How the Quaternary climatic change affects present hydrogeological system on the Chinese Loess Plateau: A case study into vertical variation of permeability of the loess-palaeosol sequence

This article systematically investigated permeability, porosity, carbonate mass percentage, and magnetic susceptibility of representative loess-palaeosol layers (from L ₁ to S ₄) on the Chinese Loess Plateau, based on analysing a sequence on the Luochuan Yuan (tableland) as a case study. The results of in situ permeability measurements illustrate that average infiltration rate of loess layers is higher than that of palaeosol layers, and that average time for the loess layers to reach quasi-steady infiltration is longer than that of palaeosol layers. In addition, loess layers have higher porosity than palaeosols on average, and it is suggested as a major reason why the loess layers have a higher permeability on average, despite complex nature of different types of the interspaces. Higher porosity (i.e. more interspaces for storing moisture/water) of the loess layers is largely determined by lower intensity of pedogenesis of loess, which is in turn ascribed to the colder/drier palaeoclimatic conditions. The difference of permeability between loess and palaeosol layers facilitates the loess units more likely to be aquifers. In this regard, the Quaternary climatic change theory can make a contribution to hydrogeology of the Chinese Loess Plateau, and the regional climatostratigraphy can be regarded as a baseline for local water resource positioning and revegetation in such a semi-arid area.