Shemulong Fm
Type Locality and Naming
The type section is located at Shemulong of Wumu village in Yanyuan County, Sichuan. It was named as Boda Formation by Sichuan geological bureau first area survey team two team in 1971, and then the lower part of the Boda Fm was renamed as Shemulong Fm in the report of 1∶200000 area survey of gold mine in 1974. [See Boda Fm for details.]
Lithology and Thickness
This formation, 380 to 598 m thick, is mainly composed of carbonates that could be divided into three parts. Lower part is mainly composed of gray, dark gray medium to thick-bedded bioclastic calcareous siltstone intercalated with thin-bedded mudstone, marl and coal seam. Middle part is gray to dark grey thick-bedded block calcarenite, bioclastic limestone intercalated with oolitic sparite, thin bedded mudstone and a few fine-medium grain feldspar quartz sandstones. Upper part is composed of gray massive calcarenite, bioclastic limestone interbedded with the same color fine-medium grain feldspar quartz sandstone.
Relationships and Distribution
Lower contact
The Shemulong Fm is conformable in contact to the underlying Baishan Fm
Upper contact
Regional extent
The formation is restricted to Yanyuan of Sichuan. Lithology and thickness vary greatly. This formation contains a lot of clastic rocks around the Jiami of Yanyuan and Xiaogaoshan of Shuanghe with 764 m thick.
GeoJSON
Fossils
It yields abundant bivalves, ammonoid Trachyceras and a small amount of brachiopods, gastropods, corals, crinoids, conodonts. Lower part contains Costatoria inaequicostata-Plagiostoma striata assemblage in the lower part. Middle part yields Elegantinia venusta. Upper part yields Burmesia lirata-Myophoria napengensis assemblage and conodont Neogondolella polygnathiformis.
Age
Depositional setting
It is interpreted as a shore shelf environment.
Additional Information