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Grasby Stephen E.. - One of the best experts on this subject based on the ideXlab platform.

  • Late Ordovician Mass Extinction caused by volcanism, warming and anoxia, not cooling and glaciation
    Geological Society of America, 2020
    Co-Authors: Bond David., Grasby Stephen E..
    Abstract:

    The Ordovician saw major diversification in marine life abruptly terminated by the Late Ordovician Mass Extinction (LOME). Around 85% of species were eliminated in two pulses 1 Myr apart. The first pulse in the basal Hirnantian has been linked to cooling and Gondwanan glaciation. The second pulse, later in the Hirnantian is attributed to warming and anoxia. Previously reported mercury spikes in Nevada, South China, and Poland implicate an unknown large igneous province (LIP) in the crisis, but the timing of Hg loading has led to different interpretations of the LIP-extinction scenario in which volcanism causes cooling, warming, or both. We report close correspondence between Hg, Mo and U anomalies, declines in enrichment factors of productivity proxies, and the two LOME pulses at the Ordovician/Silurian Boundary stratotype (Dob’s Linn, Scotland). These support an extinction scenario in which volcanogenic greenhouse gases caused warming around the Katian/Hirnantian Boundary that led to expansion of a pre-existing deep-water oxygen minimum zone, productivity collapse and the first LOME pulse. Renewed volcanism in the Hirnantian stimulated further warming and anoxia and the second LOME pulse. Rather than being the odd-one-out of the “Big 5” extinctions with origins in cooling, the LOME is similar to the others in being caused by volcanism, warming and anoxia

  • Late Ordovician mass extinction caused by volcanism, warming, and anoxia, not cooling and glaciation
    'Geological Society of America', 2020
    Co-Authors: Bond, David P.g., Grasby Stephen E..
    Abstract:

    The Ordovician saw major diversification in marine life abruptly terminated by the Late Ordovician mass extinction (LOME). Around 85% of species were eliminated in two pulses 1 m.y. apart. The first pulse, in the basal Hirnantian, has been linked to cooling and Gondwanan glaciation. The second pulse, later in the Hirnantian, is attributed to warming and anoxia. Previously reported mercury (Hg) spikes in Nevada (USA), South China, and Poland implicate an unknown large igneous province (LIP) in the crisis, but the timing of Hg loading has led to different interpretations of the LIP-extinction scenario in which volcanism causes cooling, warming, or both. We report close correspondence between Hg, Mo, and U anomalies, declines in enrichment factors of productivity proxies, and the two LOME pulses at the Ordovician-Silurian Boundary stratotype (Dob's Linn, Scotland). These support an extinction scenario in which volcanogenic greenhouse gases caused warming around the Katian-Hirnantian Boundary that led to expansion of a preexisting deepwater oxygen minimum zone, productivity collapse, and the first LOME pulse. Renewed volcanism in the Hirnantian stimulated further warming and anoxia and the second LOME pulse. Rather than being the odd-one-out of the "Big Five" extinctions with origins in cooling, the LOME is similar to the others in being caused by volcanism, warming, and anoxia

Thomas J Algeo - One of the best experts on this subject based on the ideXlab platform.

  • mercury in marine ordovician silurian Boundary sections of south china is sulfide hosted and non volcanic in origin
    Earth and Planetary Science Letters, 2019
    Co-Authors: Jun Shen, Thomas J Algeo, Jiubin Chen, Noah J Planavsky, Qinglai Feng, Jinling Liu
    Abstract:

    Abstract Mercury (Hg) enrichment in stratigraphic successions is now widely used as a proxy for volcanic inputs, often for the purpose of documenting a relationship between large igneous province (LIP) magmatism and ecosystem perturbations. Earlier studies of Hg in Ordovician/Silurian Boundary (OSB) sections in South China and Laurentia identified transient spikes in Hg/TOC ratios, on the basis of which a link between volcanism and the Late Ordovician mass extinction (LOME) was claimed. However, Hg enrichments must be tested based on normalization to their main host phase, and Hg/TOC is a suitable proxy only if Hg is mainly complexed by organic matter in the sediment. Here, we demonstrate that Hg in three OSB sections in South China (Qiliao, Yanzhi, and Jiaoye) is overwhelmingly associated with pyrite, as shown by r(Hg–TS) > 0.9 (versus r(Hg–TOC) Δ 199 Hg) values (+0.11 ± 0.03‰) that are inconsistent with volcanic inputs. We therefore infer that previous reports of Hg enrichments in OSB sections were due to the presence of Hg-rich sulfides, and that Hg data from both the present and earlier studies provide no evidence of any volcanic influences on the LOME. The results of the present study highlight the need for caution in applying the Hg proxy for volcanic inputs and the importance of evaluating the main host phase of Hg in paleo-marine sediments.

