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Bradley D Cramer - One of the best experts on this subject based on the ideXlab platform.
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Paleobiogeography, high-resolution stratigraphy, and the future of Paleozoic biostratigraphy: Fine-scale diachroneity of the Wenlock (Silurian) conodont Kockelella walliseri
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Bradley D Cramer, Lennart Jeppsson, Axel Munnecke, Mark A. Kleffner, Carlton E. Brett, Patrick I. Mclaughlin, Christian SamtlebenAbstract:The Wenlock Epoch of the Silurian Period has become one of the chronostratigraphically best-constrained intervals of the Paleozoic. The integration of multiple chronostratigraphic tools, such as conodont and graptolite biostratigraphy, sequence stratigraphy, and delta C-13(carb) chemostratigraphy, has greatly improved global chronostratigraphic correlation and portions of the Wenlock can now be correlated with precision better than +/- 100 kyr. Additionally, such detailed and integrated chronostratigraphy provides an opportunity to evaluate the fidelity of individual chronostratigraphic tools. Here, we use conodont biostratigraphy, sequence stratigraphy and carbon isotope (delta C-13(carb)) chemostratigraphy to demonstrate that the conodont Kockelella walliseri, an important guide fossil for middle and upper Sheinwoodian strata (lower stage of the Wenlock Series), first appears at least one full stratigraphic sequence lower in Laurentia than in Baltica. Rather than serving as a demonstration of the unreliability of conodont biostratigraphy, this example serves to demonstrate the promise of high-resolution Paleozoic stratigraphy. The temporal difference between the two first occurrences was likely less than 1 million years, and although it is conceptually understood that speciation and colonization must have been non-instantaneous events, Paleozoic paleobiogeographic variability on such short timescales (tens to hundreds of kyr) traditionally has been ignored or considered to be of little practical importance. The expansion of high-resolution Paleozoic stratigraphy in the future will require robust biostratigraphic zonations that embrace the integration of multiple chronostratigraphic tools as well as the paleobiogeographic variability in ranges that they will inevitably demonstrate. In addition, a better understanding of the paleobiogeographic migration histories of marine organisms will provide a unique tool for future Paleozoic paleoceanography and paleobiology research. (C) 2010 Elsevier B.V. All rights reserved
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high precision u pb zircon age constraints on the duration of rapid biogeochemical events during the ludlow epoch Silurian Period
Journal of the Geological Society, 2015Co-Authors: Bradley D Cramer, Mark D Schmitz, Warren D Huff, Stig M BergstromAbstract:Precise determinations of the rates and durations of Palaeozoic biogeochemical events are largely unavailable. Here, we present two new high-precision U–Pb (zircon) dates from volcanic ash deposits from the Ludlow Series (Silurian System) of Podolia, Ukraine, that yielded weighted mean 206 Pb/ 238 U dates of 424.08 ± 0.20 (0.29) [0.53] Ma and 422.91 ± 0.07 (0.21) [0.49] Ma (analytical, tracer and total uncertainties). These new dates bracket the largest post-Cambrian global carbon cycle perturbation (Lau Excursion) and constrain the ‘Ludlow Rise’ in 87 Sr/ 86 Sr. These chronostratigraphically well-controlled dates improve the calibration of the Silurian time scale and provide the first determinations of the rates of biogeochemical change during the Ludlow Epoch. Supplementary material: U–Pb geochemical methods, data and CL imagery are available at http://www.geolsoc.org.uk/SUP18798.
