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The global stratotype section and point of the Silurian-Devonian boundary

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Abstract

The GSSP at Klonk near Suchomasty in the Barrandian area, central Bohemia, Czech Republic, is situated in a full marine sequence of alternating bituminous limestone and calcareous shale layers with dominance of hemipelagic laminites. After international acceptance of the GSSP in 1972, recent investigations focused on chitinozoan and conodont biostratigraphy, trilobites, ostracodes, phyllocarids, taphonomy and sedimentology.

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... The GSSP is within Bed 20, a 7À10 cm unit immediately below the sudden and abundant occurrence of U. uniformis uniformis and U. uniformis angustidens in the upper part of that bed (Jaeger, 1977). Chlupáč and Hladil (2000) reviewed the stratigraphy of the type section and summarized the detailed subsequent work on the faunal and floral sequence at the GSSP. The combination of graptolite faunas with subsequent conodont data has enabled the Silurian-Devonian boundary to be recognized in most parts of the world, for example, now in South America (Mestre et al., 2017). ...
... kitabicus and the current GSSP shall define the base of a future formal Upper Pragian Substage ( Fig. 22.2 (Slavík and Hladil, 2004, pl. 1, fig. 9); (C) locality map showing the GSSP position; (D) lithological log with ranges of important index fossils in relation to the GSSP (based on data from Chlupáč andHladil, 2000, and; with updated taxonomy). proposed to be raised to a level near the entry of Eolinguipolygnathus excavatus Morphotype 114 sensu (Carls and Valenzuela-Ríos, 2002;Becker, 2009). ...
... The third-order Klonk Event (Jeppson, 1998) at the base of the Devonian is characterized by some faunal overturn (conodonts, graptolites; e.g., Chlupáč and Kukal, 1988;Chlupáč and Hladil, 2000) and a globally significant carbon isotope spike (see isotope stratigraphy). It can be correlated with the Hüinghausen Event of shallow-water facies (Jansen, 2016). ...
Chapter
All seven Devonian stages have been defined by Global Boundary Stratotype Sections and Points (GSSPs), but revisions of the base of the Emsian and of the Devonian–Carboniferous boundary are ongoing. Most of the Devonian Period was a time of exceptionally high sea-level stand and inferred widespread equable climates, but glaciations occurred immediately before its end in the south polar areas of Gondwana (South America, Central, and South Africa). There is even evidence for contemporaneous mountain glaciers in tropical latitudes (in the Appalachians of eastern North America). The cold-water Malvinocaffric Province of southern Gondwana existed throughout the Early Devonian but disappeared stepwise in the Middle Devonian. Most present-day continental areas and shelves were grouped in one hemisphere, creating a giant “Proto-Pacific” or Panthalassa Ocean, whose margins are poorly preserved in allochthonous terrains. Following the tectonic events of the Caledonian Orogeny of Laurasia, many “Old Red Sandstone” terrestrial deposits formed. After the closure of the narrow Rheic Ocean early in the Devonian, Eovariscan tectonic movements affected Middle and Late Devonian strata in the western Proto-Tethys of Europe and North Africa. Other active fold belts existed in western North America (early Antler Orogeny), polar Canada, in the Appalachians, in the Urals, along the southern margin of Siberia, in NW China, and in eastern Australia. The Devonian is the time of greatest carbonate production, with a peak of reef growth, and of the greatest diversity of marine fauna in the Paleozoic. Forests became established near the end of the Middle Devonian. Aquatic tetrapods appeared early in the Middle Devonian and diversified in the Upper Devonian.
... The GSSP is within Bed 20, a 7À10 cm unit immediately below the sudden and abundant occurrence of U. uniformis uniformis and U. uniformis angustidens in the upper part of that bed (Jaeger, 1977). Chlupáč and Hladil (2000) reviewed the stratigraphy of the type section and summarized the detailed subsequent work on the faunal and floral sequence at the GSSP. The combination of graptolite faunas with subsequent conodont data has enabled the Silurian-Devonian boundary to be recognized in most parts of the world, for example, now in South America (Mestre et al., 2017). ...
... kitabicus and the current GSSP shall define the base of a future formal Upper Pragian Substage ( Fig. 22.2 (Slavík and Hladil, 2004, pl. 1, fig. 9); (C) locality map showing the GSSP position; (D) lithological log with ranges of important index fossils in relation to the GSSP (based on data from Chlupáč andHladil, 2000, and; with updated taxonomy). proposed to be raised to a level near the entry of Eolinguipolygnathus excavatus Morphotype 114 sensu (Carls and Valenzuela-Ríos, 2002;Becker, 2009). ...
