Authigenic Carbonate and the History of the Global Carbon Cycle

Schrag, Daniel P.; Higgins, John A.; Macdonald, Francis A.; Johnston, David T.

doi:10.1126/science.1229578

Cited by 447 publications

(327 citation statements)

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“…Conversely, the consistent δ 13 C signature of the dolomites can be used for chemostratigraphic purposes as an indicator of marine water δ 13 C values. This result is unexpected, given the hypothesis that light δ 13 C values would characterize authigenic carbonate in deeper marine settings (Schrag et al, 2013), but is consistent with the low organic carbon content of the sediments (Kunzmann et al, 2015 record values <0.3 %).…”

Section: Geochemistry and Petrologymentioning

confidence: 73%

The Late Cryogenian Warm Interval, NE Svalbard: Chemostratigraphy and genesis

Fairchild

Bonnand²,

Davies

et al. 2016

Precambrian Research

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms At the base of E3, interstratification of cap carbonate with ice-rafted and redeposited glacial sediments occurs. Early diagenetic stabilization of carbonate mineralogy from a precursor, possibly ikaite, to calcite or dolomite is inferred. E3 is predominantly dolomitic silt-shale, with sub-millimetre lamination, lacking sand or current-related sedimentary structures. Thin fine laminae are partly pyritized and interpreted as microbial mats. Dolomite content is 25-50%, with δ 13 C values consistently around +4‰, a value attributed to buffering by dissolution of a precursor metastable carbonate phase. Local calcite cement associates with low δ 13 C values. The carbonates form silt-sized, chemically zoned rhombic crystals from an environment with dynamically changing Fe and Mn. Three-dimensional reconstructions of cm-scale disturbance structures indicate that they represent horizontally directed sock-like folds, developed by release of overpressure into thin surficial sediment overlying an early-cemented layer.A shoaling upwards unit near the top of E3 displays calcium sulphate pseudomorphs in dolomite in the north, but storm-dominated limestones in the south, both being overlain by peritidal oolitic dolomites, exposed under the succeeding Wilsonbreen glacial deposits. There is no Trezona δ 13 C anomaly, possibly implying top-truncation of the succession.Regular 0.5 m-scale sedimentary rhythms, reflecting subtle variations in sediment texture or composition occur throughout E3 and are interpreted as allocyclic. They are thought to be mainly primary in origin, locally modified slightly during early diagenetic cementation. Rhythms are proposed to represent ca. 18 kyr precession cycles, implying 6-8 Myr deposition between glaciations.

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Section: Geochemistry and Petrologymentioning

confidence: 73%

The Late Cryogenian Warm Interval, NE Svalbard: Chemostratigraphy and genesis

Fairchild

Bonnand²,

Davies

et al. 2016

Precambrian Research

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“…A stronger case can be made against the second hypothesis, that the source of 13 C enrichment in Lomagundi-aged carbonates was the burial of 13 C-depleted authigenic carbonates in other (unsampled) settings (30). Oxidation of organic carbon via bacterial sulfate reduction during early diagenesis would have led to the precipitation of authigenic carbonates but, at the same time, would have also led to the precipitation of 34 S-depleted pyrite, resulting in correlative enrichments in both 13 C and 34 S in shelf carbonates, in contradiction with the observed inverse correlation.…”

Section: Discussionmentioning

confidence: 99%

The rise of oxygen and siderite oxidation during the Lomagundi Event

Bachan

Kump

2015

Proc. Natl. Acad. Sci. U.S.A.

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The Paleoproterozoic Lomagundi Event is an interval of 130-250 million years, ca. 2.3-2.1 billion years ago, in which extraordinarily 13 C enriched (>10‰) limestones and dolostones occur globally. The high levels of organic carbon burial implied by the positive δ 13 C values suggest the production of vast quantities of O 2 as well as an alkalinity imbalance demanding extremely low levels of weathering. The oxidation of sulfides has been proposed as a mechanism capable of ameliorating these imbalances: It is a potent sink for O 2 as well as a source of acidity. However, sulfide oxidation consumes more O 2 than it can supply CO 2 , leading to insurmountable imbalances in both carbon and oxygen. In contrast, the oxidation of siderite (FeCO 3 proper, as well as other Fe 2+ -bearing carbonate minerals), produces 4 times more CO 2 than it consumes O 2 and is a common-although often overlooked-constituent of Archean and Early Proterozoic sedimentary successions. Here we propose that following the initial rise of O 2 in the atmosphere, oxidation of siderite provided the necessary carbon for the continued oxidation of sulfides, burial of organic carbon, and, most importantly, accumulation of free O 2 . The duration and magnitude of the Lomagundi Event were determined by the size of the preexisting Archean siderite reservoir, which was consumed through oxidative weathering. Our proposal helps resolve a long-standing conundrum and advances our understanding of the geologic history of atmospheric O 2 .carbon isotopes | oxygen | siderite | carbon cycle | Great Oxidation Event R econstructing the geologic history of atmospheric oxygen is among the foremost scientific challenges of our time (1). The level of atmospheric oxygen (pO 2 ) without doubt played a key role in the evolution of the Earth System (2), exerting a major influence on the biosphere, especially the evolution of metazoans (3). With no direct way of measuring oxygen concentrations in deep geologic time, the stable isotopes of carbon recorded in marine limestones provide key constraints (4). Carbon enters the ocean−atmosphere system through volcanoes and weathering of carbon-bearing sedimentary rocks and can exit in one of two ways: (i) uptake during photosynthesis and burial of organic carbon leading to O 2 production and (ii) reaction during weathering and formation of CaCO 3 in the ocean. The carbon isotopic record tells us how carbon was partitioned between these two sinks: A δ 13 C value of 0‰ indicates that ∼80% of incoming carbon was buried as carbonate carbon and 20% as organic carbon. Positive excursions in δ 13 C are unusual and indicate that a larger fraction of carbon was fixed and buried as organic carbon and, with it, a larger amount of O 2 was produced.Following the indications for the first rise of O 2 in the atmosphere (5, 6) is the largest and most protracted period of 13 C enrichment in the geologic record, known as the Lomagundi Event (Fig. 1). Limestones and dolostones with extreme carbon isotopic values of + 8‰ to greater than + 15‰ occur g...

