黄土高原S_1古土壤的地球化学特征及其对物源的指示  

GEOCHEMICAL CHARACTERISTICS OF LAST INTERGLACIAL PALEOSOLS IN THE CHINESE LOESS PLATEAU AND ITS IMPLICATIONS TO LOESS PROVENANCE

作　　者：汪海斌[1] 于英鹏[1,2] 刘现彬[1] 冯兆东[2,3] 

机构地区：[1]兰州大学西部环境与气候变化研究院,兰州730000 [2]兰州大学资源环境学院,兰州730000 [3]Department of Geology, Baylor University

出　　处：《第四纪研究》2011年第2期338-346,共9页Quaternary Sciences

基　　金：国家自然科学基金青年基金项目(批准号:40801005);西部环境变化国家创新研究群体科学基金项目(批准号:40721061)资助

摘　　要：对黄土高原中部的蓝田剖面与黄土高原西部的定西和天水剖面的S_1古土壤的化学元素进行了对比。3个剖面的Al-Ti-Zr比值接近,La/Th和Ce/Pb比值以及稀土元素配分模式各与上大陆地壳的接近,表明黄土高原S_1古土壤的来源粉尘经历了多次的搬运-沉积循环过程,而使物源呈现均一的特性。物源的均一性初步保证了地球化学指标的空间比较的可行性。The loess-paleosol sequence in the Chinese Loess Plateau holds a record of history of East Asia Summer Monsoon and Winter Monsoon variations. A lot of geochemical indicators have been developed to indicate the strength of Summer Monsoon and Winter Monsoon. The geochemical indicators of summer monsoon intensity are mostly related to chemical weathering, while the geochemical indicators of winter monsoon strength are dominantly related to sorting processes. However, besides the weathering and sorting processes, the composition of source rock is also a major factor affecting the chemical composition of detrital sediment. Thus,the homogeneity of source material or the degree of source mixing should be assessed when using those geochemical indicators to reconstruct climatic change. In order to examine the mixing degree of loess material, we investigated the geochemistry of three last interglacial paleosol （S1）sections from northwest to southeast in the Chinese Loess Plateau using X-Ray Fluorescence and Inductive Coupled Plasma Mass Spectrometry methods. The three sections are Dingxi section （35°35＇N, 104°37＇E） with 6-m thick, Tianshui section （ 34°34＇N, 105°46＇E ） with 5-m thick, and Lantian section （34°10＇N, 109°19＇E）with 5.5-m thick, including bottom part of L1, the whole S1, and upper part of L2 respectively. There is clear geographic differentiation of soil formation for these three sections. The S1 of Dingxi section consists of 3 sub-soil units and 2 intervening loess units. The S1 of Tianshui section consists of an A horizon （0. 8m） ,an accretionary Bt horizon（2.5m） ,and a Bk horizon（1.2m）. The S, of Lantian section consists of an A horizon（0.4m） ,a Bt horizon（2.6m）,and a BC horizon（1, lm）. The ternary plots of stable elements, Al-Ti- Zr, a robust method to indicate sediment provenance, show a confined cloud in each loess-paleosol section,and the clouds are almost overlapped when they are in the same plot frame. This highly suggested the homogeneity of l

关 键 词：黄土 古土壤 地球化学 物源 

分 类 号：P941.74[天文地球—自然地理学]