Quan xin shi huang tu ji lu de gu qi hou yan hua ji ci hua lu he li du can shu ling min xing tan tao

Climate change is closely related to people＇s livelihood,Holocene is the nearest geologic epoch we are living. Holocene climate change is therefore particularly important to human beings. It is known that aeolian loess deposit in China is one of the best geological recorders for paleoclimatie change. As position of Holocene loess is on the top layer of loess sequence, it may be easily disturbed by human activities. That is why the achievement of studying paleoclimatic change based on Holocene loess is not high so far. Here we report a continuous and integrity Holocene loess section in Baicaoyuan （ 36~ 14. 390＇N, 105 ~08. 032＇E） , Huining County, Gansu Province. This high resolution section is located in the northwest edge of Loess Plateau. The total thickness of the section we sampled is 2.2m, 110 samples were sampled with 2cm interval. Among them, the thickness of Lo is lm, with pale yellow color, loose, massive ,many grass roots and wormholes. The thickness of So is 0. 96m,with black brown color, hard texture ,white calcium toadstools,many grass roots and wormholes; the thickness of L1 is 0.24re,with many pores showing looser than Lo , its color is also light than that of Lo. The section recording the evolution of Holocene climate change can be beautifully correlated with oxygen isotope of stalagmite in Sanbao and Hulu. This record showing the cold and dry Younger Dryas event is during about 12.5 - ll.5ka period; the Holocene Climate Optimum （with higher temperature and precipitation）is during about 10.5-5.2ka period. However, climate is not stabilizing during the Holocene Climate Optimum; it becomes dry and cold gradually since 5.2ka. Baicaoyuan,Sanbao and Hulu Cave are all in the East Asian monsoon area. They have the similar evolution, so their similar tendency of curves indicates a general evolution process of Holocene paleoclimate. The evolution of Holocene climate change follows closely to the solar radiation, we thus attribute its driving factor to variation of orbital parameter, the most direct factor driving global change. Magnetic susceptibility and median particle diameter are the two important substitution indexes of paleoclimatic change. Although they all record the evolution of Holocene climate change,magnetic susceptibility curve is smooth, the median particle diameter curve fluctuates frequently. Thus the median particle diameter records in more detail （e. g. 8.2ka cold and dry event）than magnetic susceptibility. That seems to indicate that, in the west part of Loess Plateau where receive less precipitation to a certain amount for pedogenesis, grain size might become a more sensitive parameter than susceptibility parameter in recording naleoclimatic variation