A morphological analysis of Tibetan limestone pinnacles: Are they remnants of tropical karst towers and cones?

Abstract

Limestone pinnacles on mountain slopes in Tibet were measured for morphological analysis and the results were compared with those from tropical towers and cones on karst mountain slopes of Shuicheng, southwest China. In the form analyses, the symmetric products (P) of Tibetan pinnacles present large differences between individual pinnacles. The plan forms, represented by long/short axes ratios (R L/S), are mostly irregular and scattered and the diameter/height ratios (R d/h) reveal that the Tibetan features could belong to any three cone or tower karst types, according to Balaze's classification of karst towers. The direction of pinnacle development seems to be primarily related to slope aspect and to geological structure. The morphological structure and orientation analyses show that pinnacle development is largely controlled by lithological and stratigraphic conditions. The closed water catchment structure, which is a basic feature in karst areas, has not been found in the limestone pinnacle areas of Tibet. The results of the form and structure analyses for the Tibetan pinnacles differ from those for tropical and subtropical karst areas. Further analysis indicates that Tibetan limestone pinnacles were formed by strong physical weathering under periglacial conditions. Four kinds of morphogenesis of the pinnacles are suggested.