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Boundary Section (boundary + section)
Selected AbstractsA 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] 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] 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] The fate of the homoctenids (Tentaculitoidea) during the Frasnian,Famennian mass extinction (Late Devonian)GEOBIOLOGY, Issue 3 2006DAVID BONDArticle first published online: 18 AUG 200 ABSTRACT The homoctenids (Tentaculitoidea) are small, conical-shelled marine animals that are among the most abundant and widespread of all Late Devonian fossils. They were a principal casualty of the Frasnian,Famennian (F-F, Late Devonian) mass extinction, and thus provide an insight into the extinction dynamics. Despite their abundance during the Late Devonian, they have been largely neglected by extinction studies. A number of Frasnian,Famennian boundary sections have been studied, in Poland, Germany, France, and the USA. These sections have yielded homoctenids, which allow precise recognition of the timing of the mass extinction. It is clear that the homoctenids almost disappear from the fossil record during the latest Frasnian ,Upper Kellwasser Event'. The coincident extinction of this pelagic group, and the widespread development of intense marine anoxia within the water column, provides a causal link between anoxia and the F-F extinction. Most notable is the sudden demise of a group, which had been present in rock-forming densities, during this anoxic event. One new species, belonging to Homoctenus is described, but is not formally named here. [source] | ||||||||||