Song Cao Gr

The Song Cau Group consists of four component formations – a lower Si Ka Fm (Ha Giang Prov.), a middle Bac Bun Fm (Ha Giang Prov.), or a Na Ngan Fm (Cao Bang Prov.) that is coeval to the lower two of Ha Giang Prov; and an upper Mia Le Fm (widespread). Earlier usage was only the lower two formations.

Synonym: Điệp Sông Cầu: Trần Văn Trị et al. 1964, ỉ 977 (S₂-D₁); Dương Xuân Hảo ei aỉ. 1975, 1980 (D₁); Phạm Đình Long 1968 (D₂e). Loạt Sông cầu: Tống Duy Thanh et al. 1986,1993,1995; Vũ Khúc et al. 2000. Bậc Eifel (part.): Vasilevskaia E.D. (in Dovjikov A.E. et al. 1965); Dương Xuân Hảo et al. 1968. - Điệp Bán Rõm: Phạm Đinh Long 1967 (Devonian). Trầm tích Di-Dje (part.): Dương Xuân Hảo et al. 1973. Các trầm tích Đevon hạ (part.): Dương Xuân Hào et al. 1975. Điệp Nà Ngẩn: Phạm Đinh Long 1973,1975 D₁; Đoàn Kỳ Thuỵ et al 1976 (D₁). Điệp Bắc Bun: Hoàng Xuân Tinh et al. 1976 (Dt); Trần Đức Lương, Nguyễn Xuân Bao 1994 (Dj); Vũ Khúc, Bùi Phú Mỹ et al 1990 (Đi)

Mainly terrigenous sediments of littoral, grading upward into shallow-sea facies. Upper part of Mia Le Fm includes carbonate components. See details in Si Ka Fm, Bac Bun Fm, Mia Le Fm, and Na Ngan Fm.

Yunnanolepis sp. has been collected, and then follows the siltstone member bearing Tongdzuylepis vietnamensis and Howittia wangi.

The interbedding of marine and deltaic sediments, littoral facies in many sections of the Bac Bun Fm often makes for difficulty in the delineation of the boundary between the Si Ka and Bac Bun formations. This is especially difficult in sections where these two formations are thin, for example, in the Ha Lang area. It is reasonable to note that the Si Ka and Bac Bun formations were formed in environments alternating between continental and deltaic-littoral facies and then, continental shelf facies. Based on this and conforming to the Stratigraphic Code of Viet Nam, the Si Ka and Bac Bun formations have been combined into the Song Cau Gr