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The Permian-Triassic Boundary in New Zealand and New Caledonia and its Relationship to World Climatic Changes and Extinction of Permian Life
In New Zealand the stratigraphic contact between Triassic and Permian is generally unconformable, and there is no faunal intergradation. Griesbachian and Dienerian (basal Triassic) faunas are not known. The Permian segment is unusually thick, almost entirely marine, and moderately fossiliferous. The penultimate faunas, characteristic of the Waiitian Stage, are normal Permian faunas, approximately equivalent to the middle Dzhulfian zones of Armenia and Iran, Japan (Gujo), upper Ferntree Group of Tasmania, and upper Bellerophonkalk of Italy and Austria. Younger faunas, equivalent to the so-called Eotriassic of Armenia and Iran, are not present, though marine rocks are found. The topmost Permian fauna, characteristic of the Makarewan Stage of New Zealand, unlike the preceding faunas, lacks any of the major brachiopod groups, such as Stropho-menida or Productida which virtually disappeared at the end of the Paleozoic era. The brachiopod genera are members of orders and families which survived into the Triassic, such as Rhynchonellida, Spiriferacea and Dielasmatidae, but the genera are characteristic of the Permian Period. It is thus possible that the Makarewan Stage represents the very latest Permian, and the most convincing transition yet known into Triassic.
The earliest Triassic in New Zealand contains poorly-dated bivalves. The earliest ammonoids are of middle Scythian, or Smithian age.
The contact between Permian and Triassic in New Caledonia is less well exposed, and falls somewhere between brachiopods and bivalves of Capitanian (= basal Tatarian) age, equivalent to the Puruhauan Stage of New Zealand and Ladinian brachiopods. Ammonoids, including Xenodiscids, have been described by Avias and Guerin (1958) as either Late Permian or Early Triassic. Some are ascribed to Xenaspis of Middle Permian (Wargal-Chhidru age) but are accompanied by the Scythian genus Meekoceras. Mid-Permian Cyclolobus has also been identified.
The sequence of Permian faunas in New Zealand provide a key to the nature of the Permian-Triassic contact. Three faunas in the sequence of eight are relatively impoverished generically, with strong affinities to faunas of eastern Australia, and coincide in age with the main glacial phases of the east Australian Permian. Overlying faunas are more diversified, and therefore, indicate relatively warmer water. Following faunas are very diverse and include Fusulinacea and reef-building corals, absent from the other faunal suites. Each warm-water fauna is followed by an abrupt faunal change to a cold-water fauna.
This pattern of three cold episodes followed by warmer faunas is also reflected widely by faunas in the Northern Hemisphere through Canada and Siberia, and the cold episodes even affected paleotropical regions such as Texas, when cold-water genera such as Yakovlevia and Spiriferella were introduced for brief times. The pattern of glaciation and amelioration is also reflected in an intricate way by the nature of sedimentation over the entire globe, particularly in the formation of coral reefs, coal measures, tillites, salt deposits and red beds.
Climatic changes provide a simple explanation of the great destruction of life at the end of the Permian Period. This is considered to have been real, affecting over 50 per cent of all life. Faunal analyses show that the genera and families which perished were essentially tropical in habitat, and that a prime cause lay in unusually high temperatures for a brief interval.
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