Analysis of evolution of the Japan Sea based on neodymium isotopes of fossil fish teeth/debris

2016 Fiscal Year Final Research Report

• Project/Area Number: 26870215
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Environmental dynamic analysis; Stratigraphy/Paleontology
• Research Institution: University of Toyama
• Principal Investigator: Horikawa Keiji 富山大学, 大学院理工学研究部(理学), 准教授 (40467858)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: ネオジム同位体 / 日本海 / IODP / 魚歯化石アパタイト / 鮮新世

Outline of Final Research Achievements

This study conducted neodymium (Nd) isotope analysis of fossil fish teeth/debris from IODP U1425 obtained in the Japan Sea. For samples with lower amount of Nd (< 20 ng Nd), we measured Nd isotopes as NdO+, allowing us to measure the isotopes with good precision. Totally, 60 Nd isotope data for fossil fish teeth/debris were obtained from U1425 for the past 10 Myr. Further, we also reconstructed Nd isotopes of fossil fish teeth/debris from the western subtropical Pacific (DSDP296) for the past 10 Myr. Based on these two records and the previously published Nd record from the subarctic Pacific, we analyzed the timing of the isolation of the Japan Sea from the Pacific Ocean due to the uplift of the northern Japan arc. According to the Nd isotope evidences for U1425 and DSDP296, the isolation of the Japan Sea from the Pacific took place around 4.5 Ma, which is obviously identified by the shift of Nd isotopes in the Japan Sea from -3.7 eNd to -5.5 eNd at that time.

Free Research Field

古海洋学