  • global and regional controls on marine redox changes across the ordovician silurian Boundary in south china
    Palaeogeography Palaeoclimatology Palaeoecology, 2016
    Co-Authors: Junxuan Fan, Thomas J Algeo, Yu Liu, Ping'an Peng
    Abstract:

    Abstract The Ordovician-Silurian (O-S) transition coincided with significant environmental and biological changes. In South China, the Yangtze Platform experienced both global and regional events at this time, including sea-level fluctuations, tectonic movements, volcanic eruptions, mass extinction, and widespread anoxia. The O-S transitional strata of the Yangtze Platform comprise organic-rich black shales that are an important oil source rock. To explore the evolution of watermass chemistry and its relationship to organic matter accumulation, we conducted an integrated Fe-S-C geochemical study (i.e., Fe-speciation, δ13Corg, δ34Spy, pyrite-S and TOC) of the O-S Boundary sections at Datianba (Chongqing Municipality) and Shuanghe (Sichuan Province). These sections were located in the restricted inner Yangtze Sea, in contrast to the previously studied Wangjiawan section, which was deposited in a more open setting of the outer Yangtze Sea. In contrast to the well-oxygenated conditions at Wangjiawan, the Datianba and Shuanghe sections record persistently anoxic, and episodically euxinic, conditions during the Hirnantian, which can be explained by the unique paleogeography and restricted hydrography of the inner Yangtze Sea. We propose that the regional Kwangsian Orogeny, which was driven by collision of the Yangtze and Cathaysia blocks, played a key role in basin development, watermass chemistry changes, and accumulation of Wufeng Formation black shales within the Yangtze Sea. The more widespread black shales of the Lower Silurian Lungmachi Formation were linked to the post-Hirnantian global marine transgression.

Storch Petr - One of the best experts on this subject based on the ideXlab platform.

  • A graptolite-rich Ordovician-Silurian Boundary section in the south-central Pyrenees, Spain: Stratigraphical and palaeobiogeographical significance
    'Cambridge University Press (CUP)', 2020
    Co-Authors: Gutiérrez-marco J. C., Storch Petr, Roqué Bernal J.
    Abstract:

    An Ordovician-Silurian Boundary section marked by an uninterrupted, relatively high rate of black shale sedimentation and abundant, diverse graptolites is described from the south-central Pyrenees. The structurally simple Estana section comprises the uppermost part of the quartzite-dominated Bar Formation and overlying black shales of late Hirnantian and early Rhuddanian age, which have been dated by graptolites to the upper Metabolograptus persculptus and lower-middle Akidograptus ascensus-Parakidograptus acuminatus biozones. Due to the absence of M. persculptus, a Metabolograptus parvulus Biozone correlative with the upper part of the persculptus Biozone is recognized below the lowest occurrence of akidograptids, which indicate the base of the Silurian System. The graptolite fauna comprise 27 species including Normalograptus minor, N. lubricus, N. rhizinus, Hirsutograptus, Korenograptus bifurcus, K. bicaudatus, K. lanpherei and Nd. shanchongensis, most of which were formerly considered to be endemic to the low-latitude palaeobiogeographical province of China, Siberia and northern North America. Two new species, N. baridaensis and N. ednae, are described. The succession of graptolite assemblages in the Estana section, and occurrence of several cosmopolitan taxa in its parvulus and lower ascensus-acuminatus biozones that are unknown elsewhere in peri-Gondwanan Europe, suggest that strata immediately surrounding the Ordovician-Silurian Boundary may be absent, highly condensed or oxic and barren of graptolites in other sections of northwestern peri-Gondwana. Common graptolite synrhabdosomes and abnormal rhabdosomes may indicate some environmental stress in the parvulus Biozone, although the rather uniform black shale lithology, total organic carbon content and δ Corg values suggest uninterrupted sedimentation under stable, anoxic conditions.PŠ appreciates the financial support provided by the Czech Science Foundation (grant no. 14– 16124S) and in-house support received from the Institute of Geology of the Czech Academy of Sciences (no. RVO 67985831). JRB paid his own expenses. Work carried out by JCGM was funded by the Spanish Ministry of Economic Affairs, Industry and Competitivity (grant no. CGL2017- 87631-P

