7.6 Enhanced Accumulation of Organic Matter: The Shunga Event

Strauß, Harald; Melezhik, Victor A.; Lepland, Aivo; Fallick, Anthony E.; Hanski, Eero; Filippov, М. М.; Deines, Yulia; Illing, Christian J.; Črne, Alenka E.; Brasier, Alexander T.

doi:10.1007/978-3-642-29670-3_6

Cited by 19 publications

(20 citation statements)

References 87 publications

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“…In an alternative hypothesis, it has been argued that the δ 13 C of organic matter within the FB (and perhaps also FC) has been locally influenced by the incorporation of 13 Cdepleted methanotroph-derived organic matter (36). We cannot completely rule out this possibility, but the large organic matter excursion as observed through the upper FC unit and into the FD is likely a global feature expressed in Gabon, Fennoscandia, and perhaps elsewhere (35).…”

Section: Resultsmentioning

confidence: 88%

“…In Fennoscandia, the 13 C-depleted organic carbon is associated within so-called shungite deposits (see SI Text and Table S1). These are a noncrystalline form of carbon believed to represent fossilized oil with carbon contents of up to 99% (35). The age of these deposits is constrained between 1,980 ± 27 Ma and 2,090 ± 70 Ma, with a preliminary Re-Os age of 2,050 Ma (uncertainty not given) on the shungites themselves (33,35).…”

Section: Resultsmentioning

confidence: 99%

“…These are a noncrystalline form of carbon believed to represent fossilized oil with carbon contents of up to 99% (35). The age of these deposits is constrained between 1,980 ± 27 Ma and 2,090 ± 70 Ma, with a preliminary Re-Os age of 2,050 Ma (uncertainty not given) on the shungites themselves (33,35). Shungite deposition therefore postdates the Lomagundi excursion, and available age constraints allow the placement of the Francevillian FD unit as contemporaneous with shungite deposition (33).…”

Section: Resultsmentioning

confidence: 99%

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Oxygen dynamics in the aftermath of the Great Oxidation of Earth’s atmosphere

Canfield

Ngombi-Pemba

Hammarlund

et al. 2013

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

122

139

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The oxygen content of Earth's atmosphere has varied greatly through time, progressing from exceptionally low levels before about 2.3 billion years ago, to much higher levels afterward. In the absence of better information, we usually view the progress in Earth's oxygenation as a series of steps followed by periods of relative stasis. In contrast to this view, and as reported here, a dynamic evolution of Earth's oxygenation is recorded in ancient sediments from the Republic of Gabon from between about 2,150 and 2,080 million years ago. The oldest sediments in this sequence were deposited in well-oxygenated deep waters whereas the youngest were deposited in euxinic waters, which were globally extensive. These fluctuations in oxygenation were likely driven by the comings and goings of the Lomagundi carbon isotope excursion, the longest-lived positive δ 13 C excursion in Earth history, generating a huge oxygen source to the atmosphere. As the Lomagundi event waned, the oxygen source became a net oxygen sink as Lomagundi organic matter became oxidized, driving oxygen to low levels; this state may have persisted for 200 million years.GOE | Paleoproterozoic | marine chemistry | Mo isotope | trace metal

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Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Oxygen dynamics in the aftermath of the Great Oxidation of Earth’s atmosphere

Canfield

Ngombi-Pemba

Hammarlund

et al. 2013

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

122

139

View full text Add to dashboard Cite

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“…These variations included fluctuations ca. 2.3-2.0 Ga owing to episodes of enhanced primary production and subsequent decomposition of organic matter known as the Lomagundi (or Lomagundi-Jatulian) and Shunga events (Medvedev et al, 2009;Canfield et al, 2013;Strauss et al, 2013). The initial upsurge in O 2 levels starting ca.…”

Section: Introductionmentioning

confidence: 99%

Variations in the abundance of photosynthetic oxygen through Precambrian and Paleozoic time in relation to biotic evolution and mass extinctions: evidence from Mn/Fe ratios

