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Charles H. Wellman - One of the best experts on this subject based on the ideXlab platform.
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A high-precision U–Pb age constraint on the Rhynie Chert Konservat-Lagerstätte: time scale and other implications
2016Co-Authors: S F Parry, S R Noble, Quentin G Crowley, Charles H. WellmanAbstract:An isotope dilution thermal ionization mass spectrometry U–Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-Lagerstätte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian–(?)earliest Emsian. Accordingly, the Pragian–Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian–Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the ‘parental' hydrothermal system to the Rhynie cherts) was unrelated to any ‘Newer Granite' intrusion. Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin.
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spore assemblages from the lower devonian lower old red sandstone deposits of the northern highlands of scotland the berriedale outlier
Earth and Environmental Science Transactions of The Royal Society of Edinburgh, 2014Co-Authors: Charles H. WellmanAbstract:Assemblages of well-preserved dispersed spores have been recovered from the ‘Lower Old Red Sandstone’ deposits of the Berriedale Outlier in the Northern Highlands of Scotland. They belong to the annulatus–sextantii Spore Assemblage Biozone (AS SAB), in the spore zonation of Richardson & McGregor (1986), indicating an Early Devonian Emsian (but not earliest Emsian or latest Emsian) age. Comparison with the spore zonation of Streel et al . (1987) suggests they may be confined to the annulatus–bellatulus Oppel Zone (AB OZ), further constraining the age to early Emsian. This new biostratigraphical datum provides an age constraint for the onset of ‘Lower Old Red Sandstone’ sedimentation in the Orcadian Basin and, in particular, northwest of the Great Glen Fault System on the Northern Highlands. In the Orcadian Basin, there is a gap between ‘Lower Old Red Sandstone’ and ‘Middle Old Red Sandstone’ sedimentation, represented by either unconformity or disconformity, which appears to be variable in duration. In the Berriedale Outlier, it is estimated to represent up to 16 million years, but with an unknown thickness of ‘Lower Old Red Sandstone’ sequence removed at the unconformity. However, this basin-wide unconformity/disconformity is likely due to minor, local rather than large-scale, regional tectonism, and the evidence suggests little, if any, syn-depositional strike-slip movement along the Great Glen Fault System during Devonian ‘Old Red Sandstone’ deposition. The described spore assemblage is the most diverse AS SAB/AB OZ assemblage described from the British Isles. However, compared to contemporary spore assemblages from elsewhere on the Old Red Sandstone continent, the Scottish material is rather depauperate, with certain key taxa absent. This probably reflects subtle ecological effects, with the Scottish material representing restricted floras of the inland intermontaine basins.
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a high precision u pb age constraint on the rhynie chert konservat lagerstatte time scale and other implications
Journal of the Geological Society, 2011Co-Authors: S F Parry, S R Noble, Quentin G Crowley, Charles H. WellmanAbstract:Abstract: An isotope dilution thermal ionization mass spectrometry U–Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-Lagerstatte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian–(?)earliest Emsian. Accordingly, the Pragian–Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian–Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the ‘parental9 hydrothermal system to the Rhynie cherts) was unrelated to any ‘Newer Granite9 intrusion. Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin. Supplementary material: Details of analytical techniques (ID-TIMS U–Pb geochronology) and photomicrographs of zircon and titanite grains recovered from the Milton of Noth Andesite are available at http://www.geolsoc.org.uk/SUP18463.
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a high precision u pb age constraint on the rhynie chert konservat lagerstatte time scale and other implications
Journal of the Geological Society, 2011Co-Authors: S F Parry, S R Noble, Quentin G Crowley, Charles H. WellmanAbstract:Abstract: An isotope dilution thermal ionization mass spectrometry U–Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-Lagerstatte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian–(?)earliest Emsian. Accordingly, the Pragian–Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian–Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the ‘parental9 hydrothermal system to the Rhynie cherts) was unrelated to any ‘Newer Granite9 intrusion. Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin. Supplementary material: Details of analytical techniques (ID-TIMS U–Pb geochronology) and photomicrographs of zircon and titanite grains recovered from the Milton of Noth Andesite are available at http://www.geolsoc.org.uk/SUP18463.