  • A graptolite-rich Ordovician–Silurian Boundary section in the south-central Pyrenees, Spain: stratigraphical and palaeobiogeographical significance
    'Cambridge University Press (CUP)', 2019
    Co-Authors: Storch Petr, Roqué Bernal Josep, Gutiérrez Marco, Juan Carlos
    Abstract:

    An Ordovician–Silurian Boundary section marked by an uninterrupted, relatively high rate of black shale sedimentation and abundant, diverse graptolites is described from the south-central Pyrenees. The structurally simple Estana section comprises the uppermost part of the quartzite-dominated Bar Formation and overlying black shales of late Hirnantian and early Rhuddanian age, which have been dated by graptolites to the upper Metabolograptus persculptus and lower–middle Akidograptus ascensus–Parakidograptus acuminatus biozones. Due to the absence of M. persculptus, a Metabolograptus parvulus Biozone correlative with the upper part of the persculptus Biozone is recognized below the lowest occurrence of akidograptids, which indicate the base of the Silurian System. The graptolite fauna comprise 27 species including Normalograptus minor, N. lubricus, N. rhizinus, Hirsutograptus, Korenograptus bifurcus, K. bicaudatus, K. lanpherei and Nd. shanchongensis, most of which were formerly considered to be endemic to the low-latitude palaeobiogeographical province of China, Siberia and northern North America. Two new species, N. baridaensis and N. ednae, are described. The succession of graptolite assemblages in the Estana section, and occurrence of several cosmopolitan taxa in its parvulus and lower ascensus–acuminatus biozones that are unknown elsewhere in peri-Gondwanan Europe, suggest that strata immediately surrounding the Ordovician–Silurian Boundary may be absent, highly condensed or oxic and barren of graptolites in other sections of northwestern peri-Gondwana. Common graptolite synrhabdosomes and abnormal rhabdosomes may indicate some environmental stress in the parvulus Biozone, although the rather uniform black shale lithology, total organic carbon content and δ13Corg values suggest uninterrupted sedimentation under stable, anoxic conditions

  • A graptolite-rich Ordovician–Silurian Boundary section in the south-central Pyrenees, Spain: stratigraphical and palaeobiogeographical significance
    'Cambridge University Press (CUP)', 2019
    Co-Authors: Storch Petr, Roqué Bernal J., Gutiérrez-marco J. C.
    Abstract:

