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Zhongwo Formation

Zhongwo Fm


Period: 
Triassic

Age Interval: 
Early Late Triassic (TJ70)


Province: 
Yunnan

Type Locality and Naming

Yunnan Geological Bureau the first area survey team in 1966 named. The named section is located in Jidiping - Zhongwo, Heqing County, Yunnan Province.

Synonym: In 1962, Zhao Jinke et al. named this set of strata as the Lanping Fm, but did not specify a named section.


Lithology and Thickness

It is mainly composed of lime-black intermediate limestone and argillaceous sandstone, interbedded with marl, shale and sandstone layers. Chert nodules can be seen in the upper part, oolitic structures are common in the lower part of limestone, unstable bauxite beds are generally found at the bottom and chert nodules are found at the top. Its thickness is 191 ~ 230 m.


Lithology Pattern: 
Sandy limestone


Relationships and Distribution

Lower contact

It is a pseudo-conformable contact with the underlying Beiya Fm of the Middle Triassic

Upper contact

It is a pseudo-conformable contact with the overlying Songgui Fm of the Upper Triassic.

Regional extent

The Zhongwo Fm is distributed in Lijiang and Heqing area, Yunnan


GeoJSON

null

Fossils

Bivalves: Halobia yunnanensis, H. superba, Angustella cf. angusta. Ammonoids: Thisbites sp. Coral: Oppelismilia sp.


Age 

Between the Beiya Fm of the Middle Triassic and Songgui Fm of the Upper Triassic, and its age is the Carnian stage of the Late Triassic.

Age Span: 

    Beginning stage: 
Carnian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
237.00

    Ending stage: 
Carnian

    Fraction up in the ending stage: 
0.85

    Ending date (Ma):  
228.76

Depositional setting

The Zhongwo Fm is a mixed deposit of marine carbonate rock and clastic rock


Depositional pattern:  


Additional Information


Compiler:  

Zhang Shunxin, Zhou Ze and Tong Jinnan.