The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Sergei Katsev - One of the best experts on this subject based on the ideXlab platform.
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Proterozoic seawater sulfate scarcity and the evolution of ocean–atmosphere chemistry
Nature Geoscience, 2019Co-Authors: Mojtaba Fakhraee, Olivier Hancisse, Donald E. Canfield, Sean A. Crowe, Sergei KatsevAbstract:In the Proterozoic, sulfate concentrations in the oceans were low and atmospheric methane levels high, according to mass balance and diagenetic models that investigate the oxidation state of the Proterozoic oceans. Oceanic sulfate concentrations are widely thought to have reached millimolar levels during the Proterozoic Eon, 2.5 to 0.54 billion years ago. Yet the magnitude of the increase in seawater sulfate concentrations over the course of the Eon remains largely unquantified. A rise in seawater sulfate concentrations has been inferred from the increased range of marine sulfide δ^34S values following the Great Oxidation Event and was induced by two processes: enhanced oxidative weathering of sulfides on land, and the onset of marine sulfur redox cycling. Here we use mass balance and diagenetic reaction-transport models to reconstruct the sulfate concentrations in Proterozoic seawater. We find that sulfate concentrations remained below 400 µM, and were possibly as low as 100 µM, throughout much of the Proterozoic. At these low sulfate concentrations, relatively large sulfate–pyrite sulfur isotope differences cannot be explained by sulfate reduction alone and are only possible through oxidative sediment sulfur cycling. This requires oxygen concentrations of at least 10 µM in shallow Proterozoic seawater, which translates to 1–10% of present atmospheric oxygen concentrations. At these oxygen and sulfate concentrations, the oceans would have been a substantial source of methane to the atmosphere (60–140 Tmol yr^−1). This methane would have accumulated to high concentrations (more than 25 ppmv) and supported greenhouse warming during much of the Proterozoic Eon, with notable exceptions during the PalaeoProterozoic and NeoProterozoic eras.
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Proterozoic seawater sulfate scarcity and the evolution of ocean atmosphere chemistry
Nature Geoscience, 2019Co-Authors: Mojtaba Fakhraee, Olivier Hancisse, Donald E. Canfield, Sean A. Crowe, Sergei KatsevAbstract:Oceanic sulfate concentrations are widely thought to have reached millimolar levels during the Proterozoic Eon, 2.5 to 0.54 billion years ago. Yet the magnitude of the increase in seawater sulfate concentrations over the course of the Eon remains largely unquantified. A rise in seawater sulfate concentrations has been inferred from the increased range of marine sulfide δ34S values following the Great Oxidation Event and was induced by two processes: enhanced oxidative weathering of sulfides on land, and the onset of marine sulfur redox cycling. Here we use mass balance and diagenetic reaction-transport models to reconstruct the sulfate concentrations in Proterozoic seawater. We find that sulfate concentrations remained below 400 µM, and were possibly as low as 100 µM, throughout much of the Proterozoic. At these low sulfate concentrations, relatively large sulfate–pyrite sulfur isotope differences cannot be explained by sulfate reduction alone and are only possible through oxidative sediment sulfur cycling. This requires oxygen concentrations of at least 10 µM in shallow Proterozoic seawater, which translates to 1–10% of present atmospheric oxygen concentrations. At these oxygen and sulfate concentrations, the oceans would have been a substantial source of methane to the atmosphere (60–140 Tmol yr−1). This methane would have accumulated to high concentrations (more than 25 ppmv) and supported greenhouse warming during much of the Proterozoic Eon, with notable exceptions during the PalaeoProterozoic and NeoProterozoic eras. In the Proterozoic, sulfate concentrations in the oceans were low and atmospheric methane levels high, according to mass balance and diagenetic models that investigate the oxidation state of the Proterozoic oceans.
Mojtaba Fakhraee - One of the best experts on this subject based on the ideXlab platform.
