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Tyokar Formation
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Tyokar Fm base reconstruction

Tyokar Fm


Period: 
Permian

Age Interval: 
P (60), Guadalupian Epoch (Middle Permian)


Province: 
Xizang (Tibet), Qinghai, Yunnan

Type Locality and Naming

The type section is located in the alignment of Supodilei-Annazangka of Tyokar County, Xiaobangda Region, Mangkang County, Tibet. It was named by the 3rd Regional Geological Survey Party under the Sichuan Bureau of Geology and Mineral Resources in 1974.

Synonym: Jiaoga Fm (spelling)


Lithology and Thickness

Limestone, Clastics and Volcaniclastsics. Composed of two lithologic associations, with a more greatly changeable lithology. The Supodilei association is represented by the section at Supodilei where it is composed mainly of grey-white and light-grey thick-bedded and massive limestones, intercalated with a small amount of calcareous shale and grey-green sandstone, with a thickness of 95 m. The Zhasuosu association is represented by the Zhasuosu section at the Annazangka, where it is composed mainly of yellow-green and grey-green thin-bedded clayey siltstone, tuffaceous conglomerate, crystal-clastic tuff, tuffaceous lava and andesitic basaltic lava, intercalated with medium- and thin-bedded bio-limestones, with a thickness of 213 m. In the Leiwuqi area it has a thickness of 1081 m.


Lithology Pattern: 
Clayey limestone


Relationships and Distribution

Lower contact

Conformable contact with the underlying Mangcuo Fm

Upper contact

Disconformable or a conformable contact with the overlying Tuoba Fm

Regional extent

Distributed in the Mongkang County, Leiniaoqi and Changdo areas of Tibet, Nangqian of Qinghai Province and Deqin of Yunnan Province, with a greatly changeable thickness in various places, for instance, its being of 1069 m at Gangzhuoyong of Nangqian County, Qinghai Province; of 1018 m at Shanhongna of Leiniaoqi County of Tibet; of 127 m at Tuobar of Changdo City, Tibet; of 455 m at Haitong of Mongkang County, Tibet; and of 720 m at Bamei of Deqin County of Yunnan Province.


GeoJSON

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Fossils

Supodilei association yields Fusulinida fossils such as Chusenella, Praesumatrina, Neoschwagerina, Verbeekina, etc., and Ammonoids fossils such as Agathiceras sp.

Zhasuosu association yielding Fusulinida represented by Praesumatrina and Ammonoids such as Agathiceras, Artinskia and Stacheoceras. In the Leiwuqi area it yields also abundant Fusulinida fossils comprising Chusenella, Afghanella, Pseudofusulina, Verbeekina, Neoschwagerina, Metadoliolina, Sumatrina, Yabeina, and Schwagerina, etc.; Coral fossils such as Ipciphyllum, Tachylasma, Allotropiophyllum, Wentzelella, Bradyphyllum and Timorphyllum; Ammonoids represented by Agathiceras.


Age 

Maokou’an Subepoch = Guadalupian Epoch (Middle Permian)

Age Span: 

    Beginning stage: 
Roadian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
274.37

    Ending stage: 
Capitanian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
259.55

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Wang Yujing

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