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Yangjia Gr

Yangjia Gr

Period: 
Triassic

Age Interval: 
Early Middle Triassic, (TJ97a)


Province: 
Jiangxi

Type Locality and Naming

The named profile is located in Yangjia, Yinggangling, Gaoan County, Jiangxi Province. Named in 1964 by the District Survey Team of Jiangxi Geological Bureau. It was named after "Yangjia Formation". The original meaning refers to a set of purple-red clastic rocks above the Daye Formation (Daye Gr; equivalent to the Lower Triassic) and below the Anyuan Fm of the Upper Triassic.

Synonym:


Lithology and Thickness

The Yangjia Gr is dominated by purple, purple-red iron sericite feldspar quartz siltstone, fine sandstone, and purple shale. 115 m thick.


Lithology Pattern: 
Siltstone


Relationships and Distribution

Lower contact

At the bottom, the purplish red sandstone and the underlying Lower Triassic Xiangcheng Fm or Yuanxi Fm are conformable contact.

Upper contact

The upper limit has not been reached. Next younger regional unit is the Anyuan Fm of Norian.

Regional extent

Mainly distributed in Gao'an Yichun, Qian Mountain, Shangrao area in the north of Jiangxi. The lithology and thickness of this group vary greatly, generally ranging from 207 to 1255 m. In the area of Wanzai Bridge, the thickness is only 66 m. Dolomite limestone is developed in the lower part or bottom, with marl in between.


GeoJSON

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Fossils

In the middle of this group contains Posidonia cf. ussurica, Volsella cf. triquetra in Yangjia Gao'an City; bivalves: Leptochondria paradoxica and Unionites spicatus etc. in Qian Mountain; and bivalves Daonella sp., Posidonia cf. wengensis in Zhongfang, Yichun City.


Age 

The age is the Middle Triassic. Jiangxi Province Regional Stratigraphic Table Compilation Group first publicly cited in 1980, and changed it name into Yangjia Group. Yin Hongfu (1982) believes that it is appropriate to tentatively set the Anisian in the Yang Jiaqun era. Wang Zunzhou et al. (1992) expanded the lithostratigraphic range of this group and classified purple-red clastic rock into Daye Formation (equivalent to the Lower Triassic) and the yellowish green clastic rock in the top (105 m thick) into Yangjia Group in page 77 of Regional Stratigraphic Table in East China, Jiangxi Province. We maintain the original meaning of the "YangJia Group", and believes that the main age of this group is the Anisian, which may have reached the Ladinian.

Age Span: 

    Beginning stage: 
Anisian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
246.70

    Ending stage: 
Ladinian

    Fraction up in the ending stage: 
0.15

    Ending date (Ma):  
240.79

Depositional setting

It is interpreted as Nearshore shallow water deposits.


Depositional pattern:  


Additional Information


Compiler:  

Zhang Shunxin, Zhang Shiyan and Tong Jinnan.