安徽郎溪黄棕色土-网纹红土理化性质及其古环境意义

发布时间：2018-01-03 22:12

本文关键词：安徽郎溪黄棕色土-网纹红土理化性质及其古环境意义　出处：《华东师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：第四纪黄棕色土-红土沉积剖面保留了原始物质来源和沉积环境的相关信息,对重现和反演我国南方第四纪时期古气候古环境具有重要的意义。本课题组在安徽郎溪县一处河流阶地面上采集了一处由上覆黄棕色土层和下部网纹红土层组成的二元相剖面。在光释光(OSL)测年技术的基础上,结合样品的粒度、元素、磁化率和色度测试,将郎溪XSF剖面与北方黄土及长江中下游沿岸的下蜀黄土进行比较。以探讨郎溪XSF黄棕色土-网纹红土剖面的物源及沉积环境特征,同时对上覆黄棕色土和下部埋藏红土的理化性状进行分析,比较两者风化成土作用差异,由此解译出由网纹红土过渡到黄棕色土所体现的古气候古环境演变信息。结果表明:1)粒度测试表明,黄棕色土和网纹红土均不含砾石(2mm),砂含量稀少,细粉砂(2～10μm)为第一众数组,10～50μm粗粉砂即"风尘基本粒组"含量位居其次,粒度组分特征指示了显著的风积成因特性;粒度组分曲线沿剖面深度垂直方向上均匀变化,说明黄棕色土和埋藏红土原始物质来源的同源性和稳定性;随着剖面深度的变化,网纹红土的粒度频率曲线细颗粒(2μm和2～10μm)处的峰变宽变高,而粗粉砂(10～50μm)处的峰降低,揭示了下部网纹红土沉积后原位经历的风化强度高于黄棕色土;2)元素测试表明,剖面元素组成以常量元素SiO2、Al2O3、TFe2O3(TFe203=Fe2O3+FeO)为主,常量元素组分在剖面内随深度变化分布均匀,说明剖面原始物质来源的同源性和稳定性;剖面风化强度指标在剖面上下部变化明显,随着剖面SA、SAF值降低,CIA值升高,表明风化淋溶作用和脱硅富铝铁化作用在逐渐增强。且风化强度指标与2μm黏粒含量具有很好的可比性,进一步说明2μm黏粒含量具有指示剖面风化强度的意义。3)磁学测试表明,黄棕色土磁性增强,网纹红土与黄棕色土相比具有极低的磁化率值,随着剖面深度的的变化,网纹层HIRM值上升显著,表示在细颗粒的磁铁矿和磁赤铁矿向粗颗粒的赤铁矿和针铁矿生成转化过程中,磁化率值大大降低,由此反映出网纹红土发育于我国南方一个高温且降水量剧增的时期,风化成土作用显著增强。4)色度测试表明,剖面L*与a*可以很好的对应,且a*值与黏粒(2μm)含量变化呈明显正相关关系,说明色度具有一定的古气候代用指标的意义。各古气候代用指标在郎溪XSF剖面黄棕色土于网纹红土之间对比显著,在网纹红土向黄棕色土过渡过程中可能蕴藏了一次重要的长江中下游地区的古气候转型事件,可以与第四纪冰川作用以及深海氧同位素曲线阶段很好的对应。5)光释光(OSL)测年结果显示,黄棕色土发育于末次冰期,其与网纹红土交界处处于末次间冰期向末次冰期过渡阶段,由网纹红土向黄棕色土的转变这一现象可能很好的记录了长江中下游地区一次由暖湿转向温凉的古气候事件。
[Abstract]:In the yellow brown soil clay deposition profile retains the information of the original material sources and sedimentary environment, has important significance to reproduce and inversion of South China during the Quaternary paleoclimate environment. The research group in Anhui Langxi County, a river terrace collected by a overlying yellow brown layer and lower reticulate the clay layer is composed of two phase profile. In optical luminescence (OSL) dating based on technology, combined with the sample size, elements, magnetic susceptibility and chroma test, the XSF of Langxi section and the North Loess and the Yangtze River along the coast of the Xiashu loess were compared. In order to investigate the XSF of Langxi yellow brown soil texture laterite profile provenance and sedimentary environment characteristics, analyzed the physicochemical properties of the overlying clay and buried in yellow brown earth and the lower part of the comparison between Weathering and pedogenesis of differences, thus interpreted by laterite transition to yellow brown The evolution of soil information of paleoclimate and paleoenvironment. The results show that: 1) size test showed that the yellow brown soil and laterite were not gravel sand content (2mm), rare, fine sand (2 ~ 10 m) for the first array, 10 ~ 50 m of coarse silt or dust the basic particle group "content ranks second, grain size characteristics indicate significant aeolian origin characteristics; grain size distribution curve along the vertical direction of uniform depth changes, illustrate the homology and stability of yellow brown soil and red soil buried raw material sources; with the depth profile, fine particle size frequency curve of reticulate red clay (2 m and 2 ~ 10 m) at the peak width becomes high, and coarse silt (10 ~ 50 m) at the peak decreased, reveals the weathering intensity lower after deposition in situ through laterite is higher than that of yellow brown soil; 2) element tests show that with constant element SiO2 Al2O3, TFe2O3 (TFe203=Fe profile elements. 2O3+FeO), major element in profile changes with depth distribution, homogeneity and stability profile shows primitive source; section weathering intensity indexes of lower in profile changes significantly, with a section of SA, SAF decreased, CIA increased, showed that the weathering and dissolution and removal of silicon and aluminum iron. Gradually increased. And the weathering intensity index and 2 m clay content has good comparability, further explains the 2 m clay content has indicated the significance of.3 weathering intensity profile) magnetic test shows that the yellow brown soil magnetic enhancement, the red soil and yellow brown soil texture compared with the very low rate of magnetization and with the depth profile, reticulate layer HIRM increased significantly, said to generate coarse hematite and goethite in fine particles of magnetite and maghemite transformation process, magnetic susceptibility value is greatly reduced, thus reflecting the reticulate red clay The development in South China a high temperature and precipitation increase during weathering pedogenesis significantly enhanced.4) colorimetric test shows that L* and a* profiles can correspond very well, and the value of a* and clay (2 m) showed a significant positive correlation between the content changes of color that has a certain alternative ancient gas when the index. The paleoclimate indicators XSF in Langxi section of yellow brown earth in contrast between laterite significantly, in laterite process to yellow brown earth in the transition is an important paleoclimate in the Yangtze River Delta transformation events can correspond to.5 and fourth Ji Bingchuan and the deep-sea oxygen isotope curve good) optical luminescence (OSL) dating results showed that yellow brown soil developed in the last glacial period, with the junction of Plinthitic red earth in late last interglacial to glacial interglacial transition stage, the reticulate red clay transition to the yellow brown soil The phenomenon may be a good record of an paleoclimate event in the middle and lower reaches of the Yangtze River from warm wet to cool.

【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S151.9;P532

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