The Namurian age lasted from 326 to 313 million years ago. It is preceded by the Visean stage/age (which corresponds to the upper Carboniferous Limestone of Great Britain) and succeeded by the Westphalian stage/age (which corresponds to the lower and middle Coal Measures of Great Britain). In the official geologic timescale of the ICS, the Namurian straddles the boundary between the Mississippian epoch (359-318 Ma) and the Pennsylvanian epoch (318-299 Ma).[1]