CO2 partial pressure, karst dissolution rate and karst micro-landforms on the Qinghai-Tibet Plateau

Abstract

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.

青藏高原是世界上最高、最大和最年青的高原。按照氣候地貌學的觀點,其干燥和寒冷的氣候條件不利于巖溶地貌的發育。筆者在青藏高原上已發現了廣泛分布的巖溶微形態。筆者用國際通用的石灰巖圓形切片,在西藏三個不同地點進行了12年的野外溶蝕試驗,揭示出青藏高原的巖溶溶蝕速率是全世界最低的,在土層中還產生沉淀現象。通過在青藏高原不同高程上測量大氣中CO2分壓,發現PCO2隨海拔高度的增加而降低。在土壤、沉積物和巖石裂隙中的PCO2也呈現同樣的變化趨勢。由于CO2含量直接影響天然水的溶蝕能力,因此可以斷定低CO2濃度是造成青藏高原上現代巖溶過程微弱的重要原因之一。其他主要原因包括干旱和寒冷氣候條件。通過對不同微地貌上溶蝕速率的計算和形態分析,可以認為,分布于高原面上的所有巖溶微形態中,現代發育的巖溶微地貌形態僅僅是那些與生物巖溶過程有關的溶痕,其他巖溶微地貌形態可能是全新世溫暖期的產物。