Co Noi Fm

Song Da Rift. The type section is located on Highway No.6, in the scction from Co Noi Fork to Co Noi Village (N= 21°08’; E= 104°10’). It was named after the holostratotype area - Co Noi.

Synonym: Hệ tầng Cò Nòi: Ivanov G. (in Dovjikov A.E. et al. 1965 - (Trias hạ); Vù Khúc (in Vũ Khúc et al.) 1965-(Trias hạ - trung); Vũ Khúc 2000, (in Vù Khúc et ai.), 2000 (Trias hạ). Diệp Cò Nòi: Vũ Khúc 1980, 1989, 1990, VQ Khúc et al. 2000 ; VQ Khúc, Bùi Phú Mỹ et al. 1990 (Trias hạ); Dinh Minh Mộng et al. 1978; Nguyền Xuân Bao et al. 1978; Phan Scm et al. 1978. Grès à Hoernesia socialis: Dcprat J. 1914. Điệp Làng Bài: Nguyền Trí Vát 1964. Điệp Bái Đằng: Vù Khúc, Trịnh Thọ, Lc Tựu 1972; Vũ Khúc 1980. Trias hạ: Phan Cự Tiến et al. 1977; Bùi Phú Mỹ et al. 1978; Đinh Minh Mộng et al. 1978; Nguyễn Xuân Bao et al. 1978; Phan Sơn elal. 1978. Điệp Tân Lọc: Phan Cự Tiến et al, 1977; Bùi Phú Mỹ et al. 1978; Dinh Minh Mộng et al. 1978; Nguyễn Xuân Bao et al. 1978; Phan Scm et al. 1978. Hệ tầng Tân Lạc: Vù Khúc et al. 2000 (Olenek).

Volcanic-ash-rich terrigenous grading upwards into limestone: Characteristic section (425 m total): (1).Red-brown siltstone, claystone and yellowish sandstone with some clayey limestone lenses; 30 m thick. Containing bivalves Eumorphotis cf. inaequicostata, Entolium discites microtis. (2). Tuffaceous sandstone with some interbeds of red-brown siltstone in the upper part; 250 m thick. (3) Yellow-gray, brownish clayey siltstone, shale with some sandstone; 35 m thick. (4) Grey marly shale and clayey limestone; 110 m thick; containing Olenekian ammonoid Tirolites cf. idrianus on a rolling boulder.

1) Claraia-Eumorphotis Assemblage of Induan age, including the following characteristic species: Ciaraia griesbachi, C. slachei, C . gerviUiaeformis, Eumorphotis sp.; 2) Tirolites - Unionites fassaensis Assemblage of Olenckian age, with the following characteristic species: ammonoids Anakashmirites nivalis, Tirolites cf. idrianus and bivalves Unionites fassaensis, Costatoria costata, Hoernesia socialis.