近8ka东亚冬季风变化的东海内陆架泥质沉积记录

Recent 8ka Mud Records of the East Asian Winter Monsoon from the Inner Shelf of the East China Sea

尝试从陆架上寻找全新世高分辨率的东亚季风替代性指标和记录.通过对位于东海内陆架闽浙沿岸泥中部的PC-6孔进行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,其下、中、上段分别对应于前滨、近滨和与现今环境基本一致的浅海沉积环境.因上段的沉积作用主要受控于东海冬季沿岸流,通过粒级-标准偏差分析,提取了相对应的粒度组分或粒度子体,该组分的平均粒径被用来作为研究东亚冬季风演化的替代性指标.分析表明,由此方法建立的PC-6孔上段粒径时间序列,较完整地反映了近8 ka来东亚古季风的演化.东亚冬季风的变化呈现出3个各具特点的阶段:7.6～5.1 kaB P.为中等强度的高频率波动;5.1～1.7 kaB P.以多期、较频繁的强盛活动为特点;1.7～0 kaB P.为稳定而较弱的时期.由PC-6孔指示的东亚冬季风活动的强盛期,均在不同区域和材料的记录中找到了相对应降温的证据,说明气候变化的区域性以至全球性联系.

High resolution proxy and record of the Holocene East Asian monsoon is presented based on AMS^14C dating and grain-size analysis from Core PC-6, located in the middle of the Yangtze Rive〉derived mud off the Zhejiang-Fujian coasts on the inner shelf of the East China Sea （ECS）. The sedimentary environments of its upper, middle and lower sections are foreshore, nearshore and shallow sea, similar to the present. The sedimentation of the upper section is controlled by the ECS Winter Coast Current, and corresponding grain-size subpopulation is identified by using grain-size vs. standard deviation. The mean grain-size of the subpopulation is used as a proxy of the East Asian winter monsoon （EAWM）, and a recent 8 ka grain-size time series is established to study the evolution of the EAWM. The series showing 3 characteristic sections of the EAWM： moderate and high fluctuation frequency during 7.6-5.1 kaB. P. ; much strengthened during 5. 1-1.7 kaB. P. ; and relatively stable and weakened during 1.7 0 kaB. P.. Periods of the strengthened winter monsoon indicated by PC-6 are all corroborated by other proxies in various areas, which show that regional and even global relationships of climate change exist.