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Topsoil magnetic susceptibility properties of Mu Us Desert in northern China and its environmental significance

Xiaokang Liu 1 ,2, Ruijie Lu1 ,2, Feifei Jia3, Jing Du1 ,2, Zhiqiang Lv1 ,2, Tengfei Li1 ,2, Lu Chen1 ,2, Yuzhen Ma1 ,2, Yongqiu Wu1 ,2
1MOE Key Laboratory of Environmental Change and Natural Disaster, Beijing Normal University, Beijing, China, 2State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing, China, 3School of Urban and Environmental Sciences, Liaoning Normal University, Dalian,liaoning province, China

In extensive arid and semi-arid regions, the magnetic susceptibility of modern soil is mainly influenced by regional precipitation. It has been found that there was a relatively significant positive correlation between frequency magnetic susceptibility (ᵡfd) and mean annual precipitation (MAP) within a certain range. Here we select two cross-sections (Z1 and Z2) along with the variation gradient of rainfall from Mu Us Desert in northern China and collect 110 topsoil samples to discuss the spatial characteristic of magnetic susceptibility as well as its environmental significance. Along Z2 section we observe that there is no systematic trend and the ᵡfd value remains relatively stable and low, which possibly relates to weakly pedogenic process in regional rock-dependent provenance. In contrast, the pedogenic degree as estimated by ᵡfd in Z1 section appears to be controlled by rainfall and exhibits a positive correlation trend between ᵡfd and MAP. On the basis of this relationship, we construct a transfer function (P=275.63+1500.77ᵡfd,R2=0.55) and employ this function to estimate quantitatively paleo-precipitation for the four Holocene aeolian sections which locate at the southern boundary of modern Mu Us Desert. Results show that variation of reconstructed precipitation is consistent with the change of lithologic property well, and it also confirms the previous study opinions from the side that the development of paleosol is dominated by precipitation in our study area. Further, based on regional comparisons, it has proven the feasibility of using frequency magnetic susceptibility to reconstruct regional paleo-precipitation. This is a useful attempt to estimate paleo-precipitation quantitatively in geographically diverse desert area and assists in the better understanding of the main material source in Mu Us Desert.