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spore assemblages from the lower devonian lower old red sandstone deposits of arran scotland
Earth and Environmental Science Transactions of The Royal Society of Edinburgh, 2009Co-Authors: Charles H. WellmanAbstract:Dispersed spore assemblages have been recovered from the Am Binnein Sandstones from the upper part of the ‘Lower Old Red Sandstone’ sequence on the island of Arran, Scotland. The spore assemblages belong with the Emphanisporites annulatus – Camarozonotriletes sextantii (AS) Spore Assemblage Biozone (SAB), indicating an Early Devonian, Emsian (but not earliest Emsian or latest Emsian) age. This is the first reliable age constraint for the ‘Lower Old Red Sandstone’ of Arran, and enables correlation with the more extensive sequence developed on the mainland in the Midland Valley of Scotland. The Am Binnein Sandstones are confirmed as correlatives of the Strathmore Group.
Jindřich Hladil - One of the best experts on this subject based on the ideXlab platform.
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early devonian lochkovian early Emsian bioevents and conodont response in the prague synform czech republic
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Ladislav Slavik, Jindřich HladilAbstract:Abstract The Devonian succession of the Prague Synform is characterized by two major lithofacies: shallow-water biodetrital, mostly crinoidal limestones that also include a reefal skeletal accumulation of Pragian age, and a more pelagic facies that is represented mostly by calcisiltites. Among the several Devonian prominent sea-level fluctuations, some can be traced globally, e.g., the Basal Pragian and Kacak events. In recent years, conodont biostratigraphy of the Early Devonian (Lochkovian, Pragian and early Emsian) of the Prague Synform has been refined. The regional subdivision of the Lower Devonian in its type area has been greatly improved by the integration of new biostratigraphic, chemostratigraphic, sedimentological, and petrophysical data that has, in turn, strengthened global correlations for this interval in Earth's history. The complete conodont biozonation of the Early Devonian interval (basal Lochkovian – earliest Emsian) in the Prague Synform includes 17 biozones, which can be applied to sections representing various depositional environments and have more global applicability than previously proposed ‘global’ conodont biozonations. The zonal scale enables a precise biostratigraphic delimitation of the major Early Devonian biotic events (Silurian-Devonian Boundary Event, Lochkovian-Pragian Event and Basal Zlichovian Event). There were major changes in the conodont fauna in response to the Silurian-Devonian Boundary and Lochkovian-Pragian events, however the Basal Zlichovian Event was only characterized by a very gradual transition in the conodont fauna. In parallel to the traditional events defined for the Prague Synform, seven other significant conodont events have been documented. These events represent major turnovers in the conodont fauna that have a direct impact on conodont biostratigraphy, specifically at a global scale. The Icriodus and Irregularis events are congruent with the lower boundaries of the Lochkovian and Pragian stages, respectively. The conodont events established in the Prague Synform largely reflect variations in the seawater depth but are generally independent of lithological changes within sections of the Prague Synform.
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Oxygen and carbon stable isotope records of the Lochkovian-Pragian boundary interval from the Prague Basin (Lower Devonian, Czech Republic)
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Hedvika Weinerová, Ondřej Bábek, Ladislav Slavik, Hubert B. Vonhof, Michael M. Joachimski, Jindřich HladilAbstract:Abstract Climate changes close to the Lochkovian-Pragian Event are still widely discussed. Carbonate δ18O and δ13C and conodont apatite δ18O from medial to distal carbonate ramp sediments were analysed to provide further stable isotope data from the stratotype area in the Prague Basin. The uppermost Silurian to lower Emsian δ18O trends are put into an updated conodont biostratigraphy framework. Carbonate δ18O and δ13C are discussed in the context of facies-dependent diagenesis. The δ13C pattern measured from different sections enables the correlation of intervals with development of different facies inside the Prague Basin. Positive δ13C shifts are often coupled with trends of decreasing computed gamma-ray (CGR) values interpreted as regressions, whereas negative δ13C shifts commonly coincide with opposite trends in CGR. The Lochkovian-Pragian boundary interval coincided with an increase in carbonate δ13C and an increase in the δ18O of conodont apatite and carbonate, which we interpret as consequence of climate cooling. Generally, the Lochkovian was warmer than the Pragian and earliest Emsian.
