Thrusting evolution in the southern Cordillera Oriental (northern Argentine Andes): Constraints from growth strata

Abstract

Growth strata and unconformities in the Cenozoic synorogenic sediments in the southern Cordillera Oriental of the northern Argentine Andes provide new evidence for the eastward migration of the Andean deformation from the Puna to the Santa Bárbara system. The growth sequences and unconformities allow us to constrain the age of the structures with greater precision and to determine the distribution of this deformation in the thrust and fold wedge over time. Thrust evolution was mainly controlled by the reactivation of earlier extensional faults of the Cretaceous Salta Rift Basin. The geometry of the inverted structures together with the general forward migration of the deformation gave rise to different thrust sequences. The foreland dipping imbricate stack of the western Cordillera Oriental developed forwards during Middle–Late Miocene, resulting in a break back thrusting sequence. Thrust propagation rate increased in Late Miocene-Early Pliocene times when the eastern part of the Cordillera Oriental developed. At that time a widespread deformation and synchronous thrusting occurred in the Cordillera Oriental. Subsequently, deformation was mainly confined to the eastern part of the Cordillera Oriental. Finally, during the Pleistocene-Holocene, deformation affected a wider zone, including the Cordillera Oriental and the Santa Bárbara System, giving rise to the reactivation of previously developed thrusts.