庐山WJ剖面第四纪网纹红土特征及其古气候意义初探

发布时间：2018-04-04 15:23

本文选题：第四纪网纹红土　切入点：赣北庐山地区　出处：《江西师范大学》2015年硕士论文

【摘要】：中国南方长江中下游地区第四纪红土剖面,一般包括黄棕色土/均质红土/网纹红土/底部的砂砾质红土(或含网纹)四个层段;野外观测发现网纹红土层中白色网纹颜色、形态结构多样化,白色网纹、红色基质以及铁锰胶膜相互包含,微观结构具有各自的独特性。以往的研究主要是将网纹红土层白色网纹和红色基质作为统一的整体,来探寻其蕴含的古气候环境信息。本文以赣北庐山WJ剖面为研究对象,分离出同层位的白色网纹和红色基质,综合运用粒度分析、元素地球化学分析、磁化率分析、色度分析以及土壤微形态学方法,详细对比研究白色网纹和红色基质的理化特征、微形态特征的异同,尝试从微观的角度探讨其中蕴含的气候环境信息。主要结论如下:1、剖面粒度组分、粒度参数、粒度频数曲线表明同一层位内部白色网纹和红色基质粒度特征相似,数据点基本重合,表明同层位的白色网纹和红色基质具有相同的母质。剖面样品的粒度频数曲线以双峰型为主体,与北方黄土以及南京燕子矶下蜀土吻合较好,粒度特征指示大部分地层具有风成特性,底部具有水成和风成的多元成因属性。粒度组分变化的总体趋势是粉砂含量自底部向顶部增加,粘土含量自底部向顶部减少。反映冬季风增强,夏季风减弱的趋势,表明中国南方气候在中更新世以来有变干冷的大趋势,且其间有干冷暖湿的气候波动。2、庐山WJ剖面自下而上,网纹红土发育程度由强变弱,直至停止发育,其化学风化程度、网纹成熟度ΔE减弱,磁化率增加;理化特征表明自中更新世以来区域气候由湿润转为相对的干冷。剖面环境代用指标表明自中更新世来,区域气候大致经历了4个阶段的气候波动:中更新世早期气候极端湿润,到中期则转为相对的干冷;但在铁锰胶膜层(第5层)冬夏季风大幅度增强,冬季异常干冷,夏季极端湿热,随后又转为相对的湿润;到中更新世晚期湿润气候继续减弱,水热状况仍达到网纹发育的条件;但到了中更新世晚期或者晚更新世,气候更为干冷,冬季风显著增强,夏季风却显著减弱,此时水热条件足以支撑网纹红土的发育,白色网纹停止发育。3、通过对白色网纹和红色基质微形态的研究发现:白色网纹和红色基质是相互包含,两者之间都存在一些裂隙或暗色胶膜。通过电子探针对白色网纹、红色基质及其过渡区域的元素研究表明裂隙或孔道在白色网纹和红色基质形成过程中具有十分重要的作用,裂隙或许先于白色网纹的形成,并促进网纹和基质之间元素物质的迁移。4、网纹的形成与Fe2O3的迁移和富集有关。白色网纹与红色基质过渡微区间Fe2O3质量百分比含量大小为:红色基质区域过渡区域白色网纹区域,并且Fe2O3元素在同层位的红色基质中富集程度和白色网纹中迁出程度近乎相等;铁锰胶膜中Fe2O3元素的分布是胶膜壁胶膜内部胶膜外部。Fe2O3元素不仅对土壤颜色、磁化率有着重要作用,而且对土壤中铁锰胶膜的形成和分布有着决定性作用。故Fe2O3在南方红土的研究中有着重要的作用,其与气候环境的关系还有待进一步研究。
[Abstract]:Chinese south of the Yangtze River region of Quaternary red clay section, including yellow brown soil / homogeneous laterite / laterite / bottom gravel clay (or reticulate) four layers; field observation found that the reticulate red clay layer in white reticulate structure diversification, white color, red net lines, matrix and iron manganese cutans are contains, the microstructure with their respective uniqueness. Previous studies mainly the reticulate red clay layer of white and red reticulate matrix as a whole, to explore the ancient climate information it contains. In this paper, Jiangxi North Mount Lu WJ profile as the object of study, isolated from the same horizon white reticulate and red matrix, analysis on the integrated use of particle size analysis, element geochemistry, magnetic susceptibility analysis, colorimetric analysis and soil micro morphology, physicochemical characteristics of detailed comparative study of white and red reticulate matrix, the micro morphology of the similarities and differences Try, from the micro perspective on the climatic and environmental information contains. The main conclusions are as follows: 1, section size fraction, grain size parameters, grain size frequency curves show the same layer inside the white reticulate and red matrix grain size characteristics of similar data points coincide, that same layer the white reticulate and red matrix with the same parent material the size of the sample. The frequency curve profile in Shuangfeng as the main body type, and the northern Loess and Nanjing Yanziji Xiashu soil in good agreement, indicating most of the formation has the grain size characteristics of Aeolian characteristics with alluvial and aeolian origin of multiple attributes. The overall trend of the bottom grain size group is a change in the silt content increased from bottom to top. The content of clay from bottom to top. Reduce reflect winter monsoon, summer monsoon weakening trend shows that the climate in the South China in Middle Pleistocene has become dry and there is a big trend. .2 dry cold and warm humid climate fluctuations, the Mount Lu WJ section from bottom to top, the vermiculated red soil development degree from strong to weak, until the cessation of development, the degree of chemical weathering, the maturity of E decreased, the increase of susceptibility; physicochemical characteristics show that since the Middle Pleistocene region by the humid climate relative to the dry section. Environmental proxies show that since the Middle Pleistocene, the regional climate has experienced 4 stages: the climate fluctuation in the early Pleistocene extreme humid climate, in the middle is relatively dry and cold; but in the Fe Mn layer (layer fifth) winter and summer monsoon greatly enhanced, cold winter anomaly, extreme summer heat, then turn to the relative the moist; to continue to weaken in the late Pleistocene, humid climate, water and heat conditions still reached reticulate development conditions; but in the late Middle Pleistocene and late Pleistocene, the climate is dry and cold, winter monsoon significantly enhanced summer monsoon is significantly The water and heat conditions weakened, at this time to support the development of Plinthitic red earth, white reticulate stop the development of.3, through the study on Micromorphology of white and red reticulate matrix: white reticulate and red matrix contain each other, there are some cracks or dark film between them. Through the white reticulate electron probe, elements of the red matrix and the transition region shows that crack or pore formation plays an important role in the process of the white and red matrix, cracks may form before the white reticulate, and promote the migration of.4 elements and matrix material between the formation and migration, Fe2O3 net and enrichment. The white reticulate and red transition matrix micro interval Fe2O3 mass percentage size: Red White reticulate matrix region transition region area, and the degree of enrichment of Fe2O3 matrix elements in the same layer of red and white in the The move out of nearly equal degree of color; the distribution of Fe2O3 elements in iron manganese cutans in the film wall film film internal external.Fe2O3 elements not only to soil color, plays an important role in susceptibility, but also has a decisive role in the formation and distribution of soil iron manganese cutans. Therefore, Fe2O3 plays an important role in the study of southern red clay, its relationship with climate and environment remains to be further studied.

【学位授予单位】：江西师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P534.63;P532

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