南海西北部16 kaBP以来沉积物的环境磁学特征及其物源指示意义  

Environmental magnetic characteristics and provenance significance of sediments in NW South China Sea since the past 16 ka

作　　者：肖春凤 孙启顺 陈亮 殷征欣 陈龙[1,2] 官玉龙 章钰桢 姜兆霞 XIAO Chunfeng;SUN Qishun;CHEN Liang;YIN Zhengxin;CHEN Long;GUAN Yulong;ZHANG Yuzhen;JIANG Zhaoxia(Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geosciences and Prospecting Techniques,MOE,College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Geology,Laoshan Laboratory,Qingdao 266237,China;Chongben Honors College,Ocean University of China,Qingdao 266100,China;South China Sea Marine Survey and Technology Center,State Oceanic Administration,Guangzhou 510300,China;Key Laboratory of Marine Environmental Survey Technology and Application,Ministry of Natural Resources,Guangzhou 510300,China)

机构地区：[1]中国海洋大学深海圈层与地球系统教育部前沿科学中心,海底科学与探测技术教育部重点实验室,海洋地球科学学院,青岛266100 [2]崂山实验室海洋地质与环境功能实验室,青岛266237 [3]中国海洋大学崇本学院,青岛266100 [4]国家海洋局南海调查技术中心,广州510300 [5]自然资源部海洋环境探测技术与应用重点实验室,广州510300

出　　处：《海洋地质与第四纪地质》2023年第1期13-26,共14页Marine Geology & Quaternary Geology

基　　金：崂山实验室科技创新项目“基于数字孪生的全球深时地貌重塑与资源环境预测”(LSKJ202204400);国家自然科学基金优秀青年基金“古地磁学”(41922026);国家自然科学基金创新群体项目“海底古地貌动态重建”(42121005);国家自然科学基金面上项目“红层的重磁化机制:实验模拟与天然样品综合研究”(42274089)。

摘　　要：南海是西太平洋最大的边缘海,对东亚季风和全球气候变化具有敏感的响应,然而目前对南海沉积物的物源分析仍存在众多争议。对南海琼东南盆地SCS-02孔的沉积物样品进行了系统的磁学分析,旨在通过环境磁学参数追踪沉积物的来源。结果表明,SCS-02岩芯的磁性矿物主要为磁铁矿和赤铁矿。自16 kaBP以来,磁性矿物的粒径和成分发生了系统变化,指示了沉积物源-汇过程的改变。15.5~16 kaBP期间,磁化率较高,粒径较粗,矫顽力也较高。海平面比现今低100多米,莺歌海出露于海平面以上,古红河口距研究区较近,红河的物质可以较容易到达沉积区,因此该时期红河贡献较大,珠江和台湾贡献较小。7.5~15.5 kaBP期间,随着海平面的迅速上升,磁性矿物组成和粒度发生了变化,总的磁性矿物含量减少,磁铁矿的含量逐渐增加,粒度变细,表明随着海平面的升高,珠江和台湾的贡献有所增加。7.5 kaBP以来,现代的海陆格局基本形成,磁性矿物组成和粒度变化较稳定,沉积物主要来源于红河和珠江。因此,环境磁学参数可以指示南海西北部沉积物的源-汇变化,为海平面变化和气候演化研究提供有效参考。As the largest marginal sea in the western Pacific Ocean, South China Sea(SCS) is sensitive to the East Asian monsoon and global climate change. The provenance of SCS sediments remains controversial. We carried out a systematic magnetic analysis on Core SCS-02 from the Qiongdongnan Basin, to trace the origin of sediments. Results show that the magnetic carriers of Core SCS-02 sediment are mainly magnetite and hematite. Since 16 kaBP, the particle size and magnetic mineralogy have shown systematic changes, indicating the change of the sedimentary source-sink process. During 15.5~16 kaBP, the sediments were with higher magnetic susceptibility, coarser grain size, and higher coercivity. The sea level was 100 m below the modern one, and the Yingge Sea was above the ancient sea level. The ancient Red River estuary was closer to the study area, leading to more material transported from the old Red River to the depositional area. During 7.5~15.5 kaBP, sea level rose rapidly, the total content of magnetic minerals decreased, but the relative content of magnetite gradually increased, and the magnetic particles became finer, indicating that the contribution of ancient Pearl River and Taiwan increased with the rise of sea level. Since 7.5 kaBP, the modern land and sea pattern had been formed fundamentally, changes in magnetic mineral composition and particle size stabilized relatively,and the sediments were mainly from the modern Red River and the Pearl River. Therefore, the environmental magnetic parameters are good proxies for the source-sink changes of sediments in the South China Sea, and provide an effective reference for the studies of sea level change and climate evolution.

关 键 词：环境磁学 磁性矿物 源-汇信息 南海西北部 

分 类 号：P736.21[天文地球—海洋地质]