Steady-state exhumation pattern in the Central Andes – SE Peru

Abstract

The Western Cordillera of SE Peru is part of the Central Andes and is situated to the west of the Eastern Andes from which it is separated by the northern termination of the Altiplano – the Inter-Andean Valley. It is a volcanic–volcano-detrital chain that developed in the Palaeogene, and is characterized by a 4000 m-high mean altitude whose origin is poorly constrained. We selected a vertical profile in the region of Abancay to trace the record the evolving uplift and erosion history of the Andean orogen. Fission-track data on both apatite and zircon crystals were completed on plutonic rocks of the Tertiary Andahuaylas–Yauri batholith. Ages ranged between 24 and 14 Ma, and 38 and 30 Ma, respectively. Thermal modelling was completed for the whole profile and does not, like age–altitude relationships, show evidence of any clear disruption of the exhumation paths since 38 Ma either by sedimentary burial and/or rapid exhumation. One of the noteworthy aspects of the data is that exhumation was steady at a rate of 0.17 km Ma-1 from the late Eocene until at least the middle Miocene (38–14 Ma). The uplift of the Western Cordillera was thus probably steady for this period with sedimentary deposition restricted to the present-day Altiplano and Inter-Andean Valley regions.