Xibiehe Fm

It was named by Li Shouqi, Zhao Zeguo et al in 1960 and published in North China Atlas of Paleontology, Inner Mongolia Fascicle (1)(1976). The type and representative section is located along the banks in the lower reaches of Borhantuxibie River, 20 km north of the Bayan Obo Sum (Temple; Township) seat in Darhan Muminggan United Banner, the Inner Mongol Zizhiqu (Su Yangzheng et al, 1983). The reference section is at 2 km south of Gaxun Sum, 6 km southwest of the representative section.

Synonym: (西别河组)

The lithology of the formation can be subdivided into three members. Lower member consists of variedly gray, grayish yellow grit with limestone partings, marl and of conglomerate at the base. Middle member is characterized by varicolored strata, with coarse-grained clastic rock and medium-to-thin-bedded limestone at the lower part, with yellowish pink to purplish red thick-bedded limestone at the middle part and with finer-grained clastic rock and heavily argillaceous limestone at the upper part. Upper member is composed of light-colored quartzose sandstone, medium-bedded limestone and argillaceous limestone, possibly also with reef limestone at the top.

The formation yields rich fossils, such as: conodonts Panderodus, Icriodus angustoides; brachiopods Protathyrisina gashaomiaoensis, Atrypoidea foxi, Linguopugnoides varians, Pinguaella enticlivatus, Conchidium, Spirigerina subquadrata, Cyrtia neimongolensis, Tenellodermis cf. matrix, Howellella koneprusensis, Spirinella; anthozoa Altajia, Diplophyllum caespitosum, Weissermelia lindstromi, Streptelasma, Mucophyllum cf. infundibula, Zelophyllum, Chlamydophyllum, Syringopora gorski, Parastriatopora crassa, Mesofavosites khalfini, Heliolites favotabulatus, Thamnopora, Romingerella elegantula, Favosites yakowlewi, Stelliporella; trilobite Encrinurus nebulosus; as well as stromatopor, orthoceras, gastropod and bivalve, etc.