Kimmeridgian

Kimmeridgian
Name	Kimmeridgian
Time start	157.3
Time end	152.1
Unit	Age
Era	Mesozoic
Period	Jurassic
Preceding	Callovian
Following	Tithonian

Kimmeridgian is an age in the Upper Jurassic series spanning approximately 157.3 to 152.1 million years ago, positioned between the Callovian and the Tithonian. The interval is recognized in regional and global chronostratigraphy and appears in stratigraphic columns used by institutions such as the International Commission on Stratigraphy, with type sections and stage definitions tied to classic outcrops in the Kimmeridge area of Dorset and other European localities.

Definition and stratigraphic placement

The formal stratigraphic definition of the Kimmeridgian stage derives from work by 19th‑ and 20th‑century geologists associated with stratigraphic syntheses by the Geological Society of London, comparative studies in the Paris Basin, and correlations with sections studied by researchers from the British Geological Survey. Boundary conventions incorporate ammonite biozones first cataloged by paleontologists influenced by the taxonomic systems of Oppel and refinements linked to chronostratigraphic frameworks promoted by the International Commission on Stratigraphy and stratigraphers working in the Western Interior Seaway and the Subalpine Basin. Global correlation uses marker fossils, magnetostratigraphy developed following methods from the Geomagnetic Polarity Time Scale community, and isotope stratigraphy adopted by laboratories affiliated with the Max Planck Society and university research groups.

Geology and lithology

Kimmeridgian successions are typified by alternating lithologies including organic‑rich mudstones, fossiliferous limestones, and siliciclastic units observed in the Wessex Basin, Paris Basin, and North Sea Basin. Notable lithofacies include bituminous shales comparable to those described from the Kimmeridge Clay Formation and carbonate platforms analogous to sequences in the Tethys Ocean margins investigated by teams associated with the University of Oxford and the Sorbonne University. Hydrocarbon prospectivity in Kimmeridgian strata has been a focus of industry studies by companies such as BP, Shell, and TotalEnergies, while sandstone reservoir analogues have been mapped in basins studied by the United States Geological Survey and the Norwegian Petroleum Directorate.

Paleontology and fossil assemblages

Kimmeridgian faunas and floras yield diverse assemblages dominated by ammonites, belemnites, bivalves, and marine reptiles documented in museum collections at the Natural History Museum, London, the Muséum national d'Histoire naturelle, and the Smithsonian Institution. Vertebrate remains include ichthyosaurs and plesiosaurs comparable to specimens curated by researchers from the University of Cambridge and the University of Bonn, while terrestrial inputs preserve dinosaur remains akin to finds reported from sites studied by teams affiliated with the Natural History Museum of Los Angeles County and the Monash University. Microfossils and palynomorphs used in biostratigraphy have been characterized by laboratories at the University of Copenhagen and the California Institute of Technology, enabling correlations with ammonite zonations first proposed by paleontologists linked to the British Museum (Natural History) and later refined by staff at the University of Paris.

Paleoenvironments and climate

Environmental reconstructions portray Kimmeridgian settings ranging from epicontinental seas like the Western Interior Seaway and North Sea embayments to tidally influenced shelves adjacent to the Tethys Ocean, with sedimentological and geochemical studies undertaken by teams from the University of California, Berkeley and the University of Leeds. Paleoclimatic interpretations using isotope geochemistry developed at institutions such as the ETH Zurich and the GEOMAR Helmholtz Centre indicate greenhouse conditions punctuated by regional variability documented in cores collected by the Integrated Ocean Drilling Program and analyzed by researchers at the Woods Hole Oceanographic Institution.

Regional correlations and subdivisions

Regional subdivisions of the Kimmeridgian have been delineated in the European Basin frameworks, the Americas (including correlations in the Western Interior Basin), the African Plate margins, and the Asian sequences studied in the Sichuan Basin and Mongolian outcrops. Biostratigraphic schemes employ ammonite zonations that link to regional stages developed by national geological surveys such as the Geological Survey of Canada and the Bureau of Economic Geology, while chemostratigraphic and magnetostratigraphic tie‑points have been contributed by programs coordinated through the International Ocean Discovery Program and university consortia including University College London.

Global significance and geological events

Kimmeridgian strata record key events relevant to Mesozoic Earth history, including episodes of regional transgression and regression affecting platforms bordering the Tethys Ocean and depositional shifts tied to tectonic processes associated with the opening of the North Atlantic and adjustments along neotectonic structures like the Alpine orogeny. These events have implications for studies of paleobiogeography conducted by researchers at the University of Tokyo and the University of São Paulo, and for understanding hydrocarbon systems explored by exploration teams from ExxonMobil and national energy agencies. The stage stands as a focal interval for multidisciplinary research combining expertise from institutions such as the Royal Society, the European Geosciences Union, and international museum networks.

Category:Jurassic