Mawddach Group
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TypeGroup
Sub-unitsDol-cyn-Afon Formation, Dolgellau Formation, Ffestiniog Flags Formation, Maentwrog Formation, Clogau Formation
OverliesHarlech Grits Group
Thicknessabout 2,400 m (7,900 ft)
| Mawddach Group | |
|---|---|
| Stratigraphic range: mid to late Cambrian | |
 Slates of the Dolgellau Formation exposed in the Golwen quarry, near Fairbourne | |
| Type | Group |
| Sub-units | Dol-cyn-Afon Formation, Dolgellau Formation, Ffestiniog Flags Formation, Maentwrog Formation, Clogau Formation |
| Overlies | Harlech Grits Group |
| Thickness | about 2,400 m (7,900 ft) |
| Lithology | |
| Primary | mudstones |
| Other | sandstones, siltstones |
| Location | |
| Region | northwest Wales |
| Country | United Kingdom |
| Type section | |
| Named for | Afon Mawddach (river) |
The Mawddach Group is a middle to upper Cambrian lithostratigraphic group (a sequence of rock strata) in Gwynedd, Wales. The name is derived from the river known as the Afon Mawddach.