Leye-Fengshan, A New Applicant of Global Geopark in Guangxi, China

摘要

Leye-Fengshan Geopark in Leye County and Fengshan County in the northwestern Guangxi,China,is in the transitional slope zone from southeastern Yunnan-Cuizhou Plateau to Guangxi Basin. It has an area of nearly 900 km2 in the subtropic monsoon climatic region and in neo-tectonic uplifting area. The geopark exposes Devonian to Neogene carbonate and clastic rocks, including a continuous sequence of Devonian to Permian carbonate rocks more than 3000 m thick. Clastic rocks surround the exposed karst and lots of allogenic water from clastic areas flow into karst areas with S type geological structure and rhombus geological structure,and they developed two big subterranean river systems in karst inlier areas, i. e. Bailang subterranean river system and Poxin subterranean river system with 81.5 km and 162 km long, they controlled the development of karst tiankeng group and very large caves (cave chambers)respectively.There are mainly 4 kinds of geologic formations in Leye-Fengshan Geopark, tiankeng ( great do-lines) ,caves(large cave chambers) ,karst gorge,Fengcong( high cone karst)and poljes. Tiankeng is the great doline with vertical cliffs around, with more than 100m in entrance diameter and in depth;it is mostly related with subterranean river at the bottom of doline. There are 27 tiankengs developed in Bailang subterranean river drainage area, which is the biggest tiankeng group in the world. Of them Dashiwei is the biggest, it is 600×420m in diameter and 613m deep at most,70000000 m3 in volume and 100000 m2 of sub-primeval forest in area. There are more than 100 caves in the geopark, Jiangzhou cave is the biggest,with 42.5km in length, 11400000 m2 in cave floor area and 28.9M m3 in volume. It formed 24 cave chambers with more than 10000 m2 in floor area, Hongmeigui cave chamber is the largest, with 50000 m2 in area,Sunlight cave chamber is the highest,with 365m high at most and 260m high in average. It is the most concentrated cave chambers area in the world for 7 of 23 cave chambers with more than 25000 m2 is here. There are also lots of light through caves and natural bridges;in particular Buliu natural bridge and Jiangzhou natural bridge are the biggest and the second biggest one in span in the world,with 177m and 144m respectively. It features typical Fengcong(cone karst)in the geopark,with about 1000m asl and 150～500m height difference between peaks and depressions,as well as lots of poljes developed between karst area and nonkarst area, for allogenic water from clastic area is more aggressive.