Kimmeridge Clay

The Kimmeridge Clay is a fossiliferous marine clay spanning the latest Jurassic into the earliest Cretaceous, with onshore deposits dated to the Kimmeridgian age of the Late Jurassic and offshore formations extending into the Berriasian stage of the Lower Cretaceous. It is exposed across southern and eastern England, forming a band stretching from Dorset in the southwest to North Yorkshire in the northeast, and it also underlies the North Sea across the Southern, Central and Northern basins, where it thickens considerably. The unit is the major source rock for oil fields in the North Sea hydrocarbon province, since offshore deposits that experienced enough heat generated substantial petroleum reserves. It carries a rich fossil assemblage of marine reptiles, including turtles, plesiosaurs, ichthyosaurs and thalattosuchians, alongside dinosaurs such as sauropods and numerous invertebrate species, documenting Late Jurassic marine ecosystems in detail. This entity documents the Kimmeridge Clay specifically as a geological formation, a Late Jurassic to earliest Cretaceous marine clay deposit.