Shizixu Fm
Type Locality and Naming
The type section is located at Shizixu, northeast of Xianghualing, Linwu County, Hunan. It was named by Li Yuyao and Zhu Sen in 1933.
Lithology and Thickness
Limestone. A suite of neritic carbonate rock formation. Can be divided into three members at Shizixu: Lower part is formed by thick-bedded limestone, ~85 m thick. Middle member by black shale intercalated with limestone, ~35 m thick. Upper part by black limestone containing chert nodules, ~140 m thick.
Within Guangxi, it is divided into two zones bounded by Dayao Mt. and the western Guizhou-Guangxi Railway. The north zone is similar to the standard section in terms of lithology, while in the south zone in central Guangxi the formation is widely distributed and dominated by dark-gray bedded limestone.
Relationships and Distribution
Lower contact
Conformable or disconformable contact with the underlying Devonian Rongxian Fm
Upper contact
Conformable contact with the overlying Huangjin Fm
Regional extent
Although the type section is in Hunan, this formation is mainly used in Guangxi. Cystophrentis is usually contained in the lower part, and Pseudouralinia in the upper part. The former is the zone fossil of Gelaohe Fm of Guizhou, while the latter is that of the Tangbagou Fm. But their coexistence is seen at Qibailong and Di’an of Du’an as well as Tianhe of Luocheng County.
GeoJSON
Fossils
At type section, the Lower part yields Coral Cystophrentis sp.; the Middle part yields Brachiopods Chonetes sp., Eochoristites sp., Fusella sp., etc.; and the Upper part yields Corals Pseudouralinia sp., Syringopora sp., etc.
South zone in Central Guangxi usually contains corals Cystophrentis sp. at the bottom, and Pseudouralinia tangpakouensis and Syringopora in the upper part. Paragenesis of Cystophrentis kolaohoensis and P. tangpakouensis is seen at Qibailong of Du’an.
Age
Depositional setting
It is interpreted as neritic carbonates
Additional Information