Llanbedrog Volcanic Group

The Llanbedrog Volcanic Group is an Ordovician lithostratigraphic group in northwest Wales. The name is derived from the village of Llanbedrog on the Llŷn Peninsula where the strata are exposed.

Outcrops

This succession of rocks is exposed around the village of Llanbedrog and in a band stretching northwestwards inland.

Lithology and stratigraphy

The Group represents an assemblage of both volcanic rocks - lavas, tuffs, breccias - and volcaniclastic sediments - mudstones, siltstones, sandstones and conglomerates. It comprises the Yoke House Formation, the Carneddol Rhyolitic Tuff Formation, the Foel Ddu Formation and, at its base, the Penmaen Formation.