南黄海沉积物磁性特征及其对物源变化的指示——以南黄海中部泥质区YSC-10孔为例

Magnetic Characteristics of Core YSC-10 Sediments in the Central Yellow Sea Mud Area and Implications for Provenance Changes

南黄海中部泥质区是东亚大陆沉积物巨大的汇,识别这一地区的物源变化对理解古气候和古海洋变化有重要作用。基于黄河和长江携带的碎屑物质在磁性特征上的差异,环境磁学参数、磁化率—中值粒径的相关性可用于指示南黄海中部泥质区物源的可能变化。根据YSC-10孔环境磁学参数变化和磁化率—中值粒径的相关关系,推测4.8 cal ka B.P.以前钻孔沉积物的物源可能主要来自黄河入海物质;4.8 cal ka B.P.以来,可能指示了长江物源的影响相对增强。区域环境演变代用指标的对比分析表明,随着中晚全新世以来东亚季风降雨带的南移和渤海西岸黄河三角洲的发育,YSC-10孔沉积物中由黄河携带的碎屑物质减少,南黄海中部泥质区的沉积速率降低,自中全新世以来与黄海暖流有关的长江入海物质主导了YSC-10孔沉积物磁性性质。

The Central Yellow Sea Mud Area is a huge sink of sediments on the East Asian continental shelf.The provenance changes in this area are important for understanding the effects of paleoclimate changes.Based on differences between magnetic mineral content of the Yellow River and the Yangtze River,environmental magnetic parameters and the correlation between magnetic susceptibility and median grain size indicate a change of provenance in the South Yellow Sea.The positive correlation between magnetic susceptibility and median grain size in core YSC-10 implies that the sediments were mainly from the Yellow River from 9.0 to 4.8 cal ka B.P.,then a negative correlation and an increase in environmental magnetic parameters after 4.8 cal ka B.P.until 2.4 cal ka B.P.indicates an increasingly dominant influence of the Yangtze River.The southward movement of the East Asian monsoon rainfall belt and the development of the Yellow River delta since the middle Holocene marked a reduction in the depositional rate of materials transported by the Yellow River.Materials carried by the Yangtze River and the Yellow Sea Warm Current were seen to increase after 4.8 cal ka B.P.