Sitai Fm
Type Locality and Naming
Western North Tianshan. The Sitai Fm was named by Luo Fazuo et al. in 1977 and published by Li Yong'an in 1982. The typical section is on south slope of Kuximugik Mountain (Kusongmuqik Mountain) north of Tamuqi, Xinjiang Weiwuerzhu Zizhiqu (Xinjiang Uygur Autonomous Region). It is the upper-middle formation of the Kusongmuqiek Gr (Kuximuqik Gr).
Synonym: （四台组）
Lithology and Thickness
In the type section, the Sitai Fm is subdivided into three parts. Lower part is composed of uneven interbedding of black medium-thick-bedded limestone, massive limestone, carbonaceous limestone, thin-bedded limestone, locally with siliceous lenses and lumps. Middle part consists of grey (locally white) dolomite, dolomitic limestone, intercalated with chert and brecciated dolomite. Upper part is black, grey dolomite, calcareous dolomite with siliceous bands or lumps. The Sitai Fm is 800 m thick.
Relationships and Distribution
Lower contact
The base is in conformable contact with the underlying Sangequan Fm (lower-middle formation of the Kusongmuqiek Gr).
Upper contact
The top is conformably overlain by the Songshutou Fm (uppermost formation of the Kusongmuqiek Gr); however, this "conformable" is indicated as a major hiatus in deposition; with the entire upper-half of Mesoproterozoic missing.
Regional extent
Western North Tianshan. It is exposed on the south slope near watershed of Kuximuqik Mountain, south of Jinghe County.
GeoJSON
Fossils
Microplants in the lower part are Asperatopsosphosphaera, Pseudozonosphaera etc. The middle bears diverse microplants: Pseudozonosphaera, Trachysphaeridium, Asperatopsosphaera, Zonosphaeridium etc.
Age
Depositional setting
Additional Information
For details on the Kusongmuqiek Gr (Kuximuqik Gr), see Neoproterozoic Erathem chapter of this Stratigraphic Lexicon of China.