Landscape and quaternary climatic changes in eastern Tibet and surroundings

Abstract

Co-operation between Chinese and German geo-scientists in Tibet and adjacentareas started in 1981 with the Sino-German Joint Expedition to the Northeastern part of the Qinghai-Xizang (Tibet) Plateau, led by Prof. Dr. Jtirgen H6vermann (G6ttingen) and Prof. Wang Wenying (Lanzhou/Xian). Later several further Sino-German Joint Expeditions were conducted in China. The editors had the opportunity of participating in one of these expeditions to Tibet in 1989 led by Prof. J. H6vermann and Prof. Li Jian (Chengdu). Based on this expedition further detailed investigations, especially in geomorphology, palaeoclimate and applied geomorphology along the eastern margin of the Tibetan Plateau, were made in summer 1991. In this volume results from this 1991 expedition (inside rectangle of Fig 1) as well as from the 1989 and 1992 expeditions (outside rectangle of Fig 1) are presented. The 1991 expedition was led by Prof. Tang Bangxing, Dr. Liu Shijian and Dr. F. Lehmkuhl, altogether six Chinese and two German scientists participated (including: Prof. Li Jian, Prof. Wang Chenghua, M. S. Li Lihua, M. S. Wang Yangchung and Dipl.-Geogr. B. Damm). Since 1989 there has also been close co-operation between the Institute of Geography of G6ttingen University, the Institute of Botany of Hohenheim University (Prof. Dr. Dr. B. Frenzel) and the Institute of Mountain Disasters & Environment (Chinese Academy of Sciences) in Chengdu. This group, too, has conducted an expedition in 1992, led by Prof. B. Frenzel and Prof. Tang Bangxing, in which the editors could also participate. The main investigation area of 1991 was the Nianbaoyeze Mountains and the adjacent areas at the margin of northwestern Sichuan Province and Qinghai. The highest peak of Nianbaoyeze (5369m) is about 800m above the surrounding peneplain. Pleistocene glacial landforms are well preserved, a few glaciers still exist. An introduction to physical geography with special reference to the Pleistocene glaciations in the eastern fringe of the Tibetan Plateau, of the Nianbaoyeze Mountains in particular, is presented by F. Lehmkuhl and Liu Shijian. Palaeo-surfaces and the history of the upper Huang He valley are analysed by F. Lehmkuhl and J. Sp6nemann. Mountain disasters were another goal of investigation. Tang Bangxing, Liu Suqing and Liu Shijian have studied debris flows and their distribution at the Minjiang throughout the catchment and in other regions in western Sichuan. Liu Shijian examines the impact of debris flows on quartz-grain surfaces, and discusses this method as a possibility to separate debris flow from morainic deposits. J. B6hner describes southeastern Tibet and the adjacent areas with respect to the varying climatic circulation. N. Niehoff contributes on the chemistry of the precipitation in this area (results of the 1992 expedition). A. Br/iuning presents observations from tree ring analysis (samples from the 1989, 1991 and 1992 expeditions) with regard to the climate of the historical period. The palaeoclimate of eastern Tibet is shown in a larger context with some results from Western and Central China. H. J. Pachur, B. W/.innemann, Linyuan Zhang, Hucai Zhang and Yuzheng Ma focus on floodplain sediments in the transition zone to the Loess Plateau near the divide between the Huang He and Yangtze river systems (see No. 1 in Fig 1). Finally, K.T. Rost focusses on palaeoclimate conditions of the Qinling Mountains and their foreland facing the Loess Plateau (No. 2 in Fig 1). The editors wish to express their sincere thanks to Prof. Dr. J. H6vermann for his effort to initiate these expeditions in Central Asia, for his support and for frequent stimulating discussions. We would like to thank not only the authors for their contributions but also the Chinese Academy of Sciences, the Deutsche Forschungsgemeinschaft, the Max-Planck-Gesellschaft and the Gesellschaft ftir Technische Zusammenarbeit for their financial support. We have to thank all members of the expeditions, including the technical and administration staff, the drivers, Tibetan horse guides etc., for the good co-operation and their help during the various expeditions.