Reconstruction of redox history of late Pleistocene Japan Sea using trace elements and Ce isotope

2015 Fiscal Year Final Research Report

• Project/Area Number: 26610166
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Stratigraphy/Paleontology
• Research Institution: The University of Tokyo
• Principal Investigator: Tada Ryuji 東京大学, 大学院理学系研究科, 教授 (30143366)
• Co-Investigator(Kenkyū-buntansha): TAKAHASHI Satoshi 東京大学, 大学院理学系研究科, 助教 (60615251) ; NAKADA Ryoichi 国立研究開発法人海洋研究開発機構, 高知コア研究所, 研究員 (50726958)
• Project Period (FY): 2014-04-01 – 2016-03-31
• Keywords: 日本海 / 溶存酸素環境 / 酸化還元鋭敏元素 / セリウム同位体比 / 深海堆積物 / 明暗互層 / 後期更新世

Outline of Final Research Achievements

Redox condition of the Japan Sea has been varied between oxic and euxinic repeatedly that resulted in deposition of light and dark sediments. This study aimed to develop a new proxy, Ce-isotope, to subdivide the oxic bottom water condition using the late Quaternary sediment cores recovered from the Japan Sea. First, composition of redox sensitive trace elements was analyzed for the sediment cores to select the samples with oxic evidence. The selected samples were subject to Ce-isotope analysis. According to degree of bioturbation and trace element contents, light layers are identified as oxic. However, analytical result of Ce-anomaly suggests the condition was still reducing below the point of Ce-reduction. Consequently, samples deposited under more oxic conditions are required to detect Ce-isotope variations reflecting more oxic paleo redox conditions. Recently, we collected new sediment cores which were deposited under more oxic conditions and suitable for Ce-isotope analysis.

Free Research Field

地質学、地球化学的手法による堆積記録解読と地球システム変動メカニズムの理解のための研究