Tectonic Evolution of the Patagonian Andes

The tectonic regime along the Andes: Present‐day and Mesozoic regimes

“…The strong extensional conditions in Early Cretaceous times have been interpreted as being produced by intense asthenospheric upwelling in an 'aborted marginal basin' between 278 and 338S (Levi and Aguirre 1981;Ä berg et al 1984;Mpodozis and Ramos 1990). However, Charrier (1984) suggested the existence of an Early Cretaceous intra-arc basin in the present-day Coastal Cordillera, based on palaeogeographic considerations, criteria followed by subsequent interpretations (Ramos 1985(Ramos , 1988Charrier and Muñoz 1994;Vergara et al 1995;Ramos and Alemán 2000;Fuentes et al 2005).…”

“…Nevertheless, when the entire Andean margin is examined, there are several cases of extreme extension that do not reach the formation of oceanic crust, as the Huarney Basin in Perú (Petford and Atherton 1995;Jaillard et al 2000;Ramos and Alemán 2000) where a heavily attenuated crust was filled with more than 9 km of volcanic products. Another example is the Central Chile Basin with several kilometres of volcanic rocks (Vergara et al 1995).…”

Constraints on deformation of the Southern Andes since the Cretaceous from anisotropy of magnetic susceptibility

“…A major thrusting event and uplift in the Paleogene has been also constrained using zircon (U-Th)/He dating from the eastern domains of the southern Patagonian Andes (Fosdick et al, 2013). The Eocene tectonics became much stronger towards the south affecting in particular Tierra del Fuego due to fast ~NE-directed subduction of the Phoenix plate between 47-28 Ma (Ramos and Aleman, 2000;Olivero and Martinioni, 2001;Kraemer, 2003;Ghiglione and Ramos, 2005;Ghidella, 2005, 2012;Ghiglione and Cristallini, 2007). Apatite fission track, and apatite and zircon (U-Th)/He ages constrained compressive events in the western domains of the Patagonian Andes to the late Oligocene (30-23 Ma;…”

“…Tectonic models proposing oroclinal bending in the Cenozoic, related to the opening of the Drake Passage between South America and Antarctica, initially received the largest consensus (Dalziel et al, 1973;Cunningham, 1993;Kraemer, 2003), but were recently challenged by paleomagnetic data from the sedimentary units of the Magallanes fold-and-thrust belt (Maffione et al, 2010;Poblete et al, 2014). Although alternative hypotheses have also emerged, suggesting a primary origin of the curvature of the Southern Andes (Ramos and Aleman, 2000), oroclinal bending models related to the closure of the Rocas Verdes marginal basin in the Late Cretaceous, proposed originally by Burns et al (1980), represent today a viable mechanism congruent with the known rotation pattern of the Southern Andes (Maffione et al, 2010;Poblete et al, 2014). The regional post-72 Ma 30° CCW rotation of the Fuegian Andes documented by Rapalini et al (2015), although occurring after complete closure of the Rocas Verdes basin, might still be associated to the tip of this major tectonic process.…”

Finding of a Holocene marine layer in Algarrobo (33°22'S), central Chile. Implications for coastal uplift

“…The structure of this area is dominated by faults and lineaments oriented in a NW and NE direction Wall et al, 1996). This region constituted a convergent margin at least since the Jurasic (Jaillard et al, 2000;Ramos and Aleman, 2000). At present, the Nazca plate is being subducted under the South American plate with a dip angle of ~30°, a convergence direction of N77°E, an obliquity or 13° and a convergence rate of 7-8 cm/year (DeMets et al, 1994;Angermann et al, 1999;Yáñez et al, 2001).…”