Luoranggou Fm
Type Locality and Naming
The type section is located in Luorang Valley ("gou" = valley), 30 km north of Songpan County, Sichuan. And it was named by the second area survey team of the Sichuan Geological Bureau in 1978.
Synonym: Fuluorangou Fm
Lithology and Thickness
It is dominated by gray and dark gray thin argillaceous limestone, with bioclastic limestone in the middle. The argillaceous content decreases from the bottom up, and the iron-magnesium content increases. It has a worm-like structure and a local pseudo-oolitic structure as a major feature of the formation. The total thickness is 250 to 302 m.
Relationships and Distribution
Lower contact
The thin slab-like argillaceous limestone with worm-like structure at the bottom of this formation is conformable in contact to the underlying Daguanshan Fm (Proterozoic marble) with the crystalline limestone.
Upper contact
The top part of this formation is also conformable in contact to the purple-red iron-bearing sandy limestone at the bottom of the overlying Hongxingyan Fm
Regional extent
Only found in Songpan, Sichuan. It is 172 m thick in the Hongxingyan area in the south, 249 m in the Luoranggou, 165-198 m in the upper reaches of the Qirangou River, 150-200 m in the Guanmenzi area in Nanping County, and 320 m in the Zhongyao ditch, reflecting the north trend of change from thick to thin.
GeoJSON
Fossils
Bivalves: Pseudoclaraia cf. wangi, Claraia cf. aurita, C. griesbachi, Eumorphotis cf. multiformis, E. reticulatus; gastropod and brachiopod fossils.
Age
Depositional setting
Shallow marine facies.
Additional Information