The Warwickshire Coalfield extends between Warwick and Tamworth in the English Midlands. [1] It is about 40km / 25 miles from north to south and its width is around half that distance. Its western margin is defined by the 'Western Boundary Fault'. In the northeast it abuts against steeply dipping shales of Cambrian age. The larger part of the outcrop at the surface consists of the Warwickshire Group of largely coal-barren red beds.[2] The Daw Mill mine near Arley within the coalfield is now Britain's biggest coal-producer.
The principal coal seams within the productive Lower and Middle Coal Measures include (in stratigraphic order):[3][4]
The Two Yard, Thin Rider, Ryder, Ell, Nine Feet and High Main merge as one massive bed of coal known as the 'Thick Coal' in parts of the coalfield.