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sea level changes vs organic productivity as controls on early and middle devonian bioevents facies and gamma ray based sequence stratigraphic correlation of the prague basin czech republic
Grid and Pervasive Computing, 2018Co-Authors: Ondřej Bábek, Jindřich Hladil, Hedvika Weinerová, Martin Faměra, Daniel Simicek, Jiři KalvodaAbstract:Abstract The Devonian marine stratigraphic record is characterized by a number of bioevents – overturns in pelagic and benthic faunal assemblages, which are associated with distinct changes in lithology. The coincidence of lithologic and biotic changes can be explained by the causal link between biotic evolution, carbonate production and relative sea-level changes. To gain insight into the sea-level history of Early and Middle Devonian bioevents (the Lochkovian/Pragian Event, Basal Zlichovian E., Daleje E., and Chotec E.) we carried out a sequence-stratigraphic analysis of carbonate-dominated successions in the Prague Basin (peri-Gondwana), a classic area of Devonian bioevents. The study is based on a basin-wide correlation of facies and field gamma-ray spectrometry (GRS) logs from 18 sections (Lochkovian to Eifelian), supported by element geochemistry and published biostratigraphic and carbon isotope data. Devonian carbonate deposition in the Prague Basin alternated between two end-member modes: an oligotrophic, homoclinal ramp (Praha and Daleje-Třebotov Formations) and a mesotrophic, distally steepened ramp (Lochkov, Zlichov, and Chotec Formations). They show contrasting facies, particularly the absence/presence of gravity-flow deposits, allochem composition, U/Th ratios, and geochemical composition (productivity proxies such as P/Al, Si/Al, Zn/Al, TOC and stable carbon isotopes). The mesotrophic systems reflect an increased availability of nutrients on the shelf during the late Lochkovian, early Emsian (Zlichovian), and Eifelian periods when sea surface temperature, pCO2, and silicate weathering rates were higher. The oligotrophic systems deposited during the Pragian–to-earliest Emsian and late Emsian (Dalejan) periods reflect reversed palaeoclimatic trends. We identified three depositional sequences (DS), DS1 (base of Pragian to early Emsian); DS2 (early Emsian to mid Emsian); and DS3 (mid Emsian to mid Eifelian). These sequences were integrated into a peri-Gondwana relative sea-level curve, which was then compared with the Euramerican sea-level curve of Johnson et al. (1985). The bioevents coincided with several sequence stratigraphic surfaces, representing variable limbs of the relative sea-level curve. On the other hand, their conspicuous coincidence with the switching intervals between the colder oligotrophic and warmer mesotrophic modes suggests that organic production linked to global climate was the primary control on biotic overturns, while sea-level fluctuations may have only amplified its effects.
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FINE-GRAINED NON-CARBONATE PARTICLES EMBEDDED IN NERITIC TO PELAGIC LIMESTONES (LOCHKOVIAN TO Emsian, PRAGUE SYNFORM, CZECH REPUBLIC): COMPOSITION, PROVENANCE AND LINKS TO MAGNETIC SUSCEPTIBILITY AND GAMMA-RAY LOGS
Geologica Belgica, 2010Co-Authors: Leona Koptikova, Petr Cejchan, Jindřich Hladil, Ladislav Slavik, Ondřej BábekAbstract:Variations in non-carbonate impurities trapped in the Lower Devonian limestone stratal successions in the Prague Synform are studied, with particular emphasis on the composition and quantities of fine-mineral grain assemblages. Different assemblages are encountered for the Lochkovian, lower Emsian and Pragian. The Lochkovian (represented by the Lochkov Formation) is characterized by pyrite-pyrrhotite assemblages with lower abundance of iron oxides and oxyhydroxides (mostly goethite) whereas the Pragian (represented by the Praha Formation) shows relatively abundant iron oxides and oxyhydroxides (mostly hematite). Major changes in magnetic susceptibility and gamma-ray spectrometric logs also coincide with the Lochkovian/Pragian boundary. Maximum values of magnetic susceptibility and relatively high Th, K concentrations above the boundary correspond to the elevated amounts of barite and Ba concentrations. This level is interpreted as a significant interval with elevated delivery of impurities of aeolian origin, deceleration of sedimentation rate together with decreased carbonate productivity. REE distributions in the Lochkovian to lower Emsian are indicative of the aeolian origin of trapped impurities. Detrital zircons found in all three stages are considered to be also of aeolian origin.
