Andrew Hollis explains the Kimmeridge Layers in this five-minute video
The Kimmeridge Clay is a sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation is the major source rock for North Sea oil.
The fossil fauna of the Kimmeridge Clay includes turtles, crocodiles, sauropods, plesiosaurs, pliosaurs and ichthyosaurs, as well as a number of invertebrate species.
Kimmeridge Clay is named after the village of Kimmeridge on the Dorset coast of England, where it is well exposed and forms part of the Jurassic Coast World Heritage Site.
Onshore it outcrops across England, in a band stretching from Dorset in the south-west, north-east to North Yorkshire. Offshore it is found throughout the Southern, Central and Northern North Sea.