Tectonic architecture of the Tarapaca Basin in the northern Central Andes: New constraints from field and 2D seismic data

The Tarapaca Basin is one of the larger basins created on the western margin of South America during the Mesozoic times. Regional studies focused their attention on understanding its Cenozoic surface structures, traditionally interpreted as a west-verging thrust and fold belt. However, its internal and deep architecture and the influence of previously developed Mesozoic extensional structures on its current structure have not been analyzed in detail. We used new field data and 2D seismic data to determine the tectonic architecture of the Tarapaca Basin. We have paid special attention to defining both the deep and superficial structures to understand its tectonic evolution. The seismic data reveal the existence of a series of half-graben structures along which Mesozoic synrift stratigraphic sequences accumulated. We also show that Upper Cretaceous and Cenozoic synorogenic sequences mainly accumulated over contractional folds (anticlines and synclines). The structure is characterized by a thick-skinned structural style dominated by structures inverted during the oblique reactivation of ancient Mesozoic normal faults and also by newly formed reverse faults in the form of shortcut and bypass faults. The presence of Upper Cretaceous to Tertiary synorogenic sequences over the contractional structures, separated by angular unconformities, allowed us to show that the basin inversion and its subsequent deformation occurred at least since the Late Cretaceous until Recent times. These results aid in understanding the role of extensional structures in the evolution of orogenic belts and can be compared with similar structures around the world.