Abstract

Carboniferous-Permian deposits are widespread in the Duyen Hai Zone (Coastal Zone) of Northeast Vietnam, but at the moment, lithostratigraphic units of these sequences used for geological mapping always are controversal debate topic and question for discussions. Previous researchs have shown that, lithostratigraphic units for Carboniferous-Permian deposits on the basis of fossil age (Dovjikov A. E. et al. 1965; Nguyen Quang Hạp 1967; Pham Van Quang 1970; Nguyễn Văn Liêm 1974, 1978, 1980; Nguyen Cong Luong 1980, 1985, 2001). Basis on characteristic lithological composition of rocks, the following lithostratigraphic units of Carboniferous-Permian deposits in the Duyen Hai Zone are recognized: Con Voi Formation (D3-C1 cv), Pho Han Formation (D3-C1 ph), Carboniferous-Middle Permian Sequence and Bai Chay Formation (P3 bc).