Petrografia, origen y paleoambiente sedimentario de las piroclastitas de la Formacion Remoredo (Jurasico Temprano), Argentina (35º30'S-70º15'W) .
Petrografia, origen y paleoambiente sedimentario de las piroclastitas de la Formacion Remoredo (Jurasico Temprano), Argentina (35º30'S-70º15'W) .
Author
Lanes, Silvia
Salani, Flavia M.
Full text
http://www.andeangeology.cl/index.php/revista1/article/view/V25n2-a0210.5027/andgeoV25n2-a02
Abstract
Mediante el analisis de las facies piroclasticas de la Formacion Remoredo que afloran alrededor de un intrusivo fenoandesitico (Andesita Cerro Negro) se reconocieron dos asociaciones de facies: la Asociacion de Tobas Brechosas y la Asociacion de Tobas. Estas se interpretaron, respectivamente, como brechas coignimbriticas proximales e ignimbritas asociadas con depositos de caidas coignimbriticas, todas derivadas de colapsos gravitacionales de columnas eruptivas. Las paleo-corrientes, estructuras internas y proveniencia de los liticos senalan a la Andesita Cerro Negro como una de las bocas de emision, sin descartar otras localizadas al oeste del area de estudio. Las tobas de la seccion media de la Formacion Remoredo se depositaron en un lago efimero mientras las restantes lo hicieron bajo condiciones subaereas. 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.