    An Ordovician–Silurian Boundary section marked by an uninterrupted, relatively high rate of black shale sedimentation and abundant, diverse graptolites is described from the south-central Pyrenees. The structurally simple Estana section comprises the uppermost part of the quartzite-dominated Bar Formation and overlying black shales of late Hirnantian and early Rhuddanian age, which have been dated by graptolites to the upper Metabolograptus persculptus and lower–middle Akidograptus ascensus–Parakidograptus acuminatus biozones. Due to the absence of M. persculptus, a Metabolograptus parvulus Biozone correlative with the upper part of the persculptus Biozone is recognized below the lowest occurrence of akidograptids, which indicate the base of the Silurian System. The graptolite fauna comprise 27 species including Normalograptus minor, N. lubricus, N. rhizinus, Hirsutograptus, Korenograptus bifurcus, K. bicaudatus, K. lanpherei and Nd. shanchongensis, most of which were formerly considered to be endemic to the low-latitude palaeobiogeographical province of China, Siberia and northern North America. Two new species, N. baridaensis and N. ednae, are described. The succession of graptolite assemblages in the Estana section, and occurrence of several cosmopolitan taxa in its parvulus and lower ascensus–acuminatus biozones that are unknown elsewhere in peri-Gondwanan Europe, suggest that strata immediately surrounding the Ordovician–Silurian Boundary may be absent, highly condensed or oxic and barren of graptolites in other sections of northwestern peri-Gondwana. Common graptolite synrhabdosomes and abnormal rhabdosomes may indicate some environmental stress in the parvulus Biozone, although the rather uniform black shale lithology, total organic carbon content and δ13Corg values suggest uninterrupted sedimentation under stable, anoxic conditions.PŠ appreciates the financial support provided by the Czech Science Foundation (grant no. 14– 16124S) and in-house support received from the Institute of Geology of the Czech Academy of Sciences (no. RVO 67985831). JRB paid his own expenses. Work carried out by JCGM was funded by the Spanish Ministry of Economic Affairs, Industry and Competitivity (grant no. CGL2017- 87631-P).Peer reviewe

  • Graptolite biostratigraphy of the Ordovician-Silurian Boundary in the eastern Pyrenees (upper Segre valley, Lleida, NE Spain)
    Sociedad Geológica de España, 2017
    Co-Authors: Roqué Bernal Josep, Storch Petr
    Abstract:

    Se presenta una sección de pizarras negras graptolíticas donde, por vez primera en España, se registra de manera continua el límite Ordovícico-Silúrico. El perfil se localiza al este de Estana (Lleida), en la Zona Axial pirenaica. El límite se localiza 2,20. m por encima del techo de la Cuarcita de Bar, cuya edad ordovícica queda aquí demostrada. Las asociaciones de graptolitos del Hirnantiense superior pertenecen a la Biozona de Metabolograptus persculptus y a la llamada "fauna pre-ascensus", en tanto que los graptolitos del Silúrico basaI corresponden a la Biozona de Akidograptus ascensus. El descubrimiento de esta sección es bastante excepcional en las plataformas del sur de Gondwana, donde los graptolitos post-glaciares son extremadamente raros. Entre las formas silúricas, se presenta el tercer hallazgo mundial de la especie Rickardsograptus ? bifurcus, definida en China y reconocida también en los Alpes Cárnicos de Austria.A unique graptolitic black-shale section ranging across the OrdovicianSilurian Boundary interval has been found in the Pyrenees (NW Spain), at Riu de Quer locality, east of the town of Estana (province of Lleida). The Ordovician-Silurian Boundary was identified 2.2 0 m above the top of the Bar Quartzite. Upper Hirnantian graptolites of the Metabolograptus persculptus Biozone and subsequent "pre-ascensus graptolite fauna " are common below the lowest occurrence of Akidograptus ascensus and associated taxa of the basal Silurian A. ascensus Biozone. The section is rather exceptional in Gondwanan Europe, where the post-glacial Hirnantian graptolites are extremely rare. Rickardsograptus? bifureus recorded among the earliest Silurian taxa is an exotic element so far known only from China and the Carnic Alps of Austri

  • Graptolite biostratigraphy of the Ordovician-Silurian Boundary in the eastern Pyrenees (upper Segre valley, Lleida, NE Spain)
    'Japanese Society of Applied Entomology & Zoology', 2017
    Co-Authors: Roqué Bernal J., Storch Petr, Gutiérrez-marco J. C.
    Abstract:

