A Study On The Denudation Rate For The Southern Slope Of The Nanling Mountains, China

The Nanling Mountains, also named Wuling, has long been well known among historians and geographers in China. The denomination of Wuling, which means five mountains in Chinese (in fact it is made up of five mountains: the Dayu mountain, the Qitian mountain, the Mengzhu mountain, the Dupang mountain and the Yuecheng mountain), appeared as early as in China's two great ancient works Huainanzi(179～122 B.C.) and Shichi (145～90 B.C.), whereas the denomination of Nanling might first appeared in some literatures of the geographers in the Tang dynasty (618～907A.D). Being an important latitudinal structural system in South China which is mostly made up of NNE strike mountains, its geologic settings complicated and mountains separated, the Nanling Mountains has a great impact on the the hydrology, climate, soil, vegetation and social customs of its both sides. Thus it makes an important geographic boundary in South China and the study on the dedundation rate for the Nanling Mountains is of great significance on the geomorphic evolution.This paper focuses on the denudation rates for the southern slope of the Naling Mountains(110°-116°E, 23°26′-26°20′N) in the past 50 years. Based on the hydrological and sedimentary data on the suspended and dissolved loads from the eastern part (the Dongjiang River valley), the middle part (the Beijiang River valley) and the western part (the Guijiang River and the Hejiang River valleys), we deduced the main erosion process within the river valleys, worked out the regional denudation rate in the past 50 years, and analysed the temporal-spatial variation and distribution of modern denudation rate for the southern slope of the Naling Mountains. Emphases were laid on the correlation between the climate and denudation. Conclusions were drawn as follows: Generally, the weathering rate in the warm-humid tropical zone is 0.025-0.050mm/a. The average of the overall mechanical denudation rates for the southern slope of the Naling Mountains is 0.063 mm/a, among which the mechanical denudation rate of the middle part (0.065 mm/a) is a little higher than those of the estern part (0.059 mm/a) and the western part (0.063 mm/a) and the mechanical denudation rate of the upper reaches is higher than that of the lower reaches; the dissolved rate is 0.021mm/a, 0.039mm/a and 0.049mm/a from the eastern part to the western part respectively with an average of 0.037mm/a., and the ratio of chemical denudation to total denudation is moderate compared with those of China (1～75％) and the world (1.64～98.76％); the average of the overall dedunation rates for the study area is 0.100mm/a and that is lower copared with those of China (0.090～1.426mm/a) and the world (0.020～1.400mm/a).