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Hala Formation

Hala Fm

Period: 
Ordovician

Age Interval: 
Katian, (33)


Province: 
Inner Mongolia

Type Locality and Naming

The type section is at Baorhantu in Baiyinaobao, Darhan Muminggan Lianheqi, Inner Mongolia. The reference section is on Bulong Hill, banks of Xibie River, 25 km northeast of Bayan Obo, Inner Mongolia (Tang Kedong et al., 1992). The Hala Fm. was named by No.1 Inner Mongolia Party of Regional Geological Survey in 1971, and was published by Inner Mongolia Compiling Group for Regional Stratigraphic Scale (1978).

Synonym: (哈拉组), Halayan Fm


Lithology and Thickness

The Hala Fm is dominated by intermediate-alkali tuff consisting of andesitic porphyrite intercalated with tuffaceous sandstone, greywacke and local breccia, limestone lenses and amygdaloidal basalt. The formation has a recorded thickness of 67-701 m.


Lithology Pattern: 
Volcanic ash


Relationships and Distribution

Lower contact

It rests conformably on the Bulongshan Fm

Upper contact

It is unconformably overlain by the Xibiehe Fm of latest Silurian. [although regional column has the next younger unit as the Xuniwusu Fm of mid-to-late Ordovician sandstone.

Regional extent

The Hala Fm is exposed in Baorhantu, with a thickness of 701 m, Bulongshan, 530 m thick, and Bayan Obo, 267.1 m thick.


GeoJSON

null

Fossils


Age 

Katian. The Hala Fm. was previously considered to be Early-Middle Silurian in age. The No.1 Inner Mongolia Team of Regional Geological Survey, Inner Mongolia Bureau of Geology and Mineral Resources (1979) suggested a Middle Ordovician age for it. Tang et al. (1992) included it in the upper part of the Baorhantu Gr, and suggested a Caradoc to Ashgill age.

Age Span: 

    Beginning stage: 
Katian

    Fraction up in beginning stage: 
0.2

    Beginning date (Ma): 
451.24

    Ending stage: 
Katian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
445.21

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Jianpo Wang and Xiaofeng Wang