La Formación Elvira en su localidad tipo. Cuenca del Colorado. Foraminíferos y edad

MALUMIÁN, N., NÁÑEZ, C. Y JANNOU, G.

Buenos Aires

Congreso; X Congreso Latinoamericano de Geología y VI Congreso Nacional de Geología Económica; 1998

The Elvira Formation, at its type section in the Elvira x-1 well, yielded a foraminiferal assemblage similar to that of the San Julián Formation, in the Austral Basin. Based on this similarity, the Elvira Formation is considered to be Early Oligocene in age. The lower part of the overlying Barranca Final Formation yielded a foraminiferal microfauna of latest Oligocene-Early Miocene age, similar to that known for the Monte León, Chenque and Carmen Silva Formations, including in its basal horizons the Spirosigmoilinella-Martinottiella Assemblage. Sedimentary rocks of middle-late Eocene age from the Colorado Basin, previously assigned to the Elvira Formation, would represent an older transgression.