Resumen

GODOY, Estanislao. Sobre el variable marco geotectónico de las formarciones Abanico y Farellones y sus equivalentes al ser de los 35°LS. Rev. Asoc. Geol. Argent. [online]. 2012, vol.69, n.4, pp.570-577. ISSN 0004-4822.

Volcanic and volcaniclastic rocks grouped into the Farellones and Abanico formations make up most of the western Andean Main Range between 32° and 35°SL New 15 Ma Ar-Ar ages from the top of the latter formations show that the overlying succession, which locally onlaps eroded volcanic edifices, is diachronic. The calcalkaline Farellones volcanic activity started during the earliest Miocene at 32°SL, while only during the middle Miocene at 34°SL. This diachronism could be related to an earlier inversion of the "Abanico basin" in its northern section, linked to a stronger basement involvement in the Miocene shortening. The crust behaved differently south of 36°SL, where a late Cretaceous orogeny is present and Miocene volcanism first disappears and then constitutes isolated outcrops migrated towards the foreland. The large batholiths that now crops out in the Chilean watershed may have locally buffered deformation. A similar control may have acted south of 39°SL, where formations of similar age to Abaniso and Farellones were deposited on top of a rigid Paleozoic basement. This rigid block would have absorbed much of the strain, even inside the Plio-Pleistocene troughs with volcanic infilling present in the area.

Palabras clave : Miocene volcanism; Diachronic volcanic arc; Andean segmentation.

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