Beisi Fm
Type Locality and Naming
It was named by Wenyou Zhang and Jiatian Chen in 1938. Type section was located between the Heli Village and Beisi Town of Laibin County, Guangxi Zhuang Autonomous Region. It was termed as “Beisi limestone” when established but was subsequently assigned to Beisi formation by Jinke Zhao et al. in 1962 and indicative of Anisian to Ladinian age. However, the Beisi formation was ascribed to the Late Early Triassic by Guangxi Oil survey team during 1960-1962, representing platform carbonate facies in Guangxi Zhuang Autonomous Region at that time. Upper formation in Luolou Gr?
Synonym:
Lithology and Thickness
The Beisi Formation mainly consisted of dolomite and limestone, which were interbedded with argillaceous limestone, oolitic limestone and conglomeratic limestone. Typically, 1-4 acidic lava and tuff beds have been found. The base of Beisi formation was marked by the occurrence of greyish shale and the top was indicated by the disappearance of conglomeratic limestone. The thickness is about 300 m.
Relationships and Distribution
Lower contact
Generally, the Beisi formation was conformably with the underlying Lower Triassic Majiaoling Fm
Upper contact
Conformable in contact with the overlying Middle Triassic Guohua Fm or Baifeng Fm
Regional extent
GeoJSON
Fossils
Full of bivalves and conodonts, with well-established assemblages. Bivalves: Eumorphotis inaequicnstata-Entolium discites murotis assemblage. Conodont zones (from lower to top): Platyvillosus costatus taxon-range zone, Pachyclacdina obliqua-Parachirognathus delicatulus assemblage zone and Neospathodus triangularis zone. Ammonoids: Anakashmirites sp., Aspenites sp., Hellenites sp., Tirolites sp., Dieneroceras sp., Pseudowenite oxvrotus, Proptychites sinensis, Xenoceltites sp.
Age
Depositional setting
Formed under nearshore shallow marine facies
Additional Information