宁镇及宜溧地区全新世中晚期典型沉积相与5 700 a B.P.前后的气候突变事件

分析宁镇及宜溧地区中晚全新世典型剖面的地层划分与特征,采用R-Q型因子分析方法估算气候变化值,揭示5 700 a B.P.前后发生在本区的干燥降温异常气候突变事件。气候曲线与沉积相序列的对比分析表明,宝华山浅棕黄色砂土夹角砾层洪-坡积相是该突变事件背景下的产物,且该突变事件还具有全球变化区域响应的征候,林峰桥同期淤泥质层中Fe3 /Fe2 比和粘土百分含量异常值进一步印证了这一论断。

Representative Sedimentary Facies and Climate Sudden Event Occurred around 5700 a B. P. since the Middle and Late Holocene in Ningzhen and Yili Region

Through analysis of characteristics of representative stratums in Ningzhen and Yili region since the middle and late Holocene,estimating the climate change values with the method of R-Q factor analysis,combined with the formation periods of the turves and buried ancient trees,we establish the comprehensively comparable chart between parts of the sequences of sedimentary facies and the transformed climate curve through pollen-spore since the middle and late Holocene.According to the comparison and contrast between macroscopical and microcosmical characteristics in sedimentary facies,a climate sudden event occurred around 5700 a B.P.has been exposed.The comparative analysis between climate curve and sequences of sedimentary facies indicates that the light brown and yellow sand,clay stratum with angular gravel in Baohuashan is the result of a dry and low temperature event,which possesses the characteristics reflecting the global change,furthermore,it is also confirmed by the clay content and Fe3 /Fe2 value in the same term miry soil stratums in Ningfengqiao.