- Email: [email protected]
Evolution of the atmosphere and ocean through time
Chemical Geology 362 (2013) 1–2
Contents lists available at ScienceDirect
Chemical Geology journal homepage: www.elsevier.com/locate/chemgeo
Editorial
Evolution of the atmosphere and ocean through time
This special volume of Chemical Geology is dedicated to Heinrich Dietrich (Dick) Holland, who passed away last year. Dick started his career in geochemistry in its formative years in the late 1940’s and continued this work until his death in 2012. He was a master of different trades with a wide range of interests and expertise from high- to low-temperature geochemistry, and from experimental science to field studies to theoretical modeling. One theme was central over at least the last 50 years of Dick’s research: he sought to understand the large-scale evolution of the atmosphere and ocean in the past, and the processes that control its modern operation. He was the first in the growing clade of brave geochemists to work extensively on deep time rocks and problems, with a particular focus on the timing and causes of the rise of atmospheric oxygen ca. 2.4 billion years ago. The transition to an oxygenated environment – arguably the greatest post-Hadean transformation of the Earth’s surface – dominated the latter decades of Dick’s career. Dick will remain with us as a scientist who shaped the field of Precambrian geochemistry, challenged us to look beyond conventional wisdom, and set an example of full dedication to intellectual endeavor. This volume is a fitting tribute to Dick’s long career in several ways. First, the papers included here cover a broad range of topics, ranging from theoretical modeling to laboratory experiments, to investigations focused on sedimentary records. They are united by a common theme: the evolution of the atmosphere and ocean and modern processes. Second, all these topics were dear to his heart, and he contributed to and initiated some of these lines of research. Third, most of the papers were written by junior to middle age scientists who were deeply influenced by Dick at conferences and in seminars, as well as through reading his influential papers and books. This last point speaks to his influence on the field and community not only as a scientist but also as a mentor and a charismatic person. The volume includes 25 papers and starts with a personal recollection of Dick as a scientist, mentor, and grand person by his former Ph.D. student, Michael Mottl. The following two papers authored by Kasting and Zahnle et al. concern atmospheric processes that led to the rise of atmospheric oxygen. Both groups agree that changes in the atmospheric hydrogen budget led to atmospheric oxidation, but they differ as to whether sinks (escape to space) or changes in sources were more important. Olson et al. and Reinhard et al. explore the extent of oxygenic oases and oxidative weathering of continental sulfides under the oxygen-free atmosphere of the Late Archean. Both papers argue for local and transient accumulations of oxygen in the water column or at the interface of the atmosphere and continents. The following two papers by Frantz et al. and Posth et al. present results of laboratory experiments on the production of non-massdependent fractionation of S isotopes by ultraviolet photolysis of SO2, and Fe-rich minerals in iron formation protoliths with variable amounts of ferrihydrite and organic matter under conditions of 0009-2541/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.chemgeo.2013.11.007
burial diagenesis. The papers highlight the complexity of the linkages between the geological records and atmospheric conditions. Specifically, Posth et al. infer that mineralogical composition of iron formations cannot be used to constrain CO2 and CH4 levels in the Precambrian atmosphere. The next 7 papers apply various chemical and isotopic redox proxies to the Late Archean and early Paleoproterozoic sedimentary record to constrain the timing and tempo of the Great Oxidation Event (GOE), and the biogeochemical cycling of S and N in surface environments before the GOE. • Maynard et al. report small, but significant, negative non-massdependent S isotope signals from Archean paleosols, a reservoir that was not previously studied for multiple S isotope composition. They infer that it could help to balance the apparent mismatch in the abundance of negative and positive multiple S isotope anomalies. • Partin et al. combine new and literature data for U concentrations in Precambrian iron formations and infer an increase in oxidative U delivery to the ocean at ca. 2.47 Ga, before the permanent loss of nonmass-dependent fractionation in S isotopes. • Cabral et al. report significant Mo enrichments and isotope fractionation in ca. 2.75 Ga black shales of the Carajás Formation, northern Brazil and suggest that either redox cycling or syndepositional hydrothermal overprint is responsible for these signatures. • Kendall et al. studied U isotope ratios in the 2.5 Ga Mount McRae Shale of Western Australia. Based on non-crustal U isotope values, Kendall et al. infer oxidative weathering either on land or in the ocean in association with oxygen oasis. • Busigny et al. report on N isotope ratios in the Mount McRae Shale and suggest that positive N isotope values from Late