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High-precision U–Pb zircon age constraints on the duration of rapid biogeochemical events during the Ludlow Epoch (Silurian Period)
Journal of the Geological Society, 2015Co-Authors: Bradley D Cramer, Mark D Schmitz, Warren D Huff, Stig M BergstromAbstract:Precise determinations of the rates and durations of Palaeozoic biogeochemical events are largely unavailable. Here, we present two new high-precision U–Pb (zircon) dates from volcanic ash deposits from the Ludlow Series (Silurian System) of Podolia, Ukraine, that yielded weighted mean 206 Pb/ 238 U dates of 424.08 ± 0.20 (0.29) [0.53] Ma and 422.91 ± 0.07 (0.21) [0.49] Ma (analytical, tracer and total uncertainties). These new dates bracket the largest post-Cambrian global carbon cycle perturbation (Lau Excursion) and constrain the ‘Ludlow Rise’ in 87 Sr/ 86 Sr. These chronostratigraphically well-controlled dates improve the calibration of the Silurian time scale and provide the first determinations of the rates of biogeochemical change during the Ludlow Epoch. Supplementary material: U–Pb geochemical methods, data and CL imagery are available at http://www.geolsoc.org.uk/SUP18798.
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U-Pb (zircon) age constraints on the timing and duration of Wenlock (Silurian) paleocommunity collapse and recovery during the “Big Crisis”
Geological Society of America Bulletin, 2012Co-Authors: Bradley D Cramer, Daniel J. Condon, Ulf Söderlund, Carly Marshall, Graham Worton, Alan T. Thomas, Mikael Calner, Vincent Perrier, Ian BoomerAbstract:High-precision isotope-dilution U-Pb (zircon) dating was conducted on three volcanic ash fall (bentonite) samples from the Swedish island of Gotland, and on a fourth bentonite from the West Midlands, England. Zircons from the Ireviken, Grotlingbo, Djupvik (Gotland), and Wren's Nest Hill-15 (West Midlands) bentonites yielded weighted mean Pb-206/U-238 ages of 431.83 +/- 0.23/0.67 Ma, 428.45 +/- 035/0.73 Ma, 428.06 +/- 0.2110.66 Ma, and 427.86 +/- 032/0.71 Ma, respectively (analytical/total uncertainties). These biostratigraphically well-controlled age dates effectively bracket the Wenlock Epoch of the Silurian Period and provide control for the duration of one of the major Paleozoic biotic events and associated perturbations to the global carbon cycle (the "Big Crisis" or lundgreni event- graptolites; the NIulde Event-conodonts; the Mulde excursion-carbon isotopes). These new data suggest an older and shorter duration for the recalibration of the Wenlock Series and demonstrate that the cascade of biological and chemical events that took place during the Big Crisis happened on time scales of tens to hundreds of thousands of years. (Less)
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the Silurian Period
A Geologic Time Scale 2004. Eds: Gradstein F. M. Ogg J. G. Smith A. G., 2012Co-Authors: Michael J Melchin, Peter M Sadler, Bradley D Cramer, Roger A Cooper, Felix M Gradstein, Oyvind HammerAbstract:Abstract: The features of the Silurian Period include a rapid recovery in biodiversity after the end-Ordovician extinction event, a highly dynamic climate accentuated by multiple short-lived events, strong eustatic sea level fluctuations and oceanic turnover, associated with extinction of moderate scale. Land colonization occurred, alongside general convergence of continental plates and low levels of faunal provincialism, closure of Iapetus Ocean, narrowing of Rheic Ocean and migration of the South Pole over South American and South African Gondwana. Figure options Download full-size image Download as PowerPoint slide
Petr Štorch - One of the best experts on this subject based on the ideXlab platform.
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Plant Diversity of The Mid Silurian (Lower Wenlock, Sheinwoodian) Terrestrial Vegetation Preserved in Marine Sediments from The Barrandian Area, The Czech Republic
Fossil Imprint, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Petr ŠtorchAbstract:Abstract Plant mega- and microfossils are described from the middle Sheinwoodian of the Barrandian area. The material comes from the Loděnice locality and the same horizon as the earliest unequivocal land plant, Cooksonia barrandei LIBERTÍN, J.KVAČEK, BEK, ŽÁRSKÝ et ŠTORCH. Its age (432 Myr) is inferred from the associated graptolite fauna, including the zonal index graptolite Monograptus belophorus. Megafossils have clear similarity with Cooksonia, due to their dichotomised axes with slightly widened subtending axes bearing putative sporangia. They document some of the plant diversity that was in place when the first proven representative of the genus Cooksonia appeared, and together with dispersed spores they provide strong and important evidence that a diversified terrestrial ecosystem had developed on the Barrandian volcanic archipelago in the peri-Gondwanan realm by the end of the Sheinwoodian Stage of the Silurian Period.