... The third-order Klonk Event (Jeppson, 1998) at the base of the Devonian is characterized by some faunal overturn (conodonts, graptolites; e.g., Chlupáč and Kukal, 1988;Chlupáč and Hladil, 2000) and a globally significant carbon isotope spike (see isotope stratigraphy). It can be correlated with the Hüinghausen Event of shallow-water facies (Jansen, 2016). ...
Chapter
: All seven Devonian stages have been defined by GSSPs, but revisions of the base of the Emsian and of the Devonian–Carboniferous boundary are currently underway. Most of the Devonian Period was a time of exceptionally high sea-level stand and inferred widespread equable climates, but glaciations occurred immediately before its end in the south polar areas of Gondwana (South America, Central and South Africa). There is even evidence for contemporaneous mountain glaciers in tropical latitudes (in the Appalachians of eastern North America). The cold-water Malvinocaffric Province of southern Gondwana existed throughout the Early Devonian but disappeared stepwise in the Middle Devonian. Most present-day continental areas and shelves were grouped in one hemisphere, creating a giant “Proto-Pacific” or Panthalassia Ocean, whose margins are poorly preserved in allochthonous terrains. Following the tectonic events of the Caledonian orogeny of Laurasia, many “Old Red Sandstone” terrestrial deposits formed. After the closure of the narrow Rheic Ocean early in the Devonian, Eovariscan tectonic movements occurred in the Upper Devonian in the western Proto-Tethys of Europe and North Africa. Other active fold belts existed in western North America (early Antler orogeny), Polar Canada, in the Appalachians, in the Urals, along the southern margin of Siberia, in NW China, and in eastern Australia. The Devonian is the time of greatest carbonate production, with a peak of reef growth, and of the greatest diversity of marine fauna in the Paleozoic. Vascular plants became established near the end of the Middle Devonian and early in the Middle Devonian tetrapods appeared, which spread and diversified in the Upper Devonian. Figure options Download full-size image Download as PowerPoint slide
... 5G). This unique acme horizon is widely recognizable worldwide (e.g., Zhivkovich and Chekhovich 1986; Jahnke et al. 1989; Havlíček and Štorch 1990; Ferretti et al. 1998; Chlupáč and Hladil 2000; Vacek 2007; Lubeseder 2008; Verniers et al. 2008; Donovan and Lewis 2009; Valenzuela−Ríos and Liao 2012). Within the upper Dnistrove Level, a thin black shale horizon with abun− dant specimens of the guide graptolite Monograptus uniformis angustidens was found (Fig. 4; see Nikiforova 1977). ...
... As advocated by Vacek et al. (2010: 270): " The facies change close to the S–D boundary and deposition of the Scyphocrinites H[orizon] might predominantly result from a biotic event unrelated to sea−level changes and local subsi− dence, rather than from sea−level rise/drop " . In general terms, comparable biotic dynamics were established in many other localities from different continents (e.g., Havlíček and Štorch 1990; Feist et al. 1997; Kříž 1998; Chlupáč and Hladil 2000; Yureva et al. 2002; Barrick et al. 2005; Suttner 2007; Manda and Frýda 2010; Zhao et al. 2011; Valenzuela−Ríos and Liao 2012). In particular, the transient collapse of the Podolian carbonate factory ( " carbonate crisis " ) correspon− ded to worldwide reef demise (Copper 2002b; Kiessling 2009), but without coeval loss in graptolite diversity (see Sadler et al. 2011). ...
