Litostratigrafie
Jura
| Sinemur | Blue Lias formation (Rét – Sinemur) |
| Hettang | Blue Lias formation (Rét – Sinemur) |
Trias
| Rét | Blue Lias formation (Rét – Sinemur) |
Silur
| Sheinwood | Dolyhir and Nash Scar limestone |
| Telych | Rhayader Mudstones formation |
| Aeron | Derwenlas formation |
| Rhuddan | Cwmere formation Haverford mudstone formation Trefawr formation |
Ordovik
Kambrium
| Kambrium stage 10 | Dolgellau formation (Jiangshanian – Kambrium stage 10) |
| Jiangshanian | Dolgellau formation (Jiangshanian – Kambrium stage 10) Ffestiniog Flags formation (Paibian – Jiangshanian) |
| Paibian | Ffestiniog Flags formation (Paibian – Jiangshanian) Maentwrog formation (Guzhangian – Paibian) |
| Guzhangian | Maentwrog formation (Guzhangian – Paibian) |
| Drum | Clogau formation Gamlan formation (Wuliuan – Drum) |
| Wuliuan | Gamlan formation (Wuliuan – Drum) Barmouth formation Hafotty formation |
| Kambrium stage 4 | Rhinog formation (Kambrium stage 3 – Kambrium stage 4) |
| Kambrium stage 3 | Rhinog formation (Kambrium stage 3 – Kambrium stage 4) LLanbedr formation (Kambrium stage 2 – Kambrium stage 3) |
| Kambrium stage 2 | LLanbedr formation (Kambrium stage 2 – Kambrium stage 3) Dolwen formation |