Late paper: Cockpit karst and geological structures in South Yunnan, China

The study area, Xichou County of Yunnan Province, at the mean elevation of 1400 m a.s.l. is located 23° 05’-23°37 ‘ N and 104° 22’-104° 58’ E. and the Tropic of Cancer is through. Topographically, it is higher in the northwest and lower in the southeast. The annual average temperature is 15.9°C and precipitation about 1300 mm a year. The limestone, dolomitic limestone and dolomite with total thickness of 4000 m occupy 72.3% of the total area. Under the function of Yenshan Movement, the carbonate formations have been revolved, folded and fractured. They distribute as the shape of an “ear” striking from NW to NE and EW. The funnels, sinkholes, depressions, stone tee th.fengcong extensively develop in the area. As the clastic rocks distribute besides the carbonate rocks and the surface rivers develop in the southwest and northeast, the middle region of carbonate terrain forms the watershed. The karst geomorpho1ogy is characterized by (1) the large depressions distribute in the waterdivid region and the small one in the two ends of the “ear”; (2)the surface rivers deeply cut down about 200-300 m, the depressions by the river valleys are more than 100 m deep in the northeast, but the rivers in the southwest are shallow, the depressions about 50-100 m deep; (3)the long axises of the depressions and fengcong in the central zone of the carbonate terrain are coincide with the geological structural line as the shape of the “ear”, but in two zones of sides that vertical to the carbonate terrain boundary; (4) the dimention of depressions in pure thick limestone is 1 arger than that in dolomitic limestone; (5) in the watershed area, the uplifting of earth crust causes the rejuvenative fengcong-depressions, while the relic fenglin-p1 ain still remains in the watershed area.