用全铁含量作为黄土替代性气候指标推算古温度  

Estimation of Paleo-temperature with Total Iron Content in Loess

作　　者：卢玉东[1] 孙建中[1] 张骏[1] 李萍[1] 

机构地区：[1]长安大学,陕西西安710054

出　　处：《干旱区地理》2005年第4期450-454,共5页Arid Land Geography

基　　金：中澳国际合作项目"黄土碳同位素;铁含量与古气候"资助

摘　　要：黄土铁含量的变化有四种机制,成壤作用在其中起了重要作用。我们分析了111个表土铁含量数据和880个黄土全铁量数据,发现临夏、洛川和西安三地的铁含量平均值在年均温——铁含量坐标上恰成一直线。但此平均值并非现代气候下的产物。现今年均温应与间冰期最高温和冰期最低温之间某一内分点的铁含量相关。按孢粉成果估计,间冰期最高温高出现今3℃。据北京出现的冰楔假型估计,冰期最冷时比现今低14℃。此内分点应在14:3处。内分点铁含量与现今年均温的相关方程为:t(℃)=5.614Fe-10.667。据此可以将铁含量曲线转换为气温曲线。Loess contains plentiful climatic records, such as the degree of soil formation, Weaver index of clay minerals, calcite/quartz, pH value, Eh （mv） value, content of CaCO3, SiO2/Al2O3, FeO/Fe2O3, CaO/MgO, （CaO＋Na2O＋K2O） /Al2O3, Sr/Ba, susceptibility, ^10Be atomicity, spore-pollen, etc., and the total ferric oxide content or total iron content in loess is one of the parameters used to reveal the plaeoclimate. Four mechanisms are involved in variation of iron content in loess, they include the dilution process from input flux variation of aeolian dust composition change of original matter in source regions, sorting process and the syngenetic pedogenisis, of which the last one is the most important to influence iron content. By analyzing the change of iron content in 111 topsoil samples and 880 loess and paleosol samples collected from 5 profiles over the Loess Plateau, it is found that the three points of the average iron contents in loess at the Linxia, Luochuan and Liujiapo profiles are just on a beeline in a coordinate of average annual temperature and iron content. The average values of iron content, however, are not the outcome of modern climate. It is considered that the values of average annual temperature are related to the values of iron content in loess of some internal equinoxes between the temperature maximum in interglacial epoch and the minimum temperature in glacial epoch. It is estimated from pollen-spore analyzed results that the maximum temperature in the interglacial epoch was 3℃ higher than that at present, while the minimum temperature in the glacial epoch was 14℃ lower than that at present based on the estimation of ice wedge in Beijing. The regression equation between the iron content of the internal equinox and the average annual temperature can be developed from iron content. However, the transforming equation works properly only for the loess regions in Shaanxi and Gansu provinces.

关 键 词：黄土 全铁含量 气候指标 古温度 

分 类 号：P532[天文地球—古生物学与地层学]