安徽宣城网纹红土理化特性及其古环境意义

发布时间：2018-03-30 08:19

本文选题：郎溪　切入点：网纹红土　出处：《华东师范大学》2015年硕士论文

【摘要】：第四纪网纹红土在我国南方热带、亚热带地区广泛分布,是研究古环境演化的重要陆相载体。前人已经对网纹红土进行了大量的研究,但是网纹红土的物源和成因还存在很大的争议。本研究在宣城郎溪剖面开展。郎溪剖面中部铁锰盘层,灰白色强网纹发育层和砖红色强网纹发育层特征明显,对于深入探讨网纹红土的物源和成因具有很有价值的指示意义。通过磁学指标、粒度指标、地球化学元素指标分析郎溪剖面网纹红土的理化特性,对比他人研究结果,得到以下结果：(1)郎溪网纹红土经历了强烈的风化作用,5μm组分含量为43%,10-50μm众数粒组含量为37%,颗粒粒径明显细于下蜀黄土和西北黄土-古土壤。粒度频率分布曲线和粒度概率累计曲线显示近源物质对郎溪网纹红土的物源有一定的贡献。(2)剖面铁锰盘之上层位,磁性矿物以SP颗粒的亚铁磁性矿物为主,铁锰盘下部灰白色强网纹发育层以反铁磁性的SSD颗粒为主。灰白色与砖红色强网纹发育层之间存在一个明显的过渡层(深度4.2-5.2m),亚铁磁性和反铁磁性的SP和SSD颗粒共存；5.2m以下反铁磁性矿物MD颗粒逐渐增加。郎溪剖面沉积过程中物质来源稳定,磁性矿物类型和颗粒大小随剖面的变化主要是由风化强度的差异导致的。(3)中国南方网纹红土中的灰色网纹具有多样化的成因。郎溪剖面灰白色强网纹发育层是在浅水环境长期浸泡后,经历蒸发过程形成。砖红色强网纹发育层是水分沿红色基质中的植物根系和裂隙渗透,使其周围的局部土体发生脱铁作用而形成的。(4) K、Li、Na和Ga在铁锰盘中亏损,Ba、Mn、Fe、Zn、Mg、Sr、Ca、Pb和Al在铁锰盘中富集。铁锰盘很可能是富含Fe、Mn、Ba等元素的地下水在剖面附近流出地表,Mn、Ba、Fe、Zn、Sr等惰性元素在地表逐渐富集形成的。
[Abstract]:Quaternary reticulated laterite is widely distributed in tropical and subtropical regions of southern China, and is an important terrestrial carrier for studying the evolution of paleoenvironment. However, the origin and origin of reticulated red soil are still controversial. This study was carried out in Langxi section of Xuancheng. The characteristics of iron-manganese disk layer, grayish white strong net grain developing layer and brick red strong net grain developing layer are obvious in the middle of Langxi section. It is of great significance to study the origin and origin of reticulated red soil. The physical and chemical properties of the reticulated red soil in Langxi section are analyzed by means of magnetic index, granularity index and geochemical element index, and the results of others' research are compared. The results are as follows: (1) Longxi reticulated red soil experienced strong weathering. The content of 5 渭 m component was 4310 ~ 50 渭 m and the particle size was 37. The particle size was obviously smaller than that of Xiashu loess and northwest loess paleosol. The particle size frequency distribution curve and grain size distribution curve were obtained. The accumulative curve of degree probability shows that the near source material has a certain contribution to the material source of Langxi reticulated red soil. (2) the upper position of iron and manganese plate in the section, The magnetic minerals are mainly ferromagnetic minerals of SP particles. The grayish white strong reticulate development layer in the lower part of the iron and manganese disk is mainly composed of antiferromagnetic SSD particles. There is an obvious transition layer between the gray-white and brick-red strong mesh developing layers (depth 4.2-5.2mg, SP and SSD particles of ferromagnetism and anti-ferromagnetism). The anti-ferromagnetic mineral MD particles increased gradually below 5.2m, and the material source was stable during the deposition process of Langxi section. The variation of magnetic mineral type and particle size with the profile is mainly caused by the difference of weathering intensity.) the gray net grain in the reticulated red soil of southern China is of various origin. After immersion in shallow water for a long time, The development layer of brick-red strong mesh is the infiltration of water along the roots and cracks of plants in the red matrix. K Li Li Na and Ga are depleted in the iron-manganese disk. The Pb and Al are enriched in the iron-manganese disk. The iron and manganese plates are probably groundwater rich in Fe, mn, Ba, etc., which flow out of the surface near the surface of the surface, such as MnBaFeFeOZN, Zn, Zn, Sr and so on. Sexual elements are gradually enriched and formed on the surface of the earth.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S15;P531

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