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| Norian | |
|---|---|
| Name | Norian |
| Color | #F4AA00 |
| Time start | 227.0 |
| Time end | 208.5 |
| Usage | Global (ICS) |
| Defined by | Stratotype and Global Reference Section |
| Strata type | Upper Triassic |
| Former names | None |
Norian The Norian is a chronostratigraphic stage of the Upper Triassic, widely used in lithostratigraphy and biostratigraphy. It succeeds the Carnian and precedes the Rhaetian in the Triassic Period, and appears in continental and marine successions across Eurasia, North America, South America, Africa, and Australasia. The stage is central to correlations involving the Carnian Pluvial Event, the evolution of early dinosaur clades, and the assembly of Pangea-related basins such as the Newark Basin and the Germanic Basin.
The Norian was originally established in European stratigraphic practice and formalized by the International Commission on Stratigraphy (ICS). Its lower and upper boundaries have been defined by biostratigraphic and magnetostratigraphic criteria tied to conodont and ammonoid zonations, with stratotypes proposed in sections such as the Hallstatt Limestone and exposures in the Southern Alps (Italy). Correlation uses marker taxa like conodonts of the genera Metapolygnathus and ammonoids like Cochloceras and Tropites, as well as radiometric tie points from volcanic ash beds dated by U–Pb zircon methods pioneered by laboratories associated with institutions such as the United States Geological Survey and the Chinese Academy of Sciences.
The Norian spans roughly 227.0 to 208.5 million years ago based on the ICS time scale and high-precision geochronology from laboratories including the Max Planck Institute for Chemistry and the Geological Survey of Canada. Its duration overlaps major events recorded in the Karoo Basin and the Jucar Basin, with magnetostratigraphic patterns tied to the Geomagnetic Polarity Time Scale. Chronostratigraphic subdivisions often include the Alaunian, Lacian, and Sevatian substages in regional schemes developed by stratigraphers at institutions like the Geological Survey of Austria and the British Geological Survey.
Norian successions exhibit varied lithologies from siliciclastic red beds to carbonates and evaporites. Classic lithostratigraphic units include fluvial and lacustrine sequences of the Chinle Formation, marine carbonates of the Dolomites, and evaporitic sequences in the Keuper of central Europe. Sedimentologists from the University of Oxford and the University of California, Berkeley have documented facies transitions reflecting alluvial plain deposits, deltaic systems, and shallow epicontinental shelf environments influenced by the Tethys Ocean and intracratonic basins such as the Paraná Basin.
The Norian is notable for diverse terrestrial and marine faunas. Terrestrial vertebrates include early saurischian and ornithischian dinosaurs recovered from formations like the Ischigualasto Formation, Santa Maria Formation, and Lourinhã Formation; these discoveries involve researchers affiliated with the Smithsonian Institution and the Museo Paleontológico Egidio Feruglio. Archosauriforms and phytosaurs appear in the Ischigualasto-Villa Unión Basin and Chañares Formation, while marine faunas include ammonoids, bivalves, and conodonts pivotal for biostratigraphy. Plant assemblages documented from the Molteno Formation and New Red Sandstone successions include gymnosperms studied by paleobotanists at the Natural History Museum, London and the Chinese Academy of Sciences.
During the Norian, continental configurations reflected the late stages of Pangea assembly with extensive continental interiors and shallow epicontinental seas along the margins of the Tethys Ocean. Tectonic activity along the Alpine orogeny and nascent rifting in regions such as the Central Atlantic Magmatic Province influenced sedimentation patterns in the Newark Supergroup and the Gondwana basins like the Gondwana Basin sequences of India and Africa. Plate reconstructions produced by teams at the Paleomap Project and the University of Texas at Austin illustrate how strike-slip and extensional regimes controlled basin development and volcanic activity linked to igneous provinces.
The Norian is correlated globally through conodont and ammonoid biozones, magnetostratigraphy, and radiometric dates. Regional subdivisions include the Germanic Keuper, the North American Chinle, the South American Los Colorados and Ischigualasto, the European Norian of the Alps, and the Asian Norian sequences of China such as the Ermaying Formation. Correlative frameworks developed by the International Paleontological Association and regional geological surveys enable detailed comparisons among the Newark Basin, Mackenzie Basin, Karoo Basin, and the Paraná Basin.
Norian strata host resources including hydrocarbons in intracratonic and foreland basins such as the Neuquén Basin and Gulf of Mexico analogs, and evaporite deposits exploited for halite and gypsum in the Germanic Basin and Zagros Belt peripheries. Mineralization associated with Norian volcanic and sedimentary successions includes stratabound ores investigated by economic geologists at the United States Geological Survey and the Geological Survey of India. Additionally, Norian fluvial sandstones form aquifers and reservoir rocks targeted by energy companies and water resource agencies.
Category:Triassic stages Category:Stratigraphy