Qingmen Fm
Type Locality and Naming
The type section is located at gully Bianqinggou of Qingmen Village, Ludian County of Chaotong city. Yunnan Province. It was named by Guizhou Petroleum Team in 1974 and is defined as a set of siliciclastic dominated deposits between Pojiao Fm bearing-Rostrospirifer tonkinensis Yunnan. Later, they were subdivided into some independent lithostratigraphic units, respectively as Chaotong Fm, Suotoushan Fm, Qingmen Fm and Bianjinggou Fm (Yun Y., 1978; Liao et al., 1979; Xian & Zhou, 1974; Xian, 1988). These stratigraphic names were clarified and clean up during the re-compilation of Yunnan lithostratigraphy in 1996 (Zhang Yuanzhi ed.), only the Qingmen Fm and Suotoushan Fms are kept.
[Figure Map showing the location of stratotype of Qingmen Formation (red line).]
Lithology and Thickness
Claystone and limestone. The formation can be roughly subdivided into two parts. Lower part, 67 m thick, consists of yellow-green and yellow-gray mudstone, sandy mudstone, intercalated with thin-bedded or lenticular limestone, and siltstone, containing relatively abundant brachiopods and tabulate corals. About 10 m thick medium- to thick-bedded limestones are at base. Upper part is dominated by the interbeds of gray-green and purple red mudstone, clayey banded limestone, 46.8 m thick, containing brachiopods and corals.
Relationships and Distribution
Lower contact
The conformable lower boundary is at the base of a 10-m thick gray medium-thick bedded limestone, which differs from the brownish-yellow thick-bedded sandstone of the underlying Pojiao Fm..
Upper contact
The upper boundary is marked by a change from yellow and yellowish-green mudstone to the thick-bedded pure quartz sandstone of overlying Suotoushan Fm.
Regional extent
The Formation is mainly distributed in the Chaotong area and extend eastward to Yiliang and Zhenxiong area.
GeoJSON
Fossils
The lower part yields abundant Brachiopods Euryspirifer sp., Nadiastrophia zhaotongensis, corals Squameofavosites wagranensis, Favosites shengi minor, F. goldfussi, Squameofavosites sp., Pachyfavosites sp., Yacutiopora bianjinkouensis, Thecostegites sp,. Calceola sp., Pseudozonophyllum sp. and few trilobites and bivalves. Some brachiopods of Kwangsia cf. yohi, Nadiastrophia sp. and corals Utaratuia cf. laevigata, Xystriphyllum sp., etc. have been reported from the upper part.
Age
Depositional setting
It is interpreted as a shallow nearshore deposits with partial lagoon condition.
Additional Information