The Evolution Research During The Late Quaterary In Xinding Basin,Shanxi

Xin Ding basin is a fault basin northern shanxi graben system,located in the periphery of ordos massif. Xin Ding basin research will help us further understand the effects of the Qinghai-Tibet plateau uplift to the outer regions. It also for the Qinghai-Tibet plateau uplift effect on Shan Xi and Shan Xi graben basin series provide more evidence.In Quaternary period Xin Ding lake basin is a loess area,if there happens lake retreat, the loess-paleosol will cover on lacustrine sediments, lake retreat will produce the fluvial terrace, from the center of the edge of the lake shore by overlying on lacustrine sediments of loess-paleosol sequence, we can judge the lake retreat is fast or slow.At the same time in lacustrine sediments showed that two kinds of sedimentary. In this paper,we collecting samples at NWJ and described the sedimentary characteristics, through the magnetic susceptibility, chemical elements, clay mineral, this experimental analysis draws the following conclusion:⑴The general area of the quaternary period Xin Ding basin,was covered the lake for a long time,after our preliminary investigation and verification found area occurred at least twice lake retreat phenomenon, and we found the lacustrine sedimentary cover loess-paleosol phenomenon. In the wild we found that Xin Ding basin has two levels of lake retreat platform, the one is on the altitude of 830 m near the NWJ and hutuo river, on this level we see lacustrine terrace is covered by the paleosol layer, the analysis of collected samples of magnetic susceptibility, we get this is S1 paleosol layer;the second terrace is on the altitude of 920 m near the south of Shui Gou Cun and the west of Xia Chang Le, in this platform we observed lacustrine sediments is covered by the paleosol layer, this soil sedimentary thickness, characteristics of soil obviously,the color is red brown, and compounded by three layer of soil, it is the most obvious S5 soil. therefore Xin Ding basin in S1 and S5 soil development period, there has hanppened lake retreat.⑵Xin Ding basin is a loess area, in east Asia climate is dry and humid appear alternately in the quaternary period, in the dry and cold climate formed loess and in the hot and humid climate formed soil. The source of lacustrine sediment is mainly the loess and paleosol,when the local was happening soil and water loss at the same time the surface water will reduce the material around the lake handling to the lake, the lake surface covered material is not same in different climate, so the lake sedimentary is also different. Through the magnetic susceptibility, clay mineral,chemical elements of testing, we concluded that: ①red clay layer and soil corresponding to the susceptibility of high value, the another material in lacustrine sediment and loess corresponding to the susceptibility of low value; ② red clay layer and soil corresponding to the chemical element of high value, the another material in lacustrine sediment and loess corresponding to the chemical element of low value; ③ red clay layer and soil corresponding to the clay mineral kaolinite of high value.we finally verify the speculation—red clay layer is similar to the soil, the another material in lacustrine sediment is similar to the loess.