青藏高原的大气CO_2含量、岩溶溶蚀速率及现代岩溶微地貌

青藏高原是世界上最高、最大和最年青的高原。按照气候地貌学的观点,其干燥和寒冷的气候条件不利于岩溶地貌的发育。笔者在青藏高原上已发现了广泛分布的岩溶微形态。笔者用国际通用的石灰岩圆形切片,在西藏三个不同地点进行了12年的野外溶蚀试验,揭示出青藏高原的岩溶溶蚀速率是全世界最低的,在土层中还产生沉淀现象。通过在青藏高原不同高程上测量大气中CO_2分压,发现P_(CO_2)随海拔高度的增加而降低。在土壤、沉积物和岩石裂隙中的P_(CO_2)也呈现同样的变化趋势。由于CO_2含量直接影响天然水的溶蚀能力,因此可以断定低CO_2浓度是造成青藏高原上现代岩溶过程微弱的重要原因之一。其他主要原因包括干旱和寒冷气候条件。通过对不同微地貌上溶蚀速率的计算和形态分析,可以认为,分布于高原面上的所有岩溶微形态中,现代发育的岩溶微地貌形态仅仅是那些与生物岩溶过程有关的溶痕,其他岩溶微地貌形态可能是全新世温暖期的产物。

CO_(2) Partial Pressure, Karst Dissolution Rate and Karst Micro-landforms on the Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is the highest, largest and youngest plateau in the world. Its arid and frigid cli-matic conditions are not suitable for the development of karst landforms based on the principles of climatic geo-morphology. However, the authors have found many micro-forms of karst features in most of places of the plateau. Therefore, the development of the karst micro-landforms on this plateau needs to be investigated. The international standard tablets for examining limestone dissolution rate have been placed in field for 12 years and the experiment reveals that the karst dissolution rate on the plateau is the lowest in the world. With the refer-ence to the CO2 partial pressures that were measured on different elevations, the authors believe that the lower C()2 pressure on the plateau, which is caused by high altitude, is one of the major causes responsible for the lowest dissolution rate. Other causes include arid and frigid conditions. Based on the results from calculation of the dissolution rates and analysis of karst geomorphology, it can be concluded that the active micro-landforms belong to bio-karst features and the appearance of other micro-landforms may be related to the warm periods in Holocene.