    [EN] A unique graptolitic black-shale section ranging across the OrdovicianSilurian Boundary interval has been found in the Pyrenees (NW Spain), at Riu de Quer locality, east of the town of Estana (province of Lleida). The Ordovician–Silurian Boundary was identified 2.20 m above the top of the Bar Quartzite. Upper Hirnantian graptolites of the Metabolograptus persculptus Biozone and subsequent “pre-ascensus graptolite fauna” are common below the lowest occurrence of Akidograptus ascensus and associated taxa of the basal Silurian A. ascensus Biozone. The section is rather exceptional in Gondwanan Europe, where the post-glacial Hirnantian graptolites are extremely rare. Rickardsograptus? bifurcus recorded among the earliest Silurian taxa is an exotic element so far known only from China and the Carnic Alps of Austria[ES] Se presenta una sección de pizarras negras graptolíticas donde, por vez primera en España, se registra de manera continua el límite Ordovícico-Silúrico. El perfil se localiza al este de Estana (Lleida), en la Zona Axial pirenaica. El límite se localiza 2,20. m por encima del techo de la Cuarcita de Bar, cuya edad ordovícica queda aquí demostrada. Las asociaciones de graptolitos del Hirnantiense superior pertenecen a la Biozona de Metabolograptus persculptusy a la llamada “fauna pre-ascensus”, en tanto que los graptolitos del Silúrico basal corresponden a la Biozona de Akidograptus ascensus. El descubrimiento de esta sección es bastante excepcional en las plataformas del sur de Gondwana, donde los graptolitos post-glaciares son extremadamente raros. Entre las formas silúricas, se presenta el tercer hallazgo mundial de la especie Rickardsograptus? bifurcus, definida en China y reconocida también en los Alpes Cárnicos de Austria.Este artículo es una contribución a los proyectos CGL2012-39471 (MINECO) y PICG 653 (IUGS-UNESCO).Peer reviewe

Detian Yan - One of the best experts on this subject based on the ideXlab platform.

  • carbon and sulfur isotopic anomalies across the ordovician silurian Boundary on the yangtze platform south china
    Palaeogeography Palaeoclimatology Palaeoecology, 2009
    Co-Authors: Detian Yan, Daizhao Chen, Qingchen Wang, Jianguo Wang, Zhuozhuo Wang
    Abstract:

    Abstract Abundance of organic matter, carbon isotopic compositions of organic matter (δ13Corg) and sulfur isotopic compositions of iron sulfide (δ34Ssulfide) across the Ordovician–Silurian (O–S) Boundary was analysed from two sections (Wangjiawan, western Hubei; Nanbazi, northern Guizhou) on the Yangtze Platform, South China. The organic abundance across the O–S Boundary at these two sections is generally high, except for the Hirnantian interval. At Wangjiawan section in western Hubei, the δ13Corg values vary from about − 30.8‰ VPDB in the mid-Ashgill to − 27.6‰ in the upper Hirnantian interval, which abruptly return to the pre-Hirnantian values. At Nanbazi section in northern Guizhou, δ13Corg values vary from − 30.5‰ to − 26.6‰ from the mid-Ashgill to the upper Hirnantian horizons, which shift negatively to the low spike at − 29.2‰ in the lowermost Rhuddanian, then increase slightly to relatively persistent values around − 28‰. Similar variation patterns of δ34Ssulfide values are unravelled at the two sections, showing a positive excursion from the mid-Ashgill to the upper Hirnantian, then a sharp negative shift in the lowermost Rhuddanian, although with different background values of δ34Ssulfide from these two sections. These data, together with those from other areas, demonstrate large climatic fluctuations from warming to cooling, then to warming, oceanic changes from and anoxic to oxygenated, to anoxic water columns, during the O–S transition. Climatic fluctuations, together with multiple oceanic anoxia and sea-level fluctuations, were likely responsible for the stepwise massive demise of the O–S biotic crisis.

Gutiérrez-marco J. C. - One of the best experts on this subject based on the ideXlab platform.

  • A graptolite-rich Ordovician-Silurian Boundary section in the south-central Pyrenees, Spain: Stratigraphical and palaeobiogeographical significance
    'Cambridge University Press (CUP)', 2020
    Co-Authors: Gutiérrez-marco J. C., Štorch P., Roqué Bernal J.
    Abstract:

