A Comparative Study On The Evolution Of Holocene Soil Strength And Climate Change In The Eastern And Western Guanzhong Basin

Holocene is the latest similar history related to human relationsmost closely. The Guanzhong Basin is located in the sensitivemonsoon evolution area of the south of the Loess Plateau, and frequent area problems are occurring here as the global changes. There are some differences between the eastern and western natural environment in the Guanzhong basin. Therefore, it is the important scientific significance that the regional comparative study of the Holocene in the Guanzhong basin should provide a great support for the climate background of the ancient environmental climate and hydrological events, and provide the basic data for the prediction of the environmental evolution and themonsoon variation trend in the east part of Guanzhong^Basin.Based on the field investigation, the Baishui YHC profile in the eastern of Guanzhong Basin and Qishan LC profile in the western of Guanzhong Basin were choosed as the research profiles. On the basis of a large number of experiments and data analysis, the Baishui YHC and Qishan LC profile from threemodules were studied comparatively and systematically, including:the basic physicochemical properties (The color parameter,magnetic susceptibility, grain size,moisture, burning vector, CaCO3 content, pH), the soil element geochemistry and the soilmicjrpmorphology and so on. On the basis of the process, we tried on the alternative indicators of climate and environment to R/S analysis, partial correlation analysis and regional analysis, to explore the essentialmeaning and environmental sensitivity of environment substitute index, to reseach the soil differences and themode of evolution, and rebuilt the Holocene environmental change history and onset and retreat of the summermonsoon in eastern and western of Guanzhong Basin. Through the regional and global correlation and inspection regional environment response in Guanzhong Basin Evolution, we reveal themechanism of the degree of soil formation and climate change in Guanzhong Basin, and themain conclusions are as follows:(1) Physical and chemical indicators at LC and YHC profile in GuanZhong basin indiacte that:magnetic susceptibility, red, yellow, clay, burning vector, hygroscopic water show the systemic change,from LI to Lt to SO increase step by step, to LO fell again; Brightness, pH and CaCO3 content showed the opposite trend, there are some abnormal fluctuations The intensity of soil development at LC profile is greater than at YHC profile.(2) Geochemical characteristics at YHC and LC profile inGuanzhong basin is tested: ①constantmobility of trace elements, elements and chemicalmolecular ratio are sensitive to changes in environment, can not only reveal the soil-paleosol cyclicity fluctuation change, but also verify the physical and chemical properties of secondary changes clear the guanzhong basin, whether for secondary weather events. For example:210-200cm,160cm, at LC profile is secondary event,but 290cm is the illusion caused by carbonate deposition,150-140cm,110-100cm and 110cm at YHC profile is climate fluctuations.②The content of various elements, themigration rate and weathering index revealed that weathering degree of the LC profile in western Guanzhong basin is higher than YHC profile in the eastern Guanzhong basin. Elementmigration rate, coefficient of silicon aluminium, and the CIA commonnly revealed that the soil is developed to middle weathering degree at LC profile and formed a faint desilication aluminized effect at So, whicht in a slightly stronger than the xifeng and Xia shu soil chemical weathering degree. YHC profile is in the lower stage of weathering andmedium weathering transition, not to take off the phenomenon of silicon,magnesium leaching is also very weak.(3) Soilmicromorphological study shows that:① based on polarization image extraction of soil pore quantitative parameters (porosity, soil pore fractal dimension, area, roundness, length, width, etc.) with othermature environmental.Proxies can be a good comparison, can reveal the holocene environmental change rule.② At the western LXY profile in western Guanzhong basin, S0,issued a large number of roots of woody vegetation clear existing lens aperture, there aremany brown-brown color in argillic horizon claymembrane gathered and a large number of iron andmanganese rusty spot, hinted itmight achieve subtropical climate; These characteristics are not found at YHC profile in eastern guanzhong basin.(4)For the first time, the evolution of soil reserch will be based on the fractal dimension of R/S analysis and regional analysis, found that ①soil development in guanzhong basin ismainly controlled by rainfall, namely summermonsoon index. Lack of effective temperature, the winter wind alternative indicators. ② soil strength has obvious difference (LC> YHC). To warm period, the soil of SO is the strongest in holocene,reached to brown soil and yellow brown soil at LC profile in western Guanzhong basin, SO in the YHC development only to brown soil stage; To subtropical climate, themain reason is that precipitation was lower in the eastern than that in the western Guanzhong basin, evaporation is significantly higher than in the western region.(5) About Climate evolution and regional response in Holocene we get new conclusions as follows:①On themillennium scale,the change trend of the western and eastern part of the Guanzhong Basin is the same:in early-Holocene, the summermonsoon begins to enhance, and the transformation of the soil happens.The climate ofmid-Holocene is themost humid and warmest period in Holocene. The late Holocene, the summermonsoon weakened again, the climate becomes cold and dry. Sensitivity to climate ofinonsoon region. (Din recording climatemutation events in the eastern and the western profile in guanzhong basin, it is sensitive to global change.7670-7200a B.P., was identified at LC profile in the western Guanzhong Basin as the event of the global summermonsoon weakened by the small amplitude cooling, but the extensive regional flood was not caused.4400-3800a B.P. and 3100a B.P. a events recorded in the eastern part of the Guanzhong Basin are sensitive to the flood response of the whole basin.〥uring the period of the new century, the eastern part of the Guanzhong Basin is a little earlier than the eastern part of the Guanzhong Basin. The speed of the summermonsoon retreat is faster in the eastern part of the Guanzhong Basin. The East and Westmonsoons in the Guanzhong Basin are slightly different, with Qinlingmountains stopping themonsoon.The main innovation points of this paper are as follows:On the basis of comprehensive analysis of the first hand experimental data, the R/S fractal dimension analysis of Various environmental alternative indicators, and the mutual verification between different indicators, get the new recognition:①The soil development in Guanzhong Basin is mainly controlled by precipitation, the soil of SO is the strongest in holocene,reached to brown soil and yellow brown soil at LC profile in western Guanzhong basin, SO in the YHC development only to brown soil stage. ②In recording to climatemutation events in the eastern and the western profile in guanzhong basin, it is sensitive to global change.7670-7200a B.P., was identified at LC profile in the western Guanzhong Basin as the event of the global summermonsoon weakened by the small amplitude cooling.4400-3800a B.P. and 3100a B.P. a events recorded in the eastern part of the Guanzhong Basin is the characteristics with the sharp drop in rainfall.