ABSTRACT
BACKGROUND: THE COAL MEASURES Once life became established on land it quickly developed a more complex habitat structure; as plants developed tree forms, so forests evolved (by the Late Devonian), and alongside this there was a great diversification of animal life. The late Devonian also saw the evolution of tetrapods (four-legged vertebrates) which emerged onto land in Mississipian times and started preying on the abundant invertebrate life already established there. By the Pennsylvanian there were extensive forests across the equatorial areas of the globe, which included the present areas occupied by north-west and central Europe, eastern and central USA, and elsewhere in the world such as southern China and South America. These forests are represented in the fossil record by coal seams, which are preserved because in these places the forests developed on mires, permanently waterlogged ground; the anoxic conditions prevented complete decay of the forest litter and thus prompted the formation of peat which, when compressed under a great thickness of later sediment, turned to coal. It was these vast beds of coal, and associated ironstones, clays, and other natural resources which, in Britain in particular, provided the raw materials for the Industrial Revolution.