Archean sediments cannot be used alone to infer surface redox conditions. • Swanner et al. suggest that production of non-mass-dependent fractionation of sulfur isotopes and preservation of detrital pyrites continued until shortly before the oldest Paleoproterozoic glaciation. • Hoffman provides a new correlation scheme for the Paleoproterozoic sedimentary successions of South Africa and the Huronian Supergroup of southern Canada based on the assumption that the loss of non-massdependent fractionation of sulfur isotopes was a single on-off event associated with the Snowball glaciation. He further infers that the GOE and the Snowball Earth glaciation happened only in the aftermath and during the second of the three inferred Paleoproterozoic glaciations, respectively, thus decoupling as far as their origin is concerned these events from other two glaciations. These studies highlight the complexity of the GOE and call for further multidisciplinary studies to resolve remaining uncertainties. In particular, the new paleoredox proxy studies add to the accumulating evidence that indicates some level of redox cycling before the beginning of the GOE. They also help define the next challenge for the Early Earth
2
Editorial
community: to determine if oxygenation was gradual, transient, or stepwise in the early Precambrian. The section on the ‘Lomagundi Event and its aftermath’ includes four papers. Master et al. report new area with Paleoproterozoic carbonates having highly positive carbon isotope values in the Ruwenzori Mountains of Uganda. Salminen et al. provide new data for the carbonate unit deposited in the aftermath of the Lomagundi Event (LE) and show that this event was not followed by significant and long-lived negative carbon isotope excursion, contrary to one recent suggestion. OssaOssa et al. report on unusual preservation of smectite in organic-rich shales of the Francevillian Series deposited during the LE in Gabon and infer that organic carbon burial might have been enhanced by clay mineral production on the continents in association with oxidizing continental weathering. Finally, Asael et al. interpret Fe speciation and Fe, Mo, and U isotope data for the black shale deposited in the immediate aftermath of the LE as being consistent with a dramatic oxygen crash immediately after the GOE. The next section on the ‘Boring Billion’ contains two papers. Conliffe et al. focus on sediment-hosted Mississippi Valley Type Pb-Zn mineralization in the Ramah Group of Labrador with fluid inclusions having high CO2 content. Sheldon suggests low pCO2 at ~1.1 Ga. Clearly, still very little is known about the ‘Boring Billion’ and we should be prepared to be surprised by further studies. Three papers focused on the Neoproterozoic. Cox et al. emphasize that Neoproterozoic iron formations linked with the Neoproterozoic ice ages are restricted to the Sturtian glacial event and were deposited inside or on rifted margins of Rodinia in association with mafic volcanic units; this relaxes the requirement for an anoxic deep ocean during their deposition. Macdonald et al. and the companion paper by Johnston et al. infer a persistently anoxic and ferruginous ocean during the Ediacaran, when the first animals evolved and large variations in C isotope values linked to ocean oxidation occurred. The data challenge the conventional wisdom concerning the link between ocean oxygenation and the emergence of animals in the Ediacaran. Arvidson et al. present a modeling approach to the evolution of seawater composition in the Phanerozoic, emphasizing controls of plate tectonics over climate, ocean circulation, and seawater composition.
The last paper of the volume by Romaniello et al. explores the paleoredox proxy potential of U isotopes in carbonates on the shallowwater carbonate platform of Bahamas. They infer that, while primary carbonate precipitates faithfully record seawater U isotope composition, bulk carbonate values are isotopically different, likely due to U incorporation during diagenesis in an H2S- and organic matter-rich diagenetic setting and U loss during post-depositional dolomitization. The volume demonstrates the cutting edge status of studies concerned with the modern and ancient atmosphere and ocean redox, highlights the complexity of the problem, and emphasizes the intellectual value of this line of research. The field will carry a strong imprint of H.D. Holland and his holistic approach to Earth System Evolution. Acknowledgements The guest editors are grateful to all the authors who contributed to this special issue, and to all the reviewers for their thoughtful comments and suggestions. The guest editors would like to thank Barbara Sherwood Lollar for editorial handling of all manuscripts, and Vijayakumar Venkataraman, Neelima Dondapati, Fei He, and Shannon Qu for their assistance with all editing aspects of this special volume.
Andrey Bekker Department of Geological Sciences, University of Manitoba, 227 Wallace Building. Winnipeg, MB R3G 2K4 Canada Corresponding author. E-mail address: [email protected]. James Kasting Department of Geosciences, Penn State University, University Park, PA 16802 USA Ariel Anbar School of Earth & Space Exploration, and Department of Chemistry & Biochemistry, Arizona State University, Tempe, AZ 85287 E-mail address: [email protected].
