Heavy mineral provenance data presented in this article reinforce evidence for significant late Palaeogene deformation and relief formation along the western margin of the Central Andean Plateau. Late Eocene–Oligocene onset of molasse-type sedimentation records initial range uplift. Strikingly different basement sources of sediments deposited to the east and west of the Late Palaeogene range indicate that initial relief development was governed by a bivergent thrust system. Significantly higher sediment accumulation rates to the east of the range compared to the west suggest that the generated relief acted already as an effective orographic barrier at that time. Higher precipitation and denudation along the eastern slope facilitated deeper erosion of the trust belt