They comprise the Carboniferous Limestone, the overlying Gritstone and the Coal Measures which occur only on the extreme margins of the area and infrequent outcrops of igneous rocks including lavas, tuffs and volcanic vent agglomerates.
They comprise the Carboniferous Limestone. They comprise the overlying Gritstone. They comprise the Coal Measures and infrequent outcrops of igneous rocks including lavas, tuffs and volcanic vent agglomerates. These Coal Measures occur only on the extreme margins of the area.