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Kaipaizileik Formation

Kaipaizileik Fm

Period: 
Permian

Age Interval: 
P (23), Guadalupian Epoch (Middle Permian)


Province: 
Xinjiang

Type Locality and Naming

The type section is located on the southwest of the Yingan Village about 28 km to the northeast of the Keping County, Xinjiang. It was named by the Compiling Group on the Regional Stratigraphic Chart of the Xinjiang Uygur Autonomous Region in 1977, and was issued publicly in 1981.


Lithology and Thickness

Clastics and Basalt. It is divisible into two subformations. Lower subformation being composed of purple and grey-green medium- and coarse-grained feldspar-lithoclastic sandstone, calcareous lithoclastic sandstone and silty siltstone, with a thickness of 926 m. The basal part of the formation consisting of grey and grey-green tuff or feldspar-rich sandstone. Upper subformation consisting of black basalt, intercalated with clastic rocks, with a thickness of 901 m. Upper subformation is part of the Tarim Large Igneous Province (LIP).


Lithology Pattern: 
Lava


Relationships and Distribution

Lower contact

Conformable contact with the black basalt of the underlying Kupukuziman Fm

Upper contact

Conformably overlain by the siltstones of the Shajingzi Fm

Regional extent

Easterly from Yingan area, the clastics in the formation are increasing in amount, and till the area of Sishichang, Shajingzi Region there are exposed only the clastic rocks of the lower part of the Lower subformation, with a thickness of 526 m, while the Upper subformation is exposed in the southwestern part of the Yingan Village and the Kaipaizileik area, and with the volcanic rocks to the west of the Yingan section are decreasing in amount remarkably.


GeoJSON

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Fossils

Lower subformation yields plant fossils (phytolites) as represented by the Autunia-Cordaites schenkii assemblage whose major species are Sphenophyllum minor, Pecopteris orientalis, Annularia gracilescens and Sphenopteris gothonii. Upper subformation yields plant fossils (phytolites) such as Sphenophyllum, Paracalamites and Sphenopteris, etc., belonging to the Maokouan Subepoch in age (Sun Bonian et al., 1993). The spore-pollen fossils are represented by the Striolatospora-Schweiterisporites-Calamospora assemblage.


Age 

WAS assigned (Permian lexicon version 2017) as Maokouan Subepoch of Upper subformation = Guadalupian Epoch (Middle Permian). However, 40Ar/39Ar plateau ages obtained from nearby sites are much older: 287.3 ± 2.0 and 287.9 ± 3.1 Ma (Wei et al. 2014) for the basalts of this formation and of the basalts in the underlying Kupukuziman Fm; which would imply a middle-Early Permian age. But, now is MUCH older –middle Early Permian (ca. 25% up in Artinskian to ca. 25% up in Kungurian) ccording to Shuzhong Shen et al. (2019, Permian integrated stratigraphy and timescale of China)!

Age Span: 

    Beginning stage: 
Artinskian

    Fraction up in beginning stage: 
0.25

    Beginning date (Ma): 
288.71

    Ending stage: 
Kungurian

    Fraction up in the ending stage: 
0.25

    Ending date (Ma):  
281.07

Depositional setting

Lower subformation is interpreted as river-facies and lake-facies deposits. Upper subformation is part of the Tarim Large Igneous Province (LIP).


Depositional pattern:  


Additional Information


Compiler:  

Hou Jingpeng, Zhu Zili