Preliminary Study on Sedimentary Organic Matter Variations in East Sea (Japan Sea)

Abstract

Four piston cores (DD08-22, DD08-48, DD09-21, and DD09-39B) from the East Sea (Japan Sea) were examined to assess past variability of primary productivity and related paleoclimate changes. Biogeochemical parameters such as CaCO3, C/N ratio, TOC(%) and carbon and nitrogen stable isotope ratios are important to determine natural carbon transport and cycling processes related to global climate changes. In DD09-21 core, the lowest C/N ratio and the highest concentration in CaCO3 were observed during LGM. In DD08-39B and DD08-48 cores on the other hand, showed CaCO3 content decreasing at the start of LGM and increasing gradually after then. DD09-21 core revealed the greatest fluctuation in all measured biogeochemical parameters especially in core depths of 80cm and 260 to 300cm (20 ka, 61 ka, and 70 ka BP respectively). Increase in TOC (%) and C/N ratio in the latter depth may indicate input of terrestrial organic matters and/or enhanced ocean surface productivity as revealed by increased CaCO3 content. In DD08-48 and DD08-22 cores, heavier δ15N ratios were found with increasing depth while in DD09-21, the ratios fluctuated having the lightest value in 280 cm and the heaviest in 50 cm. This study requires further research to provide strong evidence for the major flux of organic matter as well as other biogeochemical proxies that are potentially helpful to reconstruct the paleoclimate variationtio, TOC(%) and carbon and nitrogen stable isotope ratios are important to determine natural carbon transport and cycling processes related to global climate changes. In DD09-21 core, the lowest C/N ratio and the highest concentration in CaCO3 were observed during LGM. In DD08-39B and DD08-48 cores on the other hand, showed CaCO3 content decreasing at the start of LGM and increasing gradually after then. DD09-21 core revealed the greatest fluctuation in all measured biogeochemical parameters especially in core depths of 80cm and 260 to 300cm