Jackson

2015

Precambrian Research

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This paper reports new information about variations in the abundance of photosynthetic oxygen through Precambrian and Paleozoic time. Non-detrital marine sediments (cherts, limestones, and dolomite) were analysed for NH 2 OH•HCl/acetic acid-extractable Mn and Fe, and the Mn/Fe ratio (a proxy for the oxidationreduction potential of the sediment at the time of deposition) was plotted against geologic age. The method has never before been applied to ancient sediments, but previously published data produced independently by other methods confirmed its applicability and underlying assumptions. The Mn/Fe ratio was unexpectedly high ca. 3.416 Ga, implying localised oxidation due to oxygen production by cyanobacteria, but fell dramatically over the interval 3.416-3.298 Ga, suggesting mass mortality or mass extinction of early Archean cyanobacteria owing to asteroid impacts. However, the ratio increased continuously, though at episodically varying rates, from a minimum at ~1.8783 Ga to a maximum at ~0.680 Ga, signifying accumulation of oxygen in the atmosphere and hydrosphere. The rate of increase was relatively high at first but dropped abruptly at some point during the interval 1.8783-1.6 Ga, possibly signaling the appearance of eukaryotic herbivores. The ratio increased exponentially from 1.6 to 0.8 Ga and then rose more rapidly from 0.8 to 0.680 Ga, indicating a late Proterozoic upsurge of oxygen production, whereupon it fell catastrophically to a minimum in the Cambrian, reflecting widespread anoxia due to mass extinction of Ediacaran organisms. The crisis at the Precambrian-Cambrian boundary was followed by a logarithmic increase from the Cambrian to the Permian, indicating a resurgence of photosynthetic activity.

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“…The Zaonega rocks record a mixed siliciclastic-carbonate depositional system, with much magmatic activity contemporaneous with sedimentation (Črne et al, 2013a,b). They also contain one of the earliest known generations of oil/asphalt and proposed hydrocarbon seeps onto the sea floor (Melezhik et al, 2009;Qu et al, 2012;Strauss et al, 2013). The Zaonega Formation and associated rocks experienced regional greenschist facies metamorphism during the 1.8 Ga Svecofennian episode of orogenesis (Volodichev, 1987).…”

Section: Introductionmentioning

confidence: 99%

Petrography and geochemistry of carbonate rocks of the Paleoproterozoic Zaonega Formation, Russia: Documentation of 13C-depleted non-primary calcite

Črne

Melezhik

Lepland

et al. 2014

Precambrian Research

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The ca. 2.0 Ga Zaonega Formation in the Onega Basin of NW Russia represents a deep-water, mixed siliciclastic-carbonate depositional system with voluminous mafic volcanism. It is typified by extremely organic-rich rocks (TOC > 40 wt%) and represents one of the earliest known episodes of oil/asphalt generation. These rocks have been inferred to archive one of the largest negative δ 13 C excursions in Earth history, one that followed and/or partially overlapped with the 2.2-2.06 Ga worldwide Lomagundi-Jatuli carbonate carbon isotopic excursion to high values and thought to be linked to the Paleoproteorozoic oxygenation of Earth's surface environments. In order to assess the post-depositional integrity of the carbonate carbon isotopic signal (δ 13 C carb) of the Zaonega rocks, we examined in detail the petrography and geochemistry of eight carbonate beds (0.3 to 0.9 m thick) from different stratigraphic levels of the formation. The range of δ 13 C values for a single bed can be as much as 17 ‰, with calcite being significantly depleted in 13 C relative to co-existing dolomite; the 13 C-depleted calcite likely formed by involvement of carbon derived from diagenetic and catagenetic alteration of organic matter possibly abetted by volcanic CO 2. The presence of calcite ± talc ± phlogopite ± actinolite indicates metamorphic reaction of dolomite with quartz, or possibly K-feldspar, in the presence of water; commonly accompanied by degassing of 13 C-enriched CO 2 , this caused further 13 C depletion of newly formed calcite. The least altered dolomite is documented in central parts of thick dolostone beds with variably calcitized margins. This dolomite is considered as the earliest and possibly primary carbonate phase, potentially recording the δ 13 C signal of the ambient seawater. The least-altered dolomite is found in two stratigraphic intervals exhibiting δ 13 C values of +8 and +4 ‰ for the middle part of the formation, and δ 13 C values of-2 and-4 ‰ for the upper part. All other beds, with δ 13 C ranging from-19 to +3 ‰, are considered to have been variably depleted in their 13 C content by post-depositional processes and therefore cannot be reliably used for assessing the carbon isotope composition of Paleoproterozoic seawater. Our results emphasise the importance of distinguishing primary versus secondary (or later) isotopic compositions in studies of carbonate rocks used for reconstruction of global environmental change.

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7.6 Enhanced Accumulation of Organic Matter: The Shunga Event

Cited by 19 publications

References 87 publications

Oxygen dynamics in the aftermath of the Great Oxidation of Earth’s atmosphere

Oxygen dynamics in the aftermath of the Great Oxidation of Earth’s atmosphere

Variations in the abundance of photosynthetic oxygen through Precambrian and Paleozoic time in relation to biotic evolution and mass extinctions: evidence from Mn/Fe ratios

Petrography and geochemistry of carbonate rocks of the Paleoproterozoic Zaonega Formation, Russia: Documentation of 13C-depleted non-primary calcite

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