[M-IS02] Evolution and variability of the Asian Monsoon and Indo-Pacific climate during the Cenozoic Era

[MIS02-P06] Correlation between Chinese stalagmite oxygen isotope record and dark-light cycles in the sediment sequence of the Japan Sea

*Tomohisa Irino¹, Arisa Seki², Kaz Mitake³, Yoshimi Kubota⁴, Ryuji Tada⁵ (1.Hokkaido University, 2.Shishu University, 3.University of Tokyo, 4.National Musium of Nature and Science, 5.Chiba Institute of Technology)

Keywords:Japan Sea, east Asian monsoon, paleoclimate, IODP, Expedition 346

Continuous sediment cores covering a period of up to 15 million years were collected from seven sites in the Japan Sea at depths ranging from about 300 to 3000 m during IODP Exp.346. The cores at depths of 900 m and deeper showed clear dark and light bandings on a scale of several to several tens of centimeters over the past 1.5 million years. In particular, the cores at depths of 900 m and deeper showed clear alternation of dark and light layers at scales of several to several tens of centimeters during the last 1.5 million years, and the patterns were found to be correlatable throughout the Japan Sea.

In this study, we examined the photographs and physical properties of these sediments in detail, established almost complete records of continuous sediment properties at each site, and reported the correlation of dark and light patterns among sites. In addition, high-precision elemental concentration data were measured using XRF scanners at three sites. Among these physical properties and elemental data, the variation of darkness and bromine content, which represent the organic matter content in sediments, is controlled by the increase of marine biological production and the enhanced conservation of organic matter during the humid periods, reflecting the millennial-scale variation of east Asian monsoon precipitation.

By taking advantage of this property, we tried a detailed correlation between the organic matter content pattern at IODP Site U1426 and the Chinese stalagmite isotope ratio. The results would improve the dating accuracy of the Japan Sea sediments and enable us to analyze a long term east Asian monsoon variability in a ultra high time resolution.