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Conodont Zones (conodont + zone)
Selected AbstractsPalaeoecological significance of a new Griesbachian (Early Triassic) gastropod assemblage from OmanLETHAIA, Issue 1 2005JAMES WHEELEY A new Early Triassic (Griesbachian) gastropod fauna from the Al Jil Formation of Oman is described. Early Triassic faunas from elsewhere (e.g. the Italian Dolomites and the western USA) are typically of low diversity and high dominance, usually attributed to environmental stress in the immediate aftermath of the end-Permian mass extinction event. The new Oman fauna has, by contrast, relatively high diversity, low dominance and a more even spread of individuals between taxa. It is the most diverse Griesbachian fauna known to date. This is attributed to the favourable (i.e. well-oxygenated) conditions under which the fauna lived. This uncharacteristic Griesbachian gastropod fauna demonstrates that, in the absence of oceanic anoxia, biotic recovery after the end-Permian extinction event may occur surprisingly quickly (within one conodont zone). The fauna is also partially silicified, which has increased its preservation potential relative to other Griesbachian gastropod assemblages. However, only one reappearing Lazarus genus is present in the Oman fauna. This suggests that there was some other control on the abundance of Lazarus genera at this time, other than the absence of silicified faunas as previously suggested. [source] High-resolution Lopingian (Late Permian) timescale of South ChinaGEOLOGICAL JOURNAL, Issue 2-3 2010Shu-Zhong Shen Abstract The Lopingian represents the last epoch of the Palaeozoic Era and is bracketed by two severe biotic mass extinctions associated with dramatic environmental changes. The Lopingian Epoch lasted about 7 millions years and was also bracketed by large volcanic eruptions with the Emeishan volcanics at the base and the Siberian traps at the top. Considerable data have accumulated recently and in this paper we attempt to summarize these findings in a high-resolution Lopingian (Late Permian) timescale that integrates currently available multiple biostratigraphic, isotope chemostratigraphic, geochronologic and magnetostratigraphic data. In South China at least 13 conodont zones, multiple polarity zones and large carbon isotope fluctuations in the Lopingian are recognized and provide the high-resolution calibration that is essential to study this Late Permian interval characterized by Earth's largest biotic extinction. We also present a global correlation chart for the marine Lopingian Series. Copyright © 2010 John Wiley & Sons, Ltd. [source] Lopingian (Late Permian) high-resolution conodont biostratigraphy in Iran with comparison to South China zonationGEOLOGICAL JOURNAL, Issue 2-3 2010Shu-Zhong Shen Abstract Lopingian (Late Permian) conodonts and stratigraphy in northwest and central Iran have become hotly debated issues recently. We here use a sample-population approach, to develop a high-resolution conodont biostratigraphic framework for the Lopingian of Iran based on a re-examination of collections studied by Sweet from the Kuh-e-Ali Bashi area, northwest Iran; samples from the Abadeh C section and a nearby Permian-Triassic boundary section in the Abadeh area; and on published data. Six Wuchiapingian conodont zones, the Clarkina dukouensis, C. asymmetrica, C. leveni, C. guangyuanensis, C. transcaucasica and C. orientalis zones, and eight Changhsingian conodont zones, the Clarkina wangi, C. subcarinata, C. changxingensis, C. bachmanni, C. nodosa, C. yini, C. abadehensis and C. hauschkei zones, are described and figured. Diagnoses of ontogenetic characteristics to population variations of all the zone-naming species are re-described based on a sample-population taxonomic concept. The high-resolution Lopingian conodont zonation in Iran is closely correlative with its counterpart in South China. However, slightly different evolutionary trends in Clarkina populations existed at the very end of the Changhsingian in Iran and South China. This reflects a geographical cline and/or facies dependence and endemism in Clarkina populations rather than stratigraphic incompleteness of sections in either Iran or South China. Copyright © 2010 John Wiley & Sons, Ltd. [source] Pomeranian basin (NW Poland) and its sedimentary evolution during Mississippian timesGEOLOGICAL JOURNAL, Issue 2-3 2008Hanna Matyja Abstract The Carboniferous sedimentary history of the Pomeranian Basin (NW Poland) begins with Hastarian open-marine carbonates and is terminated with ?lower Asbian terrestrial deposits in the north-eastern part and, ?upper Asbian or Brigantian, open-marine shales in the south-western part of the basin. The ?latest Viséan, Serpukhovian and early Bashkirian was a period of regional non-deposition and erosion. In the Upper Bashkirian,Gzhelian strata, an alluvial depositional environment was recognized. The Mississippian depositional history of the area has been punctuated by several, regional-scale events: (1) during the late Famennian,early Tournaisian times anoxic conditions developed over the entire basin. The results of both conodont and miospore studies show the presence of a stratigraphic gap within this sequence (which also show extremely reduced thicknesses), that comprises the uppermost Famennian (Middle and Upper praesulcata conodont zones) and the lowermost Hastarian (sulcata,sandbergi conodont zones). This stratigraphic gap probably resulted from some chemical and/or hydrodynamical factors rather than from any tectonic uplift; (2) volcanic activity on the nearby East European Craton (EEC), which was the source of large amounts of detrital (volcaniclastic) material supplied to the Pomeranian Basin during the Early crenulata,?early anchoralis-latus chrons (late Hastarian,early