The basement of the Andean Frontal Cordillera in the Cordón del Plata (Mendoza, Argentina): Geodynamic Evolution.

HEREDIA, N., FARÍAS, P., GARCÍA SANSEGUNDO, J., GIAMBIAGI, L.

ANDEAN GEOLOGY

SERVICIO NACIONAL GEOLOGIA MINERVA

Año: 2012 vol. 39 p. 242 - 257

0718-7092

The Andes Paleozoic Basement of the Cordón del Plata is formed by two sets of rocks showing different stratigraphy, structure and metamorphism. The lower one is represented by the Alto Tupungato Formation, pre-carboniferous in age (Devonian?). These rocks have been affected by folds and associated cleavage, developed under low-metamorphic conditions and related with the Chanic orogenic event (Upper Devonian-Lower Carboniferous). The alto Tupungato Fm. is pre-orogenic to the Chanic deformation event and must have been deposited in an ante-arc basin located on the active margin of Chilenia, before its collision with the passive margin of Gondwana. The upper set rest unconformably over the Alto Tupungato Fm. and is constituted by the El Plata Fm., Upper Carboniferous in age, and the Rio Blanco Conglomerates, probably Upper Carboniferous-Permian in age. These rocks have been affected by thrusts and associated folds, verging to the east, formed under epimetamorphic conditions. This deformation can be related with the SanRafaelic Orogen (Gondwanan Cycle). The El Plata Fm. was deposited in a back-arc basin while the Rio Blanco conglomerates must have been deposited in a retro-arc basin, both on the active margin of Gondwana. The Choiyoi Group, essentially volcanic and Permo-Triasic in age, rest unconformably over the mentioned series. These rocks were deposited in a pre-orogenic extensional context, associated to the starting of the Alpine Cycle. This cycle lead to the uplift of the Frontal Cordillera during the Cenozoic and the deposition of thick continental series at the base of the Cordon del Plata in Neogene times.