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Carbon and oxygen isotope record across Pridoli to Givetian stage boundaries in the Barrandian basin (Czech Republic)
Palaeogeography Palaeoclimatology Palaeoecology, 1997Co-Authors: Jana Hladikova, Jindřich HladilAbstract:Abstract Carbon and oxygen isotope composition and the chemistry of limestones, clayey limestones and shales were studied across stage boundaries from Pridoli to Givetian in the Barrandian basin. No substantial isotopic shifts were found at the Pragian–Emsian and Emsian–Eifelian boundaries. A gradual shift in δ13C values from −2.6 to +3.6‰ was observed in Pridoli and Lochkovian limestones. This shift is inferred to have been related to a combination of higher productivity, increased deposition of organic matter and shallowing of the basin. The global Kacak–otomari event just below the Eifelian–Givetian boundary is marked by an abrupt change in carbon isotopic values from about 1 to 3‰ in pelagic carbonates. No δ13C shift was found in shallow-water carbonates at the Eifelian–Givetian boundary. High δ18O values up to −1.3‰ in Pragian, Emsian and early Eifelian limestones indicate that the Barrandian basin was relatively isolated from the world ocean during those intervals. Lower δ18O values up to −7.5‰ in late Eifelian limestones may indicate the end of isolation.
Daniel Goujet - One of the best experts on this subject based on the ideXlab platform.
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The growth of the skull roof plates in Arabosteus variabilis (Acanthothoraci, Placodermi) from the Early Devonian Jauf Formation (Saudi Arabia): Preliminary results
Paleontological Journal, 2014Co-Authors: S. Olive, Daniel Goujet, Henri Lelievre, Pascal JanvierAbstract:The skull roof growth of Arabosteus variabilis (Acanthothoraci), from the Pragian-Early Emsian of Saudi Arabia is studied on the basis of well-preserved growth lines on the dermal plates. A clear tendency towards growth in length, i.e. allometry in length, can be observed for all studied skull roof plates of Arabosteus variabilis as well as for the skull roof in general. Each studied plate displays particular growth shaping the skull roof according to its position in the skull roof pattern, e.g., the preorbital plate controls the shape of the part of the orbit and the nuchal plate retains the relative proportions in the skull roof during growth.
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first devonian dipnoans vertebrata sarcopterygii from spitsbergen
Comptes Rendus Palevol, 2006Co-Authors: Gael Clement, Daniel Goujet, Vincent Dupret, Vincent PernegreAbstract:Abstract For the first time, dipnoan remains are described from the Devonian of Spitsbergen. According to the stratigraphy and the associated vertebrate fauna, they are considered as Late Emsian–Early Eifelian in age. Unfortunately remains are too sketchy and non-diagnostic to be referred or compared to a known Devonian dipnoan. This new material, determined as Dipnoi gen. et sp. indet., is nevertheless important in biostratigraphical and palaeobiogeographical points of view, since it is amongst the earliest dipnoan occurrences, and the first one in the Devonian of Spitsbergen. To citer this article: G. Clement et al., C. R. Palevol 5 (2006) .
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systematic palaeontology vertebrate palaeontology paleontologie systematique first devonian dipnoans vertebrata sarcopterygii from spitsbergen
2006Co-Authors: Gael Clement, Daniel Goujet, Vincent Dupret, Vincent PernegreAbstract:AbstractFor the first time, dipnoan remains are described from the Devonian of Spitsbergen. According to the stratigraphy and theassociated vertebrate fauna, they are considered as Late Emsian–Early Eifelian in age. Unfortunately remains are too sketchy andnon-diagnostic to be referred or compared to a known Devonian dipnoan. This new material, determined as Dipnoi gen. et sp.indet., is nevertheless important in biostratigraphical and palaeobiogeographical points of view, since it is amongst the earliestdipnoan occurrences, and the first one in the Devonian of Spitsbergen. To citer this article: G. Clement et al., C. R. Palevol 5(2006).© 2006 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.ResumePremiere occurrence de dipneustes (Vertebres sarcopterygiens) dans le Devonien du Spitzberg. Des restes de dipneustesdu Devonien du Spitzberg sont decrits pour la premiere fois. D’apres la stratigraphie et la faune de vertebres associee a ces restes,ils sont consideres comme etant d’âge Emsien superieur a Eifelien inferieur. Les specimens sont malheureusement trop rares et peudiagnostiques pour pouvoir etre attribues ou meme compares aux autres dipneustes devoniens decrits. Ce nouveau materiel,determine comme Dipnoi gen. et sp. indet., est neanmoins important, du double point de vue biostratigraphique et paleobiogeo-graphique. En effet, ces specimens de dipneustes, parmi les plus anciens decouverts, sont les premiers a etre signales dans leDevonien du Spitzberg. Pour citer cet article : G. Clement et al., C. R. Palevol 5 (2006).© 2006 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
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primitive jaw structure in an articulated brachythoracid arthrodire placoderm fish early devonian from southeastern australia
Journal of Vertebrate Paleontology, 2001Co-Authors: Gavin C. Young, Herve Lelievre, Daniel GoujetAbstract:A unique ‘buchanosteid’ arthrodire specimen from Emsian limestones at Burrinjuck represents the complete articulated remains of the head and cheek, and most of the trunk armor bones from a single fish, together with well-ossified braincase and jaw cartilages. The structure of the toothplates and jaws are described, and compared with primitive brachythoracid material from Saudi Arabia of similar age. Both the palatoquadrate and meckelian cartilages are well preserved, and perichondrally ossified as single elements. As previously described in some phlyctaeniids, the dermal gnathal elements carry crowded denticles similar to the normal tubercular ornament, enlarged along anterior and lateral margins. Six characters concerning gnathal plates of brachythoracids, which have been used in phylogenetic analysis, are discussed and reformulated.
