Highland Cattle - North Yorkshire Moors
The geology of the North York Moors is dominated by rocks of the Jurassic period. They were mostly laid down in subtropical seas 205 to 142 million years ago. Fluctuations in sea level produced different rock types varying from shales to sandstones and limestones derived from coral. These marine and delta deposited rocks are superbly exposed on the Yorkshire coast from Staithes to Filey.
Lower Jurassic At the beginning of the Jurassic period shales, clays and thin limestones and sandstones were deposited in a shallow sea. These deposits are many metres thick and include layers of ironstone of various thicknesses and the rocks from which alum is extracted.
Middle Jurassic A period of gradual uplift happened when mudstone and sandstone were deposited on a low lying coastal plain crossed by large rivers. Occasionally this land area was inundated by the sea and at these times calcarious rocks containing marine fossils were deposited. These are the Ravenscar Group of rocks. The Oxford Clay was deposited at the end of this era.
Upper Jurassic Towards the end of the Jurassic period the land again sank beneath the sea. At first the sea was shallow and calcareous sandstones and limestones were deposited. These are the Corallian rocks of the Tabular Hills towards the south of the area. Overlying the Corallian rocks is the Kimmeridge Clay which underlies the Vale of Pickering but this is not exposed at the surface.