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Two global isotopic events, the early Sheinwoodian (early Wenlock) and that at the Silurian–Devonian transition, have been comprehensively studied in representative carbonate successions at Kytayhorod and Dnistrove, respectively, in Podolia, Ukraine, to compare geochemistry and biotic changes related correspondingly to the Ireviken and Klonk events. These two large−scale isotope excursions reveal different regional ecosystem tendencies. The well−defined increasing trend across the Llandovery–Wenlock boundary in siliciclastic input, redox states and, supposedly, bioproductivity, was without strict correlative relations to the major 13C enrichment event. The environmental and biotic evolution was forced by eustatic sea−level fluctuations and two−step climate change toward a glaciation episode, but strongly modified by regional epeirogeny movements due to location near the mobile Teisseyre−Törnquist Fault Zone. Thus, the global early Sheinwoodian biogeochemical perturbation was of minor depositional significance in this epeiric sea, as in many other Laurussian domains. Conversely, the Podolian sedimentary record of the Klonk Event exhibits temporal links to the abrupt δ13C anomaly, overprinted by a tectonically driven deepening pulse in the crucial S–D boundary interval. This carbon cycling turnover was reflected in the regional carbonate crisis and cooling episodes, paired with a tendency towards eutrophication and recurrent oxygen deficiency, but also with major storms and possible upwelling. Faunal responses in both Podolian sections follow some characters of the Silurian pattern worldwide, as manifested by conodont changeover prior to the major early Sheinwoodian isotopic/climatic anomaly. This contrasts with the relative brachiopod and chitinozoan resistances in the course of the Ireviken Event. Also, during the Klonk Event, a moderate faunal turnover, both in benthic and pelagic groups, occurred only near the very beginning of the prolonged 13C−enriched timespan across the system boundary, possibly due to progressive dysoxia and temperature drop. The characters point to a peculiarity of the Klonk Event by comparison with the Silurian global events, and some similarity already to the succeeding Devonian transgressive/anoxic episodes.
... The wider boundary interval at Klonk was described particularly by Chlupác et al. (1972), Chlupác and Kukal (1977), Hladil (1991Hladil ( , 1992, Kȓíz (1992), Chlupác and Hladil (2000) and in diverse special papers. It was also incorporated into many Guidebooks of symposia, conferences and excursions dealing with variable geoscience problems. ...
... The rate of sedimentation was estimated at about 20 m per million years (Chlupác and Hladil 2000). The highfrequency cyclicity, expressed by couplets of dark limestones and calcareous shales (104 in the Lower Lochkovian part of the Klonk section) was calculated by Chlupác (2000). ...
Article
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The first international stratotype, selected according to modern stratigraphic principles, is the section with the Silurian-Devonian boundary at Klonk in the Barrandian area, Czech Republic. Its approvement at the XXIV IGC in Montreal, 1972 deeply influenced the further development of stratigraphic principles and praxis in achieving an objective base for definition of global chronostratigraphic units, later followed in establishments of GSSP in different parts of the global stratigraphic column. The procedure of the establishment, present status and correlative value of the Silurian-Devonian boundary stratotype are reviewed, confirming the suitability of its selection.
... The section at Klonk near Sucho- masty (central Bohemia, Czech Republic) is the first global stratotype of system boundary selected after a worldwide discussion and with application of modern stratigraphic methods and procedures. It was approved by the Silurian-Devonian Boundary Committee in 1971 (Rabat Meeting and subsequent vote) and ac- cepted by the International Commission on Stratigra- phy and IUGS at the session of the 24th International Geological Congress in Montreal, 1972(see Chlupáč et al. 1972, Raaben 1973, McLaren 1977, Chlupáč & Kukal 1977, Chlupáč & Hladil 2000. After 1972, the international interest in the Klonk section markedly increased and several excursions with foreign partici- pants visited this site per year. ...
... occurs in the late Přídolí, whilst Nostolepis was identified within the lower Lochkovian parts of the section. However, both genera co-occur at other localities (see Chlupáč & Hladil 2000). ...
... Selected sedimentological aspects of these boundary deposits were discussed by Hladil (1991,1992). More recently, Chlupáč and Hladil (2000) and Chlupáč and Vacek (2003) summarized and reviewed some of the earlier information. Magnestratigraphic data were published by Crick et al. (2001), while research on the carbon, oxygen, and strontium isotopes was conducted by Hladíková et al. (1997) and Frýda et al (2002). ...
... This section consists of a rhythmic sequence of allochthonous limestones and autochthonous shales, where the "sudden and abundant occurrence" of M. uniformis does not necessarily demonstrate reworking. Confirmed by the occurrences of associated fossils, e.g. of trilobites, conodonts, or chitinozoans and spores, the boundary level can be recognized in most parts of the world (Chlupáč and Hladil, 2000). ...
