Age : 290 to 354 million years ago
The start of the Carboniferous was marked by a major rise in sea-level which covered almost all of England and Wales. A gradual shallowing of the sea and formation of extensive deltas feeding from a landmass to the north (Scotland) led to the establishment of terrestrial conditions by the end of the Period.
A tropical climate predominated with the British Isles occupying an equatorial location.
The shallow tropical seas of the Lower Carboniferous were rich in marine life, particularly corals, brachiopods and trilobites. On land dense forests of ferns and horsetails grew on low-lying deltas during the Upper Carboniferous. The buried remains of these forests now form the coal beds found in the Coal Measures of the midlands and northern England.
Towards the end of this period the coming together of tectonic plates to form a supercontinent known as Pangea, led to a major phase of mountain building (the Variscan Orogeny). The main mountains were formed in Europe, but southern Britain felt the force of the collision, which produced spectacular folds in the Devonian and Carboniferous rocks along the north Devon coast at Hartland Quay. The deformative pressure reduced northwards and more gentle folds formed the Mendip Hills. Associated with this period of mountain-building was the intrusion of the granites found in south-west England and the attachment of the serpentinite of the Lizard Peninsula, a small piece of ocean crust which was pushed up and ‘welded’ onto the continental landmass.
Marine limestones (the Carboniferous Limestone) deposited during the Lower Carboniferous now outcrop widely forming the Mendip Hills, Avon Gorge, Derbyshire Peak district, the Yorkshire and Northumberland Dales. The overlying Millstone Grit forms upland areas in the Midlands and northern England (Peak District, Pennines, Forest of Bowland) while the Upper Carboniferous Coal Measures outcrops adjacent to the Millstone Grit, but forming lower-lying land, from Bristol, northwards to Cumbria and across to County Durham.