Field trip guide: Andean Cordillera and backarc of the south-central Andes (~38.5°S to 37°S)

Abstract

The Andes of the Neuquén Mesozoic basin have experienced multiple episodic tectonic events as a consequence of the changes of the plate tectonic boundary configuration. Each episode of deformation has overprinted the previous one, making it difficult to unravel the Andean tectonic history. The first deformation event took place in the uppermost Cretaceous with the formation of the Agrio fold-and-thrust belt. This event was related to the shallowing of the subducting plate recorded by the migrationof the volcanic arc toward the foreland. During the late Oligocene-early Miocene, an extensional event, related to the steepening of the subducted plate, affected only the hinterland region causing the opening of the Cura Mallín basin. This basin was closed during the late Miocene, together with the development of a new fold-and-thrust belt that reactivated the previous structures. During the Late Tertiary, two more episodes of extension and compression affected the Andean area. The trip focuses on the field evidence that documents this complex history of evolution by looking at evidence ofthe sequence of the distinct tectonic events.