抄録
Sakurajima volcano is the most active volcano in Japan. The Yokoyama core (JMA-V44) was drilled on the western foot of this volcano in 2009. This core consists of volcanic soil (0 to -1.30m in depth), volcanic fan deposits (-1.30 to -49.60m), marine sediments (-49.60 to -59.60m), non-welded normal-graded dacite pumice lapilli tuff (PFD1; -59.60 to -69.34m), marine sediments (-69.34 to -73.22m), and weakly-to-non welded dacite pumice lapilli tuff (PFD2; -73.22 to -100.60m). Geochemical features of essential pumice in PFD1 coincide with ones of the 12.8-ka Sakurajima-Satsuma tephra (P 14), that is the largest product of Sakurajima volcano in 11km3 of volume and erupted at the beginning of the Younger Kitadake stage. On the other hand, essential pumice in PFD2 differs from the products of Sakurajima volcano in major and trace element contents. PFD2 pumice has lower Ti, P and heavy REE contents than Sakurajima ones. PFD2 presumably belongs to basement formations of Sakurajima volcano and Aira caldera and topographically forms the wall of Aira caldera.
