Xikuangshan Fm
Type Locality and Naming
The type section is located at Xikuangshan Hill near Lengshuijiang City of Hunan Province.
It was named by Tian Qijun (=C.C. Tien), Wang Xiaogin and Xu Zhanyi in 1929.
Lithology and Thickness
Limestone. The Xikuangshan Formation can be subdivided into three members in ascending order: Lower member, Tuzitang Limestone, 40 m thick, consists of medium- to thick-bedded bioclastic limestone with a few beds of shale.
Middle member, Nitangli Iron-bearing Bed, 5-40 m thick, is composed of yellowish-green shale and chlorite shale with clayey limestone and 1 to 2 beds of purplish-red oolitic hematite.
Upper member, Magunao Limestone, 100-300 m thick, is the main part of the Formation and is composed of nodular limestone and bioclastic limestone intercalated with calcareous sandstone in the middle part.
Relationships and Distribution
Lower contact
The Formation has a conformable contact to the underlying thin-bedded shale-limestone of Changlongjie Shale, and is easy separated based on the appearance of thick-bedded limestone.
Upper contact
Regional extent
The lithology of the Formation is relatively persistent throughout the Hunan Province, but the Nitangli Iron-bearing Bed is only distributed in the area north of Lengshuijiang, with commercial importance in the Ningxiang area.
GeoJSON
Fossils
Lower member, Tuzitang Limestone, yields brachiopoda of Yunnanellina -Yunnanella Assemblage Zone.
Middle member, Nitangli Iron-bearing Bed, contains brachiopoda of Hunanospirifer-Yunnanella Assemblage Zone, bryozoan and crinoids.
Upper member, Magunao Limestone, contains conodont Palmatolepis rhomboidalis, P. Marginifera.
Age
Depositional setting
Sedimentary facies analysis indicates that the Tuzitang Limestone is related to storm deposits, that the iron beds are related to a sandy bar which may have shifted from south to north, and that the Magunao Limestone shows a lagoon facies.
Additional Information