Contents lists available at ScienceDirect
Chemical Geology journal homepage: www.elsevier.com/locate/chemgeo
Editorial
Evolution of the atmosphere and ocean through time
This special volume of Chemical Geology is dedicated to Heinrich Dietrich (Dick) Holland, who passed away last year. Dick started his career in geochemistry in its formative years in the late 1940’s and continued this work until his death in 2012. He was a master of different trades with a wide range of interests and expertise from high- to low-temperature geochemistry, and from experimental science to field studies to theoretical modeling. One theme was central over at least the last 50 years of Dick’s research: he sought to understand the large-scale evolution of the atmosphere and ocean in the past, and the processes that control its modern operation. He was the first in the growing clade of brave geochemists to work extensively on deep time rocks and problems, with a particular focus on the timing and causes of the rise of atmospheric oxygen ca. 2.4 billion years ago. The transition to an oxygenated environment – arguably the greatest post-Hadean transformation of the Earth’s surface – dominated the latter decades of Dick’s career. Dick will remain with us as a scientist who shaped the field of Precambrian geochemistry, challenged us to look beyond conventional wisdom, and set an example of full dedication to intellectual endeavor. This volume is a fitting tribute to Dick’s long career in several ways. First, the papers included here cover a broad range of topics, ranging from theoretical modeling to laboratory experiments, to investigations focused on sedimentary records. They are united by a common theme: the evolution of the atmosphere and ocean and modern processes. Second, all these topics were dear to his heart, and he contributed to and initiated some of these lines of research. Third, most of the papers were written by junior to middle age scientists who were deeply influenced by Dick at conferences and in seminars, as well as through reading his influential papers and books. This last point speaks to his influence on the field and community not only as a scientist but also as a mentor and a charismatic person. The volume includes 25 papers and starts with a personal recollection of Dick as a scientist, mentor, and grand person by his former Ph.D. student, Michael Mottl. The following two papers authored by Kasting and Zahnle et al. concern atmospheric processes that led to the rise of atmospheric oxygen. Both groups agree that changes in the atmospheric hydrogen budget led to atmospheric oxidation, but they differ as to whether sinks (escape to space) or changes in sources were more important. Olson et al. and Reinhard et al. explore the extent of oxygenic oases and oxidative weathering of continental sulfides under the oxygen-free atmosphere of the Late Archean. Both papers argue for local and transient accumulations of oxygen in the water column or at the interface of the atmosphere and continents. The following two papers by Frantz et al. and Posth et al. present results of laboratory experiments on the production of non-massdependent fractionation of S isotopes by ultraviolet photolysis of SO2, and Fe-rich minerals in iron formation protoliths with variable amounts of ferrihydrite and organic matter under conditions of 0009-2541/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.chemgeo.2013.11.007
burial diagenesis. The papers highlight the complexity of the linkages between the geological records and atmospheric conditions. Specifically, Posth et al. infer that mineralogical composition of iron formations cannot be used to constrain CO2 and CH4 levels in the Precambrian atmosphere. The next 7 papers apply various chemical and isotopic redox proxies to the Late Archean and early Paleoproterozoic sedimentary record to constrain the timing and tempo of the Great Oxidation Event (GOE), and the biogeochemical cycling of S and N in surface environments before the GOE. • Maynard et al. report small, but significant, negative non-massdependent S isotope signals from Archean paleosols, a reservoir that was not previously studied for multiple S isotope composition. They infer that it could help to balance the apparent mismatch in the abundance of negative and positive multiple S isotope anomalies. • Partin et al. combine new and literature data for U concentrations in Precambrian iron formations and infer an increase in oxidative U delivery to the ocean at ca. 2.47 Ga, before the permanent loss of nonmass-dependent fractionation in S isotopes. • Cabral et al. report significant Mo enrichments and isotope fractionation in ca. 2.75 Ga black shales of the Carajás Formation, northern Brazil and suggest that either redox cycling or syndepositional hydrothermal overprint is responsible for these signatures. • Kendall et al. studied U isotope ratios in the 2.5 Ga Mount McRae Shale of Western Australia. Based on non-crustal U isotope values, Kendall et al. infer oxidative weathering either on land or in the ocean in association with oxygen oasis. • Busigny et al. report on N isotope ratios in the Mount McRae Shale and suggest that positive N isotope values from Late Archean sediments cannot be used alone to infer surface