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Nanxin Formation
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Nanxin Fm base reconstruction

Nanxin Fm

Period: 
Cretaceous

Age Interval: 
Early Cretaceous, K1nx, (31a)


Province: 
Yunnan

Type Locality and Naming

The Yunnan First Regional Geological Survey Team erected the Nanxin Formation in 1973. The section for the designation is in Nanxin of the Longxian County of Yunnan.

Synonym or coeval: Mangang Fm.


Lithology and Thickness

The Nanxin Formation is roughly divided into two members. Lower member is mainly represented by brown red and brick-red arkose sandstone, intercalated with purple red mudstone, siltstone and conglomerate. Upper member is dominated by purple red and brown red mudstone with siltstone and fine sandstone. It is 1495.5 m thick.


Lithology Pattern: 
Clayey sandstone


Relationships and Distribution

Lower contact

The base of the formation is a conformable contact marked by purple red thick-bedded massive medium and fine-grained quartz sandstone with sandy mudstone is distinguished from the underlying Jingxing Fm made up of purple red mudstone with siltstone.

Upper contact

The top is a conformable contact bounded by the appearance of purple brown, gray purple and purple gray green greatly thick-bedded -massive sandstone at the base of the overlying Hutousi Fm.

Regional extent

The formation occurs throughout the central western and eastern Yunnan. It does not vary considerably in thickness. It is 1630.3 m at Shuolayakou of Deqen, 860.9 m in Changputang of Eryuan, 761 m in Jiangtoucun of Weishan, 825.2 m in Xiaocun, 1010.8 m in Kuqiaodi of Zhenyuan, 1780.6 m in Dapojiao, 144.6 m in Mamushu of Puer, and 1822.5 m in Zhonghianiu of Mojiang. Partly coeval with Mangang Fm.


GeoJSON

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Fossils

The formation yields bivalves Nippononaia mekongiconcha sp., Nakamuranaia chingshanensis, N. subrotunda, N. elongata; ostracods Monosulcocypris subovata, M. longa, M. subelliptica, M. gigantea, M. yunnanensis, M. ventriconvexa, M. reticulata, Ziziphocupris simakovi, Rhinocypris tuberculata; and Charophytes Atopochara trivolvis, Nodoclavator puchangheensis.


Age 

Partly coeval with Mangang Fm.

Age Span: 

    Beginning stage: 
Aptian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
121.40

    Ending stage: 
Albian

    Fraction up in the ending stage: 
0.75

    Ending date (Ma):  
103.68

Depositional setting

It is of fluvial deposition.


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao