The northern Patagonia Somuncura plateau basalts: a product of slab-induced, shallow asthenospheric upwelling?
Article first published online: 1 DEC 2003
Volume 13, Issue 2, pages 117–121, April 2001
How to Cite
De Ignacio, C. , López, I. , Oyarzun, R. and Márquez, A. (2001), The northern Patagonia Somuncura plateau basalts: a product of slab-induced, shallow asthenospheric upwelling?. Terra Nova, 13: 117–121. doi: 10.1046/j.1365-3121.2001.00326.x
- Issue published online: 1 DEC 2003
- Article first published online: 1 DEC 2003
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, when 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 extremely oblique subduction of Farallon, to the birth of the Nazca plate and roughly perpendicular convergence between South America and Nazca.