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Angjie Formation
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Angjie Fm base reconstruction

Angjie Fm

Period: 
Permian

Age Interval: 
P1, (48), Artinskian Stage (Cisuralian Epoch; late Early Permian)


Province: 
Xizang (Tibet)

Type Locality and Naming

The type section is located in the area of the Angjie−Xila Mt. area 4.5 km east of Yongzhu Village, Shenzha (Xianza) County in lake region, Tibet. The reference section is at the south slope of Deriangma Mt. to Xila Mt., 6 km east of Yunzhug Township. It was named by the Comprehensive Geological Reconnaissance Expedition under the Geological Bureau of Tibet (Lunzhu Jiacuo, Li Cai et al. in 1978), and formally adopted by Yang Shipu and Fan Yingnian in 1982.

Synonym: Anji Fm (spelling)


Lithology and Thickness

Sandstone. Gray and gray-green pebbled quartzose feldspar-rich sandstone, pebbled siltstone, and gray-green shale intercalated with thin-bedded clayey limestone, or limestone lenses, with few fossils. 633 m thick.


Lithology Pattern: 
Sandstone


Relationships and Distribution

Lower contact

Conformable contact with the underlying Laga Fm.

Upper contact

Conformable contact to the overlying Xiala Fm, or Langmaria Fm

Regional extent

Anji Fm is distributed in the area of Shenzha County, Tibet.


GeoJSON

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Fossils

Permian Lexicon entry: Brachiopods: Neospirifer, Spiriferina, Marginifera and Cancrinella; Moss corals: Fenestella, Ramiporidra, Streblascopora, Stenopora, Pamirella and Dyscritella; Ostracoda: Bairdia, Aparchites, Cytherellina, Orthonaria and Rectobairdia.

Carboniferous Lexicon entry: Bivalve Trigonotreta sp.; brachiopods Stenoscisma cf. pudoni and Marginifera cf. orientalis; corals Meniscophyllum stereoseptatum and Plerophyllum angjiense. In the limestones are contained the cold-water bivalve Eurydesma fauna typical of Gondwana facies, which is closely related to till sheets. In the Deriangma section, Trigonotreta, an important element of the above fauna, is also found, and associated with a group of small non-dissepiment solitary Corals. Therefore, it is doubtless that the stratum should belong to the Gondwana stratum of glacio-fluvial deposits


Age 

Was attributed to "late Carboniferous", but now assigned to the Longlinian Stage of the Chuanshanian Series = Artinskian Stage (middle of Cisuralian Epoch; mid-Early Permian). Shuzhong Shen et al (2019; Permian integrated stratigraphy and time scale) assign it to the Artinskian through upper Kungurian.

Age Span: 

    Beginning stage: 
Artinskian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
290.51

    Ending stage: 
Kungurian

    Fraction up in the ending stage: 
0.5

    Ending date (Ma):  
278.84

Depositional setting

It is interpreted as river-deltaic facies and cold-water neritic facies. "It is doubtless that the stratum should belong to the Gondwana stratum of glacio-fluvial deposits"


Depositional pattern:  


Additional Information

In Gondwana stratigraphy, the formation is interpreted as corresponding to the Lyon Gr of Australia, the Kashmir agglomerate, and the lower part of Nilawan Gr of Yanling.


Compiler:  

Fan Yingnian and Wang Yujing

GeoJSON estimate by Longgang Ye and Yuyin Li (Chengdu Univ. Tech. students)