Study On Holocene Environment Of Keshiketeng County, Inner Mongolia

Keshiketeng county ,Inner Mongolia,lies in the interjunction of the Daxinganling Mountains and Qilaotu Mountains of the spread of the Yanshan Mountains. Since Quaternary Period, because of the rising of the Daxinganling Mountains and the Yanshan Mountains this area is the boundary of the geology, geomorphy and climates of the East and West China and North China and Northeast China , and it is the sensitive area of the environmental change, too. Therefore, the area is typical to study the environmental change of China , even of the globe since Quaternary Period, especially since the Holocene Epoch. The studies on this area can help gain the succession of the past environmental changes with high discernibiliry and provide the confident references for precisely reestablishing past environmental changes.This paper is based on the project of the establishment of the National Geopark of Keshiketeng. And the author mainly studies the Holocene environment, doing the experiments of the grain-size analysis myself. The main results as the following:1 .After the grain-size analysis of the Holocene stratigraphic section has been carried out and many experiments done; the previous processing program of grain-size analysis is gained. The samples were tested by advanced laser grain-size instrument. The depositional environments in different areas are reestablished in terms of the analysis of the sedimentary characteristics of various strata. It is thought that the Holocene original sediments were the result of the aeolation in the area, but the stream action influence the formation of deuterogenic loess. This stream action mainly include torrent or sheet flood, not other water action.2.The curve of median diameter well showed the grain-size characteristics of the area , which is negatively correspond with the curve of the susceptibility. The median diameter can be regarded as the effectively alternating indication of the environments in the paper.3.There is much correspondence between the curve of the susceptibility and the strata. Based on the analysis of the susceptibility, it can be concluded that the area has undergone many climatic fluctuations from dry-cold to warm-wet.4.According to the sporopollen assemblages, the types of the vegetation cover, climates and its evolution can be gained. In the paper, based on the characteristics of sediments and the susceptibility, the sporopollen diagram was divided into five palynofloral zones by trying to use the cluster analysis of the ordered samples and the Program of C++ . In the area, the Holocene climate alternately changed from cold to warm and from dry to wet and is mainly cool-dry. The species and genera of the vegetation cover mainly consisted of warm-dry plants whose main typeis the alternation of the forest grassland or grassland.5.And it can be concluded that this area is well correspondent with Daihai Lake which have been highly studied by correlating them.