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Sporophytes of polysporangiate land plants from the early Silurian Period may have been photosynthetically autonomous
Nature Plants, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Viktor Žárský, Petr ŠtorchAbstract:Ancient fossil Cooksonia plants from the Czech Republic are among the largest known early polysporangiate plants from when vascular plants were colonizing the land. They were of sufficient size to support effective photosynthesis. The colonization of land by vascular plants is an extremely important phase in Earth’s life history. This key evolutionary process is thought to have begun during the Middle Cambrian^ 1 Period and culminated in the Silurian/Early Devonian Period (interval about 509–393 million years ago (Ma)), and is documented primarily by microfossils (that is, by dispersed spores, phytodebris including fragments of algae, tissues, sporangia and cuticles), tubes and rare megafossils^ 2 . A newly recognized fossil cooksonioid plant with in situ spores from the Barrandian area, Czech Republic, is of the highest importance because it represents extremely ancient megafossil evidence of land plant diploid generation: sporophytes (~432 Ma). The robust size of this plant places it among the largest known early polysporangiate land plants and it is probable that it attained adequate size for both aeration and effective photosynthetic competence. This would mean not only that sporophytes were photosynthetically autonomous but also that the they might have been able to sustain a relatively gametophyte-independent existence.
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sporophytes of polysporangiate land plants from the early Silurian Period may have been photosynthetically autonomous
Nature plants, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Viktor Žárský, Petr ŠtorchAbstract:The colonization of land by vascular plants is an extremely important phase in Earth’s life history. This key evolutionary process is thought to have begun during the Middle Cambrian 1 Period and culminated in the Silurian/Early Devonian Period (interval about 509–393 million years ago (Ma)), and is documented primarily by microfossils (that is, by dispersed spores, phytodebris including fragments of algae, tissues, sporangia and cuticles), tubes and rare megafossils 2 . A newly recognized fossil cooksonioid plant with in situ spores from the Barrandian area, Czech Republic, is of the highest importance because it represents extremely ancient megafossil evidence of land plant diploid generation: sporophytes (~432 Ma). The robust size of this plant places it among the largest known early polysporangiate land plants and it is probable that it attained adequate size for both aeration and effective photosynthetic competence. This would mean not only that sporophytes were photosynthetically autonomous but also that the they might have been able to sustain a relatively gametophyte-independent existence.
Milan Libertín - One of the best experts on this subject based on the ideXlab platform.
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Plant Diversity of The Mid Silurian (Lower Wenlock, Sheinwoodian) Terrestrial Vegetation Preserved in Marine Sediments from The Barrandian Area, The Czech Republic
Fossil Imprint, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Petr ŠtorchAbstract:Abstract Plant mega- and microfossils are described from the middle Sheinwoodian of the Barrandian area. The material comes from the Loděnice locality and the same horizon as the earliest unequivocal land plant, Cooksonia barrandei LIBERTÍN, J.KVAČEK, BEK, ŽÁRSKÝ et ŠTORCH. Its age (432 Myr) is inferred from the associated graptolite fauna, including the zonal index graptolite Monograptus belophorus. Megafossils have clear similarity with Cooksonia, due to their dichotomised axes with slightly widened subtending axes bearing putative sporangia. They document some of the plant diversity that was in place when the first proven representative of the genus Cooksonia appeared, and together with dispersed spores they provide strong and important evidence that a diversified terrestrial ecosystem had developed on the Barrandian volcanic archipelago in the peri-Gondwanan realm by the end of the Sheinwoodian Stage of the Silurian Period.
