Evolution of the Sierras de Córdoba, Argentina

Abstract

Located in the southeastern part of the Sierras Pampeanas (Argentina), the Pampean Ranges of Córdoba show the evolution at the western margin of the Rio de la Plata craton, from extensional stages during Neoproterozoic times to compressive stages during the Pampean orogeny. The Cumbre de Gaspar Group represents distal deep-sea clastic sedimentation deposited in a passive margin environment, very possibly during a time of incipient oceanization. The Santa Sabina Group, representing shelf sedimentation, rests conformably on the Cumbre de Gaspar Group. Stocks of granites and granodiorites of calc-alkaline affinity intruded the Cumbre de Gaspar Group during the early Pampean or earlier. The polyphase Pampean orogeny involves several distinct metamorphic and orogenic events. Metamorphism is discussed using the chemical composition of minerals. The major effect of the Pampean orogeny was the formation of a pile of westward thrust blocks. The Rio de la Plata craton, thrust above its marginal basin, forms the uppermost unit. The intrusion of the El Pilon granite (dated at 520 ± 5 Ma) post-dates these tectonic and metamorphic events. After this main orogenic event, the domain remained permanently located on the cratonic side of younger Famatinian and Andean orogenic events. The Mermela Group probably corresponds to the molasse of the Pampean orogeny and to the base of a new sedimentary cycle. It is difficult to distinguish Famatinian tectonics in the Sierras de Córdoba because the main orogeny occurred further west. However, this orogenic cycle is marked by the intrusion of the large Achala batholith. During the late Palaeozoic and Mesozoic the Sierras de Córdoba remained a stable platform. The whole region was rejuvenated by the Andean orogeny, which induced tilted blocks in its foreland and the Pocho volcanics of shoshonitic affinities.