Las ignimbritas de la Formación El Palque (Permo-Triásico), Calingasta, provincia de San Juan, Argentina

VALLECILLO, G; CABALLERO, M.M., ROCHER, S., ESPÍN, E. Y RIVEROS, S.

Revista CIENCIAS

EFU editorial de la UNSJ

Lugar: San Juan; Año: 2010 p. 29 - 37

0327-4446

This paper deals with the ignimbrite pyroclastic facies, associated to interbedded clastic rocks and mesosilicic volcanic igneous rocks, located in the Frontal Cordillera at the Calingasta river section, in San Juan province. These rocks belong to Choiyoi Group, a volcanic, pyroclastic and clastic complex, assigned to Early Permian-Late Triassic interval. The ignimbritic facies can be grouped in three categories: a) lapillitic ignimbrites welded, b) ignimbrites not welded and c) ignimbrite fine tuffs. Considering their massive bedding, disorganization and thickness, it suggested that a and b facies were accumulated under the action of dense pyroclastic flows sst. related to the existence of a relatively near explosive volcanism. The c facies has been altered on pumice fragments, related to high vesicularity event. Based on the caracteristics of the facies and their associations, an explosive volcanism of restricted plinian type with deposits located near the emitting center or ?vent? is interpreted.