[M-IS01] 津波堆積物

[MIS01-P10] 福島県北東部における2011年東北地方太平洋沖地震による津波堆積物の堆積学的・地球化学的特性の経年変化

*泉 賢太郎¹、奈良山 郁朗¹、阿部 朋弥² (1.千葉大学教育学部、2.産業技術総合研究所地質調査総合センター)

キーワード：津波堆積物、経年変化、福島県

To evaluate how sedimentological and geochemical characteristics of tsunami deposits temporally change, we collected samples of the 2011 Tohoku-oki tsunami deposits and the underlying and overlying deposits at several sites in northeastern region of Fukushima Prefecture. In this study, thickness, grain size, sedimentary structures and organic-matter content of the tsunami deposits were observed and analyzed. As a result, thicknesses of the tsunami deposits do not show significant temporal change from at least 2014 to 2019. In addition, soft-X observations show that laminae are observed in tsunami deposits at several sites, suggesting that original sedimentary structures have been preserved in the past nearly 8 years. On the other hand, grain-size and organic-matter analyses of the tsunami and underlying deposits revealed that at least some portions of the tsunami deposits have been transported into the underlying deposits, resulting in sediment homogenization. It is assumed that this sediment homogenization has been caused by bioturbation mainly of meiobenthos whose body size is similar to sediment grain size.