S F Parry - One of the best experts on this subject based on the ideXlab platform.
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A high-precision U–Pb age constraint on the Rhynie Chert Konservat-Lagerstätte: time scale and other implications
2016Co-Authors: S F Parry, S R Noble, Quentin G Crowley, Charles H. WellmanAbstract:An isotope dilution thermal ionization mass spectrometry U–Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-Lagerstätte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian–(?)earliest Emsian. Accordingly, the Pragian–Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian–Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the ‘parental' hydrothermal system to the Rhynie cherts) was unrelated to any ‘Newer Granite' intrusion. Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin.
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a high precision u pb age constraint on the rhynie chert konservat lagerstatte time scale and other implications
Journal of the Geological Society, 2011Co-Authors: S F Parry, S R Noble, Quentin G Crowley, Charles H. WellmanAbstract:Abstract: An isotope dilution thermal ionization mass spectrometry U–Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-Lagerstatte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian–(?)earliest Emsian. Accordingly, the Pragian–Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian–Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the ‘parental9 hydrothermal system to the Rhynie cherts) was unrelated to any ‘Newer Granite9 intrusion. Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin. Supplementary material: Details of analytical techniques (ID-TIMS U–Pb geochronology) and photomicrographs of zircon and titanite grains recovered from the Milton of Noth Andesite are available at http://www.geolsoc.org.uk/SUP18463.
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a high precision u pb age constraint on the rhynie chert konservat lagerstatte time scale and other implications
Journal of the Geological Society, 2011Co-Authors: S F Parry, S R Noble, Quentin G Crowley, Charles H. WellmanAbstract:Abstract: An isotope dilution thermal ionization mass spectrometry U–Pb zircon age of 411.5 ± 1.3 Ma obtained from an andesitic lava occurring within the Lower Devonian Rhynie Outlier (Aberdeenshire, NE Scotland) effectively dates the Rhynie Chert Konservat-Lagerstatte. Biostratigraphical constraints on the Rhynie Chert-bearing succession indicate that this age lies within the interval early (but not earliest) Pragian–(?)earliest Emsian. Accordingly, the Pragian–Emsian boundary must post-date or closely approximate to 411.5 ± 1.3 Ma, while the Lochkovian–Pragian boundary must predate 411.5 ± 1.3 Ma. Integration of this new high-precision age with an improved temporal framework for late Caledonian intrusive activity in NE Scotland suggests that the Rhynie hot-spring system (the ‘parental9 hydrothermal system to the Rhynie cherts) was unrelated to any ‘Newer Granite9 intrusion. Rhynie was instead powered by a basaltic andesite magma whose generation and ascent were directly linked to the transcurrent fault movements responsible for the formation of the Rhynie basin. Supplementary material: Details of analytical techniques (ID-TIMS U–Pb geochronology) and photomicrographs of zircon and titanite grains recovered from the Milton of Noth Andesite are available at http://www.geolsoc.org.uk/SUP18463.
Ladislav Slavik - One of the best experts on this subject based on the ideXlab platform.
