Pu Tra Fm
Type Locality and Naming
The type section is located along the stream situated 2.6 km southeast of Nam Cong Village, Pu Tra Mt, Pu Sam Cap area (Lai Chau Province) (N = 22°10’; E = 103°35’). It was named by Bui Phu My et al. (1978) under the “Paleogene system” term.
Synonym: Hệ tầng Pu Tra: Trần Đức Lương, Nguyễn Xuận Bao 1988, Trịnh Dánh (in Phan Cự Tiến et al.) 1989, (in va Khúc et al.) 2000; Bùi Phú Mỹ (in Vũ Khúc, Bùi Phú Mỹ et al.) 1990.
Tectonogène formation de syénỉte norien: Lacroix A. 1933; Fromaget J. 1952.
Pateogen; Bùi Phú Mỹ et al. 1971, 1978; Phan Cự Tiến et al. 1977; Phạm Đức Lương (in Trần van Trị et al) 1997.
Lithology and Thickness
The Pu Tra Fm is composed of alkaline tuffaceous agglomerate and red-brown trachytic tuffs with an inclination of 20<30°. The tuffaceous agglomerate is composed of fragments of feldspar, trachyte, porphyritic trachyte, leucitophyre, black clay shale and sandstone, among them trachytc fragments play the main role. The thickness of the formation is about 300-400 m.
Relationships and Distribution
Lower contact
Unconformably rests upon upper Cretaceous Yen Chau Fm.
Upper contact
Not given.
Regional extent
Restricted to the Pu Sam Cap Mtn and Tam Duong areas (Lai Chau Province)
GeoJSON
Fossils
None; but close relationship to intrusives of syenite and porphyritic syenite datd as 29-56 Ma.
Age
Depositional setting
Localized volcanism.
Additional Information