赣中玉华山泥炭地沉积来源的粒度端元法分析与2000 aBP以来气候环境重建

Climatic and environmental changes since 2 kaBP by End Member Modeling analysis on grain size data from a peatcore of Yuhua Mountain, Jiangxi Province

利用江西玉华山沼泽泥炭地YSH-2钻孔的沉积物进行AMS14C测年,建立年代框架,结合该孔粒度参数、粒级组分、粒级-标准偏差、端元分析法分析,探寻响应气候变化的粒级组分,重建2000 aBP以来气候环境。结果表明,玉华山泥炭地沉积物粒度组成以细粉砂(4~16μm)为主,中粗粉砂(16~64μm)次之;运用端元分析法得出3个端元,其中端元组分EM1代表水动力搬运来的较细组分,指示气候的干湿状况,EM2是反映土壤的成壤改造作用的组分,EM3是突发性的气候变化带来的组分。通过偏差法得出的敏感组分10.473~16.535μm,结合上述3个端元的变化规律,得出近2000 a的干湿变化:(1)0—300 AD阶段,降水逐渐增多,气候由干转湿;(2)300—500 AD气候由湿润转入干旱,但整体较干;(3)500—650 AD气候波动与突发性洪涝灾害都较少,是稳定且持续的湿润期;(4)650—900 AD,气候波动较大,变化频繁,总体偏干;(5)900—1400 AD是较为湿润的时期,其中有100年的频繁波动期;(6)1400—1800 AD为小冰期,此区域的气候变化分为湿-干-湿的3个阶段。

Based on the AMS14^C dating of a peat core from Mt Yuhua in Jiangxi Province,China,we explore how grain size varies in response to climate changes.We then reconstruct climate change since 2000 aBP through grain size analysis,grade-standard deviation method,and endmember model.Our results show that the sediments in the peatland of Mt Yuhua are mainly consisting of fine sand(4~16μm)and coarse silt(16~64μm).Three end-members EM1,EM2,and EM3 represent,respectively,fine components transported by hydrodynamics,soil-forming components,and components that reflect abrupt climate changes.Grade-standard deviation indicates a range of sensitive components between 10.473 and 16.535μm.Our reconstruction shows,first and foremost,an increase in precipitation between AD 1?300,Which was fellowed by a generally dry condition in AD 300?500 and a wet condition in AD 500?650,the latter period probably witnessed fewer climate fluctuations and floods.Despite an overall dry condition,climate fluctuated greatly in AD 650?900,and,while AD 900?1400 was relatively humid,the climate was not stable for a brief duration of 100 years.The Little Ice Age(LIA),spanning over 500 hundred years from AD 1400 to 1800,can be roughly divided into three stages,each governed by a wet,dry,and wet condition.The palaoclimatic reconstruction in this study is proved to be reliable when compared withδ18O data collected from Dongge cave and the humidity index of Jiangnan region.