[1] Tohoku Univ, Inst Geol & Paleontol, Grad Sch Sci, Sendai, Miyagi 9808578, Japan
[2] Osaka Univ, Grad Sch Sci, Dept Earth & Space Sci, Toyonaka, Osaka 5600043, Japan
[3] Univ Tokyo, Tokyo 1130032, Japan
[4] Natl Inst Adv Ind Sci & Technol, Tsukuba, Ibaraki 3058567, Japan