PALAEOPEDOSEDIMENTARY AND ANTHROPOGENIC CHARACTERISTICS IN HOLOCENE LOESS PROFILES OF CHINA

Holocene loess-palaeosol profile is of special importance in loess-based palaeo-climatic studies as it usually serves as the basis for interpreting the eco-environmental conditions under which the older loess-palaeosol sequences were developed. In China, a long agricultural history on the Loess Plateau has caused extensive destruction of natural vegetation cover and led a profound modification on the Holocene loess profiles. Micromorphology, heavy minerals, pollen and soil properties are examined in three typical Holocene loess profiles at three locations along a south-north transect across the Loess Plateau. Results show that the profile consists of a palaeosol layer developed in the middle Holocene, which is underlain by the Malan loess and covered human disturbed fresh loess. The palaeosols were well preserved, consisting of an upper humus-rich (AB) horizon and a clay-rich (Bt) horizon. The humus-rich horizons are intensely weathered, contain precipitated calcitic material derived from the overlying modern loess, and have both high pollen content and diversity. Clay coatings are common in the clay-rich horizons. The pedogenetic types of the palaeosols varied from Ustalfs to Argiustolls and Haplustepts in the USA system along the S-N transect with paleo-bioclimatic pattern of the middle Holocene. The cover layers (Ap horizons) are newly-deposited loess of the later Holocene, 10%-25% of which in the south area was caused by human activities such as application of plaggen manure and irrigation with sediment¨Crich water.