Wuchiaping Fm
Type Locality and Naming
The type section is located in the area of Wujiaping Village 12 km to the west of the Nanzheng County Town, Hanzhong Region, Shaanxi Province. It was named by Lu Yanhao in 1956.
Synonym: Wujiaping Fm
Lithology and Thickness
Limestone. Basal part is known as the Wangpo Shale Member, and is composed of variegated bauxitic shale or claystone, intercalated with carbonaceous limestone, bauxite, coal seams and lenticular limestone, yielding plant fossils (phytolites), with a thickness of 2 m. Lower part, known as the Cherty Limestone Member, is composed of medium- and thick-bedded cherty concretion or band-bearing clastic limestones, cherty limestone and cherty layers, with a thickness of 202 m. Upper part consists of massive limestone, with a thickness of 180 m.
The thickness of the formation is commonly of 50-100 m, in the Diebu area of Gansu Province its thickness is of 113 m, and is known as the Dieshan Fm. In the Guangyuan region of Sichuan Province and the Changyang area of Hubei Province the overlying strata are known as the Dalong Fm is less than 100 m thick. In the area of development of the platform-margin beach-facies deposits in the Yunnan-Guizhou-Guangxi region the formation is commonly over 500 m thick, and is composed of light-grey medium-bedded limestone, with its base consisting of claystones or trihydrallite.
On the Yangtze platform region, it is stable in lithology, and is commonly divisible into the Lower Clastic-rock Member and the Upper Limestone Member. In the Guangyuan area of North Sichuan, the Wuxue area of Hubei Province, the Jiujiang area of Jiangxi Province, Northwest Hunan and the Shigan and Guiding areas of Guizhou Province the Clastic-rock Member contains coal seams. In the northern and southern parts of Guizhou Province, the Wuchiaping Fm (Wujiaping Fm) is subdivided into three members (Wang Yu et al., 1963): The Lower Jiyaopo Member, which is composed of medium-, and thin-bedded cherty-bands limestone; the Middle Ganqiao Member or Duansha Member, which is composed of thin-bedded siliceous rocks and claystones, locally containing coal seams; and the Upper Mulaichong Member, which is composed of light-colored thick-bedded limestone, yielding abundant Codonofusiella. The Guizhou Provincial Bureau of Geology and Mineral Resources (1987) had designated the Palaeofusulina-yielding limestone of the Changhsingian Stage to the Mulaichong Member of the Wuchiaping Fm.
Relationships and Distribution
Lower contact
Conformable or a disconformable contact with the light-grey massive limestone in the top part of its underlying Maokou Fm
Upper contact
Conformable contact with the overlying Changxing Fm or the Dalong Fm.
Regional extent
Distributed in the late Permian carbonate platform of the Yangtze region, including south Shaanxi, east Sichuan, Hubei Province, northwest Jiangxi, northwest Hunan and Guizhou provinces.
GeoJSON
Fossils
In the Liangshan Mt. area this formation yields Fusulinids represented by the Codonofusiella zone, Gollowayinella meitienensis zone, Palaeofusulina minima-Nankinella minor subzone; corals represented by the Liangshanophyllum zone; Conodonts as presented by the Clarkina liangshanensis-C. bitteri zone; Foraminifera represented by the Hemigordius wuchiapingensis assemblage; and algae represented by Permocalculus fragilis, etc., belonging to the early stage of the Late Permian Epoch = called "Wuchiapingian stage" (now the international stage)
Age
Depositional setting
It is interpreted as a carbonate platform.
Additional Information