Environmental change during the Holocene in western China on a millennial timescale

Recent data on the evolution of the inland lakes, loess-palaeosol sequences, and glacier variations in western China are briefly reviewed. The lake history shows three distinct stages in the Holocene, i.e., low water levels before 7500 BP, a stage of expansion during the climatic optimum between 7500 and 3500 BP, and contraction after 3500 BP. Three stages (wooded grassland, mixed woodland, wooded grassland becoming steppe) also appear indicated by the Holocene loess/palaeosol sequence in the Lanzhou region, the optimal period for soil development being between 7500 and 3500 BP. There were seven periods of glacier advance: the continental glaciers advanced at about 8300, 5700, 4000, and 400 BP in northwestern China and the maritime glaciers advanced at about 3000, 2000, 1000, and 200 BP. It is suggested that the climatic changes show two periodicities during the Holocene, namely at intervals of about 2500 and 1000 years.