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Phong Hanh Formation

Phong Hanh Fm

Period: 
Cambrian

Age Interval: 
Middle Cambrian to Early Ordovician; Cm-S ph, (23)


Province: 
Middle Trung Bo

Type Locality and Naming

The stratotype of the formation has not been indicated. The exposures of the formation in the Phong Hanh area are about 1 km2, and are intruded by younger granitoids.

Synonym: Hệ tầng Phong Hanh: Trân Tinh et al. 1997 (Cambro - Silurian) Hệ tầng Pô Cô (part.): Trần Đức Lương, Nguyễn Xuân Bao 1988 (Neoproterozoic - Lower Cambrian), Hệ tầng A Vương (part.): Trần Đức Lương, Nguyễn Xuân Bao 1988 (Cambrian - Ordovician), Các hệ Cambri - Silur: Trần Tính el al. 1994


Lithology and Thickness

Sandstone (Quartz-rich) and Siltstone (quartz-sericite schist, clayey shale). According to Tran Tinh (1997) the Phong Hanh Fm includes 3 parts: Lower part: black-grey argillite and clayey shale with interbeds of andesitic- porphyritoids, porphyroids (1-2 m) and banded cherty shale; in some boreholes there are some interbeds of dolomitic marble. Thickness: 200-400 m. Middle part: quartz-rich sandstone, argillite, andalusite schist, cherty shale; in the sandstone and schist beds there are micro-veins of quartz-magnetite. Thickness: 300-400 m. This part is exposed in the Cho Dao mountainous area. Upper part: thin-bedded quartz-sericite schist interbedded with white-grey quartzite; quartzite beds contain micro-veins of quartz accompanied by magnetite in the form of fissure fillings. Thickness: 500 m. This part includes small exposures at Dien Dien, Hoi Tin extending in a NE-SW trend to Phong Nien. The total thickness of the formation in this section is about 1000-1300 m


Lithology Pattern: 
Sandy claystone


Relationships and Distribution

Lower contact

Upper contact

Unconformably covered by Mesozoic volcanics (Mang Yang Fm) and Cenozoic basalts

Regional extent

The formation occurs discontinuously in the Phong Hanh Mt area from Dien Dien, Ngan Son through Phong Nien to Nui Dao Mt (Phong Hanh iron deposit) areas of Phu Yen and Binh Dinh provinces.


GeoJSON

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Fossils


Age 

The Phong Hanh Formation has been referred to Middle Cambrian – early Ordovician based on dating of intrusions and estimated correlation to other regions. The finding of fossils will be necessary for a more more precise dating of the formation.

Age Span: 

    Beginning stage: 
Wuliuan

    Fraction up in beginning stage: 
0.0

    Beginning date (Ma): 
509.00

    Ending stage: 
Floian

    Fraction up in the ending stage: 
1.0

    Ending date (Ma):  
471.26

Depositional setting

The Phong Hanh Fm has been referred to Cambrian-Silurian (?) on the basis of the low degree of metamorphism of its sediments. The finding of fossils will be necessary for a more precise dating of the formation.


Depositional pattern:  

Additional Information


Compiler:  

Tran Van Tri and Vu Khuc (Editors; Geology and Earth Resources of Viet Nam, General Dept. of Geology and Minerals of Viet Nam; completed in Dec., 2011), with additional details from Tong-Dzuy Thanh and Vu Khuc (Editors; Stratigraphic Units of Viet Nam, 2nd edition; 2011; English edited by A. Boucot).