The Kimmeridge Clay in DorsetIntroductionThe Kimmeridge Clay Formation is the penultimate land formation of the British Jurassic succession. William Smith was the first to document this distinct formation on his 1815 map and name it Oaktree Soil. In 1817 he gave the name Oaktree Clay to the layers of clay between the "Portland Rock" and the "Coral Rag and Pisolite", but in 1816 Webster was the first to describe the formation in detail and changed its name for the name now known as Kimmeridge Clay. Formation after the English village of Kimmeridge on Dorset's 'Jurassic Coast', a location frequently visited by fossil hunters. (Cox and Welsh, 1981). The sediments of the Kimmeridge Clay Formation were deposited during the Late Jurassic about 160 to 145 million years ago. The outcrop and subcrop of the Kimmeridge Clay in England extend from Dorset to North Yorkshire, but due to the lack of inland exposure, all stratigraphic studies of the formation have been carried out in the coastal sections between Weymouth and Swanage in Dorset (Figure 1) (Cox and Gallios, 1981) Figure 1: Outcrops of the Kimmeridge Clay Formation in the Dorset area are largely, but not completely, exposed on the surface at Kimmeridge. The thickness cannot therefore be measured directly. Seismic reflection profiles carried out by British Petroleum Ltd showed that the total thickness of the zone is between 535 m and 585 m (Gallois, 2000). The Kimmeridge Clay is arguably the most economically important rock unit in all of Europe as it forms one of the principal rocks of the North Sea. source rock, but on the coasts of England and Wales it has distinctive logarithmic responses and physical properties. Such rocks are of primary interest to the oil industry as...... middle of paper ......d, just above the range limit of Aulacostephanus ( Arkell, 1947) and at the lower limit of the distribution area of ​​Pectinatities (Cope, 1967). The total thickness of the Kimmeridge region is therefore approximately 508 meters. However, in contrast, units from the middle of the Eudoxus zone to the top of the formation are clearly visible in the Formation. From the base of the formation to the Eudoxus Zone, the strata are made up almost entirely of bioturbated shell clays and between the beds, oil and bitumen horizons are present. The upper Eudoxus Zone to the upper Pectinatus Zone is composed of kerogen-rich mudstones and coccolith limestone..