Study On Loess In Baotou Area

Loess, deep sea sediment and polar region ice core have been considered to be threemost valuable information store in the study of Past Global Changes (PAGES). As one ofthem, Chinese loess attracts many researchers from over the world, and a great deal ofprogress has been made through their research. Their research offers extremely abundantand reliable materials for restoring and reconstructing Quaternary paleoclimate andpaleoenvironment. Base on such background mentioned above, the author makes plentyof study on loess profiles in Baotou Area, Inner Mongolia. With the loess as a studymaterial for paleoclimate and paleoenvironment, the author intend to extract paleoclimateand paleoenvironment information among it and study the evolution trend of climate andenvironment. Base on large scale field investigation to the loess of Baotou Area, Dananyaozi loessprofile which is located in the northern piedmont of the Daqingshan Mountain andXiminbu loess profile which is located in northern ORDOS plateau have been selected asthe research object. According to field survey and laboratory analyses including grain sizeanalysis, pollen analysis, mineral components analysis, magnetic susceptibility, carbonand oxygen isotope analysis and dating technology such as thermoluminescence, manyimportant paleoclimate materials are obtained as follows. Grain size analysis and the calculation results of grain size parameter including meangrain size, sorting coefficient, skewness kurtosis have shown that the loess in Dananyaoziis aeolian sediment. But individual layers are aeolian sediment and alluvial deposit. Xinminbu loess profile had formed during 37.19±2.83~15.72±1.21×104a B.P. and 65吉林大学硕士学位论文:内蒙包头地区黄土研究Dananyaozi loess profile 23.66 ± 1.82~18.13 ± 1.38 × 104aB.P. by means ofthermoluminescence. All dating results show that the loess in Xinminbu and Dananyaozihad been forming in the middle Pleistocene. The results of Pollen analysis correspond tothe above dating results. Thermoluminescence dating results and field macroscopic observation show theloess in Baotou Area belong to the upper Lishi loess. The 1-5th layer, 6-8th layer, 9-11thlayer, 12th layer and 13-23 layer in Xinminbu loess profile correspond to layer L4, layerS3, layer L3, layer S2 and L2. Especially the L2 layer include two layers of paleosol that aretemporarily L2S/ and L2S//. The 1-9th layer of Dananyaozi loess profile correspond tolayer S2 (Layer S2 had formed during 18×104~23.6×104a B.P.). According to lithology assorting principle and range of values of mean grain size,value of mean grain size are all larger than 7φ in every layer loess in Dananyaoziprofile ,except for the 1st and the upper part of 9th layer. It is similar with value of meangrain size of paleosol which are in normal aeolian loess. The 1st and the upper part of 9thlayer belong to slity mild sand clay. And the 4th layer and the upper part of 5th layerbelong to slity heavy clay. The layers whose mean grain size are 7-9φ are slity mild clay. Base on pollen and lithology research, the time that is from 23.66±1.82×104a B.P.to 18.13±1.38×104a B.P. is relatively temperature and humid climate age. Thecharacteristics are that the occupation ratio of clay particle ingredient (<5μm) that ishigher than normal Lishi loess is 54.32%. At the same time, all the Kd value (coarse silt /fine silt) are 1ess than 1.00. And most of the Kd value is from 0.20 to 0.50. These Kdvalue are less than S2 paleosol, s in Luochuan loess profile. So, the loess section is typicalpaleosol accumulation. The test result of magnetic susceptibility indicates that the regular changes ofmagnetic susceptibility value disclose the variation feature of paleoclimate in Dananyaozi 66吉林大学硕士学位论文:内蒙包头地区黄土研究loess profile. The analytical results of pollen analysis in...