δ13C and δ15N values of sedimentary organic matter in the East Sea (Sea of Japan): indicator as terrestrial contribution and redox potential of bottom water

Abstract

The effect of sea level change in the East Sea (Sea of Japan) is fundamental to the anoxia of bottom water resulting from the stagnant, strongly-stratified water-column with lomited ventilation during the glacial periods. Here we present extraordinarily co-varied δ13C and δ15N values of sedimentary organic matter, representing distinct negative anomalies for the thick and thin dark laminated mud layers during the late Quaternary. The most plausible cause to induce such peculiar isotope variations seems to be the anoxic diagenetic condition in the in the bottom water during the glacial period. The reduction of δ13C values may be attributed to the selective preservation of δ13C-depleted organic compounds and simultaneously the decrease of δ15N values may be due to bacterial growth adding δ15N-depleted biomass to the residual materials. The anoxic decay of sedimentary organic matter leads to the negative excursion of both isotope, although the enhanced terrestial organic detritus during the glatial is an additional contribution.