Fangshankou Fm
Type Locality and Naming
The type section is located on the southern slope of the Baijian Mt. 35 km the southeast of Fangshankou, Dunhuang City, Gansu Province. It was named by Zhu Weiyuan and Shen Guanglong in 1977.
Lithology and Thickness
Volcaniclastics and Volcanics. Lower part is composed of purple volcanic breccia, intercalated with pebble-bearing tuffaceous lava, lavatic tuff and tuffaceous sandy shale. Upper part of the formation is composed of grey-green intermediate pebble-bearing lavatic tuff, which has gradually transformed into grey-brown rhyolite. Thickness is over 2517 m.
Relationships and Distribution
Lower contact
Its basal volcanic effusive rocks overlap unconformably onto the upper Carboniferous Series or the lower Permian Series (Jinta Fm )
Upper contact
Unclear contact between it and the overlying strata. Partly coeval with Hongyanjing Gr of clastics in same region (put under it for graphic purposes)
Regional extent
Distributed at Fangshankou to the north of Dunhuang City, Hongliuxia of Anxi County (in the vicinity of Daqi Mt.), and Heishan of Minqin County. While easterly entering the territory of the Jilin Desert of Badan County there occurs already intermediate-acidic lava, with a thickness of over 2743 m.
GeoJSON
Fossils
Lower part of the formation yields plant fossils (phytolites) such as Callipteris altaica, C. zeilleri, Fascipteris sp., Pecopteris cf. anderssonii, Cordaites cf. principalis.
Age
Depositional setting
It is interpreted as continental intermediate-acidic effusive rocks.
Additional Information