Yangbazhai Fm
Type Locality and Naming
The type section is located at the Yangbazhai of the Baliu Country, Muojiang County, Yunnan Province (101°03′, 23°02′). It was named by the Bureau of Geology and Mineral Resources of Yunnan Province in 1990.
Lithology and Thickness
Siltstone. Lower part is composed of black and grey-green siltstone and clayey siltstone, intercalated with quartz-sandstone, lithoclastic sandstone and intermediate-acidic layered tuff, locally with limestone and siliceous rocks. Upper part is composed of interbeds of grey-yellow and grey-black siltstone, together with fine- and coarse-grained sandstones, locally intercalated with coal layers or coal seams.
Relationships and Distribution
Lower contact
Disconformable contact with the underlying Daxinshan Fm or the Lazhuhe Fm, and the Baliu Fm
Upper contact
Overlain by Changxing Fm
Regional extent
Distributed in a NW-trend, and is getting thicker from north to south and from west to east, with a maximum thickness of 3869 m. In the Daxinshan area of the Zhendong region of Simao County the formation does not contain volcanic rocks and coal, and is composed of grey-black sandstone and siltstone, intercalated with sandy conglomerate, with a thickness of 269.9 m. In the Waigu Village of Weishan Mt., Najing area of Pu’er City, Wenbang County and Wudukeng area of Jiangcheng County the formation is composed of sandy siltstone, intercalated with carbonaceous siltstone and thin coal layers or coal seams, with tuff, marl and limestone intercalations occurring locally, with a thickness of 285.7-1189 m. In the Taizhong area of Jingdong County, the Zhedong area of Zhenyuan County, and the Yangbazhai area of Muojiang County the formation is composed of sandy siltstones, intercalated with carbonaceous shale, coal seams, siliceous rocks and limestone, with a thickness of 1139-3869 m; and there are found intercalations of tuff, basalt and andesite all over the region.
GeoJSON
Fossils
The major biological fossils comprise Plant fossils (phytolites) such as Gigantopteris nicotianaefolia, Lepidodendron acutangula; Brachiopods such as Leptodus tenuis, L. nobilis, Dictyoclostus margaritatus; Trilobites such as Pseudophillipsia chongqingensis; and Ammonoids such as Leptogyroceras cf. dongshanglinense, etc.
Age
Depositional setting
It is interpreted as mainly shallow-sea continental-shelf facies deposits, and is characterized by a local development of littoral swamp-facies deposits.
Additional Information