Lai Chau Fm
Type Locality and Naming
Eastern side of Muong Te Basin. The type section is located Muong Lay Townlet area, along the Song Da River (N= 22°00’; E= 103°10’). It was named by Bui PhưMy 1990 after type region of Lai Chau.
Synonym: Hệ tầng Lai Châu: Dovjikov A.E. et al 1965; Bùi Phú M ỹ (ìn Vũ Khúc, Bùi Phú Mỹ et al 1990); Vũ Khúc 2000, {in Vũ Khúc et al.) 2000. Bộc Carni: Trịnh Thọ (ỉ'n Trân Văn Tri et al. 1977); Bùi Phú Mỹ et al. 1978.
Lithology and Thickness
Claystone; Black-grey, thin-bedded clayey shale containing many pyrite concretions interbedded with dark grey claystone, grey, medium-bedded siltstone and some light-grey fine-grained sandstone containing much feldspar and muscovite, locally, black-carbonaceous material; 400 m thick.
Relationships and Distribution
Lower contact
Destroyed by faults in type area. Regionally, the next older units are the Song Da Fm (Dien Bien Province) or Bac Son Fm (Lai Chau Province)
Upper contact
Unconformably underlies the Norian-Rhaetian Suoi Bang Fm (= the Muong Va Fm if Suoi Bang is classified as a Suoi Bang Gr). Locally (Lai Chau – Son La province boundary), the partly-coeval Pac Ma Fm reef limestone of upper Carnian is present.
Regional extent
This band extends along the submeridional Lai Chau-Dien Bien Fault separating the two basins of Song Da – Tu Le and Muong Te. It extends from the valley of the Nam Na River through Muong Lay Townlet to the northern end of the large Dien Bien Valley. It is considered equivalent to the Song Boi Fm distributed in the NW margin of the Song Da – Tu Le Basin.
GeoJSON
Fossils
Halobia austriaca, H. cordillerana vietnamica, H. comata, Discotropites sp., and Sagenites sp., etc.
Age
Depositional setting
The Lai Chau Fm is characterized by fine-grained terrigenous sediments mainly of deep-water facies
Additional Information