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early devonian lochkovian early Emsian bioevents and conodont response in the prague synform czech republic
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Ladislav Slavik, Jindřich HladilAbstract:Abstract The Devonian succession of the Prague Synform is characterized by two major lithofacies: shallow-water biodetrital, mostly crinoidal limestones that also include a reefal skeletal accumulation of Pragian age, and a more pelagic facies that is represented mostly by calcisiltites. Among the several Devonian prominent sea-level fluctuations, some can be traced globally, e.g., the Basal Pragian and Kacak events. In recent years, conodont biostratigraphy of the Early Devonian (Lochkovian, Pragian and early Emsian) of the Prague Synform has been refined. The regional subdivision of the Lower Devonian in its type area has been greatly improved by the integration of new biostratigraphic, chemostratigraphic, sedimentological, and petrophysical data that has, in turn, strengthened global correlations for this interval in Earth's history. The complete conodont biozonation of the Early Devonian interval (basal Lochkovian – earliest Emsian) in the Prague Synform includes 17 biozones, which can be applied to sections representing various depositional environments and have more global applicability than previously proposed ‘global’ conodont biozonations. The zonal scale enables a precise biostratigraphic delimitation of the major Early Devonian biotic events (Silurian-Devonian Boundary Event, Lochkovian-Pragian Event and Basal Zlichovian Event). There were major changes in the conodont fauna in response to the Silurian-Devonian Boundary and Lochkovian-Pragian events, however the Basal Zlichovian Event was only characterized by a very gradual transition in the conodont fauna. In parallel to the traditional events defined for the Prague Synform, seven other significant conodont events have been documented. These events represent major turnovers in the conodont fauna that have a direct impact on conodont biostratigraphy, specifically at a global scale. The Icriodus and Irregularis events are congruent with the lower boundaries of the Lochkovian and Pragian stages, respectively. The conodont events established in the Prague Synform largely reflect variations in the seawater depth but are generally independent of lithological changes within sections of the Prague Synform.
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Oxygen and carbon stable isotope records of the Lochkovian-Pragian boundary interval from the Prague Basin (Lower Devonian, Czech Republic)
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Hedvika Weinerová, Ondřej Bábek, Ladislav Slavik, Hubert B. Vonhof, Michael M. Joachimski, Jindřich HladilAbstract:Abstract Climate changes close to the Lochkovian-Pragian Event are still widely discussed. Carbonate δ18O and δ13C and conodont apatite δ18O from medial to distal carbonate ramp sediments were analysed to provide further stable isotope data from the stratotype area in the Prague Basin. The uppermost Silurian to lower Emsian δ18O trends are put into an updated conodont biostratigraphy framework. Carbonate δ18O and δ13C are discussed in the context of facies-dependent diagenesis. The δ13C pattern measured from different sections enables the correlation of intervals with development of different facies inside the Prague Basin. Positive δ13C shifts are often coupled with trends of decreasing computed gamma-ray (CGR) values interpreted as regressions, whereas negative δ13C shifts commonly coincide with opposite trends in CGR. The Lochkovian-Pragian boundary interval coincided with an increase in carbonate δ13C and an increase in the δ18O of conodont apatite and carbonate, which we interpret as consequence of climate cooling. Generally, the Lochkovian was warmer than the Pragian and earliest Emsian.
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FINE-GRAINED NON-CARBONATE PARTICLES EMBEDDED IN NERITIC TO PELAGIC LIMESTONES (LOCHKOVIAN TO Emsian, PRAGUE SYNFORM, CZECH REPUBLIC): COMPOSITION, PROVENANCE AND LINKS TO MAGNETIC SUSCEPTIBILITY AND GAMMA-RAY LOGS
Geologica Belgica, 2010Co-Authors: Leona Koptikova, Petr Cejchan, Jindřich Hladil, Ladislav Slavik, Ondřej BábekAbstract:Variations in non-carbonate impurities trapped in the Lower Devonian limestone stratal successions in the Prague Synform are studied, with particular emphasis on the composition and quantities of fine-mineral grain assemblages. Different assemblages are encountered for the Lochkovian, lower Emsian and Pragian. The Lochkovian (represented by the Lochkov Formation) is characterized by pyrite-pyrrhotite assemblages with lower abundance of iron oxides and oxyhydroxides (mostly goethite) whereas the Pragian (represented by the Praha Formation) shows relatively abundant iron oxides and oxyhydroxides (mostly hematite). Major changes in magnetic susceptibility and gamma-ray spectrometric logs also coincide with the Lochkovian/Pragian boundary. Maximum values of magnetic susceptibility and relatively high Th, K concentrations above the boundary correspond to the elevated amounts of barite and Ba concentrations. This level is interpreted as a significant interval with elevated delivery of impurities of aeolian origin, deceleration of sedimentation rate together with decreased carbonate productivity. REE distributions in the Lochkovian to lower Emsian are indicative of the aeolian origin of trapped impurities. Detrital zircons found in all three stages are considered to be also of aeolian origin.
