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:2.90-2.70 ka B.P.的增强期,2.64-2.35 ka B.P.的减弱期和2.35-1.80 ka 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~ 22.1mum)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:2.90-2.65 ka B.P.属于中等频率波动的冬季风强盛期;2.64 ka B.P.左右东亚冬季风由强转弱,2.60-2.35 ka 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。
英文摘要:
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 index(CIA and Rb/Sr)of the Core MZ05,this study indicated that the chemical weathering activity of source area was gradually strengthened during 2.90-2.70 ka B.P.,and weakened at 2.64-2.35 ka B.P.and 2.35-1.80 ka B.P.All these fluctuations reflect the variations of intensity of the East Asian summer monsoon(EASM)during the late Holocene.And,the mean grain-size of fine sections(1.2~22.1mum)of the Core MZ05 indicates the frequent fluctuations of East Asian winter monsoon(EAWM)during late Holocene, i.e.,strong and moderate fluctuation frequency during 2.90-2.64 ka B.P.,suddenly weakened around 2.64 ka B.P.,gradually strengthened during 2.60-2.35 ka B.P.,and relatively stable and weakened during 2.35-1.82 ka 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 changes. 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.