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Mentougou Gr

Mentougou Gr

Period: 
Jurassic

Age Interval: 
Lower-Middle Jurassic, (TJ59a)


Province: 
Beijing

Type Locality and Naming

It was named by Ye Liangfu as the “Mentougou Coal Series” in 1920. The naming section is located at Mentougou Gully of West Hills of Beijing. Upward succession of the Xingshikou Fm, Nandaling Fm, Yaopo Fm and Longmen Fm

Synonym: （门头沟群）


Lithology and Thickness

Lower part is composed of pebble-bearing gritstones, gritstones, siltstones, mudstones and coal beds; Upper part consists mainly of conglomerates and sandstones. The formation represents major coal-bearing strata of Jurassic in the western part of Beijing City.


Lithology Pattern: 
Coarse-grained sandstone


Relationships and Distribution

Lower contact

It overlies older strata of different geological times.

Upper contact

It is in a disconformable contact with the overlying Jiulongshan Fm. However, Huang (2019) states "the Longmen Formation (the so-called Jiulongshan Formation in northern Hebei Province)", therefore this equivalence (?) would also imply a disconformable upper contact with the Tiaonjishan Fm.

Regional extent

It is distributed in the Mentougou Gully, Zhaoji Mt, Datai, Da’an Mt and Zhaitang area of Baihua Mts, as well as in the area of the Jiulong Mt-Daliang area of the Xiangyu Valley and Mao’er Mt and Huangyuan Gully of Fangshan County. There are found exposures of the group also in the Jixian Basin of Hebei Province.


GeoJSON

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Fossils

Its upper part yields abundant plant fossils and a small amount of bivalve fossils (for the name list of the fossils see that for the Yaopuo Fm and Longmen Fm).


Age 

Schematic strat column in the previous "red Chinese Lexicon" had implied that the Mentougou Gr was Hettangian-Aalenian. Diying Huang (2019; Jurassic integrative stratigraphy and timescale of China. Science China: Earth Sciences, v. 62) re-assigns the Longmen Fm (which he considers as equivalent) as Bathonian through mid-Oxfordian followed by a Tiaojishan Fm of mid-Oxfordian through mid-Kimmeridgian. However, because the current Jurassic lexicon has separated the Jiulongshan Fm as above the Longmen Fm, then for graphic purposes these are placed as mid-Callovian through mid-Oxfordian and Bathonian through mid-Callovian, respectively. And, for the basal Xingshikou Fm, Huang (2019) assigns as mid-Pliensbachian through mid-Toarcian. Therefore, Huang (2019) interprets that the majority of the Early Jurassic (and also Norian-Rhaetian) is absent (used here).

Age Span: 

    Beginning stage: 
Pliensbachian

    Fraction up in beginning stage: 
0.5

    Beginning date (Ma): 
188.55

    Ending stage: 
Callovian

    Fraction up in the ending stage: 
0.5

    Ending date (Ma):  
163.41

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Jingeng Sha (coordinator)