THE KUBUQI DESERT OF CHINA: DUNE LANDSCAPE DUE TO INTERACTIONS BETWEEN FLUVIAL AND AEOLIAN PROCESSES AND HUMAN IMPACT

As the only sand sea occurring in the semiarid regions of northern China, i.e., in the northern part of Erdos Plateau and southern bank of the Yellow River, Kubuqi Desert, 17,000 km² in area deserves particular attention since all other Chinese sand seas are located in arid zones. Our research aims are to date the ages of the dunes, and to examine regional changes of palaeoclimate and the geomorphological processes and triggering factors for the formation of the dune landscape of the Kubuqi. Field investigation has been carried out in the entire desert, and outcrops showing sedimentary changes have been carefully studied in the field. Sand drift potentials in the sense of Fryberger and Dean (1979) were assessed on the basis of wind data from weather stations closest to the study area. Our chronology is based on OSL (Optically Stimulated Luminescence) dating. Palaeoenvironmental indicators, such as contents of total carbon and total organic carbon, magnetic susceptibility and grain size were measured to decipher palaeoenvironmental changes and to understand the nature of this desert landscape. Human impact was evaluated mainly on the basis of descriptions about human activities in historical books. Our results show that most of the dunes are lying on the bedrock landscape and on river terraces and thus the fundamental configuration of the landscape has not been changed by the occurrence of the dunes. Our OSL data, mainly of Holocene age, should not be regarded as the initial chronology of the sand sea because they mostly reflect aeolian activities only along river channels. Although the palaeoenvironmental proxies of sections demonstrate potential deterioration of climate during the late Holocene, we find out that large areas of this sand sea were still used for farming and grazing during some epochs of the last 2000 years. The drying up of flooding plains due to diversion of water from the Yellow River for irrigation has greatly contributed to the extension of the dunes. The abundant fluvial sediments along the Yellow River have been very crucial to the formation of the sand sea. The occurrence of the Kubuqi sand sea suggests that a dune landscape could be formed in semiarid regions in 2000 years if there are sufficient sands and effective winds.