Nam Pia Fm
Type Locality and Naming
In the Nam Pia Stream mouth, situated on the right side of the Song Da River, Lai Chau Province (N = 22° 06’; E = 103° 16'). Described by Bùi Phú Mỹ et al. (1971)
Synonym: In the Cam Thuy area (west Thanh Hoa Province) the formation was described by Pham Van Quang as the Co Mi Fm (S2-D1 cm) and a considerable part of the Trung Son Fm (D2e ts). tầng Nậm Pla: Tống Duy Thanli 1978, 1980; rống Duy Thanh el al. 1986, 1988, (in Vù Khúc e1 ai), 2000 (D,); Ta Hoa Phuong, Wcyant M., 1994 (D,). Điệp Nậm Pì'à: Bùi Phú Mv (in Vũ Khúc, Bùi Phủ Mỹ el al.) 1990 (D1);
Bậc Eifel (part.): Dovjikov A.E, cí ai. 1965, Dương Xuân I láo et al 1968. Hệ Devon, ihống dưới: Bùi Phú Mỹ et al. 1971. Hệ tằng Cò Mi: Phạm Văn Quang, 1973 (S2-D1). Hệ tầng Trung Sơn (part.): Phạm Văn Quang, 1973 (D2C). Điệp Suối Tra (part.): Nguyễn Vĩnh, 1977 (D1). Diệp Bàn Nguồn (part.): Nguyễn Vĩnh, 1977. Các trầm tích Devon hạ - Eifeii'. Dương Xuân Hào (in Trần Văn Trị et al. 1977).
Lithology and Thickness
Claystone, Limestone, Conglomate: The Nam Pia Stream mouth scction (holostratotypc), total thickness of over 350 m, is composed of the 4 following members. (1). Puddingstonc, conglomerate and very-coarse-grained sandstone, 10 m thick. (2). Thick-bedded, coarse-grained quartzite, with some interbeds of clay shale in the upper part, 90 m thick. (3). Black-grey clay shale interbedded with marl and quartzitc, 120 m thick; containing Squameofavosites sp., Pachyfavosites sp., Favosites sp. (4). Black-grey clay shale interbedded with marl and limestone lenses in the upper part, 170 m thick;
Relationships and Distribution
Lower contact
Unconformable upon the Sinh Vinh Fm (O-S sv). The Nam Pia Fm rests in “pseudo-conformity” upon sandstone of the Dong Son Fm (O1ds)
Upper contact
Conformably underlies the Ban Pap Gr
Regional extent
The Nam Pia Fm is widespread in West Bac Bo, from the upper course of the Song Da River (Lai Chau Province) following the eastern margin of the Song Ma Structure to the west and east of Thanh Hoa Province. On the Tua Chua Heights, it is composed of marl and limestone interbedded with scricitc schist and sandstone. In the Than Hoa Province, it is distributed mainly in narrow bands surrounding the Cam Thuy – Ba Thuoc Anticlinorium.
GeoJSON
Fossils
These sediments contain abundant fossils, such as Favosites subnitellus, Squameofavosites cechicus, Sqf. baolacensis, Sqf. sokolovi, Sqf. vanchieni, Sqf. brusnitzini, Paraheliolites minutus, Chaetetipora vietnamica, Howittia wangi, Euryspirifer tonkinensis, Iridistrophia aff. praeumbracula, Schellwienella lantenoisi, Douvillia pattei etc.. Upper clay-marl member contains abundant fossils including Favosites brusnitzini, F. cf. preplacenta, F. stellaris, F. alpina, F. gregaiis, F. subiatus, F. saurini, F. cf. apina, F. ottiliae, Sapporipora phumyi, Squameofavosites sp., Emmonsia cf. yenlacensis, Gracilopora nana, Cladopora rectilineata, Caiiapora sp., Alveolites sp., Lecomptia (?) ramosa, Syringopora sp., Thecoslegites sp., Chaetelipora muonglaensis, GrypophyUum (?) sp., Hexagonaria sp., Clathrodictyon sp.
[Figure: Nậm Pìa Fm: Brachiopod and Tabulate fossils (images courtesy of Prof. Ta Hoa Phuong, Vietnam Natl. Univ. Hanoi)]
Age
Depositional setting
Additional Information