Late Caradoc early Ashgill algal reef mounds.

11 identified reef building genera

Also Webby, pers. comm.:
The 80-m thick reef-bearing interval at Dongzhuang comprises six superposed reefs, the lower, a  large, 30 m-high, wedge-shaped shelf-edge reef, bounded top and bottom by massively bedded, calcarenitic, bank-type deposits, and dominated by 'algal' constituents (Solenopora, Palaeoporella, Ajakmalajsoria), and cyanophytes (Hedstroemia, Girvanella) that contributed mainly a bafflestone facies. Basin-facing, outer flanks of this reef show wedge-shaped talus, up to 30 m thick, with clasts up to 80 mm across.  

The rest of the reefal series comprises back-stepping, partially stacked, patch reefs, dominantly of coral, stromatoporoid and stromatolitic contributors. They have an overall thickness of 40 m and a width of more than 100 m. Corals include rugosan Favistina, and tabulates Paleofavosites, Syringoporella and Halysites. The stromatoporoids are Ecclimadictyon and Clathrodictyon, characteristically sheet-like to more massive. The flanking bioclastic limestones include clasts with pelmatozoan debris, brachiopod fragments, gastropods, bryozoans and 'algae'. All these reefs, except the first which is small (2 m high) and stromatolitic, include corals and stromatoporoids, and they are 3 to 4 m high, with flanking (and enveloping) rudstones. The series appears to represent a shelf-edge complex with back-stepping, asymmetrical form, between a thick rudstone blanket on-shelf, and a narrow rudstone halo to the deeper transgressing shales of slope and basin.	