Permeability and paleoenvironmental implications of loess–paleosol sequence from Jingyang Loess Plateau

Abstract

Eolian loess in China contains abundant information about paleoclimate evolution, but there have been few studies of the relationship between the changing permeability of loess and the paleoenvironment. To investigate how loess–paleosol permeability responds to climate change, 342 undisturbed soil samples were collected from the Jingyang Loess Plateau in the Guanzhong Basin. Permeability was measured by a TST-55 permeameter and soil microstructures were observed with a scanning electron microscope (SEM). The results showed that: (1) the permeability of the loess layers was higher than that of the paleosol layers; (2) loess–paleosol sequence permeability had a four-stage accumulation history; (3) the degree of permeability anisotropy (DPA) of most of the loess was greater than 1, whereas that of the paleosol layers were less than 1; (4) loess and paleosol microstructures were consistent with the results obtained by permeability, whose changes had been mainly caused by the pedogenesis controlled by the Quaternary climate. The higher permeability of the loess layers was largely the result of lower pedogenesis intensity due to the cold/dry climatic conditions at the time when the sediments were deposited. Conversely, the lower permeability of the paleosol layers was the result of higher pedogenesis intensity under warm/wet climatic conditions. Based on the permeability, DPA, and soil microstructures, we concluded that the gradual uplift of the Qinling Mountains and the changes in the intensity of the East Asian monsoon had played important roles in controlling the evolution of the climate in the Guanzhong Basin. Therefore, loess permeability can reflect Quaternary climate change and provide a new research method for interpreting the characteristics of the Jingyang Loess Plateau.