Article
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The boundaries of the Devonian, Carboniferous, and Permian stages of the Global Stratigraphic Reference Scale (abbreviated to Global Stratigraphic Scale—GSS) are described in relation to the biostratigraphic and/or lithostratigraphic units of the Regional Stratigraphic Reference Scales (abbreviated to Regional Stratigraphic Scales—RSS) of Central and West Europe, East Europe, Tethys, South China (eastern Tethys), and North America. In their type regions the boundaries of GSS units rarely coincide with those of homonymous RSS units. Moreover, the definitions of some RSS units have changed several times over the last decades, and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts. The stratigraphic framework proposed in our global Devonian–Carboniferous–Permian Correlation Chart 2003 [DCP 2003 (Devonian–Carboniferous–Permian Correlation Chart 2003, Menning, M., Schneider, J. W., Alekseev, A. S., Amon, E. O., Becker, G., von Bitter, P. H., Boardman, D. R., Bogoslovskaya, M., Braun, A., Brocke, R., Chernykh, V., Chuvashov, B. I., Clayton, G., Dusar, M., Davydov, V. I., Dybova-Jachowicz, S., Forke, H. C., Gibling, M., Gilmour, E. H., Goretzki, J., Grunt, T. A., Hance, L., Heckel, P. H., Izokh, N. G., Jansen, U., Jin Y.-G., Jones, P., Käding, K.-Ch., Kerp, H., Kiersnowski, H., Klets, A., Klug, Ch., Korn, D., Kossovaya, O., Kotlyar, G. V., Kozur, H. W., Laveine, J.-P., Martens, Th., Nemyrovska, T. I., Nigmadganov, A. I., Paech, H.-J., Peryt, T. M., Rohn, R., Roscher, M., Rubidge, B., Schiappa, T. A., Schindler, E., Skompski, S., Ueno, K., Utting, J., Vdovenko, M. V., Villa, E., Voigt, S., Wahlman, G. P., Wardlaw, B. R., Warrington, G., Weddige, K., Werneburg, R., Weyer, D., Wilde, V., Winkler Prins, C. F., Work, D. M., 2004). Abschlußkolloquium DFG-Schwerpunktprogramm 1054: Evolution des Systems Erde während des jüngeren Paläozoikums im Spiegel der Sedimentgeochemie. Abstracts Univ. Erlangen, Germany, 2004, p. 43.] (herein abbreviated to DCP 2003, and cited as DCP, 2003 in references) is an attempt to reduce these errors.The DCP 2003 is the stratigraphic base for Project 1054 of the Deutsche Forschungsgemeinschaft (DFG) ”The evolution of the Late Palaeozoic in the light of sedimentary geochemistry”. This composite time scale has been carefully balanced, as far as data allows, to remove unnecessary, artificial compression and expansion of time intervals, biozonations and depositional events. The ages selected in DCP 2003 are markedly different to those in the Geologic Time Scale 1989 [GTS 1989 (Harland, W.B., Armstrong, R.L., Cox, A.V., Craig, L.E., Smith, A.G., Smith, D.G., 1990). A geologic time scale 1989. Cambridge Univ. Press, Cambridge.; Harland, W.B., Armstrong, R.L., Cox, A.V., Craig, L.E., Smith, A.G., Smith, D.G., 1990. A geologic time scale 1989. Cambridge Univ. Press, Cambridge, pp. 1–263.] and in Gradstein and Ogg [Gradstein, F.M., Ogg, J., 1996. A Phanerozoic time scale. Episodes 19 (1/2), 3–4, insert.), whereas they are closer to those of the Geologic Time Scale 2004 [GTS 2004; Gradstein, F.M., Ogg, J.G., Smith, A.G., 2004. A Geologic Time Scale 2004. Cambridge Univ. Press, Cambridge, pp. 1–589.]. Mostly, the ages are rounded to the nearest 0.5 Ma in order to avoid estimates of questionable accuracy, whereas ages of 0.1 Ma in the GTS 2004 and their error bars of ± 0.4 Ma to ± 2.8 Ma for the Devonian to Permian stage boundaries suggest an improved accuracy. In contrast, in the DCP 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows.
... The Pridoli-Lochkovian boundary is characterized by a significant faunal change (Chlupáč and Hladil, 2000). Close to the boundary two blooming events of floating Scyphocrinites occurred that resulted in the widespread deposition of coarse-grained echinoderm limestones (Scyphocrinus-Limestone of Bohemia and Carnic Alps). ...
