宮縁育夫 Eruption Age of Komezuka at Aso Volcano, Japan

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Eruption Age of Komezuka at Aso Volcano, Japan
Yasuo MIYABUCHI
Komezuka Volcano, located in the northwestern part of the post-caldera central cones of Aso Volcano, SW
Japan, is a basaltic monogenetic volcano comprising a scoria cone (-1*῍-2* m in basal diameter ; 2* m in height)
and lava ﬂows (+*./ km, ; /+*1 m-). We obtained +.C ages of -,*1*.* years BP from a buried soil below silty
ash underlying Komezuka lava, which corresponds to -,-1*῍-,,+* cal years BP, and ,,10*.* years BP (,,3/*῍
,,11* cal years BP) from a soil above silty ash overlying Komezuka lava. The age of soil below the lava suggests
that the eruption age of Komezuka Volcano is about -,-** cal years BP. The eruption age is consistent with the
age of Ojodake Volcano (-,0** cal years BP) whose lava underlies Komezuka lava. In the northwestern part of
the post-caldera central cones, Late Holocene monogenetic volcanic activity commenced with sub-plinian
eruptions and lava extrusion from Kishimadake Volcano at approximately .,*** cal years BP, followed by
sub-plinian eruptions and lava extrusion from Ojodake Volcano at -,0** cal years BP, and ceased with strombolian
eruptions and lava extrusion from Komezuka Volcano at -,-** cal years BP.
Key words : Komezuka Volcano, scoria cone, lava ﬂow, eruption age, Aso Volcano
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Faculty of Education, Kumamoto University, Kurokami
,῍.*῍+, Kumamoto 20*῍2///, Japan.
Corresponding author : Yasuo Miyabuchi
e-mail : [email protected]

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