A regional aridity phase and its possible cultural impact during the Holocene Megathermal in the Guanzhong Basin, China

Evidence of climatic variations and the impact of past farming was identified in a Holocene loess profile near Xi'an in the Guanzhong Basin, China. Detailed studies of the profile indicate that crop cultivation began at 7000 yr BP in the Neolithic and carried on to present in the area. Disturbance of the profile by cultivation has not masked evidence of changes in aeolian dust deposition and bio-pedogenic processes caused by climatic variations. Increased dust deposition indicates that a remarkable aridity phase occurred from 6000 to 5000 yr BP during the Holocene Megathermal (8500-3000 yr BP). The aridity and intensified aeolian dust deposition interrupted the formation of the brown soil developing under a warm-humid subtropical climate during the Megathermal. The palaeosol S-0, normally associated with the Megathermal period, is thus separated into two distinct soils, namely S-0(1) and S-0(2). This variability in Megathermal climate may have been widespread across northwestern China. It is also possible that the marked decline in Neolithic culture in the periods of the middle and late Yangshao Culture (6000-5000 yr BP) in the Guanzhong Basin can be attributed to the climatic aridity at the time.