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Carbonate rocks of the Rhenohercynian and Saxothuringian zones of the Variscan Mountains, Prague Syncline, Carnic Alps, Montagne Noire, Pyrenees, and Cantabrian Mountains were investigated for δ13Ccarb. The values were measured on bulk carbonate, selected carbonate components and cements. Many of the studied carbonates are interpreted to exhibit primary marine δ13C values with only some showing evidence of diagenetic alteration. A δ13C curve is presented for the entire Devonian time interval. Positive δ13C excursions are documented in the woschmidti-postwoschmidti, sulcatus, kitabicus, Upper serotinus, kockelianus, Middle varcus, falsiovalis, Upper rhenana, linguiformis to Middle triangularis, and Middle to Upper praesulcata conodont Zones. Some excursions are recorded worldwide and interpreted to be of global significance as e.g. at the Silurian–Devonian and Frasnian–Famennian boundaries. Some of the others are described for the first time from Central and Southern Europe, and their global nature has to be verified by further investigations. Most δ13C excursions coincide with sea-level changes and the deposition of black shales. A coupling of changes in sea-level, weathering intensity, nutrient supply, organic carbon production, and climate is assumed as driving force of the carbon isotope excursions.
... The se− quence in the stratotype is formed by the alternation of fine−grained mostly dark grey limestone layers and dark grey calcareous shale interbeds. Chlupáč and Hladil (2000) esti− mated that the average duration of one couplet consisting of dark limestone and calcareous shale (0.25 m thick on the av− erage) may correspond to about 16.4 Ka. The ratio of original shale thickness/recent shale thickness is estimated to be about 6:1 to 8:1 (Jindřich Hladil, personal communication 2007). ...
Article
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Turek, V. 2009. Colour patterns in Early Devonian cephalopods from the Barrandian Area: Taphonomy and taxonomy. Acta Palaeontologica Polonica 54 (3): 491–502. DOI: 10.4202/app.2007.0064. Five cephalopod specimens from the Lower Devonian of Bohemia (Czech Republic) preserve colour patterns. They in− clude two taxonomically undeterminable orthoceratoids and three oncocerid nautiloids assigned to the genus Ptenoceras. The two fragments of orthocone cephalopods from the lowest Devonian strata (Lochkovian, Monograptus uniformis Zone) display colour patterns unusual in orthoceratoids. They have irregular undulating and zigzag strips that are pre− served on counterparts of adapertural regions of specimens flattened in shale, despite their original aragonitic shell having been completely dissolved. These are probably the result of the proteinous pigment inside the shell wall, being substituted during diagenesis by secondary minerals leaving only an altered trace of the original shell. Orthoceratoids from sediments unsuitable for preservation of this feature discussed here thus demonstrate an exceptional case of preservation of colour patterns, not only within Devonian cephalopods but also within other Devonian molluscs. Three specimens of Ptenoceras that preserve colour patterns come from younger Lower Devonian strata. Oblique spiral adaperturally bifurcating bands are preserved in P. alatum from the Pragian and zigzags in P. nudum from the Dalejan. Juvenile specimen of Ptenoceras? sp. from the Pragian exhibits highly undulating transversal bands—a pattern resembling colour markings in some Silu− rian oncocerids. Dark grey wavy lines observed on the superficially abraded adapical part of a phragmocone of nautiloid Pseudorutoceras bolli and interpreted formerly to be colour markings are here reinterpreted as secondary pigmented growth lines. Other Devonian fossils including a single brachiopod and several gastropods from the Barrandian Area with preserved colour patterns are mentioned. Variety of cephalopod colour patterns, their taxonomic significance, function and significance for palaeoecological interpretation, palaeoenvironmental conditions favouring colour pattern preserva− tion and systematic affiliation of taxa with colour pattern preserved are discussed. Vojtěch Turek [vojtech.turek@nm.cz], Národní muzeum, Přírodovědecké muzeum, paleontologické oddělení, Václavské náměstí 68, 115 79 Praha 1, Czech Republic.
... Following much debate, the stratotype boundary was eventually agreed at 8 m above the base of the Lochkov Formation within the classic Barrandian sequence at Klonk, near Prague, Czech Republic, and at the base of the uniformis graptolite Biozone. A more recent borehole drilled across the boundary has documented further the graptolite and sedimentological data (Chlupàč & Hladil, 2000). In Britain, the Downtonian is therefore at least mainly of Silurian age, although the boundary between it and the overlying Dittonian part of the Old Red Sandstone has not yet been precisely correlated with the stratotype basal Devonian section in the Czech Republic. ...
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The global correlation standards now agreed for the Ordovician and Silurian systems, and partly so for the Cambrian System, are summarized. Correlation of the international series and stages with the traditional and revised British series and stages is reviewed, as well as with those in North America (Laurentia).
