Abstract

CISTERNA, Clara E; COIRA, Beatriz  and  KOUKHARSKY, Magdalena. Subaqueous basic effusions of arenig age in northern Famatina system, northwest Argentina. Ser. correl. geol. [online]. 2012, vol.28, n.2, pp.53-66. ISSN 1666-9479.

This paper focuses on the analysis of the Ordovician successions that outcrop along the Sierra de Las Planchadas - Narvaez, northern Famatina System. They are the earliest records of the Arenig of the region, as evidenced by the fossiliferous content and the overlying deposits of dacitic lavas, volcaniclastic resedimented syn-eruptive facies and volcanogenic facies, which complete the column. The analyzed sections from north to south are: - Quebrada Larga - Punta Colorada section, mainly composed of lavic facies and related autobreccias and hyaloclastites facies. - Quebrada Larga - Punta Pétrea section, that display several lavic facies (basalts, andesites and dacites) in associating with hyaloclastic and pillow breccias. To the upper portions of the profile are syn- eruptive resedimented volcaniclastic facies (breccias and psamites) and volcanogenic members, mainly represented by psamitic and pelitic rocks with fossils. - Vuelta de Las Tolas section, where the basic lavas and related autobreccias underlying the volcanogenic deposits. The comparative analysis of the chemical basic lavas characteristics indicates that they are of the same nature and show tholeiitic affinities. This study indicates that the Arenigian volcanic events were began as effusions related to a volcanic island arc, with submarine basalts and during their emplacement were produced in situ fragmentation processes, generating great volumes of autobreccias and hyaloclastites deposits.

Keywords : Subaqueous basalts; Hyaloclastites; Arenig; Famatina System.

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