Lithostratigraphy
Silurian
| Rhuddanian | Phu Ngu formation (Katian – ?Rhuddanian) |
Not placed in stage
Phong Hang formation (?Upper Ordovician – ?Lower Silurian), Tan Mai formation (Upper Ordovician – Lower Silurian), Song Ca formation (Upper Ordovician – Lower Silurian), Sinh Vinh formation (Upper Ordovician – Lower Silurian), Co To formation (Upper Ordovician – Lower Silurian), Long Dai formation (Upper Ordovician – Lower Silurian)
Ordovician
| Hirnantian | Phu Ngu formation (Katian – ?Rhuddanian) |
| Katian | Phu Ngu formation (Katian – ?Rhuddanian) |
Not placed in stage
Phong Hang formation (?Upper Ordovician – ?Lower Silurian), Tan Mai formation (Upper Ordovician – Lower Silurian), Song Ca formation (Upper Ordovician – Lower Silurian), Sinh Vinh formation (Upper Ordovician – Lower Silurian), Co To formation (Upper Ordovician – Lower Silurian), Long Dai formation (Upper Ordovician – Lower Silurian)