Las orogénesis del Paleozoico Inferior en el margen proto-andino de América del Sur, Sierras Pampeanas, Argentina

RAPELA, C.W.; CASQUET, C.; BALDO, E.G.; DAHLQUIST, J.A.; PANKHURST, R.J; GALINDO, C.; SAAVEDRA, J.

JOURNAL OF IBERIAN GEOLOGY

SERVICIO PUBLICACIONES

Lugar: Madrid; Año: 2001 vol. 27 p. 23 - 41

1698-6180

The proto-Andean margin of Gondwana was the site of at least two orogenies between the break-up of the Rodinia supercontinent, at the end of the Neoproterozoic, and the new continental amalgamation of Pangea at the end of the Carboniferous. Both orogenies were preceded by a period of ocean opening and passive margin sedimentation and ended with ocean subduction, development of cordilleran-type magmatic arcs and continent-continent collision. The Pampean orogeny took place in a relatively short period of time in the early Cambrian (535- 520 Ma; subduction ? magmatic arc stage and continental collision), and ended with the orthogonal accretion of a semiautochthonous microcontinental fragment - the Pampean Terrane- to the Gondwana margin. On the other hand, the Famatinian orogeny spanned a longer period of time in the Ordovician and Silurian (499-435 Ma). During this orogeny the exotic Precordillera Terrane was accreted to the margin of Gondwana (460 Ma). This terrane, probably of Laurentian provenance, consists of a Grenvillian basement (1.1 Ga) and a Lower Paleozoic sedimentary cover of the carbonate platform type. Accretion was probably oblique to the Gondwana margin, and the eastern margin of the Precordillera Terrane was thoroughly affected by Famatinian deformation and regional metamorphism. The basement to the Upper Paleozoic and Mesozoic Andean belts, situated to the west of the Precordillera, also appears to be formed by Grenvillian metamorphic rocks, so that the greater part of the Central Andes between 26ºS and 34ºS are established upon allocthonous terranes. The Lower Paleozoic paleogeography of continental masses involved in the collision is not still fully understood.