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Yemahe Formation

Yemahe Fm

Period: 
Mesoproterozoic

Age Interval: 
Xishanian (Ectasian) Xs (28)


Province: 
Hubei

Type Locality and Naming

Central-westernmost Hubei. The Yemahe Fm was named by Li Quan, Leng Jian et al. in 1987. The naming section is located along Tiechanghe-Qiaodonggou, Tianjiashan Medicinal Herbs Farm, Shennongjia Forest District, Hubei Province. Middle formation (7 of 11 in Lexicon) of Shennongjia Gr.

Synonym: （野马河组）


Lithology and Thickness

The formation is composed of grey, brownish-grey and greyish thick-bedded massive dolomite, laminated dolomite, sandwiched with purple-red dolomite, stromatolite dolomite, siltstone and quartz sandstone. Stromatolites found in the formation mostly formed a large-sized reef. Oblique bedding, agitated bedding, intraclasts and oolites are seen in the dolomite. The formation is 1370 m thick.


Lithology Pattern: 
Dolomite


Relationships and Distribution

Lower contact

The base contacts conformably with the underlying Taizi Fm

Upper contact

The top is conformably overlain by the Wenshuihe Fm

Regional extent

Central-westernmost Hubei. The Yemahe Fm is distributged mainly in Shennongjia Forest District and Xujiazhai, Duchangguang, Dagushi, etc., in Dahong Mountains.


GeoJSON

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Fossils

The main stromatolite taxa are: Baicalia baicalica, B. yemaheensis, Jurusania yemaheensis, Tungussia cf. confusa, T. nodosa. Microalgae include Cephalophytarion giganteum, Heliconema sp.


Age 

SHRIMP U-Pb date on zircon in a tuff in the Yamahe Fm is 1220 Ma in the Yemahe Fm (Li Huaikun et al., 2013). Schematic stratigraphic column shows as late Xishanian (6 of 6 in Ectasian).

Age Span: 

    Beginning stage: 
Ectasian

    Fraction up in beginning stage: 
0.8

    Beginning date (Ma): 
1,240.00

    Ending stage: 
Ectasian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
1,200.00

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Extracts from The Mesoproterozoic Erathem (chapter in Stratigraphic Lexicon of China, draft of 2022) by Gao Linzhi, Ding Xiaozhong, Zhang Chuanheng, Zhang Heng.