Abstract

PERALTA, Silvio H. El Silúrico de la sierra de La Invernada, Precordillera de San Juan: implicancias estratigráficas y paleogeográficas. Rev. Asoc. Geol. Argent. [online]. 2013, vol.70, n.4, pp.477-487. ISSN 0004-4822.

A Silurian siliciclastic succession, assigned to the Tucunuco Group, composed of the La Chilca/Los Bretes (Hirnantian? to early Wenlock), and the Los Espejos (middle Wenlock to Ludlow) formations, is described on the eastern flanck of the sierra de La Invernada, at the Central Precordillera. In the Gualilán area, the La Chilca Formation is composed by of silt and sand thickening and coarsening upward sequence (shallowing), exhibiting a facies change towards the south to bioturbated shale named "Facies Pachaco of the Tambolar Formation", which formally is here redefined as Los Bretes Formation, its type section is located at the cerro Blanco de Pachaco. The Los Espejos Formation shows a marked southward onlap toward south, but it is not exposed in the San Juan River area; there, its deposits appear reworked into the Los Sombreros Formation. The Punta Negra Formation paraconformably overlies the Los Espejos Formation (Gualilán area), and to the Los Bretes Formation (Pachaco area) and, in turn, it erosively underlies the Los Sombreros Formation, which age is assigned to the Devonian post-Punta Negra Formation on the basis of its stratigraphic relationship, and lithological and paleobiological features. The Silurian succession shows a relative distal position in comparison with its correlatives from the Central Precordillera. The facies change of the La Chilca Formation and the southward onlap of the Los Espejos Formation, are interpreted as a result of northward tilting of the Silurian basin.

Keywords : Silurian; La Invernada Range; Precordillera; San Juan; Argentine.

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