Research On The Paleo-Environment Information Of Xiashu Loess At Nanjing And Zhenjiang

Loess is one of the most important geological agents for the Quaternary environmental research. The loess sediment is widely distributed in China for our natural geography position and special environment. Therefore, we can get lots of paleo-environment information from the research on the loess.The Chinese loess, especially North China loess has been systematically studied and been used as a reference to some other climate indicators by the researchers from various aspects. Recently, the importance of the North China loess has been realized by the scientist, and the index that can show the climate change and the loess s provenance ource has been widely used in the research of Xiashu-loess.Xiashu-loess is distributed in the marginal area of Chinese loess, which could be easily affected by the summer monsoon and sensitive for the ancient monsoon changing. Therefore, the Xiashu-loess is an important information carrier for the ancient climate change.This research study the physical-chemical characteristics formation process and provenance of the Xiashu-loess through the research on the two loess profile from Nanjing-Zhoujiashan and Zhengjiang-Chuanshan. The paleo environment information is gotten from several methods, like particle size distribution analysis, magnetism analysis, the geochemical element analysis and DRS diffuse reflection spectrum analysis.Through those parameters comparison of the two profiles, combined with the data of Shengshan-island and Northwest China loess, we find the physical-chemical characteristics of the Xiashu-loess. And the special environment of pedogenic process has been discussed from the following aspects:1. The particle size analysis show Xiashu-loess is controlled by the zonal distribution of Chinese loess, this is a powerful evidence that the provenance of the loess is far away from the Xiashu-area. However, the higher concentration of the sand grains (8.55%-10.07%) shows the local differences, which could be influenced by the proximal material or the local topography. Therefore, the provenance could be polygenic.2. Most of the magnetic partials in Nanjing-Zhoujiashan are the ferrous magnetic minerals. The incomplete antiferromagnetic minerals, ferrous magnetic mineral, SD、 PSD and SP is the majority in profile of ZJ-CS, while the coarse particle magnetic materials, like PSD、MD is the minority. The high proportion of the secondary super paramagnetic particles indicates that the formation environment of the loess is kind of wet and warm, and the chemical weathering plays a major role in pedogenesis process during this time.3. The proportion of the carbonate (1.01%～1.30%) is a magnitude lower than the Northwest China loess (>10%), which could be mainly influenced by the position difference of the two area. And the degree of carbonate leaching intensity, Rb/Sr value, CIA and Ki-value could be used as the direct indexes for the temperature and humid of the pedogenic environment.4. Through the diffuse reflection spectrum test and analysis of the Nanjing and Zhengjiang loess, we found that the magnetic susceptibility of ancient soil was influenced by the incomplete antiferromagnetic minerals hematite and goethite in the loess. There peak exist in the figure of diffuse reflection spectrum, which are distributed in the position of 435nm、535nm and 565nm wavelength, and the two former is goethite, the later is the hematite. The higher peak of hematite indicates that the higher proportion of the hematite in the magnetic material.