汾渭盆地250 kaBP以来黄土粒度记录的环境信息

The environment information recorded on the grain size of loess in Fenwei river basin since 250 ka

通过对汾渭盆地西师村黄河第三级阶地上沉积的黄土地层粒度分析发现,沉积物的粒度组份变化曲线能够很好地反映黄土-古土壤地层序列的变化,粒径<5μm和>30μm组份的体积分数曲线分别是东亚夏季风和冬季风的良好替代性指标．通过粒度分析所绘制的各粒级组份体积分数曲线显示,古土壤S2和S1发育时期,夏季风加强,并且分别在225,121,101,85 kaBP处出现峰值;在40 kaBP左右,夏季风有所加强,形成一层弱古土壤Sm．黄土L2和L1堆积时期,冬季风加强,峰值分别出现在185,155,138,15 kaBP处．西师剖面的黄土记录整体上反映了最近250 ka以来汾渭盆地东亚季风的演化过程,为这一地区在最近250 ka以来的东亚季风演化研究作了有益补充．

The analysis of grain size in loess stratigraphy of Xishi, which is on the third terrace of the Yellow River in the Fenwei Basin, reveals the variation of loess stratigraphy. The percentage of grain size below 5 μm and above 30 μm are reliable indicators reflecting the variation of East Asian Monsoon. The curve of the percentage of the grain size indicates that the summer monsoon was strengthened in S2, S1 and Sm, reaching the strongest periods in about 225, 121, 101, 85 and 40 kaBP and the winter monsoon was strengthened in L2 and L1, reaching the strongest periods in about 185, 155, 138 and 15 kaBP. The archive in the section of Xishi has recorded the process of evolution of East Asian Monsoon since 250 ka and it will benefit the research on the evolution of East Asian Monsoon from 250 ka to now.