to undertake deep reprocessing of the available industrial seismic lines. A 150-km-long seismic section of the basin, recorded with Vibroseis and dynamite sources, was reprocessed. Extended correlation applied to the Vibroseis seismic data yielded reliable results down to 9 sec two-way travel time. Acoustic horizons identified within this interval include the deepest synrift deposits in the axial part of the basin and a deep oblique discontinuity in the crust. On this basis, a complete cross section of the basin was made. This study documents the asymmetry of the rift, with a prominent zone of thermal uplift in the northern edge. Truncation of the Paleozoic beds and identification of a deep oblique discontinuity at 7–8 sec (18–21 km deep) suggest that a northward-dipping detachment controlled the asymmetry of the system. The rift structure is mildly modified by folding related to Cenozoic tectonic inversion in the southern sector of the basin. This inversion was controlled mainly by strike-slip displacements along the previous normal faults.

Low-temperature thermochronological ages of samples from the central Andes correlate with major tectonic events during Late Cretaceous and Cenozoic times. Apatite fission-track (AFT) ages show prominent clusters during the Early–Late Cretaceous in the Coastal Cordillera and the Cordillera de Domeyko; Paleocene–Oligocene ages in the western Puna Plateau and Cordillera de Domeyko; and latest Eocene–Pliocene ages in the Eastern Cordillera. These ages track the expansion of the Andean orogenic edifice, the eastern front of which migrated rapidly eastward ~200 km and ~150 km during late Eocene and Pliocene times, respectively. During the intervening time interval, ca. 35–5 Ma, the orogenic strain front migrated slowly eastward through the Eastern Cordillera. A second cluster of Cretaceous ages in the Eastern Cordillera and Santa Bárbara Ranges documents exhumation related to extension in the Salta rift. The highly unsteady pace of orogenic wedge propagation suggests that kinematics controlled local climate, rather than vice versa. The frequency of AFT ages is anticorrelated with magmatic production in the central Andean arc and the rate of convergence between the Nazca and South American plates. We propose a link between AFT bedrock cooling ages in the central Andes and exhumation related to cyclical processes of shortening, wedge propagation, magmatism, and removal of dense roots from beneath the magmatic arc and thickened hinterland region. In particular, periods of sustained exhumation associated with local crustal shortening alternate with periods of rapid eastward wedge propagation during which exhumation was more spatially diffuse across the high-elevation hinterland. Episodes of spatially confined exhumation are correlated with periods of relatively low magmatic production in the central Andean arc and relatively slow or declining plate convergence rates. We speculate that shortening in the upper crust was contemporaneous with underthrusting of lower crust and mantle lithosphere beneath the magmatic arc. Because of thermal inertia, melting of these underthrusted rocks lagged behind the shortening events themselves, thus producing the observed temporal anticorrelation between rapid shortening-induced exhumation and arc magmatism.

Abstract Structures mapped in the southern Cordillera Oriental of the Andes show an unexpected geometry in an east–west cross-sectional view, with a remarkable predominance of west-directed thrusts. Although some of the Andean structures trend north–south perpendicular to the main east–west direction of Andean shortening, many of them clearly differ from this expected orientation. This peculiar structural style has been largely related to the inversion of the Cretaceous Salta Rift Basin; however, some of these anomalously trending Andean folds and faults do not result from the inversion of Cretaceous faults. This lack of inversion of some Cretaceous structures becomes evident where west-dipping extensional faults rest in the footwall of west-directed thrusts instead of developing east-directed thrusts, as would be expected. Detailed study of several structures and examination of the geometry and facies distribution of several basins highlight not only the role played by the inversion of Cretaceous extensional faults on the geometry of the Andean structures, but also that played by basement anisotropies on the development of both the Cretaceous extensional faults and the Andean contractional structures.

Abstract The study area is located within the Central Andes, a complex region composed of different structural styles. The region is characterized by highly elevated basement cored ranges, which abruptly break the foreland plain. These ranges were uplifted mainly by deep detached high-angle faults or by the inversion of former extensional faults of the Cretaceous rift. Palaeozoic orogenies generated crustal scale discontinuities in the basement, some of them reactivated during the Andean orogeny. Sedimentary sequences and layers architecture in the basins bordering ranges recorded the tectonic evolution of the region. Basement, syn–rift, post-rift and three foreland stages were interpreted in the seismic sections according to the arrangement of the horizons and the main outcropping geological units in bordering ranges. Based on seismic data sets and field data, here we document a particular style of activation of basement faults. Thick-skinned structures that are not always related to the tectonic inversion but to the reactivation of older basement anisotropies represent a paradox since they were not active during the rifting stage. A flat slab subduction and a subsequent angle recovery conditioned the structural evolution of the area.