Sillar
Páginas: 2 (422 palabras)
Publicado: 9 de septiembre de 2012
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EL SILLAR DE AREQUI PA (PERU): CARACTERISTICAS DE LOS DEPOSITOS DE FLUJOS PIROCLASTICOSDE LA QIJEDRADA Ai-;AS HUAYCO
6. Salae
Alvarez
‘,
N. Vatin-PQrignon’,G. Poupeauz
11 Universidad
National
San Agustin,
UJNSA), Casilla
1203, Joseph Cedex,
Arequipa, Fourier France
Per-Q (UJF)
2) Laboratoire de Gbologie, de Grenoble, 15, rueMaurice
URA CNRS 69, UniversitO Gignoux, 38031 Grenoble
Abstract The ash-f low tuff (sillar) consists of two individual flows units: the earlier pyroclastic flow (3-4 m thick) is a fine to mediumgrained, white to light gray, moderately welded and unsorted pumiceous deposit containing pumice clasts and andesi tic lithic fragments, crystals and scattered juvenile shards of dark glass (obsidians);the later pyroclastic flow (S-6 m thick) differs in some aspects: massive white ash, homogeneous densely welded deposit and unit with abundant fine columnar joints. The age of eruption is uncertainand presumably Upper Pliocene by correlation with an ash-flow tuff from the Bolivian Altiplano (Perez Fm. 1 Key words: stratigraphic characteristics, deposit i onal section, Arequipa, Peru ash-f 1owtuff, sillar,
est form6 de deux unit&a pyroclastiques: la (sillar) Le tuf cendreux et consiste en un depat h grain fin, premi &-e coul be a 3-4 m d’Cpaisseur contenant des ponces et des fragmentsmoyennement consolid8, blanc-gris, de5 cristaux libres et des dchardes juveniles de andesitiques, de laves la derni Pre coul be est bpaisse de S-6 m et (obsidiennesl; verre noir differe de la pr&c&dentepar plusieurs aspects: unit@ blanche, massive, plus grande et presence riche en cendres fines, homogbne, consolidation de joints columnaires. L’Gge de ce d4p6t est incertain mais probablement avec untuf cendreue de 1’Altiplano du Pliocene suparieur par analogie bolivien (Formation Perez). Mots-cl&s: ponceuses, caracteristiques des d@psts, coupe stratigraphique, sillar, coul &es pyrocl asti ques...
_I
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333
EL SILLAR DE AREQUI PA (PERU): CARACTERISTICAS DE LOS DEPOSITOS DE FLUJOS PIROCLASTICOSDE LA QIJEDRADA Ai-;AS HUAYCO
6. Salae
Alvarez
‘,
N. Vatin-PQrignon’,G. Poupeauz
11 Universidad
National
San Agustin,
UJNSA), Casilla
1203, Joseph Cedex,
Arequipa, Fourier France
Per-Q (UJF)
2) Laboratoire de Gbologie, de Grenoble, 15, rueMaurice
URA CNRS 69, UniversitO Gignoux, 38031 Grenoble
Abstract The ash-f low tuff (sillar) consists of two individual flows units: the earlier pyroclastic flow (3-4 m thick) is a fine to mediumgrained, white to light gray, moderately welded and unsorted pumiceous deposit containing pumice clasts and andesi tic lithic fragments, crystals and scattered juvenile shards of dark glass (obsidians);the later pyroclastic flow (S-6 m thick) differs in some aspects: massive white ash, homogeneous densely welded deposit and unit with abundant fine columnar joints. The age of eruption is uncertainand presumably Upper Pliocene by correlation with an ash-flow tuff from the Bolivian Altiplano (Perez Fm. 1 Key words: stratigraphic characteristics, deposit i onal section, Arequipa, Peru ash-f 1owtuff, sillar,
est form6 de deux unit&a pyroclastiques: la (sillar) Le tuf cendreux et consiste en un depat h grain fin, premi &-e coul be a 3-4 m d’Cpaisseur contenant des ponces et des fragmentsmoyennement consolid8, blanc-gris, de5 cristaux libres et des dchardes juveniles de andesitiques, de laves la derni Pre coul be est bpaisse de S-6 m et (obsidiennesl; verre noir differe de la pr&c&dentepar plusieurs aspects: unit@ blanche, massive, plus grande et presence riche en cendres fines, homogbne, consolidation de joints columnaires. L’Gge de ce d4p6t est incertain mais probablement avec untuf cendreue de 1’Altiplano du Pliocene suparieur par analogie bolivien (Formation Perez). Mots-cl&s: ponceuses, caracteristiques des d@psts, coupe stratigraphique, sillar, coul &es pyrocl asti ques...
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