Langmuqiao Fm
Type Locality and Naming
The type section of Langmuqiao Formation is located at Pujidi Village, close to Langmuqiao Village in Qilubai Township (103°31’E, 23°11’N). It lies 1.6 km southwest of the Qilubai Town, or about 28 km southeast of the seat of Mongzi City. It was measured by the Guangxi Bureau of Geology and Guangxi Reginald Survey Team in 1965. The Langmuqiao Formation was published by Geological Bureau of Guangxi Zhuang Autonomous Region (1965). The name is derived from Langmuqiao Village in Qilubai Miao Autonomous Township, Mengzi City (county level), Honghe Hani-Yi Autonomous Prefecture, southern Yunnan Province, and was originally appeared in a 1964 manuscript by the No. 4 Brigade of Yunnan Regional Geological Survey Team.
Synonym: （浪木桥组）
Lithology and Thickness
The Langmuqiao Formation is mainly a clastic sequence, with siliceous and phosphoric rocks. The formation in the type section is divided into 4 lithologic beds, from bottom up; (1) grey, dark grey, and yellowish green conglomerate (20 m thick); (2) greyish black, carbonaceous shale intercalated with siltstone and limestone lenses (15 m); (3) black, dark grey thin platy siliceous rock intercalated with dark grey limestone lenses and phosphorite (20 m); (4) carbonaceous shale (23 m). In this type section, the Langmuqiao Formation is incompletely exported due to fault cutting, the exposed strata is only 78 m thick.
Relationships and Distribution
Lower contact
The Langmuqiao Fm rests disconformably on the Pingbian Fm of Ediacaran System. The lower boundary of the formation is defined by the disconformably plane.
Upper contact
It is in fault contact with overlying Chongzhuang Fm in the type section, but other sections in the Mengzi-Pingbian area show the Langmuqiao Fm and Chongzhuang Fm are in conformable contact. The upper boundary is marked by appearance of thick-bedded quartzose siltstone at the base of the Chongzhuang Fm.
Regional extent
The Langmuqiao Formation is exposed in the southwestern corner of the Yangtze Area of South China Region, restricted merely to the area belonging to the Honghe Hani-Yi Autonomous Prefecture in the mid-southern Yunnan (Mengzi and Pingbian counties). The formation varied in thickness, ranging 342.6 to 695.2 m
GeoJSON
Fossils
There is no fossil found from the lower part of the formation, whereas the upper part yields trilobites Estaingia sp., Hupeidiscus sp., and Metaredlichia sp., and brachiopods and bradoriids.
Age
Depositional setting
Additional Information