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Sporophytes of polysporangiate land plants from the early Silurian Period may have been photosynthetically autonomous
Nature Plants, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Viktor Žárský, Petr ŠtorchAbstract:Ancient fossil Cooksonia plants from the Czech Republic are among the largest known early polysporangiate plants from when vascular plants were colonizing the land. They were of sufficient size to support effective photosynthesis. The colonization of land by vascular plants is an extremely important phase in Earth’s life history. This key evolutionary process is thought to have begun during the Middle Cambrian^ 1 Period and culminated in the Silurian/Early Devonian Period (interval about 509–393 million years ago (Ma)), and is documented primarily by microfossils (that is, by dispersed spores, phytodebris including fragments of algae, tissues, sporangia and cuticles), tubes and rare megafossils^ 2 . A newly recognized fossil cooksonioid plant with in situ spores from the Barrandian area, Czech Republic, is of the highest importance because it represents extremely ancient megafossil evidence of land plant diploid generation: sporophytes (~432 Ma). The robust size of this plant places it among the largest known early polysporangiate land plants and it is probable that it attained adequate size for both aeration and effective photosynthetic competence. This would mean not only that sporophytes were photosynthetically autonomous but also that the they might have been able to sustain a relatively gametophyte-independent existence.
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sporophytes of polysporangiate land plants from the early Silurian Period may have been photosynthetically autonomous
Nature plants, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Viktor Žárský, Petr ŠtorchAbstract:The colonization of land by vascular plants is an extremely important phase in Earth’s life history. This key evolutionary process is thought to have begun during the Middle Cambrian 1 Period and culminated in the Silurian/Early Devonian Period (interval about 509–393 million years ago (Ma)), and is documented primarily by microfossils (that is, by dispersed spores, phytodebris including fragments of algae, tissues, sporangia and cuticles), tubes and rare megafossils 2 . A newly recognized fossil cooksonioid plant with in situ spores from the Barrandian area, Czech Republic, is of the highest importance because it represents extremely ancient megafossil evidence of land plant diploid generation: sporophytes (~432 Ma). The robust size of this plant places it among the largest known early polysporangiate land plants and it is probable that it attained adequate size for both aeration and effective photosynthetic competence. This would mean not only that sporophytes were photosynthetically autonomous but also that the they might have been able to sustain a relatively gametophyte-independent existence.
Stig M Bergstrom - One of the best experts on this subject based on the ideXlab platform.
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high precision u pb zircon age constraints on the duration of rapid biogeochemical events during the ludlow epoch Silurian Period
Journal of the Geological Society, 2015Co-Authors: Bradley D Cramer, Mark D Schmitz, Warren D Huff, Stig M BergstromAbstract:Precise determinations of the rates and durations of Palaeozoic biogeochemical events are largely unavailable. Here, we present two new high-precision U–Pb (zircon) dates from volcanic ash deposits from the Ludlow Series (Silurian System) of Podolia, Ukraine, that yielded weighted mean 206 Pb/ 238 U dates of 424.08 ± 0.20 (0.29) [0.53] Ma and 422.91 ± 0.07 (0.21) [0.49] Ma (analytical, tracer and total uncertainties). These new dates bracket the largest post-Cambrian global carbon cycle perturbation (Lau Excursion) and constrain the ‘Ludlow Rise’ in 87 Sr/ 86 Sr. These chronostratigraphically well-controlled dates improve the calibration of the Silurian time scale and provide the first determinations of the rates of biogeochemical change during the Ludlow Epoch. Supplementary material: U–Pb geochemical methods, data and CL imagery are available at http://www.geolsoc.org.uk/SUP18798.
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High-precision U–Pb zircon age constraints on the duration of rapid biogeochemical events during the Ludlow Epoch (Silurian Period)
Journal of the Geological Society, 2015Co-Authors: Bradley D Cramer, Mark D Schmitz, Warren D Huff, Stig M BergstromAbstract:Precise determinations of the rates and durations of Palaeozoic biogeochemical events are largely unavailable. Here, we present two new high-precision U–Pb (zircon) dates from volcanic ash deposits from the Ludlow Series (Silurian System) of Podolia, Ukraine, that yielded weighted mean 206 Pb/ 238 U dates of 424.08 ± 0.20 (0.29) [0.53] Ma and 422.91 ± 0.07 (0.21) [0.49] Ma (analytical, tracer and total uncertainties). These new dates bracket the largest post-Cambrian global carbon cycle perturbation (Lau Excursion) and constrain the ‘Ludlow Rise’ in 87 Sr/ 86 Sr. These chronostratigraphically well-controlled dates improve the calibration of the Silurian time scale and provide the first determinations of the rates of biogeochemical change during the Ludlow Epoch. Supplementary material: U–Pb geochemical methods, data and CL imagery are available at http://www.geolsoc.org.uk/SUP18798.
