忻定盆地第四纪中晚期湖盆演化研究

发布时间：2018-02-13 19:49

本文关键词： 忻定盆地黄土沉积湖相沉积红色粘土层湖退　出处：《上海师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：忻定盆地是山西地堑系北部一个断陷盆地,位于鄂尔多斯地块的边缘。对忻定盆地的研究有助于加深我们对青藏高原隆升对高原本身及外缘地区的影响的认识,同时为青藏高原阶段性隆升对山陕地堑系列盆地的影响这一研究提供更多的佐证。第四纪时期忻定湖盆长期为湖泊所占据同时这里也是一个黄土堆积区,湖盆如果发生湖退,黄土-古土壤就会覆盖在湖相沉积层之上,一次湖退便会产生一阶湖积台地,从盆地的边缘到盆地的中心通过上覆在湖相沉积层之上的黄土-古土壤的序列,我们可以判断这次湖退是快速的还是缓慢的。在湖相沉积物中发现了两种沉积物质一种是红色粘土层另外一种是非红色粘土层。本文在南王就(NWJ)三个剖面采集了样品,对沉积剖面进行描述,并且通过对样品磁化率、化学元素、粘土矿物的实验分析得出了以下结论:⑴在第四纪中晚期忻定盆地的广大区域,长期为湖泊所占据,经过我们的初步调查和验证发现区域内至少发生两次湖退现象,出现了湖相沉积层之上覆盖黄土-古土壤的现象。在野外我们发现忻定盆地有两级湖退台地,第一级台地海拔高为830m,在南王就及滹沱河附近,在这级台地上我们看到湖相层之上覆盖了古土壤层,通过对采集所得样品的磁化率进行分析,我们得到覆盖在其上的为S1古土壤;第二级台地海拔高度为920m左右,分布于水沟村南沟及下长乐西沟,在这级台地我们观察发现湖相沉积层上覆盖了红棕色的古土壤层,这层古土壤沉积层厚、特征明显、颜色以红棕色为主,并且由三层古土壤复合而成也就是常常所说的红三条,它就是成壤作用最明显、最强的S5古土壤层。因此忻定盆地在S1、S5古土壤发育时期,发生强烈的湖退现象。⑵忻定湖盆这个区域是一个黄土堆积区,在第四纪时期东亚的气候是干冷和湿热交替出现的,在气候处于干冷的时期形成黄土而在气候湿热的时期形成古土壤。湖相沉积的的物源主要是黄土和古土壤,当发生水土流失时表层的水土流失会把湖泊周围的物质搬运到湖泊里,不同的气候时期湖泊周围地表所覆盖的物质也是不相同的,因此被带入湖泊沉积的物质也是不同的。通过对黄土沉积和湖相沉积两类沉积磁化率、化学元素和粘土矿物的测试,我们得出:①湖相沉积物中的红色粘土层同黄土沉积物中古土壤对应磁化率高值,非红色粘土层与黄土对应磁化率的低值;②湖相沉积物中的红色粘土层同黄土沉积物中古土壤对应化学元素高值,非红色粘土层与黄土对应化学元素低值;③湖相沉积物中的红色粘土层同黄土沉积物中古土壤粘土矿物高岭石对应着高值。最终我们验证了之前的推测——湖相沉积物中的红色粘土层和黄土沉积物中的古土壤相对应,非红色粘土层和黄土相对应。
[Abstract]:Xinding basin is a faulted basin in the northern part of Shanxi graben system, located on the edge of Ordos block. The study of Xinding basin is helpful to deepen our understanding of the influence of the uplift of the Qinghai-Tibet Plateau on the plateau itself and the outer margin. At the same time, it provides more evidence for the study of the influence of the stage uplift of the Qinghai-Xizang Plateau on the Shanshan graben series basins. In the Quaternary period, the Xinding lake basin was occupied by lakes for a long time and this area is also a loess accumulation area, and if the lake basin retreats, Loessis-paleosol cover the lacustrine sediments, and once the lake retreats, it produces a first order of lacustrine terraces, from the edge of the basin to the center of the basin, through the sequence of loess-paleosols overlying the lacustrine sediments. We can tell whether the lake retreating is fast or slow. Two kinds of sedimentary material have been found in the lacustrine sediments, one is red clay layer and the other is non-red clay layer. In this paper, samples were collected from three sections of NWJ. The sedimentary profile is described, and through the experimental analysis of the magnetic susceptibility, chemical elements and clay minerals of the samples, the following conclusions are drawn: 1 was occupied by lakes for a long time in a large area of the Xinding basin in the middle and late Quaternary. Through our preliminary investigation and verification, we found that there were at least two lake retreating phenomena in the area, and there was a phenomenon of loess-paleosol overlying the lacustrine sedimentary layer. In the field, we found that there are two grade lake retreating platforms in Xinding Basin. The first stage is 830m above sea level. In Nanwang and near the Hutuo River, we can see that the lake facies layer is covered with paleosol layer, and the magnetic susceptibility of the collected samples is analyzed. We got the S1 paleosol covered on it, the second stage is about 920m above sea level and distributes in the Nangou of Shuigou Village and the Xigou of Lower Changle. In this stage, we observed and found that the paleosol layer of lake facies was covered with reddish brown paleosols. This layer of paleosol is thick, distinctive, mainly red-brown in color, and composed of three layers of paleosol, which is often called the red three bands, which is the most obvious earth-forming effect. The strongest S 5 paleosol layer. Therefore, during the development period of S1 and S5 paleosols, a strong lake retreat occurred in Xinding basin. The area of Xinding Lake basin is a loess accumulation area, and the climate of East Asia appeared alternately in dry, cold and humid heat during the Quaternary period. Loess is formed in dry and cold climate and paleosol is formed in humid and hot climates. The source of lacustrine deposition is mainly loess and paleosol. When soil erosion occurs, soil and water loss on the surface carries the material around the lake into the lake, and the material covered by the surface around the lake is different in different climatic periods. So the materials brought into the lake deposits are different. By testing the magnetic susceptibility, chemical elements and clay minerals of the loess and lacustrine deposits, We have obtained the corresponding high magnetic susceptibility between the red clay layer in the lacustrine sediments and the paleosols in the loess sediments. The red clay layer in the lacustrine sediments corresponding to the magnetic susceptibility of the loess and the non-red clay layer corresponds to the high value of the chemical elements in the paleosols of the loess sediments. The red clay layer in the lacustrine sediments with low value of chemical elements corresponding to the loess and the paleosol clay mineral kaolinite in the loess sediments correspond to high values. Finally, we verified the previous conjecture-lacustrine sediments. The red clay layer in the soil corresponds to the paleosol in the loess sediment. The non-red clay layer corresponds to loess.
【学位授予单位】：上海师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P534.63

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