period. At this time the part of the Earth's crust which would later become England lay in the equatorial zone and was covered from time to time by shallow tropical seas. Repeated cycles of inundation led to the development of a series of cyclothems; the laying down of layers of limestone, shale and sandstone with occasional coal seams.

Shortly afterwards, (c. 295 million years ago) molten rock once again intruded the sedimentary succession,