    An Ordovician-Silurian Boundary section marked by an uninterrupted, relatively high rate of black shale sedimentation and abundant, diverse graptolites is described from the south-central Pyrenees. The structurally simple Estana section comprises the uppermost part of the quartzite-dominated Bar Formation and overlying black shales of late Hirnantian and early Rhuddanian age, which have been dated by graptolites to the upper Metabolograptus persculptus and lower-middle Akidograptus ascensus-Parakidograptus acuminatus biozones. Due to the absence of M. persculptus, a Metabolograptus parvulus Biozone correlative with the upper part of the persculptus Biozone is recognized below the lowest occurrence of akidograptids, which indicate the base of the Silurian System. The graptolite fauna comprise 27 species including Normalograptus minor, N. lubricus, N. rhizinus, Hirsutograptus, Korenograptus bifurcus, K. bicaudatus, K. lanpherei and Nd. shanchongensis, most of which were formerly considered to be endemic to the low-latitude palaeobiogeographical province of China, Siberia and northern North America. Two new species, N. baridaensis and N. ednae, are described. The succession of graptolite assemblages in the Estana section, and occurrence of several cosmopolitan taxa in its parvulus and lower ascensus-acuminatus biozones that are unknown elsewhere in peri-Gondwanan Europe, suggest that strata immediately surrounding the Ordovician-Silurian Boundary may be absent, highly condensed or oxic and barren of graptolites in other sections of northwestern peri-Gondwana. Common graptolite synrhabdosomes and abnormal rhabdosomes may indicate some environmental stress in the parvulus Biozone, although the rather uniform black shale lithology, total organic carbon content and δ Corg values suggest uninterrupted sedimentation under stable, anoxic conditions

  • A graptolite-rich Ordovician-Silurian Boundary section in the south-central Pyrenees, Spain: Stratigraphical and palaeobiogeographical significance
    'Cambridge University Press (CUP)', 2020
    Co-Authors: Gutiérrez-marco J. C., Storch Petr, Roqué Bernal J.
    Abstract:

    An Ordovician-Silurian Boundary section marked by an uninterrupted, relatively high rate of black shale sedimentation and abundant, diverse graptolites is described from the south-central Pyrenees. The structurally simple Estana section comprises the uppermost part of the quartzite-dominated Bar Formation and overlying black shales of late Hirnantian and early Rhuddanian age, which have been dated by graptolites to the upper Metabolograptus persculptus and lower-middle Akidograptus ascensus-Parakidograptus acuminatus biozones. Due to the absence of M. persculptus, a Metabolograptus parvulus Biozone correlative with the upper part of the persculptus Biozone is recognized below the lowest occurrence of akidograptids, which indicate the base of the Silurian System. The graptolite fauna comprise 27 species including Normalograptus minor, N. lubricus, N. rhizinus, Hirsutograptus, Korenograptus bifurcus, K. bicaudatus, K. lanpherei and Nd. shanchongensis, most of which were formerly considered to be endemic to the low-latitude palaeobiogeographical province of China, Siberia and northern North America. Two new species, N. baridaensis and N. ednae, are described. The succession of graptolite assemblages in the Estana section, and occurrence of several cosmopolitan taxa in its parvulus and lower ascensus-acuminatus biozones that are unknown elsewhere in peri-Gondwanan Europe, suggest that strata immediately surrounding the Ordovician-Silurian Boundary may be absent, highly condensed or oxic and barren of graptolites in other sections of northwestern peri-Gondwana. Common graptolite synrhabdosomes and abnormal rhabdosomes may indicate some environmental stress in the parvulus Biozone, although the rather uniform black shale lithology, total organic carbon content and δ Corg values suggest uninterrupted sedimentation under stable, anoxic conditions.PŠ appreciates the financial support provided by the Czech Science Foundation (grant no. 14– 16124S) and in-house support received from the Institute of Geology of the Czech Academy of Sciences (no. RVO 67985831). JRB paid his own expenses. Work carried out by JCGM was funded by the Spanish Ministry of Economic Affairs, Industry and Competitivity (grant no. CGL2017- 87631-P

  • A graptolite-rich Ordovician–Silurian Boundary section in the south-central Pyrenees, Spain: stratigraphical and palaeobiogeographical significance
    'Cambridge University Press (CUP)', 2019
    Co-Authors: Storch Petr, Roqué Bernal J., Gutiérrez-marco J. C.
    Abstract:

