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.
Outcrops The rocks are exposed across the Harlech Dome and southern Snowdonia.British Geological Survey 1:50,000 scale geological map (England & Wales) sheets 118, 119, 149
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 (in descending order i.e. oldest last) the Dol-cyn-Afon Formation, the Dolgellau Formation, the Ffestiniog Flags Formation, the Maentwrog Formation and the Clogau Formation.http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=MWG (BGS on-line lexicon of rock units)
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