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the pragian Emsian conodont successions of the barrandian area search of an alternative to the gssp polygnathid based correlation concept
Geobios, 2004Co-Authors: Ladislav SlavikAbstract:Abstract Six Pragian-Emsian boundary sections in the Barrandian area, western of Prague, provided evidence of well detectable entries of Latericriodus fauna probably at the earliest Emsian beds (particularly Latericriodus bilatericrescens gracilis Bultynck). The chance to find icriodontid conodonts increases with latest part of Praha Fm., which is apparently of Emsian age, whereas polygnathids are sparsely preserved to absent. The high icriodontid/polygnathid ratio links together all these Barrandian sections, although their open-sea depositional environments range widely from deep troughs with rapid calciturbidite accumulation (Pod Barrandovem section) to relatively starving slope environments on elevations (Na Požarech sections). The reports on polygnathid occurrences around the Pragian-Emsian boundary beds of the Barrandian area are much biased by poor reproducibility of the results (the conodonts cannot be found again) as well as by different levels where they were randomly found and/or by major taxonomic problems with the “kitabicus” and “dehiscens” definitions and their stratigraphic use. Apart from the GSSP in the Zinzilban Gorge (Uzbekistan) and its “kitabicus” boundary, the newly introduced “gracilis” biostratigraphic-marker concept preserves the major volume of the Pragian and respects also approximately the base of the traditional Emsian. These “gracilis” entries are clustered around the dark-colored “graptolite-bearing interval” beds, which largely form a prominent lithological marker within the latest, light gray-colored Dvorce-Prokop Limestone of the Barrandian area. This “gracilis” biostratigraphic marker has a promising correlation potential relative to Spanish and Moroccan sections.
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lower devonian conodonts from the karlik valley and na branzovech sections in the barrandian area czech republic and their significance for pragian conodont zonation
Acta Geologica Polonica, 2001Co-Authors: Ladislav SlavikAbstract:Two Early Devonian sections used for this study display a markedly different facies development and lie on opposite limbs of the central Barrandian synform, in the stratotype area of the Pragian Stage. The present biostratigraphical information based on 18 species with a total of 350 conodont specimens is mostly related to the late Lochkovian and early Pragian, whilst the remaining parts of the Pragian involve mostly long-range conodont species. The late Lochkovian conodonts correspond to two zones eurekaensis and delta . The latest Lochkovian zone pesavis was found in the northwestern limb, but not on the opposite side. The absence of pesavis Zone in the south (Koneprusy) and, as it has been newly shown, in the south-east of the central Barrandian synform (Karlik Valley) suggests that a prominent lowstand sedimentary starvation affected much larger areas than only the tops of elevated ridges. The lower two thirds of the Pragian sequences can be zoned using two newly suggested conodont zones steinachensis and serratus , respectively, that are defined by the first and last occurrences of these taxa. The occurrence of Latericriodus steinachensis (AL-RAWI) eta morph. marks the lower third and the entry of Pelekysgnathus serratus serratus JENTZSCH corresponds to the base of the middle third of the Pragian. The newly suggested stratigraphical applicability of these two species can effectively substitute the pre-existing sulcatus and kindlei subdivisions that have no zonal species representation in the stratotype area. The first occurrence of Latericriodus bilatericrescens bilatericrescens (ZIEGLER) seems to indicate the base of the Emsian in the Na Branzovech section. The entry of this taxon is connected with the black-shale Graptolite Event within the latest Dvorce-Prokop Limestone that is several beds higher than the levels usually considered for entry of a debatable taxon Polygnatus pireneae . The base of the Graptolite Event gives better chance for the correlation of the Pragian-Emsian boundary than any of the underlying levels. Evolution of the Barrandian conodont assemblages shows many parallels with those of Morocco and Carnic Alps.