Fangmachang Fm
Type Locality and Naming
The type section is located to the west of Fangmachang area, Daba District, Zhada County, Tibet (E 79°55′, N 31°15′); with its reference section being situated in the Chaga Gully, Bolin District, Zhada County, Tibet (E 79°30′, N 31°20′). It was named by the Regional Geological Survey Party under the Tibetan Geological Bureau in 1987.
Synonym: （放马场组）
Lithology and Thickness
Composed of black and grey-black silty shale, intercalated with fine-grained sandstone, black shale and black silty shale, with the shales being rich in calcareous concretions. Its thickness is of 580 m.
Relationships and Distribution
Lower contact
The black shale and silty shale in its basal part are in a disconformable contact with the limestone and bioclastic limestone of the underlying Bolin Fm.
Upper contact
Its top part with its black shale rich in concretions is in a conformable contact with the grey fine-grained quartz-sandstone from the basal part of the overlying Gajie Fm (Gagyai Fm) of Lower Cretaceous.
Regional extent
The formation is distributed extensively in the areas of Mayang District, Fangmachang and Nuba of Daba District, Chaga Gully of Bolin District and Caili of Pulan District, Zhada County, Tibet, with a consistent lithology and a thickness of 240 m to 580 m.
GeoJSON
Fossils
In the Zhada area the formation yields bivalves, Brachiopoda, belemnites and ammonites, with the ammonites being represented by the Himalayites-Blanfordiceras assemblage and the Virgatosphinctes- Aulacosphinctoides assemblage; and Brachiopoda, by Ptilorhynchia quadplicata. The bivalves are represented by Lopha marshi, Entolium cf. cingulutum, E. disciforme, Eligmus rotundus, Deltoideum marginoplicata; of the Belemnites there occur Belemnopsis ugligi, and B. gerardi.
Age
Depositional setting
Additional Information