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Xueshan Formation
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Xueshan Fm base reconstruction

Xueshan Fm

Period: 
Cretaceous

Age Interval: 
Early Cretaceous, Aptian –Albian, (6b) K1xsh


Province: 
Qinghai, Xizang (Tibet)

Type Locality and Naming

Qiangtang Basin. The Xueshan Formation was erected by the Qingzang party of the Comprehensive Study Team of the Department of Petroleum under the Ministry of Geology and Mineral Resources in 1966. The section for the designation is in Wenquan of Qinghai (Jiang Zhongti, 1983). The reference section is on the southern slope of the Nazigang Snow Mountain northwest of the Jiangai Snow Mountain of Xizang (87°40′E; 34°00′N) (Jiang Zhongti, 1983).


Lithology and Thickness

The Xueshan Formation is built up by gray siltstone interbedded with silty mudstone, with limy mudstone and marl partings. Lower part is represented by gray medium-bedded and schistose siltstone, locally with micrite and gray and gray green moderately thick-bedded siltstone. Upper part is brown, gray green and gray siltstone, fine sandstone with clayey siltstone and silty mudstone partings. The Xueshan Formation is about 560 m thick.


Lithology Pattern: 
Siltstone


Relationships and Distribution

Lower contact

The base marked by gray medium-bedded schistose siltstone with micrite is gradational with the underlying Qiangmulequ Fm (J3) (central South Qiangtang column TJ37). Entry for central North Qiangtang column 31 suggests underlain by Zhaworong Fm; for which D.P. Xi et al. (2019, China Integrated Strat and TimeScale) may have generalized as Suowa Fm (which underlies the Zhaworong Fm in this lexicon stratigraphic scale).

Upper contact

The top of the formation is not observed. Regionally, the Paleocene Tuotuohe Fm is above. Generalized column for Qiangtang by D.P. Xi et al. (2019, China Integrated Strat and TimeScale) puts the upper Cretaceous Abushan Fm as next higher unit.

Regional extent

The present formation is mainly distributed in the Wenquan (about 560 m thick) and Nazigang (more than 220 m thick) areas. It has a persistent lithology.


GeoJSON

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Fossils

In the Wenquan area, it yields freshwater bivalves of Early Cretaceous Protocardia sp., P. interta, Lamprotula sp., Paranipponaia cf. paucisulcata, Trigonioides (Wakinoa) sp., Nippononaia aff. wakinoensis, Gervillellasp sp.; and in the Nazigang area, gastropods Ataphanus sp. In the marine intercalations at Tumen, it yields foraminifera Orbitolina birmanica, O. trochus, Hedbergella sigali, Bigenerina sp. and Textularia sp. (Wan et al., 2003).


Age 

Shown as uppermost Berriasian (base dashed from mid-Berriasian to mid-Valangian) through mid-Aptian by D.P. Xi et al. (2019, China Integrated Strat and TimeScale).

Age Span: 

    Beginning stage: 
Berriasian

    Fraction up in beginning stage: 
0.8

    Beginning date (Ma): 
138.78

    Ending stage: 
Aptian

    Fraction up in the ending stage: 
0.5

    Ending date (Ma):  
117.30

Depositional setting

It belongs to continental deposition with marine intercalations of Early Cretaceous


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao