Acta Geographica Sinica ›› 1982, Vol. 49 ›› Issue (2): 123-135.doi: 10.11821/xb198202002

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AN ANALYSES ON THE PALAEOGEOGRAPHIC ELEMENTS OF KARST DEVELOPMENT IN THE WUMIN BASIN, GUANGXI

Lin Jun-shu1, Zhang Yao-guang1, Wang Yan-ru1, Zhao Zhong-ru2   

  1. 1. Institute of Geography, Academia Sinica;
    2. Museum of Guangxi Zhuang Autonomous Region
  • Online:1982-04-15 Published:1982-04-15

Abstract: By analysing the distribution of caves and terraces, the lithology of sediments, the ancient vertebrate fossils and sporo-pollens in the Wumin Basin, the conclusions may be drawn as follows:1. During the tertiary, the Wumin B.isin was under erosion-denudation condition. The present peak-top planation surface of 230-300 m above the sea level represents an old peneplain. In the Quaternary, the basin with its current Karst features was gradually developed.2. In the Quaternary, the paleoclimate experienced several great fluctuations with humid-hot conditions alternating with dry-cool climates. For instance, the accumulation of Gigantopitheeus fauna fossils in the Ganxu Cave in the early Middle Pleistocene, as well as Elephas maximus fossils and Liqidamber-Polypodiaceae-Ptcris-Cyatheaeeae monsoon forest sporo-pollens complex in the late period of Late Pleistocene, all reflect a humid-hot environment.3. The rhythemic variations of the paleoclimate eventually lead to an unbalance of corrosion intensity. In addition, the base-level fluctuation which were resulted from the neotectonic movements and the global paleoclimatic variations resulted in an obvious differntiation of Karst development intensity both temporal and spatial. The stratified caves in different level bear evidence to such a process.4. As the latitude in the Wumin Basin being rather low, the duration of humid-hot periods has been longer and, when entering into the dry-cool periods, the ampli-tude of temperature lowering has been less conspicuous. These are very favorable for corrosion action. For example, the corrosion-denudation intensity in the Elephas-peat accumulated period (about 30000-40000BP. as dated by C14 and corresponding to a sub-interglacial stage of W黵m glaciation) was more than double that of present to-day.Consequently, the "peak-forest" (Fenglin) landscape in the Wumin Basin is a typical tropical karst topography, which has undergone repeated humid-hot environ-ments since the Quaternary. To a certain extent, it represents the case nearby the tropic of cancer in South China.From this, it may be seen that the palaeogeographic conditions are a basic evi-dence to study the development of the karst geomorphology and exogenic process, as well as to divide the basic karst geomorphologic types.