Keywords: 
• reef

Abstract: Since the reefs and banks were found as significant reservoirs from the Upper Ordovician Lianglitag Formation, Tazhong Slopebreak I, debate on the reef aspects of morphology, magnitude, etc. still exist. We analy the regional reef biotic components, community structures and sedimentary backgrounds, and furthermore, synthetically interpret the reef sedimentary successions. Reefs are classified as the catalogues of coralframework reef, stromatoporoidlithisid spongia framework reef, lithisid spongia stromatoporoid framework reef, algae stromatoporoid framework reef respectively based on their biotic differentiations. These reefs differ from the former cases such as the stromatolites of the Precambrian, archeaocyathus reefs of the Cambrian, Calathium reefs of the Early Ordovician as well as the carbonate mudmounds of the Early Ordovician ecologically and lithologically, marked by their higher biodiversity, more complex of the ecological characteristics and magnitude. The reefcomplexes are generally more than tens meters showing in the frillcores. Reefs and banks stack horizontally and vertically. Therefore, extensions of the reefs and banks enhance the widespreading of the reefcomplexes along the Slopebreak.