Characteristics and Age of Eruption Cycle Producing Tateno Lava at Aso Volcano, Southwestern Japan

概要

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The Tateno lava is the thickest lava flow distributed in the western part of post-caldera central cones of Aso Volcano, SW Japan. A pumice-fall deposit underlying the lava was identified, and it was correlated to Aso central cone pumice 4 (ACP4), one of the key tephra layers in and around Aso caldera. A noncarbonized root sample was discovered just below ACP4, and its 14C age was measured to determine the age of the eruption cycle producing ACP4 and the Tateno lava. The AMS 14C age was >43, 200yrs BP, which corresponded to >ca. 46cal ka. The age is consistent with a K-Ar age (51±5ka) for the Takanoobane lava, which occurs above the Tateno lava. In the western part of Aso central cones, two thick felsic lava flows, the Tateno lava (dacite) and the Takanoobane lava (rhyolite), were discharged at an interval of a few hundreds years around 50ka, and they accompanied precursor plinian pumice-fall deposits.