%0 Journal Article
%A De Ignacio San José, Cristina
%A Lópe, Iván
%A Oyarzun Muñoz, Roberto
%A Márquez González, Álvaro
%T The northern Patagonia Somuncura plateau basalts: a productof slab-induced, shallow asthenospheric upwelling?
%D 2001
%@ ISSN: 0954-4879, ESSN: 1365-3121
%U https://hdl.handle.net/20.500.14352/60261
%X The Meseta de Somuncura forms the largest basaltic plateau (20 000 km2 ) of southern Argentina (extra-Andean domain). Most of these tholeiitic to alkaline rocks were extruded at ~ 25 Ma (late Oligocene). The absence of rifting±thinning processes, plume activity, or slab-window phenomena leaves only one major possibility for the generation of Somuncura: asthenospheric ('OIB-like') corner flow leading to a transient thermal anomaly above the subducting plate. It is suggested herein that the intake of hot asthenosphere was forced into a favourable topography (concave-up) of the subducting plate, hen a major plate reorganization event (Farallon to Nazca)was taking place in late Oligocene to early Miocene time. The fast and vigorous intake of asthenosphere would have been induced by slab roll-back, leading to decoupling of the subducting plate. The Somuncura volcanic episode can be regarded as a marker of the passage from the extremelyoblique subduction of Farallon, to the birth of the Nazca plate and roughly perpendicular convergence between South America and Nazca.
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