The giant Upper Yangtze Pb–Zn province in SW China: Reviews, new advances and a new genetic model
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Keywords:
Dolostone
Large igneous province
Isotope Geochemistry
Early Triassic
Early Triassic
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Chinese geologists have correctly interpreted the sequence in south China as including the youngest known marine Permian (Changxingian Stage), followed by earliest Triassic, strata with Otoceras (Griesbachian Stage, Gangetian Substage). Most of the Changxingian ammonoids are known only from China but one recently described species, Shizoloboceras fusuiense, is evidently congeneric with Paratirolites vediensis, which characterizes latest Permian (Dorashamian) beds of the south U.S.S.R. and Iran. This indicates that the youngest Permian beds of Iran and China are correlative. Alternative correlations which have been suggested, namely with Changxingian including beds younger than Dorashamian, and Gangetian correlative with Dorashamian, are rejected. Below the Changxingian is the Lopingian (or Wuchiapingan), characterized by a variety of early otocerataceans. Lopingian is more or less correlative with Dzhulfian.South China is the only known place where ammonoids of Dzhulfian (= Lopingian), Dorashamian (= Changxingian), and Gangetian (lowermost Triassic) ammonoids occur in a formational sequence. It does not necessarily follow that the Changxingian–Gangetian interval was one of faunal continuity and continuous deposition. Paleozoic-type brachiopods that locally occur in the basal metre of the Triassic formations do not establish that the relationship between the Permian and Triassic formations is transitional. The boundary between these formations is distinct. Probably, these brachiopods are derived from the subjacent Permian strata and are not natural members of the Triassic fauna.
Early Triassic
Conodont
Sequence (biology)
Correlative
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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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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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The Permian ended with the largest of known mass extinctions in the history of life. This signal event has been difficult to recognize in Antarctic non-marine rocks, because the boundary with the Triassic is defined by marine fossils at a stratotype section in China. Late Permian leaves ( Glossopteris ) and roots Vertebraria ), and Early Triassic leaves ( Dicroidium ) and vertebrates ( Lystrosaurus ) roughly constrain the Permian–Triassic boundary in Antarctica. Here we locate the boundary in Antarctica more precisely using carbon isotope chemostratigraphy and total organic carbon analyses in six measured sections from Allan Hills, Shapeless Mountain, Mount Crean, Portal Mountain, Coalsack Bluff and Graphite Peak. Palaeosols and root traces also are useful for recognizing the Permian–Triassic boundary because there was a complete turnover in terrestrial ecosystems and their soils. A distinctive kind of palaeosol with berthierine nodules, the Dolores pedotype, is restricted to Early Triassic rocks. Late Permian and Middle Triassic root traces are carbonaceous, whereas those of the Early Triassic are replaced by claystone or silica. Antarctic Permian–Triassic sequences are among the most complete known, judging from the fine structure and correlation of carbon isotope anomalies.
Early Triassic
Stratotype
Paleosol
Chemostratigraphy
Tetrapod (structure)
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