Silurian of the San Juan Precordillera, western Argentina: stratigraphic framework

PERALTA, S H; PÖTHE DE BALDIS, E. D.; LEÓN, L. I.; PEREYRA, , M. E.

San Juan-Salta-Jujuy

Congreso; 9th International Symposium on the Ordovician System, 6th International Graptolite Conference and 2003 Field Meeting Subcommission on Silurian Stratigraphy, San Juan; 2003

Universidad Nacional de San Juan, Universidad Nacional de Tucumán

ABSTRACT: Silurian rocks of the Precordillera of San Juan Province, Western Argentina, belong to an almost continuous sedimentary cycle beginning in the Late Ordovician (Hirnantian) and ending in the Early-Middle? Devonian. This cycle is bounded at the base by an erosional surface related to the worldwide Hirnantian glacial event, and at the top by the Chánica tectonic phase. In the Central Precordillera, Silurian rocks are represented by the Tucunuco Group and its equivalent Tambolar Formation, and, in the Eastern Precordillera, by the Don Braulio and Rinconada formations. In the Western Precordillera, at the present time, Silurian rocks are not adequately documented, notwithstanding the reported finding of shelly fauna mentioned in the Calingasta Formation by Xicoy (1963, in Furque and Cuerda, 1979), which has been not further constrained. For this reason, the Western Precordillera is not considered in this paper.Siliciclastic Silurian units of the San Juan Precordillera are characterized by their coarsening-thickening upward sequence paraconformable boundaries (drowning surfaces), and conformable, regressive, depositional system-tracks controlled by sea-level changes (Peralta, 1990; Astini and Piovano, 1992; Astini and Maretto, 1996). Their fossil contents, ferriferous (ironstones) and phosphate deposits, and predominance of biogenic and HCS structures; and associated bioclastic accumulations are also documented.