Sunjiagou Fm

The type section is located at Sunjiagou, Ningwu County, Shanxi Province. It was named by Liu Hongyun et al., in 1959.

Siltstone and Marl. The formation in the region of Taiyuan City of Shanxi Province is composed of purple and grey-purple siltstones, intercalated with two layers of medium-, and fine-grained yellowish-pink and purple feldspar-rich sandstones, with its lower part being intercalated with several bands of blue-grey marls, and with the siltstones in its middle and upper parts containing calcareous concretions, with a thickness of 81.5 m.

In the southeastern part of the North China Massif the formation is divisible in ascending order into the following three members: namely the Pingdingshan Sandstone Member, the Marl Member, and the Gypsum & Calcareous Concretions Member. The marl (commonly known as the fresh-water limestone) and gypsum represent fairly important marker horizons for the formation, and are commonly found to occur only in the areas to the south of Taiyuan City, and the further to the north, the less they are developed. And in the areas of Southeast Shanxi, North Hebei, Northwest Henan, East Henan, Huainan and Huaibei Cities they have changed into limestone lenses, calcareous concretions and fibrous gypsum bands.

The Sunjiagou Fm yields Plant fossils (phytolites) represented by the Rhipidopsis lobata-Ullmannia aff. Bronnii assemblage. In the Liulin and Linxian Counties of Shanxi Province, and the Yiyang and Jiyuan Counties of Henan Province there had been discovered 30 genera and 44 species of plant fossils (phytolites) in what is known as the Ullmannia bronnii-Yuania magnifolia assemblage. Among the Spore-pollen fossils of the formation it is the gymnosperm pollen (including pleridosperm) that is the primary one, of which the bivesiculate pollen is predominant, including Cordaitina, Alisporites, Vitreisporites, Illinites, Protohaploxypinus, Taeniaesporites, Lueckisporites virkkiae and Jugasporites, etc. In the area of the Pingding Mt. together with the spore-pollen fossils there occur also Acritarch fossils such as Baltisphaeridum, etc.

In the Yiyang and Yongcheng areas of Henan Province the formation yields such bivalve fossils as Anthraconaia sp., Abiella sp., Pisidiidae, etc.; Gastropoda fossils represented by Planorbis sp., etc. In the Fengfeng area of Hebei Province and the Yongcheng area of Henan Province the formation yields Ostracod fossils such as Panxiania, Darwinula, etc. In the area of Pingding Mt. both of the second and the first members of the formation yield the Lingula sp. of the brachiopod fauna fossils.

The Vertebrate fossils are found to occur at the top of the Sunjiagou Fm in the Baode area of Shanxi Province, comprising such as Shihtienfenia permica, with the lower part of the Sunjiagou Fm in the Liulin area of Shanxi Province yielding Shansisaurus xuecunensis, Sanchuansaurus elaphrosis, Huanghesaurus liulinensis, etc.; the Sunjiagou Fm in the Lishi area of Shanxi Province yields Pareiasauridae cf. sutosaurus, Shihtienfenia permica, etc.

It is interpreted as basically continental deposits, with the brackish deposits, or locally the marine deposits being found to occur only on the southern margin of the region.