南黄海北部DLC70-3孔沉积物磁化率特征及其对古冷水团的指示

Magnetic Susceptibility Characteristic of the Sediments of DLC70-3 Core in Northern South Yellow Sea and Its Significance to Paleo-Cold Water Mass

对长71.2m的南黄海北部DLC70-3孔沉积物粒度、磁化率和总有机碳(TOC)进行了实验分析。结果显示,DLC70-3孔沉积物的磁化率值与平均粒径呈正相关关系,与w(TOC)呈负相关关系,表明以陆源碎屑输入为主的陆架海区沉积物中的磁性矿物以粗颗粒为主;由于w(TOC)均值非常低,因此不能将磁化率低值全部归结为有机质稀释作用的结果,主要可能是沉积速率大所致。此外,磁化率值受到沉积物所处氧化还原环境的控制,氧化环境下磁化率值高,还原条件下磁化率值低。冷水团沉积层位的沉积物是在较强的还原条件下形成的,因此,磁化率指标可以指示古黄海冷水团的形成演化,将磁化率指标与同一钻孔中微体古生物指标指示的古冷水团层位进行对比,得出了完全一致的结果,从而为今后研究区的古冷水团演化研究提供了新的指标。

DLC70-3, a 71.2 m long core was obtained in northern 5outh Yellow oea, ana analysis of grainsize, magnetic susceptibility and TOC was carried out on the sediments. The results show that the mag- netic susceptibility was positively correlated with the grain-size while negatively correlated with the TOC, indicating that the coarse magnetic minerals dominate in terrigenous clastic materials on the shelf sea area. Due to the extremely low average content of the TOC, low-value magnetic susceptibility was probably catlsed by a high sedimentation rate, but less affected by the dilute effect of the organic matters. In addi- tion, magnetic susceptibility was controlled by the redox conditions of sediments, shown as high values under the oxidation conditions and low values in the reducing environment. Sediment in cold water mass position is formed under the condition of strong reduction. Therefore, magnetic susceptibility consistent with micropaleontology proxy could also indicate the layers of the paleo-cold water mass, and it becomes a new indicator for research of the evolution of the paleo-cold water mass.