Our Present Knowledge of the Permian of the Great Plains
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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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Abstract 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.
Early Triassic
Ladinian
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Moderately well-preserved Late Permian to Middle Triassic radiolarians are identified in chert beds that occur in the Shan-Thai Block of northern Thailand. These radiolarians are identical to the faunas of the Late Permian Neoalbaillella ornithoformis and N. optima Assemblage Zones and the Triassic Parentactinia nakatsugawaensis and Triassocampe coronata Assemblage Zones reported in chert sequences of Japan. We discovered the radiolarian faunas, apparently indicating Late Permian and Early Triassic ages, in almost continuous sequences of chert and shale exposed in the north of Chiang Mai. The occurrence of these radiolarian faunas provides important data to solve the P/T (Permian/Triassic) boundary in pelagic sequences. Our present discovery also furnishes significant data to reconstruct the paleobiogeography of Mainland Thailand during Late Permian to Middle Triassic times. Fifty species belonging to 35 genera, including three unidentified genera, are investigated taxonomically. Four new species Pseudospongoprunum? chiangdaoensis, Cenosphaera igoi, Cenosphaera? rugosa, and Tlecerina? apsornae are described.
Radiolaria
Early Triassic
Conodont
Biochronology
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This paper gives a brief account of some interesting aspects of Permian stratigraphy in China as well as in other regions. Approval of an integrated chronostratigraphic scheme to replace the traditional standard succession in the Urals is significant. This scheme will not only serve as a working template for the Subcommission in defining the GSSPs for intra Systemic boundaries following the concept and procedures of modern stratigraphy, but also as a catalyst for developing a more reliable global correlation of the Permian. Increasing data of magnetostratigraphy, isotopic ages and sequencestratigraphy make it possible to erect a correlation between the proposed standard and other Permian successions. In China, as a consequence of implementing multi categories of stratigraphic classification, a Chinese chronostratigraphic scheme consisting of three series and 8 stages was established based on updated data on Permian cono donts, fusulinids, ammonoids and palynomorphs. The well established chronostratigraphic units such as the stratotypes of the Permian Triassic boundary, the Changhsingian Stage, and even the Lopingian Series were basically accepted as the global standard of the Upper Permian. The base of the Permian System in China, which has been traditionally placed at basal level of the Kungurian Stage for more than half a century, is now in agreement with the international standard. However, the proposed international and Chinese chronostratigraphic units need to be enhanced through defining the GSSP for its basal boundary, refining the standard stratigraphic sequences, subdivisions and inter regional correlation. And correlation of post Artinskian successions is far from precise because of the strong biogeographic differentiation.
Chronostratigraphy
Magnetostratigraphy
Stratotype
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Foraminifers from the Upper Permian Bellerophon Formation, Permian-Triassic "transitional beds" and lowermost Triassic "streaky limestone member" of the Luka Formation in the Luka dection, western Slovenia are described and illustrated. Four new species of foraminifers are described: Multidiscus zhiriensis, M. dinaridicus and Globivalvulina lukachiensis from the Upper Permian, and Lingulonodosaria slovenica from the lowermost Triassic. The assemblage of Late Permian foraminifers consists of species characteristic of the Changhsingian of many regions in the Tethys: northwestern Caucasus, Transcaucasia, Iran, Turkey, northern Italy, northwestern Serbia, northeastern Hungary, and South China. Unfortunately, the uppermost part of the Bellerophon Formation in the Luka section is represented by dolomite and does not contain foraminifers. The Permian-Triassic boundary interval is represented by carbonate "transitional beds" deposited in a shallow restricted marine environment that contains foraminifers and conodonts. The species "Cornuspira" mahajeri, "Earlandia" gracilis, and "E." tintinniformis, marking the lower boundary of the Triassic worldwide based on foraminifers, are found both below and above the first appearance of the conodont species Hindeodus parvus in the Luka section. These species appear to be ecological species and their appearance coincideswith a stressful shallowwater environment. The first intervalwith nodosariid foraminifers appears 2mabove the P/T boundary and a second one is approximately 5m above the boundary. Both of these intervals with nodosariids are within the range of the conodont species H. parvus and within the I. staeschei – I. isarcica conodont Range Zone.
