Redefinicion de la formacion farellones en la Cordillera de los Andes de Chile Central (32-34°S)

Abstract

ABSTRACT. Based on a new and more complete reference stratigraphic section exposed at the northern flank of Cerro La Gloria, north of the Aconcagua valley, a redefinition of the Farellones Formation is proposed. This new reference section and the modified section exposed at Farellones should now be considered the composite stratotype of the formation. As redefined the Farellones Formation includes a lower, rhyolitic-dacitic, tuffaceous to ignimbritic member, and an upper member made up of basaltic andesites, intruded by rhyodacitic domes. While the former is probably related to caldera-type eruptions, the latter represents an interfingering of flows and tephra from stratovolcanoes. Between parallels 33° and 34°S the outcrops of the formation are restricted to its upper member, as is the case in the Farellones area. At that locality, where previous authors included altered flows and pyroclastic rocks that could correspond to the Abanico Formation, the lower member is not represented.