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宝鸡固川盆地全新世黄土-土壤剖面元素地球化学特征

Geochemical characterization of the Holocene loess-soil profile in the Guchuan Basin of Baoji city
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摘要 通过考察,在渭河上游固川盆地发现了含有典型古洪水滞流沉积层的全新世黄土-古土壤剖面.根据地层学对比和光释光(OSL)测年,确定渭河上游流域在3200~3000aB.P.发生了特大古洪水事件.通过测定该剖面中的元素含量,获得了一系列的地球化学参数指标,结果显示:地层剖面中古洪水滞流沉积层与其下部的古土壤层和黄土层具有显著的差异,这说明古洪水沉积层与黄土层的物质来源不同;黄土是沙尘暴的直接沉积物,古洪水滞流沉积层则是地表土壤和风化层被流水搬运和沉积过程中发生了二次分选,且其未经过明显的风化成壤改造,因而它又与古土壤的理化性质有明显的区别.全新世气候变化规律的综合分析显示,在万年尺度内的特大洪水一般发生在气候突变转折时期.由于气候波动变化,降水变率增大,特大洪水事件的发生比较频繁. By field investigation in the upper reaches of the Weihe River, the Holocene loess-soil profile containing the typical palaeoflood slackwater deposit was found in the Guchuan Basin. According to stratigraphic configuration and OSL dating for slackwater deposits and Loess- paleosol samples, the age of the extreme palaeoflood is fixed between 3 200 a B. P. and 3 000 a B. P.. Through the analysis of microelements,a number of geochemical parameters were obtained. The results show that geochemical elements included in the palaeoflood slackwater deposit distinctly differ from paleosol layer below slackwater flood deposits and other loess layer in the profile. It shows the material sources of slackwater flood deposits is different from loess soil. Loess is the direct deposits of dust storms. While the slackwater flood deposits are secondary separation in the process of transporting by water, and without obvious weathering of soil improvement, so it is different from paleosol layer in physical and chemical properties. Combining with climatic change in the late Holocene, the results show that extreme floods usually occurred when the climatic changed abruptly. Because of the instable and highly variable climate change and the intensified rain,the extreme floods occurred frequently.
出处 《陕西师范大学学报(自然科学版)》 CAS CSCD 北大核心 2013年第5期83-90,共8页 Journal of Shaanxi Normal University:Natural Science Edition
基金 教育部博士点基金优先发展领域项目(20110202130002) 陕西省教育厅重点实验室项目(11JS011) 陕西省教育厅科学研究计划资助项目(12JK0475) 宝鸡市科学技术研究发展计划项目(12SF5-2) 宝鸡文理学院院级重点项目(ZK12050)
关键词 全新世 黄土-土壤 古洪水滞流沉积物 地球化学 Holoeene loess-soil palaeoflood slackwater deposits geochemical characterization
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