Fengjiawan Fm
Type Locality and Naming
Western Henan. The Fengjiawan Fm was named by the Qinling Party of Regional Geo-logical Survey, Ministry of Geology in 1959. The type locality is near Fengjiawan Village, Duguan Township, Lushi County, Henan Province. It is the uppermost formation of the Guandaokou Gr.
Synonym: (冯家湾组)
Lithology and Thickness
In the typical section, the Fengjiawan Fm is composed of argillaceous dolomite intercalated with dolomitic slate. Lower part consists of yellow-brown, grey-purple, greyish-green thin-bedded platy dolomite sandwiched with slate and stromatolite-reef dolomite. Middle part is composed of thick-bedded grey-white, grey-purple muddy reef dolomite, containing stromatolite, and grey-white thick-bedded dolomite. Upper part is grey-white dolo-rudite intercalated with chert-banded dolomite and oolitic chert. The formation is 242 m thick in the type locality. It is measured as 378 m in Jiudinggou, Luanchuan; as 200-300 m in Shipo-Chen'ergou-Luonan, and pinches out in the area west of Fuzhuanghe and Wenyuhe.
Relationships and Distribution
Lower contact
The base is in conformable contact with the underlying Duguan Fm.
Upper contact
The top is a disconformity with the overlying Luoquan Fm Tillite (Nanhuan/Crogenian); but schematic stratigraphic column shows it is regionally also overlain by the Luanchuan Gr (Qb/Tonian; which may encompass Dazhuang Fm of early Qb/Tonian of Neoprot column 22 of this region?).
Regional extent
It distributed only in Luanchuan and Lushi counties, Henan, and in Luonan County, Shaanxi Province.
GeoJSON
Fossils
The stromatolites are rich, including Clavaphyton f. in the lower part, and Conophyton garganicum var. mordiscum, Colonnella wulanwudongensis in the middle part.
Age
Depositional setting
Additional Information