Late Jurassic geology
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| Late Jurassic geology | |
|---|---|
| Name | Late Jurassic |
| Color | #F5DEB3 |
| Time start | 161.5 |
| Time end | 145.0 |
| Caption | Marine limestones and continental sandstones from the Late Jurassic |
Late Jurassic geology The Late Jurassic epoch was a dynamic interval marked by continental fragmentation, widespread carbonate platforms, prolific volcanism, and diverse biotas. It records key transitions preserved in stratigraphic successions studied across regions such as Western Europe, North America, South America, Africa, Asia, and Antarctica. Research integrates data from institutions including the Geological Society of America, the British Geological Survey, the United States Geological Survey, and the Chinese Academy of Sciences.
Overview and Chronostratigraphy
The Late Jurassic corresponds to the Oxfordian, Kimmeridgian, and Tithonian stages of the Jurassic system and is defined by biostratigraphic markers such as ammonite zonations recognized in classic sections like the Kimmeridge Clay Formation and the Solnhofen Limestone. Chronostratigraphic frameworks rely on correlations between ammonite, belemnite, and radiolarian zones tied to timescales produced by the International Commission on Stratigraphy and calibrated with magnetostratigraphy developed in regions including Italy and Germany. High-resolution chemostratigraphy (carbon isotope excursions) from outcrops in Portugal, United Kingdom, and France refines stage boundaries and correlates marine to continental successions studied by teams at the Max Planck Society and the Smithsonian Institution.
Plate Tectonics and Paleogeography
Plate reconstructions place continents at mid to high latitudes relative to their present positions, with the northern part of Pangaea splitting into Laurasia and Gondwana and the opening of proto-oceanic gateways such as the early North Atlantic Ocean rift systems. Transform and rift provinces along margins of North America and Europe are documented by structural studies in the Iberian Peninsula and the Appalachian Basin. The breakup influenced dispersal routes examined in paleobiogeographic analyses of faunal provinces between Africa, South America, and India, and constrained by sedimentary records from basins like the Neuquén Basin and the Sichuan Basin.
Sedimentary Environments and Lithostratigraphy
Late Jurassic stratigraphy preserves thick marine carbonates, epicontinental shales, and continental siliciclastics. Notable lithostratigraphic units include the Morrison Formation (fluvial), the Kimmeridge Clay Formation (marine shale), and the Solnhofen Limestone (lagoonal). Facies models developed for carbonate platforms in the Bahamas Bank analogues inform reconstructions of reefal systems preserved in the Tethys Ocean margins of Greece and Turkey. Turbidite systems in the Western Interior Seaway and paralic successions in the North Sea basin record sediment routing influenced by relative sea-level changes constrained by sequence stratigraphy practiced by researchers from the University of Cambridge and the University of California, Berkeley.
Marine and Terrestrial Paleoclimate
Isotopic and palynological evidence indicate warm greenhouse conditions with attenuated latitudinal gradients and episodic basinal anoxia. Oxygen isotope records from belemnites and brachiopods studied in Scandinavia and Japan suggest surface temperatures consistent with humid subtropical belts described for parts of Europe and North America. Paleobotanical assemblages from the Morrison Formation and the Yanliao Biota imply seasonal precipitation patterns reconstructed by investigators at the Chinese Academy of Sciences and the Museum für Naturkunde. Oceanic anoxic events of smaller magnitude than Mesozoic extremes influenced organic-rich shale deposition in basins such as the Kimmeridge Clay Formation and the Paris Basin.
Magmatism, Orogeny, and Basin Development
Late Jurassic magmatic episodes affected continental margins and intra-plate settings, including the Karoo-Ferrar large igneous province links to magmatism recorded in South Africa and Antarctica. Orogenic activity along the northern margin of the Tethys Ocean involved the early stages of the Alpine Orogeny, producing foreland basins documented in the Carpathians and the Iberian Meseta. Rift-related extension produced pull-apart basins in the proto-North Atlantic and influenced hydrocarbon-prone depocenters like the North Sea and the Gulf of Mexico precursor basins investigated by teams from BP and Shell as well as national surveys.
Fossil Record and Biostratigraphic Correlates
The fossil record is exceptionally rich, with marine invertebrates such as belemnites, ammonites, and bivalves providing zonations; vertebrate assemblages include dinosaurs from the Morrison Formation (e.g., specimens curated at the American Museum of Natural History), marine reptiles in Europe and South America, and avian precursors in the Solnhofen Limestone preserved at the Bavarian State Collection for Paleontology and Geology. Palynological records from the Boreal Realm and the Tethyan Realm enable correlation between marine and continental successions used by researchers at the Natural History Museum, London and the Field Museum.
Economic Geology and Natural Resources
Late Jurassic rocks host significant hydrocarbon source and reservoir systems, including the organic-rich Kimmeridge Clay Formation as a major source for North Sea oil fields developed by United Kingdom operators and the North Sea sector. Continental clastics of the Morrison Formation are less prospective for hydrocarbons but are important for groundwater and construction aggregate resources managed by regional authorities in Colorado and Utah. Mineralisation related to Jurassic magmatism produced metallogenic signatures investigated in the Karoo Basin and in parts of Patagonia, while marine carbonate platforms supply dimension stone exploited in Germany and Italy.