sentences:  There are less extensive areas in northeast Wales and along the north coast into Anglesey where similarly aged rocks characterize the landscape.The sequence includes Carboniferous Limestone at its base, followed by coarse sandstones (The ‘Millstone Grit’ of the north and the ‘Twrch Sandstone’ of the south), then mudstones and finally the Coal Measures which comprise a thick succession of mudstones, sandstones and of course coal seams.Though mid Wales lay above sea level during Carboniferous times, shallow tropical seas extended across much of north and south Wales and it was in these environments that a succession of types of limestone were deposited.