末次冰期以来南海北部下陆坡区沉积有机质地球化学特征及其意义

Geochemical characteristics of sedimentary organic matter from the lower slope facies of northern South China Sea since the last glacial and significance

选取南海北部下陆坡-深海平原过渡带典型沉积柱状样,通过对其沉积有机质的整体有机地球化学特征进行表征,探讨了南海下陆坡-深海平原区沉积有机质在冰期/间冰期旋回中的赋存状态、来源变化以及与古气候环境之间的相应关系。结果表明,总有机碳(TOC)、总氮(TN)和有机质稳定碳同位素(δ13Corg)与冰期/间冰期旋回有明显的对应关系,冰期时对应高值,间冰期时对应低值;而有机质稳定氮同位素(δ15N)表现为全新世时其值偏低,末次冰消期其值偏高,与气候旋回没有相关性;C/N值和δ13Corg值都表明南海北部下陆坡沉积有机质来源是陆相和海相的混源,且在末次冰期/间冰期尺度上主要以海相来源为主。

The content and source of organic matter and paleoclimate/paleoenvironment in the glacial-interglacial climate cycles were investigated concerning the core samples collected from the northern South China Sea. Significant relationships were observed among total organic carbon （TOC）, total nitrogen （TN）, δ13Corg and climatic cycles, generally with higher values for the glacial stage than those for the interglacial period. δ15N did not reveal distinct relationship between glacial and interglacial climate cycles. Lower values of δ15N were observed during the Holocene compared to the last deglaciation. C/N ratios and stable carbon isotope composition （δ13Corg） suggested mixed origins from both terrigenous and marine organic matter within the down-slope of the northern South China Sea, with more contribution from the marine source.