A revised graptolite biostratigraphy for the lower Caradoc (Upper Ordovician) of southern Scotland
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Synopsis Biostratigraphical evaluation of graptolites from more than 160 localities in the lower Caradoc of southern Scotland does not differentiate a discrete assemblage diagnostic of the Climacograptus bicornis peltifer Biozone. The lowermost Caradoc Nemagraptus gracilis Biozone is redefined by the partial-range of N. gracilis below the appearance of Climacograptus bicornis s.l. The succeeding C. bicornis Biozone is divisible into (1) a lower Subzone of Orthograptus apiculatus and Dicranograptus ziczac, identified also by the appearance of Amplexograptus leptotheca, Dicranograptus tardiusculus and several other taxa, and (2) an upper Subzone of Climacograptus wilsoni, marked by the first appearance of C. wilsoni. Nemagraptus gracilis and Didymograptus (s.l.) superstes range into the lower part of the apiculatus-ziczac Subzone, above which is a poorly characterized interval that is approximately equivalent of the ‘peltifer’ Biozone of former usage. The bicornis Biozone is the approximate equivalent to the C. bicornis Biozone of North America, and, at least in part, of the foliaceus, (or multidens) Biozone of southern Britain. It is succeeded in Scotland by the clingani Biozone.The present paper deals with two sections of Huang’ai,Shengping and Tianlingkou Formations
in Gongcheng,Guangxi Autonomous Region used to be regarded as of Cambrian age due to the lacking of
fossils.In 1997 Ordovician graptolites indicating mainly Middle Ordovician were first discovered from the
rocks,and briefly reported in 1999.The details of these two sections are presented herein,and biostrati-
graphy discussed.The sections,located in the northeast of Gongcheng,Guangxi with considerably abun-
dant Ordovician graptolites,include the following 8 graptolite zones(in descending order):8.Nemagrap-
tus gracilis,7.Pterograptus elegans,6.Nicholosonograptus fasciculatus,5.Acrograptus ellesae,4.Undu-
lograptus austrodentatus,3.Exigraptus clavus,2.Isograptus caduceus of.imitatus,1.Didymograptus
(E.)abnomis.The graptolite biozones are comparable with those in SE China,Australia,Canada,North
America and Great Britain.The succession is believed to be representative of deep-water‘Isograptus’fa-
cies in the Zhujiang Region of South China.
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Zhen, Y.Y. & Percival, I.G. March 2017. Late Ordovician conodont biozonation of Australia—current status and regional biostratigraphic correlations. Alcheringa 41, xxx–xxx. ISSN 0311-5518.Seven conodont biozones are recognized in the Upper Ordovician of Australia. The Pygodus anserinus, Belodina compressa and Phragmodus undatus–Tasmanognathus careyi biozones are successively represented in the Sandbian. Although the Erismodus quadridactylus Biozone of the late Sandbian North America Midcontinent succession was previously recognized in the Stokes Siltstone of the Amadeus Basin and the Mithaka Formation of the Georgina Basin in central-north Australia, we argue for a middle–late Darriwilian age for these two units. Four conodont biozones, from oldest to youngest the Taoqupognathus philipi, T. blandus, T. tumidus–Protopanderodus insculptus and Aphelognathus grandis biozones, are established in the Katian of eastern Australia. Taoqupognathus species are particularly useful in correlation of the lower–middle Katian successions of eastern Australia with contemporary rocks in other parts of eastern Gondwana and peri-Gondwana, such as with the three major terranes of North and South China and Tarim. These regions, together with Sibumasu and eastern Australia, were part of the Australasian Superprovince during the Late Ordovician, with a strong palaeobiogeographic identity signalled by domination of Taoqupognathus, Tasmanognathus and Yaoxianognathus. Longstanding difficulties for precise correlation with the well-established North American Midcontinent or Baltoscandian successions in the Late Ordovician, owing mainly to strong endemism of the Australian faunas particularly from shallow-water settings, have been resolved by integration of regional conodont biostratigraphic schemes. The conodont biozonation of the Australian Upper Ordovician reviewed herein also provides a crucial chronological reference for better constraining the temporal and spatial range of Late Ordovician tectonostratigraphic events across the intracratonic basins of northern and western Australia and orogenic belts of eastern Australia.Yong Yi Zhen* [yong-yi.zhen@industry.nsw.gov.au] and Ian G. Percival [ian.percival@industry.nsw.gov.au], Geological Survey of New South Wales, W.B. Clarke Geoscience Centre, 947–953 Londonderry Road, Londonderry NSW 2753, Australia.
