Serie Correlación Geológica (Dec 2011)
Periodos eruptivos e inter-eruptivos en el Grupo Choiyoi de la Precordillera mendocina
Abstract
Eruptive and inter-eruptive stages in the Choiyoi Group of the Mendoza Prec ordillera. In the area of the Cerro Siete Colores, located east of Uspallata, in the Mendoza Precordillera, appears a set of volcanicand sedimentary rocks which were assigned to the acidic section of the Choiyoi Group. The sedimentary rocks reach 300 m thickness. The volcanic rocks represent a highly explosive period that includes two eruptive events with large volumes of rock, being the first generated by a single-surge current followed by quasi-steady phase sustained currents. The second eruptive event represented by highly-welded ignimbrites, can be correlated with the emplacement of domes of late Lower Permian age. It shows a considerable areal reduction compared to the first event, as well as a generalized stage of subsidence.The first inter-eruptive sedimentary event is made up by conglomerates, sandstones, limestones and mudstones that represent dense flows, lahars, lagoon and river environments. The latter have the largest areal development and are constituted by limestones where stromatolite, verme and palynomorph remains were recognized. The second inter-eruptive event is almost exclusively represented by lagoon systems and was probably larger than the first.The morphology and the thickness of the depocenters were conditioned by the previous structure of the Bonilla (Cambro-Ordovician) and Santa Elena (Carboniferous) formations, as well as by a widespread system of faulting during the last volcanic events of the Choiyoi Group.
