【作者】 黄臻；

【导师】 王建力；

【作者基本信息】 西南大学 ， 第四纪地质学， 2010， 硕士

【摘要】 粒度分析技术在第四纪古环境研究中运用得非常成熟,它对于查明沉积物的物质来源、搬运介质和动力、沉积环境以及它们的变化都具有重要意义。粒度是沉积物最重要的特征之一,在古环境分析及重建研究中具有非常重要的地位。不同沉积物由于搬运介质及强度的不同,颗粒组成也相异,因此通过粒度分析可以研究沉积物的形成环境及其搬运动力特征。本研究以长江三峡巫山地区第四纪沉积物粒度分布特征为主要内容,在野外考察基础上选择了1个第四纪沉积物典型剖面和与本区大致同纬度的2个四川中部遂宁地区红色风化壳剖面,通过对这些样品进行粒度特征分析,探讨各种粒度参数在剖面中的变化特点和分布规律。论文主要得出了以下几点结论：(1)、根据野外实地观察,望天坪剖面土壤质地较为均一,可以分为两层,即剖面上部的棕黄色层与下部棕红色层,下部水分含量较上部多,这与南方较多红土剖面相类似。(2)、从剖面的粒度组成特征上看,砂(>63μm)含量极少,平均值为0.7%；粉砂(4～63μm)含量最高,平均值为68.64%,为众数粒组；黏粒(<4μm)含量次之,平均值为30.66%,为次众数粒组；风尘基本粒组10～50μm含量较高,平均值为52.07%,推测其成土母质有一定的风成特性。(3)、从粒度分布曲线上及粒度参数上看,剖面上部(棕黄色土层)呈单峰分布形态,并拖有细尾,与风成黄土相类似,可能指示了沉积后经历了风化成壤作用；剖面下部(棕红色土层)的峰态更加复杂,在单峰为主体的背景下拖有细尾以及粗尾,反映了其沉积动力的多元性,与南方红土相类似。平均粒径以及中值粒径等粒度参数较为细小,平均值分别为12.5μm及7.75μm,剖面上部(棕黄色土层)分别为13.89μm及10.19μm,下部(棕红色土层)分别为9.96μm与6.75μm,上部粒径值更接近与风成黄土,下部更接近与南方红土,可能反映了先经过风化再经历风成的沉积顺序。(4)、综合巫山望天坪剖面的粒度组成、分布曲线、粒度参数以及磁化率等指标,并与北方黄土及南方红土的对比,因为它与两者都有相似性,因此不能简单地将其成因归结于“风成堆积”或“风化成土”,而更倾向于经历了这两种过程,反映了南方第四纪环境的多样性及复杂性。望天坪剖面粒度的纵向变化趋势,可能反映了南方气候在第四纪晚期有变干冷的趋势,但其环境意义有待在年代测定及其他环境指标对比研究的基础上作进一步探讨。更多还原

【Abstract】 Grain-size analysis is a matrual method in the research of Quaternary environmental research,it is the material for the identification of sediment sources, transport media and power, sedimentary environments and their changes are of great significance. Grain-size is one of the most important feature of sediments in the paleo-environment analysis and treconstruction. Because of different sediment transport medium and the intensity of the different composition of the particles are different, so grain-size analysis can be studied through the formation of sediment environment and its dynamic handling characteristicsIn this paper, Wangtianping profile,is located on the left bank of Yangzi river,is selected as research site as deserving of unique grain-size distribution of Quaternary sediments.,based on the investigation in the field selected a typical profile of Quaternary sediments and with roughly the same latitude in this area of the two central Suining, Sichuan region red weathering crust sections, through the grain size characteristics of these samples were analyzed to explore a variety of grain size parameters in the profile changes in the characteristics and distribution. Thesis come to look at a few conclusions:(1)According to field site observation, to look on the soil texture is more uniform floor section can be divided into two layers, namely, the upper section of the brown layer and the lower brown layer, lower moisture content than the upper level, and this with the South more clay profile is similar.(2) From the profile in terms of grain-size characteristics of sand(>63μm) content is extremely low, with an average of 0.7%; silt (4～63μm) content in the highest, with an average 68.64 percent, for public Counting Unit;clay (<4μm) content followed a mean of 30.66% for the second mode grain group; eolian basic grains group with higher levels of 10～50μm, with an average of 52.07%, suggesting the soil-forming parent materials have a certain style into a feature.(3)From the grain-size distribution curve and the parameters point of view, the upper section (brown-yellow soil) showed single-peak distribution pattern, and drag a small tail, and aeolian loess is similar to post-deposition may direct experience the role of wind into soil; profile lower (red-brown soil) and kurtosis more complex, in a single peak as the main drag and refined against the backdrop of the end as well as the coarse tail, reflecting the diversity of its sedimentary dynamics, and the southern red soil is similar to.The average particle size as well as the median grain size parameters such as the relatively small size, average values are 12.5μm and 7.75μm, the upper section (brown-yellow soil) were 13.89μm and 10.19μm, lower (red-brown soil) were 9.96μm and 6.75μm, the value of the upper particle size is closer to the wind into the loess, the lower part closer to the South red clay, may reflect the first pass through weathering and go through a sequence of eolian deposition.(4) A comprehensive look on Wangtianping profile,the grain-size composition, distribution curves, parameters and magnetic susceptibility and other indicators, and with the northern and southern red clay loess contrast, because it is both similar, so we can not simply to be the causes attributed to "wind-stacking," or "wind turned into earth" but more likely to experience these two processes, reflecting the diversity of the South Quaternary environmental and complexity. Wang Ping-day trends in the vertical profile of particle size, may reflect the late Quaternary climate in the South have changed the trend of dry and cold, but its environmental significance to be in the dating and other environmental indicators on the basis of comparative study for further exploration.更多还原