渭河上游地区樊家城黄土-古土壤剖面Rb、Sr、Ba存留特征及意义

Composition Characteristics and Significance of Rb, Sr and Ba of Fanjiacheng Loess-paleosol Profile in the Upper Reaches of the Weihe River

选择渭河上游樊家城全新世黄土-古土壤剖面为研究对象,对该剖面元素Rb、Sr、Ba含量和磁化率、粒度、CaCO3进行了测定。结果表明:Rb、Sr、Ba含量及Rb/Sr、Ba/Sr比值与磁化率、粒度、CaCO3含量显著相关,能够指示渭河上游地区全新世的气候变化。剖面中古土壤层的磁化率、黏粒、Rb/Sr、Ba/Sr以及元素Rb、Ba含量高于黄土层,CaCO3、Sr含量小于黄土层,指示渭河上游地区古土壤层(S0)形成时期主要受夏季风影响,气候温暖湿润,淋溶作用强,风化成壤作用强;而黄土层形成时期主要受冬季风影响,气候相对冷干,淋溶作用弱,风化成壤作用弱。在全新世中期,古土壤层S^10与S^20之间的黄土夹层,反映了渭河上游地区在全新世大暖期的6 000~5 000 a BP期间气候显著恶化。

The Holocene loess-paleosol profile of Fanjiacheng in the upper Weihe River was selected as the research object, and the contents of Rb, Sr, Ba, magnetic susceptibility, grain size and CaCO3 in the profile were measured. The results show that Rb, Sr, Ba and Rb/Sr ratio, Ba/Sr ratio are significantly correlated with magnetic susceptibility, particle size and CaCO3, which can indicate the Holocene climate change in the upper Weihe River. The magnetic susceptibility, clay, Rb/Sr, Ba/Sr ratio and elements Rb and Ba in the paleosol layer in the profile are higher than those in the loess layer, while the contents of CaCO3 and Sr are lower than those in the loess layer, suggesting that the paleosol layer(S0) in the upper Weihe River was mainly affected by summer monsoon, with a warm and humid climate, and it further indicated the leaching degree, weathering and pedogenesis were strong. The formation period of loess layer was mainly affected by winter monsoon, with a relatively cold and dry climate, and it further indicated the leaching degree, weathering and pedogenesis were weak. The loess interlayer between the paleosol layers S^10 and S^20 reflected the significant deterioration of climate in the upper Weihe River during the period of 6 000-5 000 a BP in the mid-Holocene.