Large Igneous Province and magmatic arc sourced Permian–Triassic volcanogenic sediments in China
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Large igneous province
Early Triassic
Island arc
Early Triassic
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Large igneous provinces are exceptional intraplate igneous events throughout Earth's history. Their significance and potential global impact are related to the total volume of magma intruded and released during these geologically brief events (peak eruptions are often within 1–5 m.y. in duration) where millions to tens of millions of cubic kilometers of magma are produced. In some cases, at least 1% of Earth's surface has been directly covered in volcanic rock, being equivalent to the size of small continents with comparable crustal thicknesses. Large igneous provinces thus represent important, albeit episodic, periods of new crust addition. However, most magmatism is basaltic, so that contributions to crustal growth will not always be picked up in zircon geochronology studies, which better trace major episodes of extension-related silicic magmatism and the silicic large igneous provinces. Much headway has been made in our understanding of these anomalous igneous events over the past 25 yr, driving many new ideas and models. (1) The global spatial and temporal distribution of large igneous provinces has a long-term average of one event approximately every 20 m.y., but there is a clear clustering of events at times of supercontinent breakup, and they are thus an integral part of the Wilson cycle and are becoming an increasingly important tool in reconnecting dispersed continental fragments. (2) Their compositional diversity in part reflects their crustal setting, such as ocean basins and continental interiors and margins, where, in the latter setting, large igneous province magmatism can be dominated by silicic products. (3) Mineral and energy resources, with major platinum group elements (PGEs) and precious metal resources, are hosted in these provinces, as well as magmatism impacting on the hydrocarbon potential of volcanic basins and rifted margins through enhancing source-rock maturation, providing fluid migration pathways, and initiating trap formation. (4) Biospheric, hydrospheric, and atmospheric impacts of large igneous provinces are now widely regarded as key trigger mechanisms for mass extinctions, although the exact kill mechanism(s) are still being resolved. (5) Their role in mantle geodynamics and thermal evolution of Earth as large igneous provinces potentially record the transport of material from the lower mantle or core-mantle boundary to the Earth's surface and are a fundamental component in whole mantle convection models. (6) Recognition of large igneous provinces on the inner planets, with their planetary antiquity and lack of plate tectonics and erosional processes, means that the very earliest record of large igneous province events during planetary evolution may be better preserved there than on Earth.
Large igneous province
Silicic
Flood basalt
Supercontinent
Felsic
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Paleomagnetic and rock magnetic experiments on the Triassic Yinkeng Formation and the Permian Changxing Formation sampled from the Permian‐Triassic type section, Changxing County, reveal that a high temperature primary direction is isolated in dolomitic samples from the Early Triassic but the Late Permian limestones samples appear to be remagnetized during the Jurassic. A Permian‐Triassic pole previously reported for the Changxing Formation from this section (Lin et al., 1985) is not in agreement with results from this study or other poles for that time interval reported for the Yangtze Block and may be remagnetized.
Early Triassic
Section (typography)
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Early Triassic
Permian–Triassic extinction event
Gymnosperm
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Permian–Triassic extinction event
Early Triassic
Extinction (optical mineralogy)
Terrestrial ecosystem
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Abstract The base of the Otoceras woodwardi Zone (stratotype in Himalayas) is accepted to define the base of the Triassic. Adoption of this convention is necessary because the Buntsandstein of Germany, the base of which provides the definition of the Permian-Triassic boundary, is not characterized for recognition throughout the world. All rocks older than the Woodwardi Zone are regarded as pre-Triassic. In terms of the four Lower Triassic stages (Griesbachian, Dienerian, Smithian, Spathian) the Woodwardi Zone is Griesbachian. Griesbachian ammonoids are assigned to 9 (possibly 11) genera. Of the 9, one is a survivor of the dominantly Paleozoic Prolecanitida. Two, assigned to Xenodiscidae, are Ceratitida with obvious Permian relatives. One, Otoceras, is the survivor of another Permian ceratitid stock. Five, paced in Ohpicer-atidae and