redox conditions. • Swanner et al. suggest that production of non-mass-dependent fractionation of sulfur isotopes and preservation of detrital pyrites continued until shortly before the oldest Paleoproterozoic glaciation. • Hoffman provides a new correlation scheme for the Paleoproterozoic sedimentary successions of South Africa and the Huronian Supergroup of southern Canada based on the assumption that the loss of non-massdependent fractionation of sulfur isotopes was a single on-off event associated with the Snowball glaciation. He further infers that the GOE and the Snowball Earth glaciation happened only in the aftermath and during the second of the three inferred Paleoproterozoic glaciations, respectively, thus decoupling as far as their origin is concerned these events from other two glaciations. These studies highlight the complexity of the GOE and call for further multidisciplinary studies to resolve remaining uncertainties. In particular, the new paleoredox proxy studies add to the accumulating evidence that indicates some level of redox cycling before the beginning of the GOE. They also help define the next challenge for the Early Earth
2
Editorial
community: to determine if oxygenation was gradual, transient, or stepwise in the early Precambrian. The section on the ‘Lomagundi Event and its aftermath’ includes four papers. Master et al. report new area with Paleoproterozoic carbonates having highly positive carbon isotope values in the Ruwenzori Mountains of Uganda. Salminen et al. provide new data for the carbonate unit deposited in the aftermath of the Lomagundi Event (LE) and show that this event was not followed by significant and long-lived negative carbon isotope excursion, contrary to one recent suggestion. OssaOssa et al. report on unusual preservation of smectite in organic-rich shales of the Francevillian Series deposited during the LE in Gabon and infer that organic carbon burial might have been enhanced by clay mineral production on the continents in association with oxidizing continental weathering. Finally, Asael et al. interpret Fe speciation and Fe, Mo, and U isotope data for the black shale deposited in the immediate aftermath of the LE as being consistent with a dramatic oxygen crash immediately after the GOE. The next section on the ‘Boring Billion’ contains two papers. Conliffe et al. focus on sediment-hosted Mississippi Valley Type Pb-Zn mineralization in the Ramah Group of Labrador with fluid inclusions having high CO2 content. Sheldon suggests low pCO2 at ~1.1 Ga. Clearly, still very little is known about the ‘Boring Billion’ and we should be prepared to be surprised by further studies. Three papers focused on the Neoproterozoic. Cox et al. emphasize that Neoproterozoic iron formations linked with the Neoproterozoic ice ages are restricted to the Sturtian glacial event and were deposited inside or on rifted margins of Rodinia in association with mafic volcanic units; this relaxes the requirement for an anoxic deep ocean during their deposition. Macdonald et al. and the companion paper by Johnston et al. infer a persistently anoxic and ferruginous ocean during the Ediacaran, when the first animals evolved and large variations in C isotope values linked to ocean oxidation occurred. The data challenge the conventional wisdom concerning the link between ocean oxygenation and the emergence of animals in the Ediacaran. Arvidson et al. present a modeling approach to the evolution of seawater composition in the Phanerozoic, emphasizing controls of plate tectonics over climate, ocean circulation, and seawater composition.
The last paper of the volume by Romaniello et al. explores the paleoredox proxy potential of U isotopes in carbonates on the shallowwater carbonate platform of Bahamas. They infer that, while primary carbonate precipitates faithfully record seawater U isotope composition, bulk carbonate values are isotopically different, likely due to U incorporation during diagenesis in an H2S- and organic matter-rich diagenetic setting and U loss during post-depositional dolomitization. The volume demonstrates the cutting edge status of studies concerned with the modern and ancient atmosphere and ocean redox, highlights the complexity of the problem, and emphasizes the intellectual value of this line of research. The field will carry a strong imprint of H.D. Holland and his holistic approach to Earth System Evolution. Acknowledgements The guest editors are grateful to all the authors who contributed to this special issue, and to all the reviewers for their thoughtful comments and suggestions. The guest editors would like to thank Barbara Sherwood Lollar for editorial handling of all manuscripts, and Vijayakumar Venkataraman, Neelima Dondapati, Fei He, and Shannon Qu for their assistance with all editing aspects of this special volume.
Andrey Bekker Department of Geological Sciences, University of Manitoba, 227 Wallace Building. Winnipeg, MB R3G 2K4 Canada Corresponding author. E-mail address: [email protected]. James Kasting Department of Geosciences, Penn State University, University Park, PA 16802 USA Ariel Anbar School of Earth & Space Exploration, and Department of Chemistry & Biochemistry, Arizona State University, Tempe, AZ 85287 E-mail address: [email protected].