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This paper is a synthesis of calcareous nannofossil biostratigraphy for the Lower and Middle Jurassic of the Mediterranean Province based on several sections from Northern and Central Italy. Nannofossil events were calibrated with ammonite biostratigraphy and, when necessary, ammonite-controlled sections in South East France were incorporated. Data derive from previously published biostratigraphies and unpublished data of the authors.The large data-set allowed estimates of reliability and reproducibility of single events. As a result, in the Hettangian-Bathonian interval we propose 47 main events based on diagenesis-resistant and common taxa, 17 events based on rare but ubiquitous taxa and 12 potential events requiring further investigations due to taxonomic problems and sporadic occurrence. A biostratigraphic scheme, consisting of 11 zones and 15 subzones, is proposed for the Tethyan Lower and Middle Jurassic. The proposed biostratigraphy is compared to recent schemes compiled for Portugal, Morocco, Switzerland and the Boreal Realm. Only 27 events are reproducible in various regions, but diachroneity of most events seems to derive from different ammonite biostratigraphies applied in different areas. A very high stratigraphic resolution is achieved in Italy/France for the Pliensbachian to Lower Bajocian interval. The Sinemurian and Bathonian are characterized by the lowest resolution, and very few sections with ammonite control and/or favourable lithologies are available for improvement of nannofossil biostratigraphy. This study confirms the potential of calcareous nannofossil biostratigraphy for dating Lower and Middle Jurassic successions as well as for intra- and inter-regional correlations.
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Abstract: Two new bryozoan species are described from the Upper Ordovician Sassito Formation of the Argentinean Precordillera: Moyerella spinata sp. nov. and Phylloporina sassitoensis sp. nov. The bryozoans are found in cool‐water carbonates. The Silurian genus Moyerella is reported the first time in the Ordovician, showing palaeobiogeographic connections with Estonia and Siberia.
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The enigmatic pentameride brachiopod Noetlingia Hall and Clarke, 1893 is revised and its stratigraphic range corrected. The type species Noetlingia tscheffkini occurs only within the upper Darriwilian (Ordovician) of the East Baltic and not in the Silurian as previously assumed. Thus, presently defined, the superfamily Porambonitoidea does not cross the boundary between the Ordovician and Silurian systems. Two other species occurring in the Lower to Middle Ordovician of South China and North America are assigned to Noetlingia.
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Abstract Graptolites from the latest Ordovician to the earliest Silurian rocks of northwest Peninsular Malaysia are described and reviewed. The fossils were collected previously by C. R. Jones and presently by the authors inside the black mudstones from the basal section of Tanjung Dendang Formation in Pulau Langgun, Langkawi, which comprises assemblages from the Hirnantian Metabolograptus extraordinarius Biozone to the Rhuddanian Akidograptus ascensus – Parakidograptus acuminatus Biozone. The latest Ordovician strata also include a Hirnantia fauna bed between the Metabolograptus extraordinarius and Metabolograptus persculptus biozones, in which shelly fossils such as Mucronaspis sp. could be recovered. A revised graptolite biozonation is proposed for the latest Ordovician to the earliest Silurian succession of northwest Peninsular Malaysia. This interval is significant for understanding the extent of mass extinction events happening right at the end of the Ordovician period and subsequent faunal change in the region.
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This first study on chitinozoans from Greenland has revealed representatives of twenty-two chitinozoan species recovered from Ordovician and Silurian beds in North Greenland. The Ordovician faunas are sirnilar to those described from North Arnerica, while the Silurian faunas are more sirnilar to those of Baltoscandia. Four distinct assemblages can be separated between Maysvillian - early Garnachian and Ludlow. The chitinozoan biostratigraphy is in agreement with that of the graptolites but differs from the conodont biostratigraphy.
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The long time interval after Pander's (1856) original conodont study can in terms of Ordovician conodont biostratigraphical research be subdivided into three periods, namely the Pioneer Period (1856–1955), the Transition Period (1955–1971) and the Modern Period (1971-Recent). During the pre-1920s, the few published conodont investigations were restricted to Europe and North America and were not concerned about the potential use of conodonts as guide fossils. Although primarily of taxonomic nature, the pioneer studies by Branson & Mehl, Stauffer and Furnish during the 1930s represent the beginning of the use of conodonts in Ordovician biostratigraphy. However, no formal zones were introduced until Lindström (1955) proposed four conodont zones in the Lower Ordovician of Sweden, which marks the end of the Pioneer Period. Because Lindström's zone classification was not followed by similar work outside Baltoscandia, the time interval up to the late 1960s can be regarded as a Transition Period. A milestone symposium volume, entitled 'Symposium on Conodont Biostratigraphy' and published in 1971, summarized much new information on Ordovician conodont biostratigraphy and is taken as the beginning of the Modern Period of Ordovician conodont biostratigraphy. In this volume, the Baltoscandic Ordovician was subdivided into named conodont zones, whereas the North American Ordovician succession was classified into a series of lettered or numbered faunas. Although most of the latter did not receive zone names until 1984, this classification has been used widely in North America. The Middle and Upper Ordovician Baltoscandic zone classification, which was largely based on evolutionary species changes in lineages and hence includes phylozones, has subsequently undergone only minor changes and has been used slightly modified also in some other regions, such as New Zealand, China and eastern North America. The great importance of conodonts in Ordovician biostratigraphy is shown by the fact that conodonts are used for the definition of two of the seven global stages, and seven of the 20 stage slices, now recognized within this system.
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