The Llangynog Inlier (Coomb Volcanic Formation) is a geologic formation that crops out in Wales, which mainly consists of volcaniclastic rocks and rhyolite, as well as dolerite, dacite and a layer of rhyolitic conglomerates. A recent study also managed to date the Inlier to between 566 and 563 Ma, which means it temporally correlates directly with the Fermeuse Formation of Newfoundland, the Beacon Hill Formation in the Charnwood Forest, and the neighboring Stretton Shale Formation in Long Mynd. It also preserves fossils dating back to the Ediacaran period.