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Tu Le Formation

Tu Le Fm

Period: 
Permian

Age Interval: 
Changhsingian, (8)


Province: 
West Bac Bo

Type Locality and Naming

Tu Le Rift. The type section is located on the Tu Le - Gia Hoi car road, situated on the right side of the Ngoi Hut Stream (N = 21°44’; E = 104°22’). Nguyen Vinh el al. 1978. It was named by Establishing this formation Nguyen Vinh (in Phan Cu Tien el al 1977) considered it as a component of the Van Chan Complex including 3 formations, namely Nam Qua, Tu Le and Ban Hat.

Synonym: - Hệ tầng Tú Lệ: Nguyễn Vĩnh (in Phan Cự Tiến và nnk.) 1977; Nguyễn Vĩnh và nnk. 1978. - Phức hệ Vàn Chắn (part.): Nguyễn Vĩnh (in Phan Cự Tiến và nnk.) 1977. - Hệ tầng Văn Chấn (part.): Nguyên Vĩnh 1978; Vũ Khúc.và nnk. 1998; Vũ Khúc, Bùi Phú Mỹ et al. 1990. - Série de Phu Sa Phin (part.): Dussault L. 1921. - Các trầm tích Jura hầu như không phân chia: Dovjikov A.E. et al. 1965. - Hệ Jura: Phạm Đức Lương (in Trần Văn Tri và nnk.) 1977.


Lithology and Thickness

Tu Le – Gia Hoi Road section spans 710 m: (1). White-grey to black-grey, thin-bedded felsite with a lenses of grey-white porphyritic rhyolite, dull-white felsite with lends of banded tuffaceous siltstone; 270 m thick. (2). Grey porphyritic rhyolite and laminated porphyritic rhyotrachyte, sericitized tuffaceous siltstone; and in the upper part, light-gray thick-bedded porphyritic rhyotrachyte; 440 m. Subalkaline volcanics in the lower part; and alkaline, potassium-dominant type corresponding to A-granite type.


Lithology Pattern: 
Lava


Relationships and Distribution

Lower contact

Pseudo-conformity onto the Tram Tau Fm. [But Tram Tau Fm entry says the opposite; left now as older than Tram Tau Fm pending clarification.; therefore, the next older regional unit might be the Suoi Be Fm volcanics.]

Upper contact

Not yet observed; but next younger regional unit is either the Tram Tau Fm, or the Nghia Lo Fm

Regional extent

Tu Le is a scenic area in Yen Bai Province’s Van Chan District. It is a small town and valley that lies on the road from Nghia Lo to Mu Cang Chai.


GeoJSON

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Fossils


Age 

Originally assigned to Late Jurassic-Early Cretaceous (as in the entry of Tong-Dzuy Thanh and Vu Khuc (2011; Stratigraphic Units of Viet Nam). Now (Tran Van Tri and Vu Khuc (2011; Geology and Earth Resources of Viet Nam), attributed to Changhsingian, on the basis of synchronous with Cam Thuy Fm, Vien Nam Fm and Suoi Be Fm volcanics. CA-ID-TIMS (Shellnutt et al., 2020, Geology) dated the rhyolite as ca. 257.5 Ma average => late Wuchiapingian

Age Span: 

    Beginning stage: 
Wuchiapingian

    Fraction up in beginning stage: 
0.7

    Beginning date (Ma): 
255.83

    Ending stage: 
Changhsingian

    Fraction up in the ending stage: 
0.3

    Ending date (Ma):  
253.54

Depositional setting

Within-plate volcanism in an intracontinental rift setting.


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).