Active exhumation in southern South America throughout the Quaternary: a general review about its development and mechanisms

ANDRES FOLGUERA; EMILIO ROJAS VERA; VICTOR A. RAMOS; GIANNI GUIDO M; BRUNO COLAVITTO; LUCÍA SAGRIPANTI; DARÍO ORTS

Marine Isotope Stage 3 in Southern South America 60 ka B.P.-30 ka B.P

Springer

Año: 2016; p. 107 - 127

A broad range of processes act and acted simultaneously during the Quaternary producing relief from the Chilean coast, where the Pacific ocean floor is sinking beneath the South American border, to the Brazilian and Argentinean Atlantic platform area. This picture shows to be complex and respond to a variety of processes that just start to be recently considered. These processes involve mountains created in a passive margin setting along vast sections of the Bazilian Atlantic coast and regions located inland, to ?current? orogenic processes along the Andean zone. On one hand, mountains in the passive margin seem to be created at the area where the forearc region eastwardly shifts at a similar rate than the westward advancing continent, and therefore can be considered as relatively stationary and dynamically sustained by a perpendicular-to-the-margin asthenospheric flow. On the other hand, the orogenic processes associated with the eastern Andes show to be highly active at two particular areas: The Subandean region, where the trench is stationary and at the Pampean flat subduction zone to the south, where a shallower geometry of the Nazca plate creates particular conditions for deformation and rapid propagation of the orogenic front creating a high-amplitude orogen. In the southern Central and Patagonian Andes, mountain (orogenic) building processes are attenuated, becoming dominant other mechanisms of exhumation such as the i) impact of mantle plumes originated in the 660 km mantle transition, ii) the retirement of ice-masses from the Andes after the Pleistocene producing an isostatic rebound, iii) the dynamic topography associated with the opening of asthenospheric windows during the subduction of the Chile ridge and slab tearing processes, iv) the subduction of oceanic plateaux linked to transform zones and v) the accretion of oceanic materials beneath the forearc region. Additionally and after last geodetic studies, vi) exhumation due to co-seismic and post-seismic lithospheric stretching associated with large earthquakes along the subduction zone, also shows to be a factor associated with exhumation that needs to be further considered as an additional mechanism from the Chilean coast to the western retroarc area.