Mesozoic extensional deformation played a key role in basin formation in Argentina. Extension persisted from Middle Triassic to Late Cretaceous, although the intensity of deformation and the areas affected varied considerably with time. Initial subsidence began in many Argentine basins, and in almost all of the hydrocarbon-producing basins, during these extensional episodes.

The sedimentary fill associated with extension can generally be divided into two units of supersequence rank--a lower, wedge-shaped succession deposited during active, fault-driven subsidence and an upper, wider-spread unit deposited during thermally driven subsidence after faulting had essentially ceased. Examples from the Middle Triassic of the Cuyo basin, Early Jurassic of the Neuquen basin, and Early Cretaceous of the Oran basin document the similarities and differences between basins formed at different times.

Even though Mesozoic extension in Argentina covered a long time span (about 150 m.y.), we believe that the various episodes are related. We favor an explanation that links the initiation of extension with subduction-driven processes along the western edge of the South American sector of the Gondwana supercontinent.