Holocene pedostratigraphic records from the southern Chinese Loess Plateau and their implications for the effects of climate on human civilization

The relationship between Holocene climate change and the evolution of civilizations, both in China and elsewhere, is of increasing research interest. Here we present the results of a study of the particle size, CaCO3 content, magnetic susceptibility, and soil microstructure of the Holocene paleosol and loess sequence at the sites of Luochuan and Lintong in the southern Chinese Loess Plateau. The results reveal that the paleosol in the late stage of the mid-Holocene is less developed than that in the early stage, and that the corresponding average annual precipitation was at least 100 mm higher than today, due to the enhancement of the summer monsoon. Climatic deterioration occurred in the middle stage of the mid-Holocene, during 6000-5000 yr BP, which was the coldest and driest stage. Four stages of monsoon change occurred in the study area during the Holocene: at 8500, 6000, 5000, and 3100 yr BP. They enable the following climatic subdivision of this interval: three cold and dry periods with enhanced winter monsoon and dust storm activity, and two warm humid periods with a strong summer monsoon and weak dust storm activity. The transformation of the monsoon climate since 3100 yr BP indicates that the modern interglacial period, compared with the last interglacial, is not typical and possesses some of the characteristics of cold and dry climates. The observed pattern of climate change since the mid-Holocene has substantially affected the development of civilization in the region. This is manifested by the frequent migration of ancient capitals caused by the onset of a cold and dry climate: the location of capitals shifted from high altitudes in the Loess Plateau to loess tableland areas on the lower altitude plains, including to the first terrace in the low-altitude plain and then to the moderately-high second terrace of the Wei River. Our results contribute to an improved understanding of the climatic drivers of human civilization in China and provide a basis for predicting future environmental changes in the region.