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Ezhai Formation
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Ezhai Fm base reconstruction

Ezhai Fm

Period: 
Jurassic, Cretaceous

Age Interval: 
Early Cretaceous, K1e, (38)


Province: 
Fujian

Type Locality and Naming

Eastern Fujian. The Ezhai Formation was erected by Li Jianhai in 1994. The section on which the formation was erected is along the Ezhai-Nanyuan river valley of the Qiaotou township of the Minhou County, Fujian. The Ezhai Formation represents the members a and b of the original Nanyuan Fm over the Changlin Fm along the Ezhai-Nanyuan river valley of the Qiaotou township of the Minhou County, Fujian, which is now considered as the second rock formation of the Nanyuan Gr and is assigned to Late Jurassic.


Lithology and Thickness

The Ezhai Formation is represented by a set of moderately acidic-acidic volcanic rocks, which is roughly divided into two members. Lower member is built up by dark gray and gray black andesite, dacite, dacitic tuff lava and tuff. Upper member is light gray and gray green rhyolitic crystal tuff lava with pyroclastic rocks, rhyolite and sedimentary rocks. It is 840.9 m thick.


Lithology Pattern: 
Volcanics


Relationships and Distribution

Lower contact

Its base is distinguished from the gray black medium- and thin-bedded tuffaceous siltstone of the underlying Changlin Fm. The formation is in eruptive-unconformable contact with the underlying Changlin Fm and older strata.

Upper contact

Its top is bounded unconformably by the occurrence of moderately acidic lava of the Chishui Fm.

Regional extent

The formation occurs to the east of the Dapu fault of the Zhenghe County of eastern Fujian. It is quite persistent in lithology. The volcanic activities increase in intensity from southwest to northeast.


GeoJSON

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Fossils

The sedimentary rocks of the upper member contain the Cupressinocladus- Brachyphyllum assemblage, estherias Yanjiestheria sp. Orthestheria sp. and vertebrata Rhynchosaurus orentalis, Trionychoidae, Teleostei.


Age 

In 1976 Zhang Wentang et al and in 1982 Cao Zhengrao et al attributed the formation to Early Cretaceous. The assignment to Early Cretaceous is adopted in this lexicon. Radiometric dates for the "Nanyuan Fm" are mainly in 142-133 Ma range => Berriasian-Valanginian; and as the middle formation in this now-upgraded Nanyuan Gr, tentatively put as Berriasian. However, the radiometric ages for the underlying Changlin Fm imply Kimmeridgian (see that entry); therefore, the base might be within the Tithonian.

Age Span: 

    Beginning stage: 
Tithonian

    Fraction up in beginning stage: 
0.7

    Beginning date (Ma): 
144.94

    Ending stage: 
Berriasian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
137.70

Depositional setting


Depositional pattern:  


Additional Information


Compiler:  

Wan Xiaoqiao