Warwickshire experienced a hot, arid climate during late Triassic times, about 230 million years ago. Layers of fine, red, wind-blown dust settled in a patchwork of shallow salt-lakes and sun-baked mudflats, surrounding the area now occupied by the Warwickshire coalfield. In the area north of Coventry, the ancient Precambrian rocks of the Hartshill ridge rose above the mudflats and crumbled and rusted in the heat. A shallow sea lay several hundred kilometres to the south-east, over parts of Germany, France and the southern North Sea.
The layers of dust are now preserved as beds of tough red clay, found in many parts of Warwickshire. Geologists refer to these rock layers as the Mercia Mudstone. Remnants of the ancient landscape still exist. In places, the red rocks are exposed amongst the greenery of modern Warwickshire, providing us with glimpses of an alien world.
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