Jiří Kvaček - One of the best experts on this subject based on the ideXlab platform.
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Plant Diversity of The Mid Silurian (Lower Wenlock, Sheinwoodian) Terrestrial Vegetation Preserved in Marine Sediments from The Barrandian Area, The Czech Republic
Fossil Imprint, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Petr ŠtorchAbstract:Abstract Plant mega- and microfossils are described from the middle Sheinwoodian of the Barrandian area. The material comes from the Loděnice locality and the same horizon as the earliest unequivocal land plant, Cooksonia barrandei LIBERTÍN, J.KVAČEK, BEK, ŽÁRSKÝ et ŠTORCH. Its age (432 Myr) is inferred from the associated graptolite fauna, including the zonal index graptolite Monograptus belophorus. Megafossils have clear similarity with Cooksonia, due to their dichotomised axes with slightly widened subtending axes bearing putative sporangia. They document some of the plant diversity that was in place when the first proven representative of the genus Cooksonia appeared, and together with dispersed spores they provide strong and important evidence that a diversified terrestrial ecosystem had developed on the Barrandian volcanic archipelago in the peri-Gondwanan realm by the end of the Sheinwoodian Stage of the Silurian Period.
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Sporophytes of polysporangiate land plants from the early Silurian Period may have been photosynthetically autonomous
Nature Plants, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Viktor Žárský, Petr ŠtorchAbstract:Ancient fossil Cooksonia plants from the Czech Republic are among the largest known early polysporangiate plants from when vascular plants were colonizing the land. They were of sufficient size to support effective photosynthesis. The colonization of land by vascular plants is an extremely important phase in Earth’s life history. This key evolutionary process is thought to have begun during the Middle Cambrian^ 1 Period and culminated in the Silurian/Early Devonian Period (interval about 509–393 million years ago (Ma)), and is documented primarily by microfossils (that is, by dispersed spores, phytodebris including fragments of algae, tissues, sporangia and cuticles), tubes and rare megafossils^ 2 . A newly recognized fossil cooksonioid plant with in situ spores from the Barrandian area, Czech Republic, is of the highest importance because it represents extremely ancient megafossil evidence of land plant diploid generation: sporophytes (~432 Ma). The robust size of this plant places it among the largest known early polysporangiate land plants and it is probable that it attained adequate size for both aeration and effective photosynthetic competence. This would mean not only that sporophytes were photosynthetically autonomous but also that the they might have been able to sustain a relatively gametophyte-independent existence.
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sporophytes of polysporangiate land plants from the early Silurian Period may have been photosynthetically autonomous
Nature plants, 2018Co-Authors: Milan Libertín, Jiří Kvaček, Viktor Žárský, Petr ŠtorchAbstract:The colonization of land by vascular plants is an extremely important phase in Earth’s life history. This key evolutionary process is thought to have begun during the Middle Cambrian 1 Period and culminated in the Silurian/Early Devonian Period (interval about 509–393 million years ago (Ma)), and is documented primarily by microfossils (that is, by dispersed spores, phytodebris including fragments of algae, tissues, sporangia and cuticles), tubes and rare megafossils 2 . A newly recognized fossil cooksonioid plant with in situ spores from the Barrandian area, Czech Republic, is of the highest importance because it represents extremely ancient megafossil evidence of land plant diploid generation: sporophytes (~432 Ma). The robust size of this plant places it among the largest known early polysporangiate land plants and it is probable that it attained adequate size for both aeration and effective photosynthetic competence. This would mean not only that sporophytes were photosynthetically autonomous but also that the they might have been able to sustain a relatively gametophyte-independent existence.