DEVONIAN BIOHERM IN LIUZHAI,NANDAN COUNTY,GUANGXI PROVINCE

The bioherm in Liuzhai,Nandan,Guangxi,occurs in the Middle Devonian Donggangling Formation on the eastern side of the Danchi fault in Guangxi.It is 4500m long and 300m wide,with a maximum thickness of 158m,and is one of the largest hioherms in Guangxi. The bioherm belongs to a barrier reef in the carbonate platform margin facies.It may be divided into the reef slope,reef core,reef base,reef crest, reef flat and reef cap.Rock types include clastic limestone,collapse breccia limestone,spheroidal stromatoporoid skeleton limestone,bioclastic sard-sized limestone,nodular stromatoporoid muddy limestone,coral limestone and micrite. Reef-building organisms are mainly spheroidal and subspheroidal stromatopoids and chaetelids,and the organisms adhering to the reef are corals,brachiopods and echinoderms.In the late Dongganglingian period the growth of the bioherm underwent two major stages and five reef-forming epochs,and by the terminal Dongganglingian time the reef-forming processes ended.