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Baitutian Formation

Baitutian Fm

Period: 
Triassic

Age Interval: 
Late Late Triassic, (TJ100)


Province: 
Yunnan

Type Locality and Naming

Named in 1965 by the Survey Team of the Yunnan First District Geological Bureau. The type locality is located in Baitutian Village, Xiangyun County, Yunnan; the reference locality is located in Mupangpu, Xiangyun County.

Synonym: This Formation originally refers to a set of continental strata containing coal in the upper part of Xiangyun Coal measures, which lies between the fine conglomerate of the overlying Jurassic Fengjiahe Fm and the siltstone and shale of the underlying Upper Triassic Luojiadashan Fm, and its age is middle to late Late Triassic.


Lithology and Thickness

It is mainly composed of yellow-green, yellow and light gray mixed with purple feldspar quartz sandstone, mudstone, silty mudstone, shale and coal.


Lithology Pattern: 
Clayey sandstone


Relationships and Distribution

Lower contact

The bottom is characterized as the appearance of light gray fine-medium-grained sandstone and siltstone with horizontal and oblique bedding distinguishes from the light gray thin argillaceous siltstone. Black shale at the top of the underlying Fuluojiadashan Fm (Luojiadashan Fm), and they are pseudo-conformable contact.

Upper contact

A continuous transition between the top and the overlying calcareous fine conglomerate at the bottom of the Lower Jurassic Fengjiahe Fm.

Regional extent

The lithology of this formation is relatively stable with a thickness of more than 1000 m, widely distributed in Dongshan Binchuan, Xiangyun County and other places, with a thickness of more than 1400 m. The maximum thickness of Xinping is about 2600 m, which can be compared with that of Baoding Fm in Yongren and Ganhaizi Fm in Pinglang, Lufeng.


GeoJSON

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Fossils

Plant fossils: Equisetites sp., Clathropteris meniscioides, Ptilozamites chinensis, Anomozamites sp.; bivalves: Yunnanophorus sp., Unionites postera; and conchostracans: Euestheria minuta and so on.


Age 

In 1942, Xie Jiarong first created the "Xiangyun Coal Series" and placed it in the Norian of the Late Triassic. Sheng Shenfu et al. (1962) believed that the Xiangyun coal measures consisted of two coal-bearing groups, the upper coal group was classified as Late Triassic Rhaetian, and the Marine coal group and the lower coal group were classified as Norian. In the same year, the Jiang Nengren believed that the upper and lower coal groups belonged to the same layer and find plant fossil Neocalamites Clathropteris, Podozamites etc. The Survey Team of the Yunnan First District Geological Bureau (1965, 1974) divided Xiangyun coal into Luojiadashan Fm and Baitutian Fm from bottom to top, which are classified into Norian and Rhaetian respectively.

Age Span: 

    Beginning stage: 
Rhaetian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
205.74

    Ending stage: 
Rhaetian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
201.36

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Zhou Huiqin, Du Yong and Tong Jinnan.