Zhigou Fm
Type Locality and Naming
The type section is located at Zhigou in southern Sichuan. It was named by Tong Zhengxiang et al. in 1990.
Lithology and Thickness
Limestone. The Lower part consists of gray to gray-white thin- to thick-bedded bioclastic micrite and micritic bioclastic limestone. Bioclastic limestone is quite common, but there are not many types of bioclasts. The brachiopods are not broken. The Upper part is dominated by gray and gray-white thick-bedded micritic calcirudite, characterized by flourishing organisms and strong hydrodynamic conditions.
Relationships and Distribution
Lower contact
Conformable contact with the overlying Lower Permian Waluo Fm
Upper contact
Conformable contact with the underlying Xinbagou Fm
Regional extent
Mainly distributed in the area west of the Yangtze Oldland and in the northwestern part of the NE-trending Jinghe structural belt in Yanbian of southern Sichuan (near Yunnan), extending northwestward from Ganhaizi via Xinbagou of Waluo to Yankou.
GeoJSON
Fossils
Lower part has fusulinids Triticites milleri and T. simplex; Conodont Streptognathodus elongatus; brachiopod Neospirifer striatus. Upper part yields Fusulinids Pseudoschwagerina sp., Robuschwagerina stanslavi and Zellia sp.; Brachiopod Schizophoria juresanensis.
Age
Depositional setting
It is interpreted as a carbonate platform. Lower part with unbroken brachiopods belongs to open sea platform deposits in a low-energy water body. Upper part characterized by flourishing organisms, unimpeded water flow and strong hydrodynamic conditions; therefore, implying that the water is not deep, being a normal sea, so that it belongs to open sea platform shoal deposits.
Additional Information