Phu Tien Fm
Type Locality and Naming
North Song Hong Basin (north Red River Basin). The type section is located borehole GK.104 drilled in the Dinh Cao Commune area, Phu Tien District (Hung Yen Province) from 3544 to 3860 m (N = 20°42’; E = 106°05’).
Synonym: Hệ tầng Phù Tién: Lê Văn Cự 1982; Trịnh Dánh 1989, 1995, (in Vũ Khúc et al. 2000); Phan Trung Điền 2000. Diệp Phù Tiên': Đỗ Bạt, Phan Huy Quynh 1982, 1985, 1997,2000. Diệp Xuân Hòa: Phạm nồng Quế 1981; Skordụli V.D. 1983. Eocene: TOTAL 1991.
Lithology and Thickness
Dominated by Conglomerate. It is composed of grey, violet-chocolate colored sandstone, silty claystone with interbeds of conglomerate, the grains of which consist generally of rhyolite, quartz, crystalline schists and quartzite. The sandstone is polymictic, with poor rounding and sorting, and the cement is calcite-sericite. The siltstone is generally violet-grey colorcd, bearing sericite and ferrous oxide. In the uppermost part of the section, there is violet-chocolate colored polymictic conglomerate interbedded with clay shale bearing lustrous glide surfaces. The thickness of t he formation in this borehole reachcs 316 m.
On the open sea of the Bac Bo Gulf, the Phu Tien Fm has been found (?) in borehole GK. 107-PA (3050-3535 m) with fine-grained conglomerate and gritstone, the grain composition of which consists mainly of granite and metamorphic rocks; these sediments are interbedded with grey, brownish, strongly laminated sandstone and claystone. They were subjected to strong secondary alteration The thickness of the formation in this area reaches about 485 m.
Relationships and Distribution
Lower contact
Prior to mid-Eocene there was only erosion on the shelf. Unconformable upon the Middle Triassic Tam Dao Fm rhyolite [Not in Lexicon] or upon the Carboniferous-Permian Bac Son Fm limestone.
Upper contact
Unconformably covered by the Dinh Cao Fm.
Regional extent
Distributed at the base of narrow grabens, which extend along deep-seated faults.
GeoJSON
Fossils
Araucatya, Kỉukisporites, Cicatricosisporiỉes, Trudopoỉlenịtes, Trudopollis, Ephedripites, Tricoỉporopolỉenỉtes forming the Trudopottis Zone which characterizes the formation. Fossils have been found only in borehole GK.104.
Age
Depositional setting
It is interpreted as a fluvial-lacustrine environment.