Reef facies 90 m thick.

Abstract of ref. 208:
Permian reefs are widely distributed in the so-called Nanpan Jiang (Nanpan River) region in the neighboring parts of eastern Yunnan, southwestern Guizhou and northwestern Guangxi. Two types of reef occurrences are recognized by their stratigraphic and geographical distributions, 1) a barrier reef belt along a carbonate platform margin and 2) reefs that rim isolated carbonate platforms that occur irregularly within basin facies deposits. The Guangnan reefs of lower Permian age occur within the barrier reef belt and are typical of reefs within the Nanpan Jiang area. These reefs are well-exposed at Dongnameng, a small village about 5 km southeast of Guangnan City and crop out on the west flank on the Guangnan anticline which has been truncated by a major fault. Basin facies deposits occur east of the fault and equivalent carbonate platform deposits occur west of the fault. A succession of reefs  occurs in the late early Permian Maokou Formation and early late Permian Wujiaping Formation. The top of the upper Permian sequence is cut out by faults on the Guangnan anticline and elsewhere is directly overlain by middle Triassic rocks. The preserved upper Permian part may be equivalent to the Wujiaping Formation. The major time of reef development, however, was during early Permian. The reefs have foundations of light gray, thick-bedded, intraclastic-bioclastic grainstones that contain abundant fossils of shallow-water benthic organisms. These limestones represent subtidal bank deposits at the platform margin and functioned as foundations for most of the Permian reefs in the Nanpan Jiang area. Reef limestones consist of light gray, massive, framestones with distinctive textures and abundant fossils. Frame-building organisms are sphinctozoans, inozoans, tabulozoans, bryozoans and hydrozoans. Frame-building organisms total 40-50% of the volume of the reef  masses. Binding organisms are dominantly blue green algae, with subordinate fistuloporid bryozoans and Tubiphytes. Accessory organisms include echinoderms, fusulinids, gastropods, brachiopods, calcareous algae and foraminifers as skeletal debris. The frame-building organisms are generally encrusted by lamellar blue-green algae, which commonly are incorporated fine-grained skeletal fragments. Well developed fibrous calcite cement fills between frame-building organisms to form a typical framestone texture. Gray, thick-bedded, bioclastic packstones and wackestones overlie the  reefs. This stratigraphic relationship suggests that reefs were drowned and that reef development ceased because of the increasing depth. Twelve species of 8 genera of sphinctozoans are described in the present paper. These include: Waagenella salinaria irregularis Zhang, Waagenella sp., Rhabdactinia cf. columnaria Yabe and Sugiyama, Rhabdactinia sp., Intrasporeocoelia hubeienisis Fan and Zhang, Intrasporeocoelia sp., Uvanella guangnanensis sp., nov., Girtycoelia sp., Colospongia cf. dubia Laube, Colospongia sp., Verticillites sp., Lichuanospongia typica Zhang, and of these Uvanella guangnanensis is a new species. Two sizes of sphinctozoans can be differentiated in the collections. The smaller genera include Waagenella, Colospongia, Girtycoelia, and Uvanella. They also make up smaller volumes of the reefs, as compared to the larger forms such as Intrasporeocoelia and Rhabdactinia. The large sphinctozoans are abundant and baffled lime muds during growth of the reefs. All of the sphinctozoans mentioned above also occur in upper Permian reefs of the Lichuan district of west Hubei Province but the diversity in the Nanpan Jiang reefs is much less that in reefs  in the Lichuan district. The sphinctozoan faunas Guangnan may be compared with those of lower Permian reefs in the Bled distric of Yugoslavia. 