La petrologia de secuencias piroclasticas y epiclasticas en el Grupo Chubut (Cretacico): area de Los Altares-Las Plumas, Patagonia Argentina.
Petrology of continental pyroclastic and epiclastic sequencesin the Chubut Group (Cretaceous): Los Altares-Las Plumas area, Chubut, Patagonia Argentina
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Manassero, Marcelo | |
| dc.creator | Zalba, Patricia E. | |
| dc.creator | Andreis, Renato R. | |
| dc.creator | Morosi, Martin | |
| dc.date | 2010-06-30 | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V27n1-a02 | |
| dc.identifier | 10.5027/andgeoV27n1-a02 | |
| dc.description | Las sucesiones volcaniclasticas de la Formacion Cerro Barcino (Grupo Chubut, Aptiano-Cenomaniano), afloran en ambas margenes del rio Chubut con 200 m de espesor. Los miembros medio: Cerro Castano (sineruptivo, 90 m) y superior, Las Plumas (intereruptivo, 110 m) son descritos con el mapeo fotogeologico, estudios de campo y laboratorio (mineralogico, petrografico y geoquimico). Las paleocorrientes se orientan hacia el noreste (Cerro Castano) y hacia el norte (Las Plumas). Se ha reconocido, por primera vez, un limite erosivo en la base del Miembro Las Plumas. Las rocas piroclasticas presentan vitroclastos planares, curviplanares, ramificados y en forma de Y, y pumicitas fibrosas. Los depositos epiclasticos incluyen fragmentos de tobas vitreas, con pigmentacion hematitica (Las Plumas). Los vitroclastos estan alterados, por procesos diageneticos, a arcillas (esmectita y rara illita) o a zeolitas. En el Miembro Cerro Castano predomina analcima, asociada a clinoptilolita, mientras que en el Miembro Las Plumas la clinoptilolita se asocia a analcima y mordenita. La sedimentacion piroclastica (lluvias de cenizas) ocurrio en extensas llanuras onduladas, donde habia discretos canales arenosos. En la base del Miembro Las Plumas, la aparicion de valles amplios poco profundos, por los cuales corrieron rios entrelazados que depositaron conglomerados y areniscas, esta relacionada a actividad tectonica-climatica. Las erupciones fueron del tipo magmatico explosivo y los intensos procesos de fragmentacion estuvieron relacionados a magmas viscosos, ricos en volatiles de composicion riolitica-dacitica. La abundancia de vitroclastos planares, curviplanares y ramificados finos, sugieren que el centro explosivo se localizaba a una distancia aproximada de 500 km probablemente hacia el oeste. | es-ES |
| dc.description | The volcaniclastic successions of the Cerro Barcino Formation (Chubut Group), of Aptian-Cenomanian age, crop out on both margins of the Chubut River with a thickness of 200 m. The Middle Member Cerro Castaño (syneruptive, 90 m) and the Upper Member, Las Plumas (intereruptive, 110 m) are described on the basis of photogeological mapping, sections, and mineralogical, petrographical and geochemical analysis. Paleocurrents are directed to the northeast (Cerro Castaño) or north (Las Plumas). An erosive boundary, located at the base of the Las Plumas Member, is reported for the first time in this contribution The pyroclastic rocks are composed, of planar, curviplanar, branching, Y-shaped shards and fibrous pumice fragments. The volcanogenic sedimentary deposits also include, vitric fragments with hematitic pigmentation (Las Plumas). Due to diagenetic processes, the glass fragments are replaced by clay minerals (smectites and scarce illite) and zeolites which also appear as cementing material. Within the Cerro Castaño Member, analcime prevails assembled with less clinoptilolite, while in the Las Plumas Member, the abundant clinoptilolite is assembled with scarce analcime and mordenite. Pyroclastic sediments (ash-fall) covered extended flat or slightly undulated plains, where discrete sandy rivers flowed. The presence of gravels and sandstones at the base of the Las Plumas Member and wide and shallow braided river channels are associated to tectonic events and seasonability. Eruptions were highly explosive derived from viscous and volatile-rich magmas. The abundance of fine planar and cuspate shards in the tuff suggest that the explosive center was located approximately 500 km probably to the west. | en-US |
| dc.format | application/pdf | |
| dc.format | text/html | |
| dc.language | eng | |
| dc.publisher | Servicio Nacional de Geología y Minería | en-US |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V27n1-a02/687 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V27n1-a02/html | |
| dc.source | Andean Geology; Vol 27, No 1 (2000); 13-26 | es-ES |
| dc.source | Andean Geology; Vol 27, No 1 (2000); 13-26 | en-US |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.title | La petrologia de secuencias piroclasticas y epiclasticas en el Grupo Chubut (Cretacico): area de Los Altares-Las Plumas, Patagonia Argentina. | es-ES |
| dc.title | Petrology of continental pyroclastic and epiclastic sequencesin the Chubut Group (Cretaceous): Los Altares-Las Plumas area, Chubut, Patagonia Argentina | en-US |
| dc.type | info:eu-repo/semantics/article | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | es-ES | |
| dc.type | en-US |
This item appears in the following Collection(s)
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Andean Geology
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