Distribution, timing, and causes of Andean deformation across South America
Résumé
The Andean Orogeny in South America has lasted over 100 Ma. It comprises the Peruvian, Incaic and Quechuan phases. The Nazca and South American plates have been converging at varying rates since the Palaeocene. The active tectonics of South America are relatively clear, from seismological and Global Positioning System (GPS) data. Horizontal shortening is responsible for a thick crust and high topography in the Andes, as well as in SE Brazil and Patagonia. We have integrated available data and have compiled four fault maps at the scale of South America, for the mid-Cretaceous, Late Cretaceous, Palaeogene and Neogene periods. Andean compression has been widespread since the Aptian. The continental margins have registered more deformation than the interior. For the Peruvian phase, not enough information is available to establish a tectonic context. During the Incaic phase, strike-slip faulting was common. During the Quechuan phase, crustal thickening has been the dominant mode of deformation. To investigate the mechanics of deformation, we have carried out 10 properly scaled experiments on physical models of the lithosphere, containing various plates. The dominant response to plate motion was subduction of oceanic lithosphere beneath continental South America. However, the model continent also deformed internally, especially at the margins and initial weaknesses.