A Study On The Depositional Environment Of Dengkou T2 Drill In Innermongolia Since The Late Pleistocene

This essay tests the grain size and susceptibility and analyzes the age of the T2 drill hole sediment in the Sun Temple area in Hetao Plain,makes a systematic division of sedimentary sequences and sedimentary facies analysis according to its characteristics such as color,structure,sedimentary structure,and organic matter content,etc.,and elaborates the sedimentary environment and the paleoclimate evolution in this region since about 26kaB.P..Results show that from 26kaB.P.to early Holocene,this region had undergone two sedimentary cycles:from 26kaB.P.to about 15 kaB.P.,river facies changed to lake shore and shallow lake facies;from 15kaB.P.to about 10kaB.P.,this change from rivers to lake environment happened again,specifically,from flood land facies to lake shore,shallow lake,and deep lake facies.Since the Holocene,there was a significant overall fluctuation in the grain size and susceptibility curve of the sediment,characterized by alternate changes between shallow lake and lake shore facies and river facies.The fluctuation also shows the great change of the lake surface and the characteristics that oxidation and reduction environment appear alternately.Combining the climatic characters showed by the grain size and susceptibility curve with previous research in terms of regional paleoclimate inversion,we can see that compared with 26kaB.P.,Holocene had shallower and narrower lakes,judged by which,the overall climatic characters in this region in Holocene is dry and rainless.From the current environmental conditions,this region is in arid and semi-arid area with little annual rainfall and huge evaporation,therefore,lakes cannot get sufficient supplies.Combined with deteriorating desertification,the condition of this region since the Holocene further continued and intensified with dry and rainless climate,shrinking lake area,and shallower lakes.