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Proterozoic seawater sulfate scarcity and the evolution of ocean–atmosphere chemistry
Nature Geoscience, 2019Co-Authors: Mojtaba Fakhraee, Olivier Hancisse, Donald E. Canfield, Sean A. Crowe, Sergei KatsevAbstract:In the Proterozoic, sulfate concentrations in the oceans were low and atmospheric methane levels high, according to mass balance and diagenetic models that investigate the oxidation state of the Proterozoic oceans. Oceanic sulfate concentrations are widely thought to have reached millimolar levels during the Proterozoic Eon, 2.5 to 0.54 billion years ago. Yet the magnitude of the increase in seawater sulfate concentrations over the course of the Eon remains largely unquantified. A rise in seawater sulfate concentrations has been inferred from the increased range of marine sulfide δ^34S values following the Great Oxidation Event and was induced by two processes: enhanced oxidative weathering of sulfides on land, and the onset of marine sulfur redox cycling. Here we use mass balance and diagenetic reaction-transport models to reconstruct the sulfate concentrations in Proterozoic seawater. We find that sulfate concentrations remained below 400 µM, and were possibly as low as 100 µM, throughout much of the Proterozoic. At these low sulfate concentrations, relatively large sulfate–pyrite sulfur isotope differences cannot be explained by sulfate reduction alone and are only possible through oxidative sediment sulfur cycling. This requires oxygen concentrations of at least 10 µM in shallow Proterozoic seawater, which translates to 1–10% of present atmospheric oxygen concentrations. At these oxygen and sulfate concentrations, the oceans would have been a substantial source of methane to the atmosphere (60–140 Tmol yr^−1). This methane would have accumulated to high concentrations (more than 25 ppmv) and supported greenhouse warming during much of the Proterozoic Eon, with notable exceptions during the PalaeoProterozoic and NeoProterozoic eras.
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Proterozoic seawater sulfate scarcity and the evolution of ocean atmosphere chemistry
Nature Geoscience, 2019Co-Authors: Mojtaba Fakhraee, Olivier Hancisse, Donald E. Canfield, Sean A. Crowe, Sergei KatsevAbstract:Oceanic sulfate concentrations are widely thought to have reached millimolar levels during the Proterozoic Eon, 2.5 to 0.54 billion years ago. Yet the magnitude of the increase in seawater sulfate concentrations over the course of the Eon remains largely unquantified. A rise in seawater sulfate concentrations has been inferred from the increased range of marine sulfide δ34S values following the Great Oxidation Event and was induced by two processes: enhanced oxidative weathering of sulfides on land, and the onset of marine sulfur redox cycling. Here we use mass balance and diagenetic reaction-transport models to reconstruct the sulfate concentrations in Proterozoic seawater. We find that sulfate concentrations remained below 400 µM, and were possibly as low as 100 µM, throughout much of the Proterozoic. At these low sulfate concentrations, relatively large sulfate–pyrite sulfur isotope differences cannot be explained by sulfate reduction alone and are only possible through oxidative sediment sulfur cycling. This requires oxygen concentrations of at least 10 µM in shallow Proterozoic seawater, which translates to 1–10% of present atmospheric oxygen concentrations. At these oxygen and sulfate concentrations, the oceans would have been a substantial source of methane to the atmosphere (60–140 Tmol yr−1). This methane would have accumulated to high concentrations (more than 25 ppmv) and supported greenhouse warming during much of the Proterozoic Eon, with notable exceptions during the PalaeoProterozoic and NeoProterozoic eras. In the Proterozoic, sulfate concentrations in the oceans were low and atmospheric methane levels high, according to mass balance and diagenetic models that investigate the oxidation state of the Proterozoic oceans.
M. C. Heredia Figueiredo - One of the best experts on this subject based on the ideXlab platform.
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An outline of early Proterozoic crustal evolution in the São Francisco craton, Brazil : a review
Precambrian Research, 1991Co-Authors: Wilson Teixeira, M. C. Heredia FigueiredoAbstract:Abstract The Early Proterozoic evolution of the Sao Francisco craton (SFC) occurred between 1.8–2.5 Ga and includes the Transamazonian cycle (1.9–2.2 Ga), one of the main periods of crustal growth affecting the South American continent. This synthesis of the available data is largely concerned with the Early Proterozoic terranes of the SFC and presents a modeled crustal evolution integrated with that of the West Congo craton. Interpretation of radiometric ages, geochemical and structural data, metamorphism (P, T conditions), and lithostratigraphical correlations leads to the characterization of three Early Proterozoic belts in the SFC, named: the Correntina-Guanambi, Itabuna and Mineiro belts. These belts are here described following a geographic scenario as given by their representatives (medium- to high-grade sequences, low-grade supracrustal sequences and intrusive igneous rocks). The anatomy and regional structures of these belts indicate that they developed along the margin of a large Archean protocontinent, although characteristic older mantled gneiss domes are also found within the Itabuna and Mineiro belts. Available isotopic evidence suggests an episodic growth of the continental crust during the Late Archean (2.6–3.2 Ga) with the formation of microcontinents that gradually coalesced around 2.6 Ga ago. After the Archean-Proterozoic transition, the tectonic evolution of the Proterozoic mobile belts evolved by mantle accretion/differentiation and crustal reworking. The main Early Proterozoic magmatic arc of the SFC is represented by the Itabuna mobile belt, whereas the Minciro belt is chiefly ensialic. The nature of the Salvador-Correntina belt is still poorly constrained by geochronological and geochemical data. By the end of the Transamazonian cycle, around 1.8–1.9 Ga ago, the SFC was fully cratonized.
