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Bulongshan Formation

Bulongshan Fm

Period: 
Ordovician

Age Interval: 
Sandbian, (33)


Province: 
Inner Mongolia

Type Locality and Naming

The type section is at Baoerhantu in Baiyinaobao of Darhan Muminggan Lianheqi, Inner Mongolia. The Bulongshan Fm was named by the No.1 Inner Mongolia Team of Regional Geological Survey in 1971, and was published by the Inner Mongolia Compiling Group for Regional Stratigraphic Scale in 1978.

Synonym: (布龙山组）

Reference Section:

The reference section is on Bulong Hill along the Xibie River, 25 km northeast of Bayan Obo in Darhan Muminggan Lianheqi.


Lithology and Thickness

The Bulongshan Fm is generally composed of interbedding knotted slate, metamorphosed silty mudstone and sandstone, and inequigranular polymictic sandstone. In the type area, the unit is characterized by silty and siliceous sandstone, pebbly sandstone, marble and ferruginous quartz sandstone. This formation has a recorded thickness of 1359 m.


Lithology Pattern: 
Sandy claystone


Relationships and Distribution

Lower contact

The Bulongshan Fm has a covered lower boundary

Upper contact

It is conformably overlain by the intermediate alkali tuff of the Halayan Fm (Hala Fm).

Regional extent

It is 427 m in Baorhantu, and an incomplete thickness of 800 m in Bayan Obo.


GeoJSON

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Fossils

The graptolites Callograptus, Desmograptus, Dictyonema, Aspidograptus and Dicranograptus have been found from the formation in left bank of the Xibie River.


Age 

Sandbian. The Bulongshan Fm was first thought to be Early-Middle Silurian. In 1979, the Inner Mongolia Party of Regional Geological Survey of Inner Mongolia Bureau of Geology and Mineral Resources suggested a Middle Ordovician age for it. Tang et al. (1992) included the Bulongshan Fm in the lower part of the Baorhantu Gr (Inner Mongolia Compiling Group for Regional Stratigraphic Scale, 1978), and considered it to be Middle-Late Ordovician in age.

Age Span: 

    Beginning stage: 
Sandbian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
458.18

    Ending stage: 
Katian

    Fraction up in the ending stage: 
0.2

    Ending date (Ma):  
451.24

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Jianpo Wang and Xiaofeng Wang