マイボツ クロ ボクド ソウ ノ ^(14)C ネンダイ カラ ミタ カンシンセイ アソ カザン テフラ ノ フンシュツ ネンダイ

Aso central cones initiated their eruptive activity just after the Aso-4 eruption, about 90,000 yrs BP and have produced large volumes of tephras and lava flows. However, few studies have been made to determine the dates of eruption. We obtained 14C ages of buried Andisols interbedded between tephra layers to determine the eruption ages of Holocene tephras from Aso volcano. The eruption ages are estimated to be 1,600 yrs BP for N2 scoria from Nakadake (N2S), 2,700 yrs BP for Ojodake scoria (OjS), 3,400 yrs BP for Kishimadake scoria (KsS) and 3,700 yrs BP for Aso central cone pumice 1 (ACP-1). In addition, the date of the last lava extrusion from Nakadake is estimated to be 4,800 yrs BP. During the last 6,300 years ash eruption of Nakadake was most active between 3,800 and 3,600 yrs BP. Sub-plinian eruptions of Kishimadake and Ojodake, which accompanied with scoria fall deposits, occurred during the period 3,400 to 2,700 yrs BP