Nam Mu Fm
Type Locality and Naming
Song Da – Tue Le Basin. The type section is located along the Nam Mit Stream, near the mouth where it empties into the Nam Mu River (N= 21°51; E= 103°42’). It was named by Bui Phu My et al. 1978
Synonym: Hệ tầng Nậm Mu: Dovjikov A.E. et al. 1965; Vũ Khúc 1965, (in Tống Duy Thanh et al.) 1995, 2000, (in VQ Khúc el at.) 2000. - Điệp Nậm Mu: Vũ Khúc 1980, 1984, 1990; Bùi Phú Mỹ (<« Vũ Khúc, Bùi Phú M ỹ el al. 1990). - Schistes carniens: Fromaget J. 1941. - Bậc Carnh VQ Khúc, Trịnh Thọ (in Trần Văn Trị et al. 1977 1977; Phan Cự Tiến et al. 1977; Bùi Phú Mỹ et al.1978; Nguyễn Xuân Bao et al. 1978; Phan Sưn et al. 1978; Tràn Đăng Tuyểt et al.1978
Lithology and Thickness
Deep-water facies of claystone and siltstone; 1200 m total. (1) Grey to dark grey claystone containing pyrite concretions, thin-bedded siltstone with some interbeds of grey sandstone, 400 m thick. (2) Light-grey sandstone with interbeds of siltstone and shale, 100 m thick. (3) Dark-grey shale with interbeds of siltstone, 700 m.
Relationships and Distribution
Lower contact
Conformably rests upon the Muong Trai Fm
Upper contact
Conformably grades upward into the Pac Ma Fm of upper Carnian (Lai Chau – Son La province border region). Overlain by Suoi Bang Fm of middle-Norian to Rhaetian (Son La Province).
Regional extent
Large bands in the Nam Mu, Nam Gion, west Quynh Nhai – Son La Province, and in many narrow bands in north Phong Tho (Lai Chau Prov.) and west Van Yetn (Son La Province).
GeoJSON
Fossils
Camian bivalves, such as Halobia austrỉaca, H. talauana, Zitteiihalobia superba, and z. comate. Also ammonoids Margaritropites fongthoensis, Juvavites cf. edgari, and Discotropites sp.
Age
Depositional setting
The Nam Mu Fm has a monotonous composition, consisting mainly of deep-marine facies of black clayey shale.
Additional Information