Kimmeridgian

The Kimmeridgian is a stage of the Late Jurassic Epoch. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma (million years ago). The Kimmeridgian stage follows the Oxfordian stage and precedes the Tithonian stage.

The stage takes its name from the village of Kimmeridge on the Dorset coast, England where the exposure is at its greatest extent. The beach at Kimmeridge Bay is a good place for looking for fossils — there are specimens on the beach washed in by the tide.

The Kimmeridge Clay formation is the source for about 95% of the petroleum in the North Sea.

Usage of the term

Historically the term Kimmeridgian has been used in two different ways. The base of the interval is the same but the top was defined by British stratigraphers as the base of the Portlandian stage ("sensu anglico") whereas in France the top was defined as the base of the Tithonian ("sensu gallico"). The differences have not yet been fully resolved, although Kimmeridge-Tithonian are now the agreed terms globally [ [http://www.es.ucl.ac.uk/people/bown/ISJS31.pdf|INTERNATIONAL SUBCOMMISSION ON JURASSIC STRATIGRAPHY, Newsletter 31, Edited by Nicol Morton and Paul Bown, August 2004] ]

Vertebrate Fauna

Ankylosaurs

Plesiosaurs

Thalattosuchians

Belemnites

Environment

The variation of fauna during the Kimmeridgian stage indicates the existence of two distinct environments, the first being a being a shallow and agitated layer abundant in pebbles and fossils and the second following environment being a calm and deep layer marked by an absence of pebbles and by an abundance of pelagic organisms, such as Ammonites.

Localities

*Guimarota

References

* [http://www.stratigraphy.org/geowhen/stages/Kimmeridgian.html GeoWhen Database - Kimmeridgian]