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Mesoproterozoic

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Jiangdong Formation

Jiangdong Fm

Period: 
Mesoproterozoic

Age Interval: 
Xishanian-Yuxian (Ectasian-Stenian), Jx – Yx (23)


Province: 
Xizang (Tibet)

Type Locality and Naming

South Tibet next to Nepal. The Jiangdong Fm was named by Mao Yanshi in 1985. The type section is at Youyiqiao-Rouqie Village, Nyalam County, Tibet. Upper formation in Nyalam Gr.

Synonym: （江东群）


Lithology and Thickness

In the type section, the formation is subdivided into lower and upper parts. Lower part is dominated by biotite leptite ["leptite" = near obsolete term for fine-grained gneissic metamorphic rock; composed of feldspar and quartz with subordinate mafic minerals], sandwiched with biotite migmatite, biotite gneiss and marble. The strata were mostly migmatized. Upper part consists of biotite leptite sandwiched with biotite quartz schist, diopside marble and hornblende-quartz schist. The thickness varies from 529 m to over 5500 m.


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

It is conformable with the underlying Quxiang Fm.

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. It is distributed in Nyalam, Gyilong, Yadong and Nanjiabawa region.


GeoJSON

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Fossils


Age 

Schematic stratigraphic section suggests span of Xishanian through Yuxian (Ectasian through Stenian).

Age Span: 

    Beginning stage: 
Ectasian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
1,400.00

    Ending stage: 
Stenian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
1,000.00

Depositional setting

From mindat.org: classic leptite has been interpreted as tectonized quartzo-feldspathic volcanic rocks


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.