汉江上游晏家棚段二级阶地风成黄土成壤特征及气候变化

Pedogenic Characteristics and Response to Climate Change of Yanjiapeng Profile on the Second River Terrace in Upper Reaches of Hanjiang River

为完善汉江上游更新世风成黄土成壤特征和气候变化资料,本研究以汉江上游晏家棚段二级阶地黄土-古土壤剖面为材料,进行粒度、磁化率和Rb/Sr的测定及对比分析。结果表明:晏家棚剖面自下而上呈现出更新世黄土(L2)-过渡性黄土(Lt)-古土壤(S1)的地层序列,剖面中古土壤(S1)的黏粒、磁化率(χlf)和Rb/Sr值均高于黄土层(Lt、L2),平均粒径(Mz)则低于黄土层,反映了古土壤(S1)风化成壤强度明显高于黄土层的特征。风化成壤特征的变化则进一步指示了古土壤形成时期受东亚夏季风影响,较温暖湿润;黄土形成时期,东亚冬季风增强,转为寒冷干旱的气候特点。

In order to reveal the pedogenic characteristics of aeolian loess and climate change in the Pleistocene in upper reaches of the Hanjiang River,the loess-paleosol profile of Yanjiapeng in the upper reaches of Hanjiang River was used as the research object,and the measurement and analysis of particle size,magnetic susceptibility and Rb/Sr were developed.The Yanjiapeng section shows a stratigraphic sequence of Pleistocene loess(L2)-transition loess(Lt)-paleosol(S1)from bottom to top.The clay particle,magnetic susceptibility and Rb/Sr value of the paleosol in the profile are higher than those in the loess layer,but the average particle size(Mz)is the opposite.It is suggested that the weathering pedogenic intensity of S1 is significantly higher than that of Lt and L2.The weathering pedogenic intensity of YJP profile indicated the influence of climate change in the Pleistocene.The paleosol layer in the upper Hanjiang River was mainly affected by summer monsoon with a warm and humid climate,and during the period of loess accumulation,the East Asian winter monsoon was strengthened,so the climate turned cold and arid.