Tempo-spatial variation of sedimentary organic matter in East/Japan Sea

Abstract

Four piston cores (DD08-22, DD08-48, DD09-21, and DD09-39B) from the Japan Sea (East Sea) were examined to assess past variability of sedimentary organic matters. 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 that is located in the western part of the East Sea, 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 concentrations decreasing at the initiation 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. 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 concentration. In DD08-48 and DD08-22 cores, heavier δ15N values were found with increasing depth while in DD09-21, the values fluctuated having the lightest value in 280 cm and the heaviest in 50 cm. We will also report the result of alkenone biomarker analysis to further provide strong evidence for the major sources of organic matter that is helpful to reconstruct the paleoenvironmental variations with gla nitrogen stable isotope ratios are important to determine natural carbon transport and cycling processes related to global climate changes. In DD09-21 core that is located in the western part of the East Sea, 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 concentrations decreasing at the initiation of LGM and increasing gradually after then. DD09-21 core revealed the greatest fluctuation in all measured biogeochemical parameters especially in