Reef complex of various reef types stacked. Largest reef is R6, which is 19 m thick.
Cumulative thickness is 30 m

Built mainly by the colonial rugose coral Thysanophyllumand the bryozoan Fistulipora, and less frequently by Syringo-pora (tabulate coral) and Lithostrotion (colonial rugose coral). Reef-dwellers include crinoids, brachiopods,solitary rugose corals, cryptostome bryozoans, foraminifers, gastropods, ostracodes, and green algae.Reefal units show four growth stages with the predominantframeworks of Thysanophyllum, Fistulipora, Thysanophyllum,and Fistulipora-Thysanophyllum, intercalated with intraclastic-crinoidal or crinoidal bank facies. The reef-crest is composedof gray thick-bedded algal peloidal packstones, fine bioclasticwackestones interbedded with brachiopod grainstones and pack-stones. The reef was formed at shallow isolated platform marginand died resulting from relative sea-level fall and rise respec-tively, which may be caused by regional rift activities. At Xiadong village, Langping, reef is about 260 m wide and 50 m thick andthe major reef-builders are colonial rugose corals (Diphyphyl-lum, Siphonodendron, and Lithostrotion), and the tabulate coralSyringopora. Reef-dwellers are solitary rugose corals, crinoids,ostracodes, brachiopods, gastropods, bryozoans, and calcareous algae.