Guanqiao Fm
Type Locality and Naming
The type section is located at Guitouling, 1 km southwest of Guanqiao Village near Liufengshan Forest Farm, northeast of Ertang Township in Wuxuan County, Guangxi Zhuangzu Autonomous Region. It was named by Wang Yu and Yu Changmin in 1965 as a member of Beiliu Formation. Wu Y. et al. (1992) promoted it as a Formation and correlated with Lutang Fm of Dale area in Xiangzhou County.
Synonym: Guangqiao Dolomite, Guangqiao Dolostone
Lithology and Thickness
Dolomite. Lower part, 212 m thick, is composed of gray to light-gray, medium- to thick-bedded unequal-grained dolomite. Middle part, 129 m thick, is medium- to fine-grained dolomite with dolomitic limestone interbeds. Upper part, 111 m thick, is fine-grained dolomite, dolomitic limestone with thin-bedded calcareous mudstone. Algal lamination, bird-eyes, bio-borings and mud crack structures are often seen in this formation, which would indicate a restricted carbonate platform environment. The total thickness is about 600 m.
[Figure - Guanqiao Fm Dolostone in the Ertang section showing the photomicrography of hypidiotopic dolomites (left) and a planar to wavy laminated appearance (right).]
Relationships and Distribution
Lower contact
The formation is conformably separated from the underlying Ertang Fm by the appearance of dolomite.
Upper contact
Conformable contact with the overlying Dale Fm..
Regional extent
It is distributed along the west side of Dayaoshan Mt., from Litang of Binyang County in south to Jinxiu Yaozu Autonomous County in north and mainly developed in Wuxuan-Xianzhou area. The mudstone content increases from south to north. In the Dale area the Lutang Fm Dolomite with similar lithology and stratigraphic position between Dale Fm and Luomai Fm is synonymous with Guanqiao Fm.
GeoJSON
Fossils
Only few fragments of Thamnopora and crinoids are observed.
Age
Depositional setting
It is interpreted as a restricted carbonate platform environment.
Additional Information