... The Barrandian sedimentary succession of Silurian–Devonian (S–D) boundary represents a geological system boundary of international importance, when following the choice of the base of the Monograptus· uniformis graptolite zone it was approved as the first global stratotype section and point (GSSP) at Klonk in the Prague Basin of the Czech Republic (Martinsson, 1977; www.stratigraphy.org/sildev.htm). A review of the significant biotic changes recorded at this reference locality is given by Chlupáč and Hladil (2000), Chlupáč and Vacek (2003) and Brocke et al. (2006). However, worldwide biodiversity shift corresponds to the generally evolutionarily 'quiet' S–D boundary (see summary in Walliser, 1996, Copper, 2002, House, 2002, Bambach, 2006 ). ...
Article
The large-scale global biogeochemical perturbation across the Silurian–Devonian (S–D) boundary, recorded in the major positive excursion of the δ13C time curve (Klonk Event) of an amplitude of 2.5 to 3.0‰ (max. 4.0‰) in Europe and up to 5.0‰ in North America, reflects a unique combination of palaeogeographic, biogeochemical and evolutionary processes in the late Caledonian geodynamic setting. The steady sulfur isotopic ratios show an overall stability of the S–D oceanic geochemical system as a whole and do not indicate any synchronous changes in anoxic deep oceanic and sediment processes. Therefore this led us to a hypothesis that the crucial changes that contributed to the recorded carbon cycling turnover are related to rapidly evolving ocean–continent–biosphere feedback. Coastal zones of the latest Silurian epicontinental seas accumulated considerable quantities of organic carbon from early vascular vegetation, which explosively expanded to inhabit vast near-coastal shallows and deltas. Large primary production of these early terrestrial plants and rapidly enhanced sedimentary burial of organic carbon were also responsible for CO2 drawdown, which have resulted in reversed-greenhouse effect and a global climatic cooling tendency. This feedback was blocked when the sea level gradually dropped and led to shrinking of the Silurian epicontinental seas and the growing climatic deterioration during the S–D transition limited primary production. Furthermore, continued processes of regressive abrasion and erosion limited the storage of organic carbon, as well as the efficiency of the carbonate factory. During the following Early Devonian greenhouse interval, marine regression and active latest Caledonian tectonism promoted progressive weathering of the sedimentary organic matter. The oxidation of C-rich deposits caused the subsequent growth of CO2 levels in the Early Devonian, culminating in the warming of global climate.
... The section at Klonk near Suchomasty (Barrandian area, Central Bohemia, Czech Republic) was approved by the Silurian-Devonian Boundary Committee in 1971 and accepted by the International Commission on Stratigraphy and IUGS at the 24 th International Geological Congress in Montreal in 1972 as the global stratotype section and point (GSSP) for the Silurian-Devonian boundary. The stratigraphy, palaeontology, and lithology of the section have been described and discussed in detail in papers by Chlupáč (1971Chlupáč ( , 1977, Chlupáč et al. (1972), Chlupáč & Kukal (1977, 1988, Hladil (1991Hladil ( , 1992, Chlupáč & Hladil (2000), and references therein. Magnetostratigraphy and strontium, carbon, and oxygen isotope data from the boundary interval have been recently studied by Hladíková et al. (1997), Crick et al. (2001), and Frýda et al. (2002). ...
... The section at Klonk near Suchomasty (Barrandian area, Central Bohemia, Czech Republic) was approved by the Silurian-Devonian Boundary Committee in 1971 and accepted by the International Commission on Stratigraphy and IUGS at the 24 th International Geological Congress in Montreal in 1972 as the global stratotype section and point (GSSP) for the Silurian-Devonian boundary. The stratigraphy, palaeontology, and lithology of the section have been described and discussed in detail in papers by Chlupáč (1971Chlupáč ( , 1977, Chlupáč et al. (1972), Chlupáč & Kukal (1977, 1988, Hladil (1991Hladil ( , 1992, Chlupáč & Hladil (2000), and references therein. Magnetostratigraphy and strontium, carbon, and oxygen isotope data from the boundary interval have been recently studied by Hladíková et al. (1997), Crick et al. (2001), and Frýda et al. (2002). ...
Article
At the GSSP for the Silurian-Devonian boundary at Klonk, Czech Republic, a comparatively poorly diversified palynomorph assemblage has been documented. The boundary interval is characterized by the predominance of thickand/or thin-walled prasinophytes (Leiosphaeridia spp., ?Pleurozonaria spp.), while the other organic-walled microfossil groups are relatively rare (chitinozoans, acritarchs, scolecodonts, certain prasinophytes, mazuelloids). The highest taxonomic diversity of palynomorphs has been documented in the uppermost Přídolí and in the lower part of the Lochkovian. Such a pattern of distribution could be connected with transgressive and regressive pulses occurring at the boundary interval.
