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Dongdu Formation

Dongdu Fm


Period: 
Triassic

Age Interval: 
Early Late Triassic, (TJ34)


Province: 
Xizang (Tibet)

Type Locality and Naming

Chen Bingwei and Ai Changxing were named in 1983. The named section is located in the north of Wara Temple, Jiangda County, Tibet. The investigation team of the Sichuan Geological and Mineral Bureau and the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (1982) distinguished a set of Lower red beds, Middle limestone beds, and Upper volcanic rocks in the Jiangdawaxu area of Tibet, representing the Carnian deposits of the Late Triassic. Collectively referred to as the Jiapila Fm, the Dongdu Fm is equivalent to the lower red layer of this original Jiapila Fm.

Synonym:


Lithology and Thickness

It is mainly composed of purple-red sandy conglomerate, sandstone, siltstone intercalated with marlstone lens, and thick purple-red conglomerate at the bottom. The gravel composition is mainly quartz, with good roundness, and the gravel diameter is mostly 2 to 3 cm. Thickness of 360 m.


Lithology Pattern: 
Aus conglomerate


Relationships and Distribution

Lower contact

It is in unconformable contact with the underlying Middle Triassic Congla Fm

Upper contact

The top is in conformal contact with the overlying Gongye Nong Fm (Gongyenong Fm).

Regional extent

Distributed in the Jiangda County, Gongjue County, and Leiwuqi County of Tibet


GeoJSON

null

Fossils

It contains few fossils; only bivalve fragments are seen.


Age 

Tong et al. (2019, Triassic integrated stratigraphy and timescale in China, Science China: Earth Sciences, v. 62, no. 1) assign it as spanning Ladinian.

Age Span: 

    Beginning stage: 
Ladinian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
241.46

    Ending stage: 
Ladinian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
237.00

Depositional setting

This group is a marine deposit.


Depositional pattern:  


Additional Information


Compiler:  

Zhang Shunxin, Ji Kaixuan and Tong Jinnan.