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An outline of early Proterozoic crustal evolution in the São Francisco craton, Brazil : a review
1991Co-Authors: Wilson Teixeira, M. C. Heredia FigueiredoAbstract:The Early Proterozoic evolution of the Sao Francisco craton (SFC) occurred between 2.5-1.8 Ga and includes the Transamazonian cycle (2.2-1.9 Ga), one of the main periods of crustal growth affecting the South American continent. This synthesis of the available data is largely concerned with the Early Proterozoic terranes of the SFC and presents a modeled crustal evolution integrated with that of the West Congo craton. Interpretation of radiometric ages, geochemical and structural data, metamorphism (P, T conditions), and lithostratigraphical correlations leads to the characterization of three Early Proterozoic belts in the SFC, named : the Correntina-Guanambi, Itabuna and Mineiro belts
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An outline of early Proterozoic crustal evolution in the São Francisco craton, Brazil : a review
1991Co-Authors: Wilson Teixeira, M. C. Heredia FigueiredoAbstract:The Early Proterozoic evolution of the Sao Francisco craton (SFC) occurred between 2.5-1.8 Ga and includes the Transamazonian cycle (2.2-1.9 Ga), one of the main periods of crustal growth affecting the South American continent. This synthesis of the available data is largely concerned with the Early Proterozoic terranes of the SFC and presents a modeled crustal evolution integrated with that of the West Congo craton. Interpretation of radiometric ages, geochemical and structural data, metamorphism (P, T conditions), and lithostratigraphical correlations leads to the characterization of three Early Proterozoic belts in the SFC, named : the Correntina-Guanambi, Itabuna and Mineiro belts
Donald E. Canfield - One of the best experts on this subject based on the ideXlab platform.
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Proterozoic seawater sulfate scarcity and the evolution of ocean–atmosphere chemistry
Nature Geoscience, 2019Co-Authors: Mojtaba Fakhraee, Olivier Hancisse, Donald E. Canfield, Sean A. Crowe, Sergei KatsevAbstract:In the Proterozoic, sulfate concentrations in the oceans were low and atmospheric methane levels high, according to mass balance and diagenetic models that investigate the oxidation state of the Proterozoic oceans. Oceanic sulfate concentrations are widely thought to have reached millimolar levels during the Proterozoic Eon, 2.5 to 0.54 billion years ago. Yet the magnitude of the increase in seawater sulfate concentrations over the course of the Eon remains largely unquantified. A rise in seawater sulfate concentrations has been inferred from the increased range of marine sulfide δ^34S values following the Great Oxidation Event and was induced by two processes: enhanced oxidative weathering of sulfides on land, and the onset of marine sulfur redox cycling. Here we use mass balance and diagenetic reaction-transport models to reconstruct the sulfate concentrations in Proterozoic seawater. We find that sulfate concentrations remained below 400 µM, and were possibly as low as 100 µM, throughout much of the Proterozoic. At these low sulfate concentrations, relatively large sulfate–pyrite sulfur isotope differences cannot be explained by sulfate reduction alone and are only possible through oxidative sediment sulfur cycling. This requires oxygen concentrations of at least 10 µM in shallow Proterozoic seawater, which translates to 1–10% of present atmospheric oxygen concentrations. At these oxygen and sulfate concentrations, the oceans would have been a substantial source of methane to the atmosphere (60–140 Tmol yr^−1). This methane would have accumulated to high concentrations (more than 25 ppmv) and supported greenhouse warming during much of the Proterozoic Eon, with notable exceptions during the PalaeoProterozoic and NeoProterozoic eras.
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Proterozoic seawater sulfate scarcity and the evolution of ocean atmosphere chemistry
Nature Geoscience, 2019Co-Authors: Mojtaba Fakhraee, Olivier Hancisse, Donald E. Canfield, Sean A. Crowe, Sergei KatsevAbstract:Oceanic sulfate concentrations are widely thought to have reached millimolar levels during the Proterozoic Eon, 2.5 to 0.54 billion years ago. Yet the magnitude of the increase in seawater sulfate concentrations over the course of the Eon remains largely unquantified. A rise in seawater sulfate concentrations has been inferred from the increased range of marine sulfide δ34S values following the Great Oxidation Event and was induced by two processes: enhanced oxidative weathering of sulfides on land, and the onset of marine sulfur redox cycling. Here we use mass balance and diagenetic reaction-transport models to reconstruct the sulfate concentrations in Proterozoic seawater. We find that sulfate concentrations remained below 400 µM, and were possibly as low as 100 µM, throughout much of the Proterozoic. At these low sulfate concentrations, relatively large sulfate–pyrite sulfur isotope differences cannot be explained by sulfate reduction alone and are only possible through oxidative sediment sulfur cycling. This requires oxygen concentrations of at least 10 µM in shallow Proterozoic seawater, which translates to 1–10% of present atmospheric oxygen concentrations. At these oxygen and sulfate concentrations, the oceans would have been a substantial source of methane to the atmosphere (60–140 Tmol yr−1). This methane would have accumulated to high concentrations (more than 25 ppmv) and supported greenhouse warming during much of the Proterozoic Eon, with notable exceptions during the PalaeoProterozoic and NeoProterozoic eras. In the Proterozoic, sulfate concentrations in the oceans were low and atmospheric methane levels high, according to mass balance and diagenetic models that investigate the oxidation state of the Proterozoic oceans.