Ivorian), caused with time the gradual shallowing of the sedimentary environment. This shallowing trend began in the Early typicus Chron (early Ivorian) and terminated with terrestrial deposits in the early Asbian. The sedimentary succession and specific phenomena recognized in this structurally unstable basin, displays a pattern partly different from that observed in some areas in Europe. It would appear that other local factors, such as tectonic mobility of the hinterland area (EEC) and the Pomeranian Basin floor, were the possible causes of observed variations and relative sea-level changes. Copyright © 2008 John Wiley & Sons, Ltd. [source] EARLY ORDOVICIAN CONODONTS FROM TARUTAO ISLAND, SOUTHERN PENINSULAR THAILANDPALAEONTOLOGY, Issue 6 2008SACHIKO AGEMATSU Abstract:, Early Ordovician conodont faunas of the Thung Song Formation on Tarutao Island, southern peninsular Thailand, consist of 14 known species belonging to 17 genera, and eight undescribed species. Utahconus tarutaoensis and Filodontus tenuis are new species. Three conodont zones: the Rossodus manitouensis Zone, the Utahconus tarutaoensis Zone and the Filodontus tenuis Zone, in ascending order, are defined in the study sections. These are coeval with the interval from the Rossodus manitouensis Zone to the Acodus deltatus - Oneotodus costatus Zone of the standard zonation in the North American Midcontinent. Based on the conodonts studied here and fossils previously reported from Tarutao Island, the Thung Song Formation is early Tremadocian to middle Arenig (Ibexian) in age. This formation is lithostratigraphically subdivided into the S1 to S5 members, and our study sections consist of the S1 to S3 members. These strata accumulated on a shelf in the Early Ordovician. The depositional environments of the limestones making up the S1 and S3 members were in deeper-shelf conditions. Limestone and shale of the S2 member formed in a shallow-water, high-energy environment. [source] A Middle,Upper Devonian Boundary Section in the Open Platform, Platform Margin Facies of Guilin, South ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009Hua LI Abstract: The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common-rare pelagic fossils, including brachiopods, corals, tentaculites, and conodonts, which may serve as a better suitable section for pelagic and neritic stratigraphic correlation. In this section, 10 "standard" conodont zones are recognized across the Givetian,Frasnian boundary, including, in descending order, the Lower hassi Zone, punctata Zone, transitans Zone, the Upper falsiovalis Zone, the Lower falsiovalis Zone, disparilis Zone, the Upper hermanni,cristatus Zone, the Lower hermanni,cristatus Zone, the Upper varcus Zone, and the Middle varcus Zone, all of which are defined by the first occurrence of their defining conodont species. The Middle,Upper Devonian (Givetian,Frasnian) boundary is defined by the first occurrence of Ancyrodella pristina in accordance with the Global Stratotype Section and Point (GSSP), which is assigned at 6.2m above the base of bed 19 in the Caiziyan section. [source] Comment on "First Record of Hindeodus,Isarcicella Population in Lower Triassic of Slovenia" by Tea Kolar-Jurkov,ek and Bogdan Jurkov,ek in Palaeogeography, Palaeoclimatology, Palaeoecology, 252: 72,81ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2009Yasheng WU Abstract: Some conodonts described by Tea Kolar-Jurkovsek and Bogdan Jurkovsek (2007) from the Permian-Triassic boundary section in the ,iri area of western Slovenia are revised in this paper. One specimen that they assigned to Hindeodus parvus is tentatively regarded as Hindeodus cf. scalaris Wu 2005. Two specimens that they assigned to Isarcicella sp. A is changed to Hindeodus parvus. One specimen that they described as Isarcicella lobata Perri and Farabegoli is changed to Hindeodus crenatus Wu (2006). One specimen that they assigned to Isarcicella turgida (Kozur, Mostler and Rahimi-Yazd) is changed to Hindeodus cf. parvus. Since these revisions, the three conodont zones that they defined have been correspondingly revised. Their first zone may belong to Hindeodus parvus zone, but it is not certain. Their second zone is changed to the Hindeodus parvus zone, and their third one remains as is. [source] Devonian Frasnian-Famennian Transitional Milankovitch Cycles and High-Resolution Stratigraphic CorrelationACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2001GONG Yiming Abstract, Four hierarchical cyclothems, superbundlesets, bundlesets, bundles and laminae, have been identified from the Devonian Frasnian-Famennian carbonate strata in Guangxi, South China. Their hierarchical structures, ratio relationships and sequence in conodont zones are continuous and stable and can be traced across different facies zones and sedimentary basins. Our data show that hierarchically organized superbundlesets, bundlesets, bundles and laminae correspond to the long eccentricity, eccentricity, obliquity or precession and sub-Milankovitch cycles respectively. Their periods were 400,000, 100,000, 33,333, 16,667 and 8,000,17,000 a, respectively. The ratios of long eccentricity to eccentricity, eccentricity to obliquity, and eccentricity to precession in the Devonian are 1:4, 1:3 and 1:6 respectively. Using these hierarchical Milankovitch cyclothems, chronostratigraphical division and correlation can be realized at a resolution of 100 ka or 10 ka at the Frasnian-Famennian transition. The time intervals of the Upper rhenana Zone, linguiformis Zone, and the Lower, Middle and Upper triangularis Zone are 0.6, 0.8, 0.3, 0.3 and 0.3 Ma, respectively. Sea-level changes of the Frasnian-Famennian transition were not coherent and synchronous at the resolution of 100 ka or 10 ka in the basin-slope carbonate sequences of Guangxi, South China. [source] | ||||||||||