摘要
测定了7MaB.P.以来灵台剖面红粘土和黄土-古土壤序列的酸不溶物Sr和Nd同位素组成。样品酸不溶物87Sr/86Sr变化可明显分为两个阶段。第一个阶段,从7MaB.P.到2.5MaB.P.,为红粘土层,酸不溶物87Sr/86Sr稳定位于高值,反映了东亚冬季风处于相对平稳的弱势。第二个阶段,从2.5MaB.P.到现在,酸不溶物87Sr/86Sr呈下降趋势,波动加强,反映了东亚冬季风不断增强,并且冬季风和夏季风交替变化加强。7MaB.P.以来灵台剖面红粘土和上覆的黄土-古土壤的Nd同位素组成一致,并揭示7MaB.P.以来,北太平洋中部沉积物与黄土高原黄土都来自相同的物源区。
Nd/144Nd and 87Sr/86Sr of acid-washed residues of red clay and o verlying loess-paleosol from the Lingtai profile of the Loess Plateau, China, w ere determined. The results show that variations in 87Sr/86Sr ratios are divided into two stages. The first stage is the lower unit (red clay), from ～7 Ma B.P. to 2.5 Ma B.P. The 87Sr/86Sr ratios are stably located at high values with an a verage of 0.722 962, reflecting the weak and stable winter monsoon. The secondar y stage is the upper unit (overlying loess-paleosol), from 2.5 Ma B.P. to the p resent. 87Sr/86Sr ratios display a gradually descending trend with time from 0.7 22 3 of ～2.5 Ma B.P. to 0.718 2 of the present, implicating a continuously enha nced winter monsoon. Red clay and the overlying loess-paleosol have very identi cal 錘d(0). It can be inferred that red clay in the Loess Plateau may be of eol ian origin as same as the overlying loess-paleosol and both have same source re gion. The difference between red clay and the overlying loess-paleosol must be attributed to the differences in environment and climate during transportation, deposition and pedogenic processes which leading to the different weathering and pedogenic intensities, rather than to the difference in source of materials. Th at most of residues of red clay have higher 87Sr/86Sr ratios than the overlying loess-paleosol implies the climate of relatively high temperature and strong ra infall during the formation of red clay.
出处
《地球化学》
CAS
CSCD
北大核心
2005年第1期1-6,共6页
Geochimica
基金
国家自然科学基金(4033100140173003)~~
