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Bainuyangpan Formation
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Bainuyangpan Fm base reconstruction

Bainuyangpan Fm

Period: 
Cretaceous

Age Interval: 
Early Cretaceous, K1b, (17c)


Province: 
Inner Mongolia

Type Locality and Naming

Its type section is located in the area of Bainuyangpan village of the Shuangshengmei township, Central Banner of Wulate, of Urad Zhongqi, Inner Mongolia (109°36′25″E; 41°27′20″N). It was named by No. 1 Regional Survey Party under the Inner Mongolian Geological Bureau in 1966, and was first cited publicly by the Compiling Group for the Stratigraphic Chart of the Inner Mongolian Autonomous Region in 1978.

Synonym: （白女羊盘组）; Bainüyangpan Fm


Lithology and Thickness

The Bainuyangpan Formation is built up by basic-acidic volcanic rocks. Its base is a layer of basalt, middle part andesite and trachyte; and top part rhyolite with tuff and marl. Lower part is composed of brown-grey and black compact massive and vesicular basalt. Middle part is composed of grey-brown, grey-purple and brown-purple trachyte ad grey-purple vesicular andesite with schistocity. Upper part is grey-yellow stratified tuffs, intercalated with grey-white muddy limestone and grey-purple rhyolitic porphyry and rhyolite. Its thickness is about 1350-3910 m


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

The lower boundary is obscure in type section. The formation is in an unconformable contact with the underlying Daqingshan Fm of early-Late Jurassic.

Upper contact

The upper boundary is overlain unconformably by the Quaternary beds in type section. It is in an unconformable contact with the overlying Lisangou Fm.

Regional extent

The distribution of the formation is controlled by the basal faults, which ranges from Qiangxiangshengdan of Siwangzi Qi in the east to Bainuyangpan of Urad Zhongqi in the west. The formation varies to some extent both in lithology and thickness. In the Zuozishan area it is mainly represented by andesitic and basaltic volcanic lava and pyroclastic rocks intercalated with purple red conglomerate, with a thickness of 410 m. In Yurudi and Shujigou, basalt and rhyolite are exposed with a thickness of 449 m. In Jinjiayaozi of the Guyang County, only basalt is exposed for several tens of meters, and both the upper and lower boundaries are obscure.


GeoJSON

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Fossils

In Bayanhe of Damao Qi, it yields a small number of estherias (conchostracans) Eosestheria sp.; ostracods Rhinocypris tugurigensis; and sporopollen Cicatricosisporites, Aequitriadites and Schizaeoisporites. It yields bivalves Arguniella cf. jorekensis, Gastropoda as represented by Valvata sp., plant fossils as represented by Pityophyllum sp., as well as Ostracoda as represented by Metacypris sp., Darwinula sp . This formation contains some fossils of Jehol Biota, implying that it possibly Early Cretaceous.


Age 

The Bainuyangpan Formation was previously of Jurassic age. In 1986, Hao Yichun et al attributed it to Early Cretaceous; in 1991 the Inner Mongolia Bureau of Geology attributed it to Late Jurassic; and in 1992 the Inner Mongolia Hydrogeological Team reassigned it to Early Cretaceous (Inner Mongolia Bureau of Geology, 1994). [Shown on China Lexicon strat chart as early Barremian, only.]. Here, the cited stratigraphic relationships and the uncertain assignment of the overlying Lisangou Fm as Valanginian suggest a Berriasian age – used here for graphic purposes.

Age Span: 

    Beginning stage: 
Berriasian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
143.10

    Ending stage: 
Berriasian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
137.70

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao; with additional information from a Jurassic-Lexicon entry