 A steepening of the subduction zone during the Late Miocene has been linked to an increase in volcanic activity and its westward migration, but it is unlikely that the pattern of activity in the southern Puna next to the Toro fault zone can be explained through this alone. A large low velocity and low seismic attenuation anomaly is found between 20 and 24°latitude south. Some geologic evidence, including geochemistry and geographic indicators, imply that lithospheric detachment did occur beneath the southern Puna.
