Abstract

FOLGUERA, A.; RAMOS, V.A.  and  VIEIRO, J.. Neogene tectonics in the southernmost extreme of the Northern Patagonian Cordillera: La Plata-Fontana lakes basin (45°S). Rev. Asoc. Geol. Argent. [online]. 2003, vol.58, n.2, pp.201-208. ISSN 0004-4822.

New anisotropic seismic data below the Andes at 45°- 46°S have revealed a striking feature: a fast polarization NW axis coinciding with the Lower Cretaceous segmentation derived from basin geometry. The geometry of the lower lithosphere would induce astenospheric flux which is not parallel to the Andean trend. Moreover, a series of Quaternary-Neogene small basins in the retro-arc are aligned with the Cretaceous extensional structure. Did transtensional reactivation of basement structures during the Neogene modify lower lithosphere geometry through activity of ancient detachments, inducing convective cells in the upper mantle? Or would the activity of the ancient detachment be linked to the opening of a slab astenospheric window and to its drag in the lower lithosphere, making the crust yield through fossilized discontinuities?

Keywords : Patagonian Cordillera; Neotectonics; Mantle Anisotropy.

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