A review about the mechanisms associated with active deformation, regional uplift and subsidence in southern South America

FOLGUERA ANDRES; GUIDO GIANNI; LUCIA SAGRIPANTI ; EMILIO ROJAS VERA; IVÁN NOVARA; BRUNO COLAVITTO; ALVAREZ ORLANDO; DARÍO ORTS; JONATHAN TOBAL; MARIO GIMÉNEZ ; ANTONIO INTROCASO; FRANCISCO RUIZ; PATRICIA MARTÍNEZ; VICTOR A. RAMOS

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2015 vol. 64 p. 511 - 529

0895-9811

A broad range of processes act and acted simultaneously during the Quaternary producing relief in the Andes and adjacent foreland zone, 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. The Geoid reflects an important change at 35ºS along the Andes that could be indicating the presence of dynamic forces pushing up the continent in the Southern Central and Patagonian Andes due to a strong asthenospheric dynamics that is absent in the north. On the other hand,  mountains created in the Atlantic passive margin setting, along a vast section of the Bazilian Atlantic coast and regions located inland 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. To the south, crustal seismicity develops mainly on the western Andean slope indicating that retroarc orogenic activity is inhibited at the retroarc zone and replaced by synthetic-to-the-subduction zone thrusts. This is explained by the rain fall pattern that changes at these latitudes  and could be determining subcritical conditions on the Chilean Andean slope. 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.