Yangjiabao Fm
Type Locality and Naming
The type section of the Yangjiabao Formation is the Yangjiabao section, measured near the Yangjiabao Vanadium Mine in Xijiadian Township by the No. 5 Geological Team of Hubei Bureau of Geology. The section lies about 13 km northeast of the Xijiadian Town, Danjiangkou, Hubei Province (111°14’27” E, 32°51’36” N). In the type section, the Fengjia’ao Formation is 14 m thick. The Yangjiabao Formation was first published by Zhu and Tao (1988). The name is derived from Yangjiabao Village of Xijiadian Town, Danjiangkou City (County level), northwestern Hubei Province. The unit was originally in a 1975 unpublished report by No, 5 Geological Team of Hubei Province.
Synonym:
Lithology and Thickness
The Yangjiabao Formation is a silicate sequence. It is composed of two parts: Lower part merely consists of light grey and grey, thin- to medium-bedded siliceous rock with laminated bedding; Upper part consists of greyish brown, medium-bedded siliceous rock, and siliceous slate.
[Zhu and Tao (1988) divided the Yangjiabao Formation into three members, including the Silicalite (=Chert) Member below, the Carbonaceous Slate Member in the middle, and the Siliceous Slate Member above. Yang et al. (1991), and followed by Chen and Jin (1996), restricted the formation to two lower members, the siliceous rock and the Carbonaceous Slate members (Bed 1−4), and referred the upper Siliceous Slate Member (Bed 5) to the overlying Yanwugou Formation.] The revised concept by Yang et al. (1991) is followed in this literature.
Relationships and Distribution
Lower contact
The Yangjiabao Fm rests conformably on underlying Tongying Fm in Hubei Province and disconformably on the Tongying Fm in Henan Province respectively. The lower boundary of the formation is marked either by disconformable plane between Töngying and Yangjiabao formations or by sudden lithological change from thick-bedded dolomite to siliceous rock.
Upper contact
It is conformably overlain by the Yanwugou Fm. The upper boundary of the formation is marked by lithological change from the siliceous slate at top of the Yangjiabao Fm to the carbonaceous slate at the base of the Yanwugou Fm.
Regional extent
The formation is exposed in the Jiangbei Slope Area of South China Region, distributed in northwestern and northern Hubei Province (Zhushan, Yinxian, Yunxi, Danjiangkou and Suixian counties) and southwestern Henan Province (Xichuan and Dengzhou counties). The thickness of the formation varies from 2 to 14 m.
GeoJSON
Fossils
No fossil was reported from the formation yet.
Age
Depositional setting
Additional Information
The revised concept by Yang et al. (1991) is followed in this book, the Cambrian System Part 1 by Peng Shanchi.