Tianjingshan Fm
Type Locality and Naming
The type section is on Tianjing Hill in Zhongwei, Ningxia. The Tianjingshan Fm was named by Ningxia Party of Regional Geological Survey in 1963, and was published by Ningxia Compiling Group for Regional Stratigraphic Scale (1980). In 1990, Ningxia Bureau of Geology and Mineral Resources divided it into lower Xialingnangou Fm and upper Tianjingshan Fm, which are separated by a calcareous slate generally developing in the dolomitic limestone or dolomite in the previously defined Tianjingshan Fm.
Synonym: (天景山组）
Lithology and Thickness
The formation is composed dominantly of gray thick-bedded argillaceous limestone, nodular chert-bearing and banded dolomitic limestone and limestone of enclosed platform to open shelf environment. In the type area, the Tianjingshan Fm is 1015 m thick.
Relationships and Distribution
Lower contact
It rests conformably on the dolomitic limestone of the Xialingnangou Fm. In Tianjing Hill, Mibo Hill and Yantong Hill, the lower part is cut by fault, and with a covered lower boundary.
Upper contact
It is conformably overlain by the slate at the base of the Miboshan Fm
Regional extent
With a persistent lithology, the Tianjingshan Fm varies considerably in thickness along the length of its outcrop. In Yantong Hill, it recorded an incomplete thickness of 950 m, and it is 1015 m thick on Tianjing Hill in Zhongwei, 914 m thick at Dananchi in central segment of Helan Mountain, 293 m thick in Qianggangling and 417 m thick in Xialing nangou of Ningxia. In some areas of Alxa Youqi, Inner Mongolia, there are also the strata of the Tianjingshan Fm (Ningxia Bureau of Geology and Mineral Resources, 1990). The Zhongliangzi Fm of Huo et al. (1989) and Qianzhongliangzi Fm and Zhongliangzi Fm of An et al. (1990) in Zhongliangzi in Helan Mountain are equivalent to the Tianjingshan Fm.
GeoJSON
Fossils
This stratigraphic unit yields cephalopods, trilobites and brachiopods. In Zhongliangzi in Helan Mountain, the conodont fauna includes lower Serratognathus-Bergstroemognathus assemblage and upper Aurilobodus leptosomatus-Loxodus dissectus assemblage (An et al., 1990).
Age
Depositional setting
Enclosed platform to open shelf environment
Additional Information