Micromorphological evidence of pedogenesis and paleoclimatic change in the Holocene loess-paleosol in the south Qinling Mountains, China

摘要

Micromorphological investigations of loess-paleosol sequence offer the potential for understanding pedogenic and paleoclimate change at the microscopic scale. However, the micromorphological study is comparatively scarce in the south Qinling Mountains, China. Here, micromorphological analysis (coarse particles, pedofeatures and voids) in conjunction with physicochemical indexes of pedogenesis (i.e., clay content, CaCO3 and Fe2O3) were carried out from two Holocene loess profiles in the upper Hanjiang River. These results show that: (i) Paleosol is considered as strongly-developed soils on basis of much finer and rounder particles, channels, more reddish color and abundant illuvial clay coatings; (ii) Lessivage (clay formation, eluviation and illuviation), intensive carbonate eluviation and rubification were identified as the major pedogenic processes of paleosol; (iii) Comparative study with Chinese Loess Plateau (CLP) indicates that loess deposits in the south Qinling Mountains experienced a much stronger pedogenesis as evidenced by multiple generations of illuvial clay and almost completely eluviation of carbonate, which implies a warmer and wetter paleoclimate in the subtropical monsoon zone. The pedogenic differences across the Qingling Mountains are mainly controlled by regional paleoclimatic differences and provide a good response to monsoon climate change in the East Asian.