Geología de los alrededores de los ríos caleufú y meliquina, provincia de Neuquén: El volcanismo de la Formación Huitrera

Abstract

A series of paleogene volcanic rocks exposed south of Villa Meliquina, located in the foothills of the Andes in the Neuquén province, has been studied in this work. It corresponds to a poorly known area from the geological point of view, located between the San Martin de los Andes and San Carlos de Bariloche localities, where outcrop a volcanic sequence assigned to the Huitrera Formation. In the surveyed area, two different structural domains affecting these outcrops were described: a western sector, in the Lago Filo Hua Hum region, where NE oriented folds and faults predominate, and an eastern sector, around the Caleufú river, dominated by NW trending and NE verging thrusts associated to anticlines. Two profiles of the Huitrera Formation were surveyed in both areas, as well as other outcrops of the volcanic rocks in the region. As a result, it was recognized that the Huitrera Formation is formed by a pyroclastic and lavic facies: the first is more dominant in the western region, while the second is fully developed in the eastern region. The lava facies is composed of lava flows of basaltic and rhyolitic composition, with porphyritic texture and frequent disequilibrium textures; in the pyroclastic facies, the vitreous tuffs are predominant with different degrees of welding. The petrographic characteristics of both facies can be correlated with the bimodal volcanism associated to lavic-pyroclastic facies previously defined for equivalent sequences in reighbouring regions. The particular distribution of the facies in the work area would mainly be controlled by the structure