Andean shortening, inversion and exhumation associated with thin- and thick-skinned deformation in southern Peru
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
AbstractA balanced cross-section spanning the Eastern Cordillera and Subandean Zone of southern Peru (1315S) constrains ~130 km (38%) of Cenozoic orogen-normal SWNE Andean deformation accommodated by thick- and thin-skinned retroarc foldthrust belt shortening that overprinted pre-Andean Triassic normal faults. Zircon and apatite (UTh)/He ages demonstrate continuous Oligocene to Miocene cooling of the Permo-Triassic Coasa pluton in the Eastern Cordillera. Zircon (UTh)/He ages (~3418 Ma) are reset and define a steep age versus elevation relationship. Apatite (UTh)/He results reveal reset ages that define two spatially separated groups with ages of ~3026 Ma and ~1711 Ma. Detrital zircon UPb geochronologic results from CretaceousCenozoic siliciclastic rocks from the Altiplano/Eastern Cordillera record Andean foldthrust belt and magmatic-arc sediment sources. Correlative Subandean Zone rocks preserve a cratonic sediment contribution, with minor Andean sediment appearing in some Cenozoic rocks. We propose that earliest Andean deformation and structural compartmentalization of the Eastern Cordillera was linked to selective inversion of inherited Permo-Triassic basement-involved normal faults that guided subsequent thick- and thin-skinned deformation. Provenance variations between the hinterland and foreland depocentres reveal competing eastern and western sediment sources, reflecting an axial zone in the Eastern Cordillera that coincided with the inherited Triassic graben and impeded sediment source mixing. Our zircon and apatite (UTh)/He ages are consistent with published constraints along strike and support pulses of Eocene to late Miocene exhumation that were likely driven by normal fault reactivation and protracted Eastern Cordillera deformation.
