[U-02] 人新世・第四紀の気候および水循環

[U02-11] 千島海溝の海底堆積物の特定有機物放射性炭素年代測定

★招待講演

*窪田 薫¹、金松 敏也¹、熊 衎昕¹、冨士原 敏也¹、大河内 直彦¹、菅 寿美¹、中西 諒²、横山 祐典^1,3、池原 研⁴ (1.海洋研究開発機構、2.京都大学、3.東京大学大気海洋研究所、4.産業技術総合研究所)

キーワード：放射性炭素、クロロフィル、海底堆積物コア

This study aims to improve the dating accuracy of submarine landslide occurrences over the past 10,000 years in the Kuril Trench by analyzing marine sediment cores containing turbidites. Marine sediment cores from the North Pacific generally lack foraminifera (due to limited surface habitation and a shallow carbonate compensation depth), making it challenging to establish a chronology for these cores. While it is possible to analyze bulk organic carbon (Bulk-TOC) for radiocarbon dating, the results are typically 1,000–2,000 years older than the actual date. By chemically purifying bulk organic matter and conducting radiocarbon dating on specific organic compounds synthesized by surface-dwelling organisms, more accurate dating can be achieved. This study focuses on chlorophyll-a, produced by phytoplankton in the surface layer of the ocean. We found that the radiocarbon age of chlorophyll-a is 200–300 years older than the dissolved inorganic carbon in the surface ocean. This result suggests that some fraction of chlorophyll-a is laterally transported and redeposited by bottom water currents and other processes. However, given that the radiocarbon date of Bulk-TOC is several thousand years older, chlorophyll-a remains a promising tool for dating marine sediments in the Kuril Trench.