[U-05] Advanced understanding of Quaternary and Anthropocene hydroclimate changes in East Asia

[U05-P04] Paleoenvironmental reconstruction through geochemical analysis of long-lived bivalve shells (Mercenaria stimpsoni)

*窪田 薫^1,2,3,4、白井 厚太朗³、杉原 奈央子³、清家 弘治⁵、南 雅代⁴、中村 俊夫⁴、棚部 一成⁶ (1.海洋研究開発機構海域地震火山部門、2.神戸大学大学院人間発達環境学研究科、3.東京大学大気海洋研究所、4.名古屋大学宇宙地球環境研究所、5.産業技術総合研究所、6.東京大学総合博物館)

キーワード：二枚貝、放射性炭素、酸素同位体、津波、地球化学

Bivalve shell is one of the most important archives of past environmental changes because some species can live more than several decades and distribute broadly (e.g., from high to low latitude, fresh/brackish/sea water). We have investigated potential of long-lived cold water bivalve, Mercenaria stimpsoni (Stimpson's hard clam) living in the western North Pacific (especially, coastal area of North East Japan). In this presentation we will show sclerochlonological and geochemical records (e.g., oxygen isotopes and radiocarbon) of both live-caught and dead specimens collected from the seafloor of NE Japan (5–20 m). From both sclerochlonology and nuclear bomb-derived radiocarbon (bomb-¹⁴C), it was found that this animal can live for more than 100 years, thus very useful for paleoeanograpic studies. It was also found that a lot of M. stimpsoni were killed by huge tsunami that hit NE Japan in March 2011, which is likely caused by disturbance of marine sediment, including seabed liquefaction.