Nam Co Fm
Type Locality and Naming
The type section is located along the Nam Muc Stream from the Nam Muc Bridge (Tuan Giao - Lai Chau Road) to Muong Muon on the Lai Chau - Dien Bien Road (N = 21° 47', E = 103°15'). It was named by Tran Dang Tuyet.
Synonym: Hệ tầng Nậm Cô (Proterozoic): Dovjikov A.E. et al. 1965. Schistes lustrés (Calédonien): Fromaget J. 1937. Hệ tầng Nậm Cô (Upper Proterozoic - Lower Cambrian): Trần Đăng Tuyết et al. 1977; Vũ Khúc, Bùi Phú Mỹ et al. 1990. Hệ tầng Nậm Cô (Sinian): Nguyễn Xuân Bao et al. 1969. Hệ tầng Nậm Lệ (Sinian - Lower Cambrian): Nguyễn Xuân Bao et al. 1969.
Lithology and Thickness
Characteristic section is about 3000 m thick: (1) Mainly two-mica schist interbedded with thick-bedded quartz-feldspar schist; 1500 m thick. (2) Thin-bedded two-mica schist interbedded with quartz-feldspar schist, quartz-feldspar-chlorite schist; over 1000 m thick. (3) Mainly quartzites interbedded with quartz-feldspar- and two-mica schist and sericite schist; over 500 m thick.
Relationships and Distribution
Lower contact
The relation of the Nam Co Fm with older sediments has not been observed.
Upper contact
The upper boundary schist and quartzite of the Fm rests unconformably below the basal conglomerate of the Middle Cambrian Song Ma Fm.
Regional extent
Distributed in isometric exposures in the Muong Lay and Tuan Giao (Dien Bien Province), Muong Lat (Thanh Hoa Province) areas, and in long bands forming the core of the Song Ma Anticline in the Song La Province.
GeoJSON
Fossils
In the uppermost part, acritarchs have been found with Zonosphaeridium sp., Trachyoligotriletum sp., Archaeohystrichosphaeridium sp., Laminarites sp. of Late Neoproterozoic-Early Cambrian age.
Age
Depositional setting
Additional Information