Changgou Fm
Type Locality and Naming
The type section is located at Changgou to Sangongdian of Changgou Township in Shangyang County, Shaanxi Province. It was named by Yang Zhihua et al. in 1991.
Lithology and Thickness
Limestone. Lower part consists of medium-bedded lithologies of banded sandy and dolomitic silt-sized to fine-grained crystalline limestone, of bioclastic limestone intercalated with a few sandy slate beds, of calcareous slate and of feldspathic quartz sandstone. Upper part is medium- to thin-bedded calc-arenite intercalated occasionally with sericite slate. The thickness is 924 m in total.
The Changgou Fm lithology in Hongxia, Sanchaxing of Fengxian County is similar to that of Changgou section of Shangyang, containing abundant fossils. At bottom, it is cut by fault and the outcrop thickness is more than 1077 m.
Relationships and Distribution
Lower contact
Conformable on the clastic rocks of the Wangjialeng Fm at the type section.
Upper contact
Underlying the Xinghongpu Fm
Regional extent
The formation is distributed at the area of Fengxian, Taibai, Ningshan, Zhen’an and Shanyang counties, Shaanxi Province where its lithology is relative uniform being mainly carbonate rock.
GeoJSON
Fossils
The Changgou Fm yields a few brachiopods Emanuella and coral Disphyllum, Alveolitella.
The Changgou Fm in Hongxia, Sanchaxing of Fengxian County yields corals: Thamnopora, Crassialveolitella, Pseudomicroplasma, Temnophyllum and brachiopods: Atrypa, Emanuella etc. The Upper part of Changgou Fm in Pingkan area of Fengxian County yields brachiopods Stringocephalus; Conodonts Polygnathus cf. xylus.
Age
Depositional setting
It is interpreted as a tidal flat to restricted basin environment.
Additional Information