Artigo Revisado por pares

Correlation of Middle Pleistocene crystal-rich tephra layers from Daisen Volcano, southwest Japan, based on the chemical composition and refractive index of mafic minerals

2011; Elsevier BV; Volume: 246; Issue: 1-2 Linguagem: Inglês

10.1016/j.quaint.2011.08.014

ISSN

1873-4553

Autores

Atsuo Kotaki, Shigehiro Katoh, Kanichi Kitani,

Tópico(s)

Paleontology and Stratigraphy of Fossils

Resumo

Analyses of chemical compositions and refractive indices of mafic minerals have been effective correlation tools, especially for crystal-rich tephra layers containing isolated volcanic glass shards. The analyses are applied to the correlation of the Middle Pleistocene tephra layers in the Kinki and Chubu districts, central Japan, with those erupted from Daisen Volcano in the Chugoku Mountains, west of the districts. On the basis of chemical compositions of hornblende phenocrysts and refractive indices of hornblende, orthopyroxene and cummingtonite phenocrysts, four groups of tephra layers in the Kinki and Chubu districts are successfully correlated to bvs2, cpm, gpm and hpm1, or DOP tephra layers of the Lowermost Member of the Daisen Tephra Formation. The correlation reveals that two tephra layers, bvs2 and cpm, with estimated eruption ages of 410 ka and 370–400 ka, respectively, are present in the Kinki district. The hpm1 tephra, about 210 ka, is also widespread and recognized at the eastern foot of Yatsugatake Volcanoes about 400 km east of the source. These tephra layers can contribute to establishing the regional correlation and chronology of the Middle Pleistocene sequences in central Japan, especially for the time from MIS 7 to MIS 11.

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