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“…Recently, attention has increased on the potential significance of authigenic carbonate production for the global carbonate reservoir (Schrag et al, 2013) and the addition of authigenic carbonate to Permian and Triassic carbonate-bearing sequences (Schobben et al, 2016;Zhao et al, 2016). The numerical exercise highlights the link between local sedimentary OC-cycling and bulkrock diagenetic stabilization, hinting at the potentially significant portion of remineralized OC sequestered by authigenic carbonates.…”

Section: The Carbon Isotopic Composition Of Thementioning

confidence: 99%

“…Embracing both ends of this spectrum could illuminate new aspects of marine sedimentary systems and ancient ocean chemistry, as well as providing a more refined understanding of the mechanisms that promote the diagenetic alteration of carbonate sediments. Clear examples of the importance of interpreting diagenetic signals have been given by the assertion that authigenic carbonate production might play a primary role in the global biogeochemical carbon cycle (Schrag et al, 2013) and in the isotopic imprint of terrestrial biomass on Precambrian carbonates (Knauth and Kennedy, 2009). …”

Section: Introductionmentioning

confidence: 99%

Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

et al. 2017

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Abstract. Bulk-carbonate carbon isotope ratios are a widely applied proxy for investigating the ancient biogeochemical carbon cycle. Temporal carbon isotope trends serve as a prime stratigraphic tool, with the inherent assumption that bulk micritic carbonate rock is a faithful geochemical recorder of the isotopic composition of seawater dissolved inorganic carbon. However, bulk-carbonate rock is also prone to incorporate diagenetic signals. The aim of the present study is to disentangle primary trends from diagenetic signals in carbon isotope records which traverse the Permian-Triassic boundary in the marine carbonate-bearing sequences of Iran and South China. By pooling newly produced and published carbon isotope data, we confirm that a global first-order trend towards depleted values exists. However, a large amount of scatter is superimposed on this geochemical record. In addition, we observe a temporal trend in the amplitude of this residual δ 13 C variability, which is reproducible for the two studied regions. We suggest that (sub-)sea-floor microbial communities and their control on calcite nucleation and ambient porewater dissolved inorganic carbon δ 13 C pose a viable mechanism to induce bulk-rock δ 13 C variability. Numerical model calculations highlight that early diagenetic carbonate rock stabilization and linked carbon isotope alteration can be controlled by organic matter supply and subsequent microbial remineralization. A major biotic decline among Late Permian bottom-dwelling organisms facilitated a spatial increase in heterogeneous organic carbon accumulation. Combined with low marine sulfate, this resulted in varying degrees of carbon isotope overprinting. A simulated time series suggests that a 50 % increase in the spatial scatter of organic carbon relative to the average, in addition to an imposed increase in the likelihood of sampling cements formed by microbial calcite nucleation to 1 out of 10 samples, is sufficient to induce the observed signal of carbon isotope variability. These findings put constraints on the application of Permian-Triassic carbon isotope chemostratigraphy based on whole-rock samples, which appears less refined than classical biozonation dating schemes. On the other hand, this signal of increased carbon isotope variability concurrent with the largest mass extinction of the Phanerozoic may proPublished by Copernicus Publications on behalf of the European Geosciences Union.

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Authigenic Carbonate and the History of the Global Carbon Cycle

Cited by 447 publications

References 37 publications

The Late Cryogenian Warm Interval, NE Svalbard: Chemostratigraphy and genesis

The Late Cryogenian Warm Interval, NE Svalbard: Chemostratigraphy and genesis

The rise of oxygen and siderite oxidation during the Lomagundi Event

Latest Permian carbonate carbon isotope variability traces heterogeneous organic carbon accumulation and authigenic carbonate formation

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