Mawddach Group


The Mawddach Group is a middle to upper Cambrian lithostratigraphic group in Gwynedd, Wales. The name is derived from the river known as the Afon Mawddach.

Outcrops

The rocks are exposed across the Harlech Dome and southern Snowdonia.

Lithology and stratigraphy

The Group comprises around 2400m thickness of mudstones, sandstones and siltstones laid down in the marine Welsh Basin during the middle to late Cambrian period. The Group comprises the Dol-cyn-Afon Formation, the Dolgellau Formation, the Ffestiniog Flags Formation, the Maentwrog Formation and the Clogau Formation.