晚全新世东亚季风高分辨率沉积记录:r来自东海内陆架泥质区的证据

摘要

对位于东海内陆架泥质区的MZ05孔浅钻岩芯进行粒度、常微量元素、AMS14 C测年分析,获得2.90-1.80 ka B.P.期间粒度和常微量元素随时间变化的高分辨率曲线.综合分析MZ05孔地球化学元素比值(CIA,Rb/Sr)曲线发现沉积物源区的化学风化强度变化可以分为3个阶段:2.90-2.70ka B.P.的增强期,2.64-2.35ka B.P.的减弱期和2.35-1.80ka B.P.的较弱期,反映该段时间内东亚夏季风的强弱变化.MZ05孔的沉积物敏感粒级(1.2～22.1μm)平均粒径指示晚全新世东亚冬季风波动频繁,呈现出3个各具特点的阶段:2.90-2.65ka B.P.属于中等频率波动的冬季风强盛期;2.64ka B.P.左右东亚冬季风由强转弱,2.60-2.35ka B.P.冬季风先减弱后增强;2.35-1.82 ka B.P.为相对稳定的冬季风弱期.东亚冬季风的演化趋势在其他气候记录中也发现相应的降温证据,揭示全球气候变化的区域性响应.研究同时发现晚全新世研究区东亚冬、夏季风在百年尺度上呈现反相位关系.%High resolution records of grain size and geochemical compositions of the Core MZ05 from the inner shelf mud wedge of the East China Sea (ECS)were obtained.After comparing two Geochemical in-dex (CIA and Rb/Sr)of the Core MZ05,this study indicated that the chemical weathering activity of source area was gradually strengthened during 2.90-2.70ka B.P.,and weakened at 2.64-2.35ka B.P.and 2.35-1.80ka B.P.All these fluctuations reflect the variations of intensity of the East Asian summer mon-soon (EASM)during the late Holocene.And,the mean grain-size of fine sections (1.2～22.1 μm)of the Core MZ05 indicates the frequent fluctuations of East Asian winter monsoon (EAWM)during late Hol-ocene,i.e.,strong and moderate fluctuation frequency during 2.90 - 2.64ka B.P.,suddenly weakened around 2.64ka B.P.,gradually strengthened during 2.60-2.35ka B.P.,and relatively stable and weakened during 2.35-1.82ka B.P.These strengthened winter monsoon events indicated by mean grain-size of the Core MZ05 are also supported by comparable climate proxies,showing regional responses to global chan-ges.Finally,we suggested that the EAWM in the study area has an anti-phase relationship with the EASM at the centennial scale during the late Holocene.