What is Kimmeridge clay?
[[File:Cliff at Kimmeridge Bay - geograph.org.uk - 165326.jpg |thumb|right|280px| Cliff at Kimmeridge Bay, [[Dorset]], England. The regular changes in the rocks ([[rhythmite]]) are caused by changes in the [[sea level]] at the time. In turn, this changes the sedimentation.]] [[File:Kimmeridge_Cliffs.JPG |thumb|right|250px|Jurassic [[shale]] cliffs of the Kimmeridge Clay formation]] The '''Kimmeridge clay''' [[Formation (geology)|formation]] is a [[sedimentary rock|sedimentary]] deposit of [[fossil]]iferous [[Ocean|marine]] [[clay]] and [[mudstone]]s. It is of [[Upper Jurassic]] age, and occurs in [[Europe]]. It gives its name to a stage in the [[Upper Jurassic]] called the '''Kimmeridgian''', lasting from 157.3–152.1 million years ago. Kimmeridge clay is perhaps the most economically important unit of rocks in the whole of Europe, because it is the major source for [[oil]] fields in the [[North Sea]]. The 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]]. It exists across England, in a band stretching from Dorset in the south-west, north-east to [[East Anglia]] and [[Kingston upon Hull|Hull]]. The [[River Humber]] Bridge's foundations are in the Kimmeridge Clay deposits under the Humber estuary. The fossil fauna of the Kimmeridge Clay includes a reptile fauna of [[turtle]]s, [[crocodiles]], [[dinosaurs]], [[plesiosaur]]s, [[pliosaur]]s and [[ichthyosaur]]s, as well as many [[invertebrate]] species such as ''[[Gryphaea]]''. == Climate == The Kimmeridge Clay was laid down in an environment which is not present on the Earth today.<ref name=Chambers/> Much of Western Europe was covered by a high sea-level: this may be related to the opening of the [[Atlantic]]. As a consequence, the UK was covered by a shallow and largely [[anoxic]] sea, perhaps less than 100m deep, with occasional landmasses.<ref>Wignall, Paul B. 1990. Benthic palaeoecology of the late Jurassic Kimmeridge Clay of England. S