Meekoceratidae, may be described as novel Ceratitida. The Griesbachian ammonoids thus include Paleozoic holdovers and novel Ceratitida. In Canada Lower and Upper substages are discriminated within the Griesbachian. Otoceras and Xenodiscus characterize the Lower Griesbachian. Ophiceratidae and Proptychites (Meekoceratidae) dominate the fauna of the Upper Griesbachian, in which Otoceras is unknown. These two substages are clearly recognizable in east Greenland, probably also in Siberia, Kashmir and at Spiti (Himalayas) and are thus of more than local significance. In Canada, Siberia, Greenland, and Spitzbergen the earliest Triassic beds have Otoceras but no Ophiceratidae or Meekoceratidae. Only in the Himalayas, where the sections are extraordinarily thin, and where individual beds may contain fossils of more than one age, is there any evidence that Ophiceratidae and Meekoceratidae occur in the earliest Triassic beds. The Lower Griesbachian is characterized by a meagre ammonoid fauna of which only Otoceras is diagnostic. It is thus impossible to identify earliest Triassic beds unless Otoceras is present. The Ophiceras-bearing beds of the Salt Range are certainly not necessarily earliest Triassic, but are more probably Upper Griesbachian. Lower Griesbachian has been definitely identified only in the Himalayas, Arctic Canada, Alaska, east Greenland, Spitzbergen and northeast Siberia. These Lower Griesbachian beds commonly, if not invariably, rest concordantly upon Permian rocks, but nowhere are the underlying Permian rocks demonstrably the youngest known beds of that System. As yet there is no known place where the youngest known Permian (e.g. the Paratirolites beds of Armenia) is followed by the earliest Triassic. The boundary everywhere seems to mark a hiatus with one or more units of the chronostratigraphic scale missing. Where the record is preserved, a world-wide event, probably an eustatic change in sea level, evidently interrupted marine sedimentation immediately before the Lower Griesbachian. A record may have been made in the ocean basins, but unless preserved in the Wharton Basin, west of Australia, it was presumably long ago swept into a subduction zone where its identity has been lost forever.
Early Triassic
Stratotype
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Summary A nesw Ophiceratid genus and species Durvilleoceras woodmani is described from the late Middle Permian Greville Formation of New Zealand, with Episageceras aff noetlingi Haniel. The horizon is close in age to the Kathwai dolomite of the Salt Range, which also has a mid-Permian Ophiceratid species, Ophiceras connectens Schindewolf. The occurrence of these two species shows that the Ophiceratidae cannot serve as an index of early Triassic rocks. The so-called basal Triassic Griesbachian Stage may prove to be closely linked to the Permian period. The key Griesbachian ammonoid genus Otoceras is related to Permian genera, with no later survivors. Moreover the widespread occurrence of Permian-type Productacea and other brachiopods in beds of the Griesbachian Stage in North America and Himalayas also suggests that the Griesbachian is Permian rather than Triassic. To judge from faunas, the start of the Triassic could be based on the incoming of numerous ammonoid families and Triassic brachiopods in the Smithian Stage. The intervening Dienerian Stage between the Griesbachian and Smithian stages is relatively barren of faunas, reflecting some sort of catastrophe at the end of the Paleozoic Era, but has mainly Permian survivors. Such a picture of the Paleozoic–Mesozoic boundary conforms with the intention if not the practice of early paleontologists.
Early Triassic
Conodont
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Large igneous province
Early Triassic
Island arc
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The ventral valve of an overtoniid productacean brachiopod generally thought to have been restricted to the late Paleozoic Era is described from the Blind Fiord Formation, Axel Heiberg Island, of Griesbachian (Early Triassic) age. It is not clear whether the specimen was derived from Permian rocks or was really of Griesbachian age. The latter appears likely from the fact that no similar specimens are known from underlying Permian. Genuine occurrences of Permian-type brachiopods in early Triassic rocks are rare. Half of the examples reported, from Armenia, Iran, and West Pakistan, are shown here to be dated erroneously, occurring in middle or late Permian rocks misdated as Triassic, Other examples, such as those from Green-land, are probably reworked because the Triassic beds conformably overlie mid-Permian rocks, and contain similar mid-Permian brachiopods, probably reworked from the underlying deposits.
Early Triassic
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Early Triassic
Permian–Triassic extinction event
Extinction (optical mineralogy)
Biota
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