... with no interruption. For more information on the lithology, stratigraphy and palaeontological content recorded from this section, please refer to Chlupáč (1953Chlupáč ( , 1977, Horný (1955), Chlupáč et al. (1972Chlupáč et al. ( , 1980, Davies and MacQueen (1977), Chlupáč and Kukal in Martinsson et al. (1977), Paris et al. (1981), Chlupáč and Kukal (1988), Jeppsson (1988, 1989, Hladil (1991Hladil ( , 1992, Kříž (1992), Chlupáč and Hladil (2000), Chlupáč and Vacek (2003), Fatka et al. (2003), Brocke et al. (2006), and Slavík (2017b). ...
Article
Conodonts from two of the most representative sections in the Prague Synform were studied in search of alternative biostratigraphic markers of the Silurian/Devonian boundary. The Na Požárech and Praha-Radotín sections, with contrasting lithologies, were chosen to study changes in conodont faunas in relation to different carbonate facies – i.e., shallower- and deeper-water carbonates around the Silurian/Devonian boundary in the type area. Apart from icriodontids, the differences in bathymetry were also expected to affect the diversity of taxa of the family Spathognathodontidae, which is generally the most abundant and the most tolerant clade found in different carbonate environments at this stratigraphic level. Although the Scyphocrinites Horizon is developed at both study localities, the microfacies analysis confirmed significant differences in depositional environments at around the Silurian/Devonian boundary. Abundant conodont material from the two sections (more than one thousand elements) showed a high diversity and disparity in both the Spathognathodontidae and Icriodontidae. Altogether, 18 taxa were identified, but many forms still require a formal description. A new spathognathodontid taxon, Zieglerodina petrea sp. nov., described herein, is easily distinguishable because of its distinct morphology in denticulation of the blade, and its first occurrence is just above the base of the Devonian in both sections. It also has been identified in conodont collections from Morocco and the Carnic Alps, as such its biostratigraphic significance can be extended to peri-Gondwana. Although the stratigraphic occurrence and global significance of this promising conodont taxon still has to be tested in other areas, current data suggest it might have a great potential for identifying the base of the Devonian in sections where critical graptolite and icriodontid taxa are missing.
... В результате таких реконструкций для нижнего девона образовалась «сборная» шкала, состоящая из ярусов, стратотипы которых находятся в различных тектонических блоках Евразии. Точки глобальных стратотипов границ ярусов тоже оказались разнесенными в разные регионы: глобальный стратотип подошвы лохкова (подошва этого яруса определяется по зональной граптолитовой последовательности и принята как основание граптолитовой зоны Monograptus uniformis) находится в разрезе Клонк Баррандиенской структуры [18]. Определение основания остальных ярусов нижнего девона происходит по конодонтовой зональной последовательности. ...
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The boundaries of the International Chronostratigraphic Chart (ICC) are associated with the natural historical stages of the Earth's development, and their boundaries are usually determined by the palaeogeographical or palaeobiological event that is recognized in most regions of the world. Studies on the standardization of the Lower Devonian ICC stages duration have lasted more than 70 years. The first stages were Gedinnian, Siegenian and Emsian, but their duration was not accurately determined. The article shows the history of the establishment of the currently used Lochkovian, Pragian and Emsian stages. The key study method of the Lower Devonian stages deposits is biostratigraphic one, based on the use of archistratigraphic pelagic fossils, i.e. revealing of the zonal sequence over the conodonts, dacrioconarids and goniatites fossils and comparing them with the standard sequence adopted by the International Geological Congress (IGC). The article contains an analysis of the discussed problems related to the determination of the position of the global boundary stratotype section and point (GSSP) of the Lower Devonian stages. The use of the magnetostratigraphic method in comparison of the sections of the Emsian stage in Barrandian and Zarafshan range is also discussed. The Lower Devonian regional strata of the Zarafshan-Gissar and Turkestan-Altay mountain regions of the Southern Tian Shan are characterized. It is shown that the zonal sequences on conodonts and dacrioconarids presented in these regions almost completely coincide with the standard Lower Devonian sequences in the International Chronostratigraphic Chart. The characteristics of zones and volume of Bursykhirmanian, Sangitovarian, Khukarian, Kunjak, and Kitab horizons are given.
