Arfordir Gogleddol Penmon is a Site of special scientific interest on the Island of Anglesey comprising about 103Ha of land along some 7 km of coastline at the south-east tip of the island. The site was designated in 2003 for a range of interests including botany, ornithology, geology and its marine environment. The geological interest is largely centred on the disused Tandinas quarry which provides the type locality for the Tandinas formation of the Carboniferous limestone. There are very good exposures in the quarry and on the sea cliffs.