동중국해, 동해퇴적물에 대한 유기물 동위원소의 조성: 고해양 변화 및 기원과의 관련성

Abstract

Significant differences in the δ13C values were seen between Holocene and glacial sediments in East China Sea (ECS) core sediments. The δ13C values were around -24.5 to -25.5‰ during the transgressive and glacial periods, whereas they ranged from -20.5 to -22.5‰ in the Holocene. The values of Holocene were about 2‰ heavier than those of the transgressive and glacial periods. This distinct difference between the Holocene and glacial periods allows discrimination of the sedimentary characteristics and source of organic matters. In East Sea core sediments, the δ13C of this core did not show distinct features that identified the source of the organic matter, although it showed a gradual upward decrease and values similar to those of the East China Sea in core top sediments. The values of δ13C and δ15N in East Sea core sediments showed relatively narrow range of variations; they show intermediate vales of two extreme values of Holocene and transgrssive periods of ECS. According to the results of Lamb et al. (2006), the organic matter was thought to have formed in the marine-dominated and freshwater-dominated dissolved organic carbon environments in the ECS during the Holocene and transgressive periods, respectively. However, compositions of organic matters in the East Sea sediment may associate with paleoproductivity variations. The enriched total organic carbon (TOC) contents between 12 and 8 ka and enriched δ15N values between 15 and 9 ka were found in the southern East Sea core, and this result was interpreted as productivity changes and potential possibility of nutrient supply from ESC. Therefore, strong coupled variation between δ15N and TOC supports the hypothesis that the East China Sea Coastal Water (ECSCW) flowed into the southern part of the East Sea during a high sea level stand.