Olivier Hancisse - One of the best experts on this subject based on the ideXlab platform.
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Proterozoic seawater sulfate scarcity and the evolution of ocean–atmosphere chemistry
Nature Geoscience, 2019Co-Authors: Mojtaba Fakhraee, Olivier Hancisse, Donald E. Canfield, Sean A. Crowe, Sergei KatsevAbstract:In the Proterozoic, sulfate concentrations in the oceans were low and atmospheric methane levels high, according to mass balance and diagenetic models that investigate the oxidation state of the Proterozoic oceans. Oceanic sulfate concentrations are widely thought to have reached millimolar levels during the Proterozoic Eon, 2.5 to 0.54 billion years ago. Yet the magnitude of the increase in seawater sulfate concentrations over the course of the Eon remains largely unquantified. A rise in seawater sulfate concentrations has been inferred from the increased range of marine sulfide δ^34S values following the Great Oxidation Event and was induced by two processes: enhanced oxidative weathering of sulfides on land, and the onset of marine sulfur redox cycling. Here we use mass balance and diagenetic reaction-transport models to reconstruct the sulfate concentrations in Proterozoic seawater. We find that sulfate concentrations remained below 400 µM, and were possibly as low as 100 µM, throughout much of the Proterozoic. At these low sulfate concentrations, relatively large sulfate–pyrite sulfur isotope differences cannot be explained by sulfate reduction alone and are only possible through oxidative sediment sulfur cycling. This requires oxygen concentrations of at least 10 µM in shallow Proterozoic seawater, which translates to 1–10% of present atmospheric oxygen concentrations. At these oxygen and sulfate concentrations, the oceans would have been a substantial source of methane to the atmosphere (60–140 Tmol yr^−1). This methane would have accumulated to high concentrations (more than 25 ppmv) and supported greenhouse warming during much of the Proterozoic Eon, with notable exceptions during the PalaeoProterozoic and NeoProterozoic eras.
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Proterozoic seawater sulfate scarcity and the evolution of ocean atmosphere chemistry
Nature Geoscience, 2019Co-Authors: Mojtaba Fakhraee, Olivier Hancisse, Donald E. Canfield, Sean A. Crowe, Sergei KatsevAbstract:Oceanic sulfate concentrations are widely thought to have reached millimolar levels during the Proterozoic Eon, 2.5 to 0.54 billion years ago. Yet the magnitude of the increase in seawater sulfate concentrations over the course of the Eon remains largely unquantified. A rise in seawater sulfate concentrations has been inferred from the increased range of marine sulfide δ34S values following the Great Oxidation Event and was induced by two processes: enhanced oxidative weathering of sulfides on land, and the onset of marine sulfur redox cycling. Here we use mass balance and diagenetic reaction-transport models to reconstruct the sulfate concentrations in Proterozoic seawater. We find that sulfate concentrations remained below 400 µM, and were possibly as low as 100 µM, throughout much of the Proterozoic. At these low sulfate concentrations, relatively large sulfate–pyrite sulfur isotope differences cannot be explained by sulfate reduction alone and are only possible through oxidative sediment sulfur cycling. This requires oxygen concentrations of at least 10 µM in shallow Proterozoic seawater, which translates to 1–10% of present atmospheric oxygen concentrations. At these oxygen and sulfate concentrations, the oceans would have been a substantial source of methane to the atmosphere (60–140 Tmol yr−1). This methane would have accumulated to high concentrations (more than 25 ppmv) and supported greenhouse warming during much of the Proterozoic Eon, with notable exceptions during the PalaeoProterozoic and NeoProterozoic eras. In the Proterozoic, sulfate concentrations in the oceans were low and atmospheric methane levels high, according to mass balance and diagenetic models that investigate the oxidation state of the Proterozoic oceans.
