Jurassic period
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| Jurassic period | |
|---|---|
 | |
| Name | Jurassic |
| Time start | 201.3 |
| Time end | 145.0 |
| Timeline | Mesozoic |
Jurassic period The Jurassic period occupies a central interval of the Mesozoic Era, spanning from about 201.3 to 145.0 million years ago and following the Triassic and preceding the Cretaceous. Major developments during this interval include the diversification of dinosaur clades, the rise of gymnosperm forests, and significant tectonic rearrangements associated with the breakup of Pangaea and the opening of the Atlantic Ocean. Important fossil sites and historical figures such as Mary Anning, Richard Owen, and expeditions like the Dawson Expedition contributed to early understanding of Jurassic life.
Overview
The Jurassic follows the end-Triassic events recognized in studies of the Central Atlantic Magmatic Province, Campanian–Maastrichtian comparisons, and chronostratigraphic frameworks developed by the International Commission on Stratigraphy and researchers at institutions such as the British Geological Survey and the Geological Survey of Canada. Global marine transgressions linked to sea-level studies by teams at the United States Geological Survey and universities produced expanded shallow continental shelves recorded in European basins like the Paris Basin, the North Sea, and the Morrison Formation analogs in North America documented by the Smithsonian Institution.
Stratigraphy and Subperiods
Stratigraphic subdivision of the Jurassic into Lower, Middle, and Upper epochs follows conventions established by the ICS and regional stratigraphers such as those working on the Toarcian, Aalenian, and Kimmeridgian stages. Type sections and stratotypes across sites in the United Kingdom, Germany, France, China, and the United States—including key formations like the Lias Group, the Bajocian successions, and the Tithonian deposits—anchor chronostratigraphic correlations used by researchers at the Natural History Museum, London and the Yale Peabody Museum of Natural History.
Paleoclimate and Paleogeography
Paleoclimatic reconstructions from isotopic studies conducted by teams at the Max Planck Society, University of California, Berkeley, and the ETH Zurich indicate generally warm greenhouse conditions with reduced polar ice, punctuated by cooler intervals such as the Toarcian Oceanic Anoxic Event detected in cores from the Newark Basin and the Paris Basin. Paleogeographic maps produced by geologists at the Paleomap Project and the University of Edinburgh show progressive rifting of Laurasia and Gondwana, initiation of the North Atlantic seafloor spreading, and the formation of basins like the Neuquén Basin and the Sichuan Basin, which influenced biogeographic patterns documented by researchers at the Natural History Museum of Los Angeles County.
Flora and Fauna
Vegetation during the Jurassic was dominated by conifers and other gymnosperms documented in floras studied at the Royal Botanic Gardens, Kew and the Smithsonian Institution National Museum of Natural History, with notable taxa comparable to modern Araucariaceae, Cycadales, and bennettitaleans described by paleobotanists at the New York Botanical Garden. Marine faunas included ammonites, belemnites, and bivalves curated in collections at the Museum für Naturkunde, Berlin and the Field Museum of Natural History, while terrestrial vertebrates saw explosive diversification of saurischian and ornithischian dinosaurs collected by expeditions led by institutions such as the American Museum of Natural History and the Natural History Museum, London. Famous genera known from this period—central to exhibits at museums like the Royal Tyrrell Museum and the Dawson Museum—include large theropods, sauropods, and early avialans whose remains have been described in papers from Harvard University and the University of Oxford.
Geologic and Fossil Record
The geologic record of the Jurassic is robust in formations such as the Morrison Formation, the Solnhofen Limestone, and the Posidonia Shale; these sites have produced iconic fossils studied by paleontologists at the Bayerische Staatssammlung für Paläontologie und Geologie, the Senckenberg Research Institute, and the Natural History Museum, London. Taphonomic research from teams at the Chinese Academy of Sciences and the University of Portsmouth has refined interpretations of Lagerstätten preservation, while biostratigraphic frameworks using ammonite zonation developed by the Palaeontological Association and chronostratigraphic correlations adopted by the International Commission on Stratigraphy integrate radiometric dates from labs at the Oak Ridge National Laboratory and the U.S. Geological Survey.
Extinction and Transition to Cretaceous
The transition from the Jurassic to the Cretaceous involves faunal turnovers documented in European basins studied by researchers at the University of Cambridge and the Université de Rennes 1, and is recorded in stage boundaries such as the Berriasian defined by stratigraphers at the Geological Society of London and the International Commission on Stratigraphy. Causes for biotic change incorporate regional tectonics linked to rifting by scientists at the British Antarctic Survey and climatic trends investigated at the National Oceanography Centre, Southampton; these factors combined to reshape marine and terrestrial ecosystems during the early Cretaceous interval recognized by paleontologists at institutions like the Natural History Museum, London and the American Museum of Natural History.