Resumo

CISTERNA, Clara Eugenia; COIRA, Beatriz  e  BRUSSA, Edsel. Volcano-sedimentary deposits of Lower Tremadocian age in sierra de Nerváez: Early volcanic episodes of the Ordovician magmatic arc, Famatinian System. Rev. Asoc. Geol. Argent. [online]. 2010, vol.67, n.3, pp.319-328. ISSN 0004-4822.

This study is focused on the analysis of the Las Angosturas section (27°42´10.2´´-27°42´10.4´´S and 67°57´20.5´´-67°56´54.8´´W), sierra de Narváez, north of the Famatina System, where a volcanic-sedimentary sequence of early Tremadoc age crops out and represents the major volumes of synsedimentary volcanites along the same regional context. We have recognized basic and acidic lavas, intercalated with massive and laminated sandstones and siltstones, locally hosting graptolites levels. These Ordovician rocks were intruded by the Las Angosturas granodiorite and some pelitic levels show typical contact metamorphism mineral assemblages. Field relations, petrography and the fossiliferous content of this sequence suggest that the effusive sin sedimentary activity along the northern Famatina System marine basin began at the early Tremadoc. The characterization of these records for Arenig deposits also ensures that the Ordovician column region developed as a result of two events of volcanism and sedimentation and it is also possible to establish new parameters for correlation with the Lower Paleozoic sequences in the northwestern Argentina.

Palavras-chave : Volcanism; Early Tremadoc; Sierra de Narváez; Famatina System; Argentine.

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