晚第四纪东海外陆架沉积作用判识与沉积环境演化

The stratigraphy of outer shelf of East China Sea has a variety of types of sedimentary systems. How to precisely identify different sedimentary processes and environments is an important but also a hard question for sedimentology of East China Sea shelf. It also provide a good chance for studying detailed sedimentary processes. Three ~100 m long boreholes, which are DH01, DH02 and DH03 from northern, central and southern parts, are reported in the project. The sedimentary processes and environments are studied based on a detailed stratigraphic framework. First, the stratigraphic framework is constructed based on AMS14C, OSL dating, paleo-magnetic analysis and oxygen isotope curve. After researching sedimentology and sequence stratigraphy of these three boreholes, a sequence stratigraphic framework is proposed. Parameters of sedimentary texture and sedimentary structures are utilized to identify sedimentary processes, reconstruct sedimentary environment and evolution. Sea-level changes and paleo-climate fluctuations are determined by isotope and element geochemistry analysis and other published data. The aim of this study is to determine the roles sea-level fluctuation and paleo-climate play in controlling sedimentary evolution of outer shelf of East China Sea.

晚第四纪东海外陆架地层沉积体系类型丰富、沉积作用复杂。如何从多尺度沉积记录中准确判识不同沉积作用与沉积环境是东海陆架沉积学研究的难点，也为陆架沉积的精细研究提供了契机。本项目以分别位于东海外陆架北部、中部和南部3根长均为约100m的沉积物岩心（DH01、DH02和DH03）为研究对象，在建立年代框架的基础上查明不同层段沉积作用与沉积演化。首先，以AMS14C测年为绝对年龄点结合古地磁漂移并参考光释光年龄和氧同位素曲线来建立DH01钻孔年代框架，将DH02和DH03与DH01钻孔对比建立“连孔层序格架”。然后，利用沉积结构参数（分选、粒度中值、偏度和峰度）和沉积构造来判识不同层段主要沉积作用、重建沉积环境与演化。而后，基于同位素、元素地球化学指标和已发表文献重建外陆架海平面与气候变化，目的在于明确晚第四纪东海外陆架沉积演化对气候、海平面变化的响应。

东海陆架受到世界级大河的供给，是世界上最宽广、平坦的陆架之一。本项目明确海平面与气候对于陆架沉积的控制作用具有重要意义。本次研究对东海陆架北部、济州岛西南泥质区的DH01长钻（100m）进行了研究，建立了其层序地层框架与年代框架，共划分为6个层序，底界年龄可能对应300-400kyr BP。本项目首次在陆架沉积中发现混合事件层，有机质的物源分析显示这些有机质主要来源于沿路侵蚀，稀土元素指示这些沉积物最初来源于韩国河流，最终明确了台风引起的陆架内垮塌是形成这些混合事件层的触发机制。本次研究拓宽了陆架重力路的搬运方式，揭示了浊流与碎屑流之间的过渡流态也是陆架一种重要的沉积物搬运方式。