Garnedd-Wen Formation

The Garnedd-Wen Formation (also known as the Garnedd-Wen Beds) is an Ordovician lithostratigraphic formation (a sequence of rock strata) in Mid Wales. The rock of the formation is a mixture of mudstones, siltstones, fine- to coarse-grained sandstones, greywackes and conglomerates. The formation extends from Dinas Mawddwy in the north-east to Tywyn in the south-west.

Geography
The Garnedd-Wen Formation is the upper strata of rock across a wide part of western Mid Wales. In particular, it forms the upper rock beds of the Tarren Hills on the south side of the Bala Fault, west of Talyllyn Lake.