Abstract

LANES, Silvia  and  SALANI, Flavia M.. Petrografía, origen y paleoambiente sedimentario de las piroclastitas de la Formación Remoredo (Jurásico Temprano), Argentina (35º30'S-70º15'W) . Rev. geol. Chile [online]. 1998, vol.25, n.2, pp.141-152. ISSN 0716-0208.  http://dx.doi.org/10.4067/S0716-02081998000200002.

The petrography, origin and sedimentary paleoenvironment of Remoredo Formation pyroclastic rocks (Lower Jurassic), 35º30'S-70º15'W, Argentina. Facies analysis of pyroclastic outcrops of the Remoredo Formation, which surround a phenoandesitic intrusive (Cerro Negro Andesite), allowed the authors to recognize two facies associations: 1- Tuff-Breccia Association and 2- Tuff Association. They were interpretad as 1- proximal co-ignimbrite lag breccia and 2- associated ignimbrites and co-ignimbrite air-fall tuffs, respectively, all of them derived from flows that were originated by gravitational column collapses. Paleocurrents, internal structures and provenance of the lithics point to the Cerro Negro Andesite intrusion as one of the source vents although not excluding others located further west of the study area. Tuffs of the middle section of Remoredo Formation were deposited into an ephemeral lake, while the rest were deposited under subaerial conditions.

Keywords : Sedimentology; Pyroclastites; Ignimbrites; Ash falls; Coignimbritic breccias; Jurassic.