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Bulagenhada Formation
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Bulagenhada Fm base reconstruction

Bulagenhada Fm

Period: 
Jurassic

Age Interval: 
Oxfordian-early Kimmeridgian, (Cret17d, TJ6b)


Province: 
Inner Mongolia

Type Locality and Naming

Erlian Basin. Named after Bulagenhada in Inner Mongolia by No.1 Inner Mongolia Regional Geological Survey Team, 1976, Explanatory Text for 1∶200 000 Scale Geological Map. Upper formation in this regional version of the Xinganling Gr.

Synonym: Bulagin Had Fm


Lithology and Thickness

Comprises mainly off-white rhyolites, tuffs, volcanic breccias and obsidian (Kosenko et al., 2021)


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

"Apparently rests unconformably" on the Daotenouer Fm.

Upper contact

The Lower member of the Aershan Fm of earliest Cretaceous rests on the Jurassic strata (e.g., Hugejiletu Fm or the Xinganling Gr – of which this is the upper formation) with an angular unconformity (named as T11 in seismic reflection sections). Locally, the Hugejiletu Fm overlies the Bulagenhada Fm with a disconformity.

Regional extent


GeoJSON

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Fossils


Age 

Guo et al. (2019; Fig. 2; based on Guo et al., 2019) suggest entire Xinganling Gr spans 163 to 153 Ma, based on U-Pb (LA-ICP-MS) dates; which they assign as Oxfordian to early Kimmeridgian. Using GTS2020, the span of this Group would be mid-Callovian through earliest-Kimmeridgian. However, the entire Xinganling Gr is placed into only the Barremian (and perhaps extending downward further into lower Cretaceous) by Kosenko et al. (2021), who did not reference Guo et al.'s study. Therefore, until this conflict is resolved, the age model for the Erlian Basin stratigraphy by Guo et al. (2019) is used here.Arbitary allocating each of the three formations in this Gr to sub-equal durations; therefore:

Age Span: 

    Beginning stage: 
Oxfordian

    Fraction up in beginning stage: 
0.7

    Beginning date (Ma): 
156.81

    Ending stage: 
Kimmeridgian

    Fraction up in the ending stage: 
0.3

    Ending date (Ma):  
153.12

Depositional setting

Lacustrine with volcanic ash beds


Depositional pattern:  


Additional Information


Compiler:  

Guo, Z.X. et al. (2019, Early Cretaceous tectonostratigraphic evolution of the Erlian Basin, NE China, Marine and Petroleumm Geology, 110: 539-564)

Enhanced with Igor N. Kosenko, Jingeng Sha and Boris N. Shurygin (2021). Upper Mesozoic stratigraphy of Sikhote-Alin (Russian Far East) and northeastern China: Non-marine and marine correlations. Part 1: Upper Jurassic-Hauterivian AND 2. Barremian-Aptian. Cretaceous Research, 124: articles 104811 (https://doi.org/10.1016/j.cretres.2021.104811) AND 104812 (https://doi.org/10.1016/j.cretres.2021.104812)