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| Jurassic System | |
|---|---|
| Name | Jurassic |
| Color | #7BA1C2 |
| Time start | 201.3 |
| Time end | 145.0 |
| Time unit | Ma |
| Caption | Marine limestones of the Solnhofen Limestone, Germany |
Jurassic System The Jurassic System is a major interval of the Mesozoic Era traditionally recognized by stratigraphers and geologists as a time marked by widespread marine transgressions, diversification of reptiles and dinosaurs, and extensive carbonate and clastic sedimentation. It is defined by a succession of chronostratigraphic units correlated globally through biostratigraphy, magnetostratigraphy, and radiometric dates developed by communities associated with the International Commission on Stratigraphy, the Geological Society of London, and national surveys such as the United States Geological Survey and the British Geological Survey. Classic outcrops in Europe, North America, Africa, and Asia have driven research by figures and institutions including Charles Lyell, Roderick Murchison, and the Natural History Museum, London.
The System is demarcated by chronostratigraphic boundaries tied to the end-Triassic extinction and the base of the Cretaceous defined by Global Boundary Stratotype Sections and Points ratified by the International Commission on Stratigraphy and discussed in journals like Nature and Geological Magazine. Correlation uses index fossils such as ammonites in studies by the Paleontological Association, magnetozones referenced with geomagnetic polarity timescales from institutions like the International Geomagnetic Reference Field, and radiometric ages produced at laboratories like the Berkeley Geochronology Center. The start and end ages are constrained by high-precision U-Pb zircon dates from tuffs reported in publications of the Geological Society of America and integrated into the Geologic Time Scale.
The System is classically subdivided into Early, Middle, and Late epochs with stages such as the Hettangian, Sinemurian, Pliensbachian, Toarcian, Aalenian, Bajocian, Bathonian, Callovian, Oxfordian, Kimmeridgian, and Tithonian recognized in European-type schemes used by the International Commission on Stratigraphy and regional schemes in North America, China, and Russia. Regional chronostratigraphic charts published by the United States Geological Survey, the Chinese Academy of Sciences, and the Russian Academy of Sciences map these stages to local ammonite, belemnite, and foraminifer zonations developed in monographs by the Paleontological Society and museum series from institutions such as the Natural History Museum, Paris.
Lithofacies across the System include widespread limestones like the Solnhofen Limestone described in works from the Bayerische Staatssammlung, marine shales exemplified by the Posidonia Shale studied by the Senckenberg Research Institute, siliciclastic sandstones in basins documented by the British Geological Survey, and evaporites recorded in North African basins investigated by the Algerian Petroleum Institute. Depositional models derive from sequence stratigraphy frameworks advanced by ExxonMobil research, the Society for Sedimentary Geology, and case studies in the Western Interior Seaway published in the Journal of Sedimentary Research. Carbonate platform development and reef analogues have been explored in field programs led by the University of Oxford and Stanford University.
Paleogeographic reconstructions for the System depict the breakup of Pangaea into Laurasia and Gondwana, with the opening of the North Atlantic and the central Atlantic documented by tectonic syntheses from the American Geophysical Union and paleomagnetic studies from the Scripps Institution of Oceanography. Plate motions inferred by the Paleomap Project and interpreted in tectonic papers by the Geological Society of America show rifting, subduction along the Pacific margin affecting terranes studied by the USGS, and the formation of intracontinental basins analyzed by the Russian Academy of Sciences and the Chinese Academy of Geological Sciences.
Fossil taxa that define biostratigraphy and evolutionary trends include ammonites cataloged in museum collections at the Natural History Museum, London, belemnites described in monographs from the Paleontological Society, marine reptiles such as ichthyosaurs and plesiosaurs curated at the Natural History Museum, Oxford, and terrestrial dinosaurs reported from localities like the Morrison Formation investigated by the Carnegie Museum of Natural History and the American Museum of Natural History. Flora and microfossils including calcareous nannofossils, dinoflagellates, and palynomorphs are studied by the International Nannoplankton Association and palynology groups at the Swedish Museum of Natural History, informing paleoecological reconstructions in journals such as Palaeogeography, Palaeoclimatology, Palaeoecology.
Economic geology during the System includes hydrocarbon source rocks exemplified by the Kimmeridge Clay investigated by the British Geological Survey, reservoir sandstones and carbonate reservoirs explored by petroleum companies like BP and Shell, and evaporite-hosted minerals documented by mining surveys from the Geological Survey of Canada. Metallic mineralization associated with Jurassic magmatism is recorded in studies by the Geological Survey of India and the South African Council for Geoscience, while industrial minerals such as building stone, limestone for cement, and phosphate deposits have been exploited by regional firms and reported in economic reports by the World Bank and UN organizations.
The System was named in the early 19th century based on work in the Jura Mountains by geologists connected to the Geological Society of London, with nomenclatural development influenced by stratigraphers such as Roderick Impey Murchison and Adam Sedgwick and later formalized by the International Commission on Stratigraphy and national bodies like the United States Geological Survey and British Geological Survey. Classic stratigraphic sections and type localities described in publications from the Geological Society of London, the Royal Society, and university presses have driven debates over stage boundaries addressed at symposia sponsored by the International Union of Geological Sciences and documented in the Geological Journal and Earth-Science Reviews.
Category:Geologic systems