Benbatu Fm

The type section is located at Saihan Gobi (i.e. Benbatu), Sonid Left Banner, Inner Mongolia. It was named by Ding Yunjie et al. in 1960.

Sandstone, Limestone and Volcanics. It is dominated by variegated clastic rocks intercalated with intermediate-basic volcanic rock and limestone. It consists of 5 members, which are ascending: Member 1, gray-green feldspar-rich sandstone, quartzite and organic limestone; Member 2, dominated by purple-red clayey slate, intercalated with sandstone and limestone; Member 3, dark-gray and black clayey-sandy limestone intercalated with conglomerate; Member 4, intermediate-basic volcanic rocks intercalated with limestone; Member 5, dominated by gray-green feldspar-rich sandstone, intercalated with limestone and sandy limestone, with purple or variegated conglomerate at bottom. Total thickness is 1962 m.

Among them, members 2, 3 and 4 are continuous sedimentation; Member 1 is represented by the Baoerhaolai section of Siziwang Banner; members 2 and 3 by the Baiyin’aobao section of Sonid Right Banner; members 3 and 4 by the Ganjuelingtala section of Sonid Left Banner; Member 5, by the Mihangao-qiaogaolu section of West Ujimqin Banner.

Member 1 is represented by an assemblage of Fusulinid Eostaffella−Brachipoda Choristites, associated with Corals Amygdalophyllum sp. and Suziyamaella sp., and also foraminifers, etc.; Member 2, represented by the Fusulinid Pseudostaffella−Profusulinella zone; members 3−5, by the Fusulinid Fusulina−Fusulinella zone, including Corals Caninia nosovi, Hillia intermedia, Rotiphyllum sp., as well as brachiopods, bryozoans, etc.

It is interpreted as dominated by the deltaic facies, intercalated with volcanic eruptive facies and normal neritic facies, with marine-continental sediments locally found in the western part, yielding plant fossils.