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JiubaoMember Formation
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JiubaoMember Fm base reconstruction

JiubaoMember Fm

Period: 
Cretaceous

Age Interval: 
Late Cretaceous, (12b) K2jb


Province: 
Xizang (Tibet)

Type Locality and Naming

The Jiubao Formation was erected by Wan Xiaoqiao in 1985. The section for the designation is on the northern side of Xiawuchupogou on the eastern side of Zongshan about 250 m southeast of the Gamba County, Xizang. Wan Xiaoqiao et al. (2000) renamed it as the Upper Member (or Jiubao Member) of the Gambacunkou Formation (see the item of Gambacunkou Formation).

Synonym: Jiubao Member


Lithology and Thickness

The Jiubao Formation (member) is represented by gray thin-bedded marl interbedded with yellow green mudstone, gray thin-bedded microcrystalline limestone interbedded with yellow green shale, and gray thin-bedded microcrystalline limestone with yellow green shale. It is 110.95 m thick.


Lithology Pattern: 
Shallow-marine marl


Relationships and Distribution

Lower contact

Its base marked by gray thin-bedded limestone that shows a gradational relationship with yellow green shale at the top of the underlying XiawuchupoMember Fm.

Upper contact

Regional extent

The present formation is exposed in Zongshan of Gamba and Gongza of Tingri areas.


GeoJSON

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Fossils

In the Zongshan area, it yields abundant Foraminifera Globotruncana coronata, G. globigerinoides, G. carinata, G. fornicata, G. schneegansi, Hedbergella orectus, H. crassa, Heterohelix globulosa, H. reussi, H. pulchra, Valvulineria parva, etc.; bivalves Ostrea (O.) cf. cymbula, Clavipholas triangularis, Gryphaeostrea cf. plicatella, Amphidonte ostracina, Pycnodonte (Phygraea) cf. pseudovesicularis, etc.


Age 


Age Span: 

    Beginning stage: 
Santonian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
85.70

    Ending stage: 
Campanian

    Fraction up in the ending stage: 
0.25

    Ending date (Ma):  
80.78

Depositional setting

It is persistent in lithology and is of normal neritic facies.


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao