“…The pre-rift sequence consists of a fractured lowgrade metasedimentary basement (Medina Formation, Late Proterozoic to Middle Cambrian; Bossi, 1969;Ramos, 2008), unconformably overlaid by the rift related sedimentary/volcanic sequence (Cretaceous to Paleogene Salta Group). The latter consists of three subgroups: (i) Pirgua, (ii) Balbuena and (iii) Santa Bárbara (Reyes and Salfity, 1973;Salfity and Marquillas, 1994). The Pirgua Subgroup (Early to Late Cretaceous), representing the syn-rift stage (Galliski and Viramonte, 1988;Salfity and Marquillas, 1994;Marquillas et al, 2005), mainly consists of red continental conglomerates and sandstones locally interbedded with alkaline volcanic rocks (Galliski and Viramonte, 1988).…”