Baiyunobo Fm

The type section is at area east of the Baiyun Hill in Erjin Qi (98°38′E, 41°35′N), Inner Mongolia. The Baiyunobo Fm was named by Zhu Ciying in 1994.

Synonym: (白云敖包组); The strata equivalent to the Baiyunobo Fm was first named the Baiyunshan Fm by No.2 Gansu Team of Regional Geological Survey in 1976, and was published by Hou Hongfei et al. (1979). The term Baiyunshan Fm was used by Lai et al. (1982), Gansu Bureau of Geology and Mineral Resources (1989) and Inner Mongolia Bureau of Geology and Mineral Resources (1991). But it is the same name with that of a Precambrian unit previously used. According to the historical priority, the present book uses the term Baiyunobo Fm.

Reference section:

The reference section is at Shanhujing in Subei County, Gansu (Inner Mongolia Bureau of Geology and Mineral Resources, 1991).

In the type area, the Baiyunobo Fm is divided into three parts. Lower part is represented by a sequence of muddy siltstone, siltstone, sandy siltstone intercalated with conglomerate, greywacke arkosic sandstone, fine-grained sandstone, andesite, andesitic and dacitic ignimbrite and jasper rock. Middle part is composed of calcirudite, edgewise limestone, clastic rock and limestone intercalated with calcareous sandstone, siltstone and andesite. Upper part is dominated by muddy siltstone.

The middle part yields corals Plasmoporella, Palaeofavosites, Heliolites, Favosites, Brachylasma, Parastriotopora, and Orthophyllum, trilobite Nileus, brachiopods Rostricellula, Sowerbyella and Zygospira.