Evolution and palaeoceological significance of the paleobiocoenosis from the Upper Ordovician strata in the Shun-6 well, central Tarim Basin

The paleobiocoenosis from the Upper Ordovician strata in the Shun-6 well, central Tarim Basin are grouped into five types:cyanobacteria community, Hedstroemia-problematicum-Tetradium community, Tetradium-Hedstroemia community, Tetradium-Solenopora community and echinoderm community. Three reef communities include cyanobacteria community, Hedstroemia-problematicum-Tetradium community and Tetradium-Hedstroemia community. The cyanobacteria community lived on the deep-water mud mounds on the platform margins. The Hedstroemia-problematicum-Tetradium community and Tetradium-Hedstroemia community lived in the shallow-water organic reefs on the platform margins. The rare Solenopora community and echinoderm community lived on the platform-margin banks. The mud mounds, Tetradium framework reefs and Hedstroemia reefs have abundant dissolution pores, but all the pores are filled with sparry calcite. There are residual pores in the bioclastic limestones of the bank facies, which has the potential to form the hydrocarbon reservoirs.