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Xiaoyan Formation
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Xiaoyan Fm base reconstruction

Xiaoyan Fm

Period: 
Cretaceous

Age Interval: 
Late Cretaceous, K2xy, (29d)


Province: 
Anhui

Type Locality and Naming

Huangshan Basin. The name of the Xiaoyan Formation was given by the No 332 Geological Team of the Anhui Metallurgy Bureau (1969) in Xiaoyan of the Shexian County, Anhui. The type locality is in the Yansi Town of Shexian, represented by the Xiaoyan section in Yansi of Shexian (29º47', 118º21').


Lithology and Thickness

The Xiaoyan Formation is a group of purple red, grayish red sandstone, lithic sandstone, intercalated with conglomerate in the lower part. Contains red laterite paleosol horizons. Cross beddings are well developed. It is over 674 m in thickness.


Lithology Pattern: 
Coarse-grained sandstone


Relationships and Distribution

Lower contact

It unconformably contacts with the underling Qiyunshan Fm.

Upper contact

Regional extent

The Xiaoyan Formation is distributed in the Shexian and Xiuning areas. Yangtze valley.


GeoJSON

{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[118.7,30.89],[119.03,31.01],[119.16,30.82],[119.03,30.05],[118.51,29.51],[118.12,29.47],[117.73,29.46],[117.49,29.65],[117.3,29.9],[117.3,30.28],[117.32,30.42],[117.44,30.56],[117.57,30.64],[117.81,30.7],[118.21,30.73],[118.7,30.89]]]]}}

Fossils

The formation yields dinosaur Wannanosaurus yansiensis and sauian Sauropoda. Outcrops of the Xiaoyan Formation yield the majority of dinosaur fossils in the southern portion of the Anhui Province.


Age 

For graphic purposes, middle half of Late Cretaceous. Basalt at base dated as ca. 98-105 Ma => begins in lower Cenomanian.

Age Span: 

    Beginning stage: 
Cenomanian

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
100.50

    Ending stage: 
Santonian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
83.65

Depositional setting

The formation belongs to fluvial and fluvial fan facies.


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao. Ages from Yu et al. (2020, Mesozoic Thrust-Nappe and Extensional Structure Frameworks in the East Segment of Southeast Yangtze Block, Southeast China. Journal of Earth Science, 31(4): 772-794.)