    An Ordovician–Silurian Boundary section marked by an uninterrupted, relatively high rate of black shale sedimentation and abundant, diverse graptolites is described from the south-central Pyrenees. The structurally simple Estana section comprises the uppermost part of the quartzite-dominated Bar Formation and overlying black shales of late Hirnantian and early Rhuddanian age, which have been dated by graptolites to the upper Metabolograptus persculptus and lower–middle Akidograptus ascensus–Parakidograptus acuminatus biozones. Due to the absence of M. persculptus, a Metabolograptus parvulus Biozone correlative with the upper part of the persculptus Biozone is recognized below the lowest occurrence of akidograptids, which indicate the base of the Silurian System. The graptolite fauna comprise 27 species including Normalograptus minor, N. lubricus, N. rhizinus, Hirsutograptus, Korenograptus bifurcus, K. bicaudatus, K. lanpherei and Nd. shanchongensis, most of which were formerly considered to be endemic to the low-latitude palaeobiogeographical province of China, Siberia and northern North America. Two new species, N. baridaensis and N. ednae, are described. The succession of graptolite assemblages in the Estana section, and occurrence of several cosmopolitan taxa in its parvulus and lower ascensus–acuminatus biozones that are unknown elsewhere in peri-Gondwanan Europe, suggest that strata immediately surrounding the Ordovician–Silurian Boundary may be absent, highly condensed or oxic and barren of graptolites in other sections of northwestern peri-Gondwana. Common graptolite synrhabdosomes and abnormal rhabdosomes may indicate some environmental stress in the parvulus Biozone, although the rather uniform black shale lithology, total organic carbon content and δ13Corg values suggest uninterrupted sedimentation under stable, anoxic conditions.PŠ appreciates the financial support provided by the Czech Science Foundation (grant no. 14– 16124S) and in-house support received from the Institute of Geology of the Czech Academy of Sciences (no. RVO 67985831). JRB paid his own expenses. Work carried out by JCGM was funded by the Spanish Ministry of Economic Affairs, Industry and Competitivity (grant no. CGL2017- 87631-P).Peer reviewe

  • Graptolite biostratigraphy of the Ordovician-Silurian Boundary in the eastern Pyrenees (upper Segre valley, Lleida, NE Spain)
    'Japanese Society of Applied Entomology & Zoology', 2017
    Co-Authors: Roqué Bernal J., Storch Petr, Gutiérrez-marco J. C.
    Abstract:

    [EN] A unique graptolitic black-shale section ranging across the OrdovicianSilurian Boundary interval has been found in the Pyrenees (NW Spain), at Riu de Quer locality, east of the town of Estana (province of Lleida). The Ordovician–Silurian Boundary was identified 2.20 m above the top of the Bar Quartzite. Upper Hirnantian graptolites of the Metabolograptus persculptus Biozone and subsequent “pre-ascensus graptolite fauna” are common below the lowest occurrence of Akidograptus ascensus and associated taxa of the basal Silurian A. ascensus Biozone. The section is rather exceptional in Gondwanan Europe, where the post-glacial Hirnantian graptolites are extremely rare. Rickardsograptus? bifurcus recorded among the earliest Silurian taxa is an exotic element so far known only from China and the Carnic Alps of Austria[ES] Se presenta una sección de pizarras negras graptolíticas donde, por vez primera en España, se registra de manera continua el límite Ordovícico-Silúrico. El perfil se localiza al este de Estana (Lleida), en la Zona Axial pirenaica. El límite se localiza 2,20. m por encima del techo de la Cuarcita de Bar, cuya edad ordovícica queda aquí demostrada. Las asociaciones de graptolitos del Hirnantiense superior pertenecen a la Biozona de Metabolograptus persculptusy a la llamada “fauna pre-ascensus”, en tanto que los graptolitos del Silúrico basal corresponden a la Biozona de Akidograptus ascensus. El descubrimiento de esta sección es bastante excepcional en las plataformas del sur de Gondwana, donde los graptolitos post-glaciares son extremadamente raros. Entre las formas silúricas, se presenta el tercer hallazgo mundial de la especie Rickardsograptus? bifurcus, definida en China y reconocida también en los Alpes Cárnicos de Austria.Este artículo es una contribución a los proyectos CGL2012-39471 (MINECO) y PICG 653 (IUGS-UNESCO).Peer reviewe