Photo 22. The impressive Lower Carboniferous limestone cliffs of Eglwyseg Rocks, near Llangollen, north-east Wales. These shallow marine reef limestones were deposited around the north- eastern margin of the Wales-Brabant massif, which formed an uplifted landmass across mid-Wales after the Caledonian Orogeny. Gradually, as this landmass shed clastic sediments (sands, silts and muds) northwards and eastwards into the Bowland Basin, these sediments prograded and aggraded over the earlier Carboniferous Limestones to form the thick beds of the so called Namurian