Carbon isotope and rare earth element composition of Late Quaternary sediment gravity flow deposits on the mid shelf of East China Sea: Implications for provenance and origin of hybrid event beds
Carbon isotope and rare earth element composition of Late Quaternary sediment gravity flow deposits on the mid shelf of East China Sea: Implications for provenance and origin of hybrid event beds
复制标题
东海中部陆架晚第四纪重力流沉积物碳同位素和稀土元素组成：对混合事件层物源和起源的启示
DOI：
10.1111/sed.12561
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发表时间：
2019
期刊：
影响因子：
3.5
通讯作者：
Xu Jun
中科院分区：
文献类型：
--
作者：
Shan Xin;Shi Xuefa;Clift Peter D.;Qiao Shuqing;Jin Lina;Liu Jianxing;Fang Xisheng;Xu Taoyu;Li Shunli;K;asamy Selvaraj;Zhao Mengwei;Zhu Ying;Zhang Hui;Zhang Dan;Wang Huawei;Li Yalong;Yao Zhengquan;Wang Sai;Xu Jun
东海陆架具有异常宽和低梯度的陆架，由含沙河流和大型河流三角洲系统提供，底流席卷海底，位于强台风路径上。在东海中陆架某岩心中发现了4个混合事件层和1个高密度浊积岩的重力流沉积。混合事件床通常包括从底部到顶部的三个或两个内部分区：(i) H1、H3和H5；或（ii） H3和H5。混合事件层的放射性碳年龄在3821 ~ 8526 yrbp之间。根据与周围岩心的相关性，混合事件可能发生在1930年至3890年之间的任何时间。混合事件层的δ 13c值与测深数据表明陆架存在局部侵蚀作用。混合事件层H1段的平均δ 13c值与H3段相似，说明H1段和H3段有机质可能来自同一源区。5个单元的上陆地壳归一化稀土元素交叉图显示，4个混合事件层和浊积岩的沉积物来源最终主要来自朝鲜河流。中等强度泥石流的部分转化加上侵蚀膨胀的附加作用可以解释东海陆架混合事件层的发生。数据表明，混合沉积物重力流沉积来源于陆架内部的断裂，随后转化为混合事件层。研究表明，混合沉积物重力流和浊度流不一定表明靠近主要河流或三角洲体系，陆架内沉积可能是沉积物的来源。泥石流和浊流不太可能是由高旋流或海啸引发的，因为两者都可能携带大陆和/或海岸的信号，而这些信号在核心中尚未被识别出来。台风是可能的触发机制。
The East China Sea Shelf has an unusually wide and low gradient shelf, supplied from sediment‐charged rivers and large river delta systems, with bottom currents sweeping the sea floor and located in the path of strong typhoons. Sediment gravity flow deposits, including four hybrid event beds and a high density turbidite, are identified in a core from the mid‐shelf of the East China Sea. The hybrid event beds typically comprise three or two internal divisions from the base to the top: (i) H1, H3 and H5; or (ii) H3 and H5. Radiocarbon ages of the hybrid event beds were in the range of 3821 to 8526 yrbp. Based on correlation with surrounding cores, the hybrid events may have happened at any time between 1930 yrbpand 3890 yrbp. Theδ13C values in hybrid event beds together with bathymetry data suggest local erosion on the shelf. The averageδ13C value for the H1 division is similar to the H3 division in the hybrid event beds, implying that the organic matter in the H1 and H3 divisions may come from the same source area. Cross‐plots of upper continental crust normalized rare earth elements in the five units reveal that the sediment source of the four hybrid event beds and the turbidite was ultimately primarily from Korean rivers. Partial transformation from a moderate‐strength debris flow with the additional role of erosional bulking can explain occurrences of hybrid event beds on the East China Sea Shelf. The data indicate that hybrid sediment gravity flow deposits were sourced from intra‐shelf failures and subsequently transformed and deposited as hybrid event beds. The study shows that hybrid sediment gravity flows and turbidity currents may not necessarily indicate proximity to a major fluvial or deltaic system and that intra‐shelf sedimentation can be a sediment source. It is unlikely that the debris flows and turbidity currents were triggered by a hyperpycnal flow or tsunami, because both can carry continental and/or coastal signals which have not been recognized in the core. Typhoons are the probable triggering mechanism.