Cao Chao, Cai Feng, Zheng Yongling, Wu Chengqiang, Lu Huiquan, Bao Jingjing, Sun Quan
Third Institute of Oceanography, State Ocean Administration, Xiamen, 361005, China.
Sci Rep. 2018 Oct 22;8(1):15577. doi: 10.1038/s41598-018-33757-5.
The sediment sources of the Yangtze Shoal were traced by analysing surface and core sediment particle size, detrital and clay minerals, carbon and nitrogen isotopes, and radioisotope dating. In the estuary, the sediments are dominated by silty clay, high stable mineral, and extremely high illite/chlorite. Stable organic carbon isotopes (δC-TOC) indicated a marine-dominated mixture. On the shoal, the sediments are mainly composed of fine sand, high unstable mineral. The δC-TOC indicated predominantly marine sedimentation. The average TOC of core sediments was ~0.26%, and the average TN was ~0.05%. The TOC/TN was 5.4-7.8, the δC-TOC was -19.8 to -22.1‰, and the age of the sediments spanned the last ~10.8 ka (Holocene). The sediments and provenance of the Yangtze Shoal have been controlled by the East Asian monsoon, sea level change, riverine sediment flux and ocean circulation. The intervals 8.3-6.3 ka and 3.8-1.5 ka, are characterized by Yangtze River sources, whereas 6.3-3.8 ka and 1.5-0.8 ka, are characterized by a source mixture with Yellow River input. Tracing the multiple sources effectively confirms the hypothesis that the southern Yangtze Shoal was a delta formed by combined sedimentation from the Yangtze River and Yellow River during times of low sea level.
通过分析表层和岩芯沉积物的粒度、碎屑矿物和黏土矿物、碳氮同位素以及放射性同位素测年，对长江浅滩的沉积物来源进行了追踪。在河口地区，沉积物以粉质黏土、高稳定性矿物以及极高的伊利石/绿泥石为主。稳定有机碳同位素（δC-TOC）表明其为以海洋为主的混合物。在浅滩上，沉积物主要由细砂、高不稳定矿物组成。δC-TOC表明主要为海洋沉积。岩芯沉积物的平均总有机碳（TOC）约为0.26%，平均总氮（TN）约为0.05%。TOC/TN为5.4 - 7.8，δC-TOC为-19.8至-22.1‰，沉积物年龄跨越了过去约10.8千年（全新世）。长江浅滩的沉积物及其物源受到东亚季风、海平面变化、河流泥沙通量和海洋环流的控制。8.3 - 6.3千年和3.8 - 1.5千年的时间段以长江来源为特征，而6.3 - 3.8千年和1.5 - 0.8千年的时间段以长江与黄河输入混合来源为特征。有效追踪多种来源证实了这样一个假说，即长江南部浅滩是在海平面较低时期由长江和黄河共同沉积形成的一个三角洲。
