近8ka东亚冬季风记录在东海内陆架的建立

Constructing a Recent 8 ka High-Resolution Record of East Asian Winter Monsoon from Sediments on Inner Shelf of East China Sea

目的在于尝试从东海内陆架上建立全新世高分辨率的东亚冬季风替代性序列.通过对位于东海内陆架闽浙沿岸泥质中部的PC-6孔（740 cm）进行AMS14C年龄测试和粒度分析,综合沉积构造、沉积层序与海平面变化讨论该孔的沉积环境,其上（0-450 cm）、中（450-540 cm）、下（540-740 cm）段分别对应于前滨、近滨和与现今环境基本一致的浅海沉积环境,其中上段的沉积作用主要受控于东海冬季沿岸流.通过计算该孔的粒级-标准偏差,提取了环境敏感粒度组分,该孔沉积物粒度由以28μm为界的2个粒度子体构成,它们的峰值即约5-6μm与102-125μm分别为对应于冬季沿岸流和波浪的敏感粒级;细粒组分（〈28μm）对应于沿岸流,为沿岸流所携带,表现为平行于海岸的横向迁移,粗粒组分对应于波浪,沉积物以垂直于海岸的纵向迁移为主.PC-6孔上段细粒组分的含量一般在85%以上,利用其平均粒径序列建立了研究东亚冬季风演化的替代性序列.

This paper probed a way to construct a high-resolution proxy of the Holocene East Asian Monsoon from sediments on the inner shelf of the East China Sea （ECS）. Based on AMS14C dating and grain-size analysis, and its changes in lithology, color, sedimentary structure and stacked pattern of cyclothems, sedimentary environment of Core PC-6, located in the middle of a mud area on the inner shelf of the ECS, was discussed. The 7.4 m core recorded the history of environmental changes during the postglacial transgression. The core＇s lower （540-740 cm）, middle （450-540 cm） and upper/mud （0-450 cm） sections belonged to foreshore, nearshore, and a relatively stable sedimentary environment of shallow sea shelf that extended to present day respectively. Sedimentation of the upper section has been formed mainly by suspended sediment delivered from the Yangtze River mouth by the ECS Winter Coastal Current （WCC） since 7.6 kyr BP. Using a mathematical method called ＂grain size vs. standard deviation＂, we can divide the Core PC-6＇s grain-size distribution into two populations at 28 μm; and their respective peaks, i.e. 5-6 and 102-125μm, are sensitive grain-size to WCC and wave. The fine population （〈28μm） is considered to be transported by the ECSWCC as suspended loads. Content of the fine population is more than 85% and changes little, representing a stable sedimentary environment in accord with the present situation. Thus, variation of mean grain-size from the fine population would reflect the strength of ECSWCC, which is mainly controlled by the East Asian winter monsoon.