Liuwan Fm
Type Locality and Naming
It was named by F.R. Cowper Reed as “Liuwan Horizon” in 1972. The naming locality is situated in the vicinity of the left bank of the Nujiang River about 25 km southwest of Baoshan City, Yunnan Province (E 99°, N 25°4′), with its reference section being located at the Datian Pass west of the Huitong Bridge over the Yunnan-Burma Road.
Synonym: （柳湾组）
Lithology and Thickness
Composed largely of limestones, intercalated with shales. Lower part consists of grey and yellow-grey medium-, and thick-bedded limestones intercalated with a small amount of calcareous shales and purple shales, with its basal part being possessed of a layer of limestones with alveolar weathering surface. Middle and Upper parts are composed mainly of grey and grey-yellow argillaceous limestones and shell limestones intercalated with mudstones, which constitute an alternating layer together with yellow-grey and purple shales and calcareous shales. Its thickness is of 666 m.
Relationships and Distribution
Lower contact
The formation overlies conformably the Mengjia Fm (Yunnan) or Marri Fm (Tibet)
Upper contact
Regionally, the schematic strat column indicates the next younger unit as Longhai Fm
Regional extent
Except for the naming locality, the formation is distributed also in the areas of Mongshi to Wanding, as well as Shuifangjie and Huangcaoba of Yongde County. Starting from the Liuwan area extending northerly along the Nujiang River till the Mali area of the Luolong County, eastern Tibet there is also found the occurrence of the Liuwan Fm. The lithology of the formation is more or less consistent from place to place.
GeoJSON
Fossils
It yields abundant Brachiopods and a small amount of bivalve fossils, with the Brachiopods belonging to the Burmirhynchia-Holcothyris zone, whose major members are Burmirhynchia praestans and Holcothyris ancile.
Age
Depositional setting
Additional Information