南黄海西部近岸陆架区末次冰期古河谷物源和充填模式研究

Study on incised river valleys and its filling sequences is one important part of paleo-environment and sequence stratigraphy research in the last decades. Two dendritic paleo-river systems have been discovered on the continental shelf of western South Yellow Sea according to geology and geophysics investigation in the recent years. This study on sequence stratigraphy of paleo-river valleys formed in the Last Glacial on the continental shelf of western South Yellow Sea (33 30′ N to 36 00′ N and 119 30′ E to 122 30′ E) will be based on 4100 km high-resolution seismic reflection profiles and data from the core drilling through one paleo-river valley, with the aim to find out the pattern for spatial combination and change of depositional facies. And then, reveal the sediment source, evolution mechanism and filling sequence of paleo-river, build its filling model. It is of important significance to the study on flow paths of Changjiang River or Huanghe River (maybe other medium rivers near the shore line), environment evolution of continental shelf in the western South Yellow Sea and its response to the global changes since the Last Glacial.

下切河谷及其充填层序是近几十年古环境与层序地层学研究的重要内容。近年来在南黄海西部陆架区开展的地质、地球物理调查，发现了两大树枝状结构的古河系。本申请项目以南黄海西部近岸陆架区（纬度33 30′-36 00′ N，经度119 30′-122 30′ E） 4100 km 高分辨率浅地层剖面和穿过主干古河谷的地质钻孔岩心资料为依据，对研究区末次冰期古河谷进行层序地层学研究，揭示古河谷沉积相的空间组合特征及其变化规律。在此基础上，阐明其物质来源、充填序列和演化机制，重塑古河谷演化历史，建立充填模式。这对于研究末次冰期以来长江、黄河以及近岸中小河流的演变历史，揭示南黄海西部近岸陆架区环境演化及其对海平面变化的响应具有重要意义。

运用浅地层地震剖面解译成果，结合地质钻孔SYS-0803上部岩心以及长江、黄河和淮河中下游河流样品测试数据，系统地分析了南黄海西部陆架区埋藏古河道网的空间展布特征和主干古河谷剖面特征，识别了古河谷充填的沉积序列。根据黏土矿物、标型碎屑矿物等参数，判定了研究区古河谷充填沉积物主要源于黄河沉积物。由此推测，末次盛冰期时研究区古河道网是由古黄河侵蚀切割地表形成的下切河谷体系。通过对浅地层地震剖面以及钻孔的岩性、黏土矿物、微体古生物和测年资料的综合分析，根据沉积环境特征的差异将古河谷发展演化过程划分成不同的阶段，建立了古河谷沉积充填模式。