Miaopo Fm
Type Locality and Naming
The type section is at Miaopo in Fenxiang 17 km northwest of Yichang City, Hubei. The reference section is at Huanghuachang 5 km northwest of Yichang City (Zeng et al., 1983). The Miaopo Fm is derived from the Miaopo Shale proposed by Zhang Wentang in 1957.
In 1962, Zhang Wentang renamed the Miaopo Shale first the Miaopo Shale Fm then the Miaopo Fm. Wang Xiaofeng et al. (1980) suggested that the upper boundary of the Miaopo Fm coincides roughly with that of the Climacograptus peltifer zone. In 1983, Zeng Qingluan et al. studied in detail the lithology and fauna of the Miaopo Fm.
Synonym: (庙坡组）
Lithology and Thickness
The formation is composed of yellow, dark gray or yellowish green hydromica claystone intercalated with thin-bedded limestone. In the type area, the Miaopo Fm is 2.5 m thick.
Relationships and Distribution
Lower contact
On the incompletely developed upper Pygodus serra subzone and the manganese nodules occurring on the discontinuity, the Miaopo Fm rests disconformably on the nodular limestone of the Guniutan Fm
Upper contact
It is conformably overlain by the limestone with polygonal cracks at the base of the Baota Fm
Regional extent
With a persistent lithology, the Miaopo Fm is restricted to Chengkou (2.7 m thick), eastern Gorge area (2.2-2.6 m thick) of Sichuan, and Hexian (1.8 m thick) of Anhui. In Hexian, no graptolite of Nemagraptus gracilis assemblage and conodont of Pygodus anserinus assemblage and Prioniodus alobatus assemblage have been found from the Miaopo Fm, indicating an upper boundary lower than in the type area.
GeoJSON
Fossils
At the three Gorges district, the Miaopo Fm includes graptolite Husterograptus teretiusculus zone, Nemagraptus gracilis zone; conodont Pygodus serra zone, Pygodus anserinus zone, Eoplacognathus yianyeensis zone Prioniodus alobatus zone; cephalopod Lituites-Tridacinoceras zone; trilobite Birmanites-Telephops zone, in ascending order. Ge Meiyu (1957) and Mu Enzhi (1959) studied the graptolite from the Miaopo Shale.
Age
Depositional setting
Additional Information