Conodont
Early Triassic
Carbonate platform
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The Early-Middle Permian(Cisuralian-Guadalupian) boundary is marked globally by tremendous changes in terms of the development of ammonoid faunas.At that time the new Order Ceratitida appeared and their first known representatives are found in the lowest part of the Middle Permian Roadian Stage.The earliest Ceratitida therefore serve as reliable markers for the boundary between the Lower and Middle Permian in the Tethyan region and North America in terms of ammonoids.In other biogeographic regions,how-ever,where Ceratitida have not been found,representatives of the families Pseudogastrioceratidae and Spirolegoceratidae play an important role in biostratigraphical subdivision.The GSSP(Global Stratotype Section and Point) between the Lower and Middle Permian is defined in the Glass Mountains of Texas based on the first appearance of the conodonts species Jinogondolella nanking-ensis.However,the first Middle Permian representatives ammonoids appear slightly below this level in the Texas section.As the Roadian Stage was originally defined by Furnish based on ammonoid data.Many ammonoid experts do not agree with a definition based on conodonts in view of a fact that a typical set of Middle Permian ammonoids existed in the Early Permian based on the conodont definiton.Ammonoid experts therefore strongly suggest that the ceratitid Paraceltites elegans and other ceratitid ammonoids should all be attributed to Middle Permian.In this study,characteristic ammonoid faunas around the boundary between the Lower and Mi-ddle Permian in China are re-identified and reviewed.Based on a number of ammonoid occurrences materials near the Kungurian-Roadian boundary previously reported,I consider that ammonoid faunas near the Lower-Middle Permian boundary mainly occur in South and northwest China.Compared with the coeval ammonoid faunas in Russia,it can be concluded that endemic elements including Pseudohaloritinae and Shou-changoceratinae dominate the ammonoid faunas near the boundary.Based on a new study of a number of the ammonoid faunas,the lower part of the Shuangbaotang Formation is assigned to the Kungurian,the middle to upper part of the formation to the Roadian;the Fanjiatun Formation to the Roadian or Wordian;the Jiala Formation from Xigaze,Tibet and the Urulung Formation at Duilongdeqing,Tibet,to Roadian.The Shuangbaotang Section in Gansu Province and the Dongwuli Section in Zhejiang Province are considered the most promising localities to solve the problem of the Kunguian-Roadian boundary in terms of ammonoids.
Conodont
Stratotype
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The Permian System in the Jilong area,southern Tibet is subdivided into the Jilong and Quburiga formations,which are composed of a set of medium-thick beded limestones,quartzose sandstones,and mudstones.Abundant fossils were found in the Permian strata,including twenty three genera and forty species of brachiopods,seven genera and ten species of anthozoans,twelve genera and four species of bryozoans,one genera and two species of ammonoids,some crinoids,and inchnofossils.Five brachiopod assemblages,one ammonoid zone,two anthozoan assemblages,one crinoid horizon,and one ichnofossil horizon were established from the Permian System in the Jilong area.On the basis of lithostratigraphic and biostratigraphic data,the Jilong Formation is regarded as the deposits of Early Permian Artinskian-Sakmarian stage,and the Quburiga Formation can be correlated to the Chihsian-Maokouan stages,with the top Quburiga Formation belonging to the Middle-Late Permian Wuchiapingian Stage.
Crinoid
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A new microcrinoid, Pentececrinus parvus (sub-order Cyathocrinoidea), from the Louisiana formation (Devonian-Mississippian) of Missouri is described and compared with other nonbrachiate crinoids possessing only three circlets of plates (IBB, BB, OO) and an anal. Such crinoids have been reported from the Mississippian, Pennsylvanian, and Permian of the United States, the lower Carboniferous of Europe, and the Permian of Timor and Russia. With the addition of Pentececrinus, it is inferred that they form a phyletic group extending from late Devonian or early Mississippian to Permian time and that known Permian representatives do not indicate regressive evolution or aberrant specialization.
Devonian
Phyletic gradualism
Late Devonian extinction
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