... The age constraints of the successions have been well-established from conodont, dacryoconarid, graptolite, and goniatite biostratigraphy (Chlupáč et al., 1998). Numerous faunistically well-documented sections provide a robust biostratigraphic framework for the lithostratigraphic units (Budil, 1995;Chlupáč and Kukal, 1977;Chlupáč et al., 1985;Chlupáč and Oliver, 1989;Chlupáč and Hladil, 2000;Kalvoda, 1995;Slavík and Hladil, 2004;Weddige, 1987). Recently, biostratigraphy of the Lochkovian/Pragian, Daleje and Choteč event intervals has been substantially improved using conodont and dacryoconarid faunas (Ferrová et al., 2012;Vodrážková et al., 2013;Slavík et al., 2007Slavík et al., , 2012Tonarová et al., 2017). ...
Thesis
The Calymenina trilobites from the Devonian of Portugal are known since the pioneer study of Delgado (1908), although at that time many of the outcrops were assigned to the uppermost Silurian. However, the only systematic study covering the entire devonian assemblages was conducted by Rodríguez-Mellado & Thadeu (1947) and needs to be updated. Portuguese devonian calymenines were recognized in stratigraphical sequences from three geological structures, all of them in the Central-Iberian Zone: Valongo Anticline, Amêndoa-Carvoeiro Syncline and Portalegre Syncline. The main aim of this work is the revision of the devonian Calymenina trilobites, using the fossil collections housed in public institutions (Museum Décio Thadeu of IST, Natural History and Science Museum of the University of Porto and Geological Museum of Portugal of LNEG). The collections were analyzed to select Calymenina specimens, which were then inventoried and studied in detail. Nearly 300 specimens were studied, with 10 identified species, being 4 left in open nomenclature. One new genus, Carringtonotus gen. nov., and two new species, Burmeisterella hexaspinosa sp. nov. and Homalonotus mamedensis sp. nov., were identified. The Calymenina assemblage from the Devonian of Portugal is exclusively represented by members of the subfamily Homalonotinae, being the 10 identified species assigned to the genera Burmeisterella, Carringtonotus gen. nov., Trimerus and Wenndorfia. Representatives of all the identified taxa were described in detail and figured. From a biostratigraphical point of view, the portuguese occurrences are in agreement with the known biostratigraphical distribution of the represented genera, except for Homalonotus, which was previously known only in the Silurian, being that the portuguese records extends its distribution to the Lower Devonian. An attempt was made to relocate the historical fossil sites, by overlapping the geological maps with Google Earth, which proved to be an unsuccessful methodology. Another attempt method was the x-ray diffraction, using samples from two fossil sites, allowing a more detailed knowledge of their mineralogical components. Full-text - https://run.unl.pt/handle/10362/75495
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The carbon and oxygen isotope composition of marine carbonates (δ13C and δ18O, respectively) are studied in the fossiliferous, stratigraphically well-constrained and remarkably expanded successions of Podolia, SW Ukraine, spanning the Silurian–Devonian transition. Significant isotopic shifts are directly comparable to previously published global secular trends in well-preserved brachiopod calcite isotopic ratios from this region, and therefore may be taken as a reliable primary record of seawater δ13C changes. The sections reveal a major positive δ13C excursion, with an amplitude above 6 ‰, beginning in the upper Pridoli and reaching peak values as heavy as +4.2 ‰ in the lowermost Lochkovian. This turnover in carbon cycling is followed by a general trend toward more negative δ13C values in the upper Lochkovian. The Podolian isotopic signals provide strong support for the previously inferred global biogeochemical perturbation across the Silurian–Devonian transition, reflecting a complex combination of palaeogeographical, biogeochemical and evolutionary processes in the late Caledonian geodynamic setting, with a likely undervalued role of the expanding vegetation in vast near-coastal shallows and deltas.
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Summary A discussion arose in 1977 regarding the nature of the Silurian/Devonian boundary bed at Klonk, and the beds below and above it. Present revision of the stratotype sequence found that most clayey limestones display a multiple and composed rhythmic arrangement of laminae. Deposition of pelagic particles, effects of traction bottom currents, and turbidite inputs are distinguishable, however, the latter are rare. Semilithified surfaces and hardgrounds were found. The boundary bed No. 20 consists of several laminated rhythms. The Devonian base, marked by first occurrences ofMonograptus uniformis corresponds to a semilithified surface, a break in deposition for several tens to hundreds of years, and a change in direction of bottom currents. A moderately rippled set at the Devonian base is only about 1 cm thick and passes again into the horizontal laminated rhythms. The deposition of the boundary bed lasted about 1.2 to 2.0 Ka. It cannot be explained as a turbidite.