赣中玉华山泥炭地沉积来源的粒度端元法分析与2 000 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 peat core of Yuhua Mountain, Jiangxi Province

  • 摘要: 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2 000 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(4~16 μm)为主,中粗粉砂(16~64 μm)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10.473~16.535 μm,结合上述3个端元的变化规律,得出近2 000 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。

     

    Abstract: Based on the AMS14C 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 2 000 aBP through grain size analysis, grade-standard deviation method, and end-member model. Our results show that the sediments in the peatland of Mt Yuhua are mainly consisting of fine sand (4~16 μm) and coarse silt (16~64 μm). 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 16.535 μm. 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 with δ18O data collected from Dongge cave and the humidity index of Jiangnan region.

     

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