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Mesoproterozoic

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Nyalam Gr

Nyalam Gr


Period: 
Mesoproterozoic

Age Interval: 
Changchengian-Jixianian-Yuxian (Calymmian-Stenian), Ch – Yx (23)


Province: 
Xizang (Tibet)

Type Locality and Naming

South Tibet next to Nepal. The Nyalam Gr was named by Zhang Qi in 1981. The naming section is situated at Boqu River bank at Youyi Bridge- Rouqie Village, north of Nyalam County, Tibet. The Nyalam Gr is the oldest crystalline basement within the region, and includes the Quxiang Fm and Jiangdong Fm. [See those for details.]

Synonym: (聂拉木群) , Namjagbarwa Gr, Saila Gr, Namunani Gr and Xixa bangma Gr are considered as different names for the Nyalam Gr.


Lithology and Thickness

Lower part (Quxiang Fm) is dominated by different gneisses of mostly metamorphosed greywacke and mudstone. Upper part (Jiangdong Fm) is composed of mica schist, leptite, migmatite and marble, in which some tectonic blocks of different ages may be mixed. It is 6000 to 10,000 m thick. [See individual formations for details.]


Lithology Pattern: 
Sandy claystone


Relationships and Distribution

Lower contact

Bottom is not seen.

Upper contact

Its upper part is in a fault contact with younger strata, such as the Rouqiecun Fm (Sinian). Regionally, the next younger unit is the Qomolangma Gr that begins in mid-Tonian.

Regional extent

South Tibet next to Nepal. The group is widely distributed in Himalaya Mountains, even extends to Bhutan and India, where it is named "Vaikrita series" in India, "Dhumpu Gneiss" in Nepal, "Dajiling Gneiss" in Sikkim, and "Thimpu series " in Bhutan.


GeoJSON

null

Fossils


Age 

Some chronological data were obtained for the group, such as 1250 Ma (U-Pb), 1800±100 Ma (Sm-Nd?). Schematic stratigraphic section suggests span of late Changchengian through Yuxian (late Statherian through Stenian).

Age Span: 

    Beginning stage: 
Statherian

    Fraction up in beginning stage: 
0.8

    Beginning date (Ma): 
1,640.00

    Ending stage: 
Stenian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
1,000.00

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.