A 700-year record (1.0-1.5 a resolution) of the East Asian winter monsoon (EAWM),based on grain-size analysis and AMS14C dating of Core EC2005 from the inner-shelf mud wedge of the East China Sea (ECS),was compared with the Dongge stalagmite δ18O record during the mid-Holocene.The upper muddy section of Core EC2005 has been formed mainly by suspended sediments derived from the Changjiang (Yangtze) River mouth since 7.3 ka BP.High precipitation and a strengthened EAWM might have played key roles in the high sedimentation rate (1 324-1 986 cm/ka) between 5.9-5.2 ka BP.The EAWM strengthened when the Asian summer monsoon weakened,especially around 5500 a BP,which corresponded to a worldwide cold event.The EAWM during the mid-Holocene shows statistically significant solar periodicities at 62 and 11 a.The 5500 a BP cold event might be resulted from orbital forcing and changes in solar activity.
To decipher the sedimentary evolution and environmental changes since the late Last Deglaciation, two gravity cores were analyzed from the western North Yellow Sea (NYS). The two cores (B-L44 and B-U35) were sampled for grain size, clay minerals, detrital minerals, and 14C dating. They are comparable in lithofaies, and the observed succession was divided into four depositional units based on lithology and mineral assemblages, which recorded the postglacial transgression. Depositional unit 4 (DU 4) (before 11.5 ka) was characterized with enrichment in sand, and was interpreted as nearshore deposits in shallow water during the Younger Dryas Event. DU 3 (11.5-9.6 ka) displayed a fining-upward succession composed of sediments from local rivers, such as the Huanghe (Yellow) River, and from coastal erosion, which clearly were related to the Early Holocene transgression. Stable muddy deposition (DU 2) in NYS began to form at about 9.6 ka, which received direct supply of fine materials from the Shandong subaqueous clinoform. It is believed that the Yellow Sea circulation system played a major role in controlling the formation of fine sediment deposition in DU 1 (after 6.4 ka) after the sea level maximum.
对位于东海内陆架浙—闽沿岸泥质带的EC2005孔岩性、粒度以及AMS14C年代进行了分析,着重探讨了研究区自末次冰消期以来的沉积速率变化,划分出4个大的沉积阶段和4次快速沉积事件。千年时间尺度上大的沉积阶段主要受控于物源供应、海平面变化以及可容空间的大小。百年时间尺度上揭示的4次快速沉积事件主要受控于东亚冬季风的增强或是气候的变冷,与中国湖光玛珥湖沉积物Ti含量以及北大西洋浮冰碎屑具有良好对应,与世界范围内存在的新仙女木事件、7300 a BP冷事件、第二新冰期(5500 a BP强降温事件)以及北大西洋1400a BP浮冰事件也均有良好的对应。全新世高海平面以来东海内陆架泥质沉积物百年时间尺度上的沉积速率可以作为东亚冬季风变化的沉积学代用指标。
