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Luojiadashan Formation

Luojiadashan Fm

Period: 
Triassic

Age Interval: 
Middle Late Triassic, (TJ100)


Province: 
Yunnan

Type Locality and Naming

The type section is located in Luojiadashan, Xiangyun County, Yunnan Province. It was named in 1974 by the survey team of the first area of the Yunnan Geological Bureau.

Synonym:


Lithology and Thickness

It is mainly composed of siltstone, fine sandstone, mudstone and shale. In the Xiangyun area, it can be divided into three parts: Lower part is dark gray, dark gray-green siltstone, fine sandstone with volcanic breccia tuff, basalt tuff and conglomerate. Middle part is gray-green, gray-white massive mudstone, sandy mudstone, and fine sandstone. Upper part is dark gray, yellowish brown silty shale, fine sandstone interbedded with coal. Its thickness is 962-2500 m.


Lithology Pattern: 
Claystone


Relationships and Distribution

Lower contact

At the bottom, the black gray-green fine sandstone and siltstone are in conformable contact with the yellow-green shale of the Yunnanyi Fm.

Upper contact

The top is in disconformable contact with the overlying fine conglomerate of the Baitutian Fm.

Regional extent

It is mainly distributed in Xiangyun, Binchuan, Chuxiong Tuanshan, Nanhua First Street, Third Street, Xinping Reservoir and other places.


GeoJSON

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Fossils

Bivalves: Costatoria napengensis-Burmesia lirata assemblage. Plants: Dictyophyllum nathorsti-Clathropteris meniscioides assemblage.


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: 
Carnian

    Fraction up in beginning stage: 
0.85

    Beginning date (Ma): 
228.76

    Ending stage: 
Norian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
205.74

Depositional setting

Marine-terrestrial transitional facies.


Depositional pattern:  


Additional Information
Compiler:  

Zhou Huiqin, Shu Wenchao and Tong Jinnan.