Black shale deposition during Toarcian super-greenhouse driven by sea level

Abstract. One of the most elusive aspects of the Toarcian oceanic anoxic event (T-OAE) is the paradox between carbon isotopes that indicate intense global primary productivity and organic carbon burial at a global scale, and the delayed expression of anoxia in Europe. During the earliest Toarcian, no black shales were deposited in the European epicontinental seaways, and most organic carbon enrichment of the sediments postdated the end of the overarching positive trend in the carbon isotopes that characterises the T-OAE. In the present study, we have attempted to establish a sequence stratigraphic framework for Early Toarcian deposits recovered from a core drilled in the Paris Basin using a combination of mineralogical (quartz and clay relative abundance) and geochemical (Si, Zr, Ti and Al) measurements. Combined with the evolution in redox sensitive elements (Fe, V and Mo), the data suggest that expression of anoxia was hampered in European epicontinental seas during most of the T-OAE (defined by the positive carbon isotope trend) due to insufficient water depth that prevented stratification of the water column. Only the first stratigraphic occurrence of black shales in Europe corresponds to the "global" event. This interval is characterised by >10% Total Organic Carbon (TOC) content that contains relatively low concentration of molybdenum compared to subsequent black shale horizons. Additionally, this first black shale occurrence is coeval with the record of the major negative Carbon Isotope Excursion (CIE), likely corresponding to a period of transient greenhouse intensification likely due to massive injection of carbon into the atmosphere–ocean system. As a response to enhanced weathering and riverine run-off, increased fresh water supply to the basin may have promoted the development of full anoxic conditions through haline stratification of the water column. In contrast, post T-OAE black shales during the serpentinum and bifrons Zones were restricted to epicontinental seas (higher Mo to TOC ratios) during a period of relative high sea level, and carbon isotopes returning to pre-T-OAE values. Comparing palaeoredox proxies with the inferred sequence stratigraphy for Sancerre suggests that episodes of short-term organic carbon enrichment were primarily driven by third-order sea level changes. These black shales exhibit remarkably well-expressed higher-frequency cyclicities in the oxygen availability in the water column whose nature has still to be determined through cyclostratigraphic analysis.

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Black shale deposition during Toarcian super-greenhouse driven by sea level

Climate of the Past Discussions ◽

10.5194/cpd-9-4365-2013 ◽

2013 ◽

Vol 9 (4) ◽

pp. 4365-4384 ◽

Cited By ~ 4

Author(s):

M. Hermoso ◽

F. Minoletti ◽

P. Pellenard

Keyword(s):

Organic Carbon ◽

Water Column ◽

Sea Level ◽

Sequence Stratigraphy ◽

Carbon Isotopes ◽

Black Shale ◽

Black Shales ◽

Positive Trend ◽

Sea Level Changes ◽

Organic Carbon Burial

Abstract. One of the most elusive aspects of the Toarcian Oceanic Anoxic Event (T-OAE) is the paradox between carbon isotopes that indicate intense global primary productivity and organic carbon burial at a global scale, and the delayed expression of anoxia in Europe. During the earliest Toarcian, no black shales were deposited in the European epicontinental seaways, and most organic carbon enrichment of the sediments postdated the T-OAE (defined by the overarching positive trend in the carbon isotopes). In the present studied, we have attempted to establish a sequence stratigraphy framework for Early Toarcian deposits recovered from a core drilled in the Paris Basin using a combination of mineralogical (quartz and clay relative abundance) and geochemical (Si, Zr, Ti and Al) measurements. Combined with the evolution in redox sensitive elements (Fe, V and Mo), the data suggest that expression of anoxia was hampered in European epicontinental seas during most of the T-OAE due to insufficient water depth that prevented stratification of the water column. Only the first stratigraphic occurrence of black shales in Europe corresponds to the "global" event. This interval is characterised by > 10% Total Organic Carbon (TOC) content that contains relatively low concentration of molybdenum compared to subsequent black shale horizons. Additionally, this first black shale occurrence is coeval with the record of the major negative Carbon Isotope Excursion (CIE), likely corresponding to a period of transient greenhouse intensification likely due to massive injection of carbon into the Atmosphere–Ocean system. As a response to enhanced weathering and riverine run-off, increased fresh water supply to the basin may have promoted the development of full anoxic conditions through haline stratification of the water column. In contrast, post T-OAE black shales were restricted to epicontinental seas (higher Mo to TOC ratios) during a period of relative high sea level, and carbon isotopes returning to pre-T-OAE values. Comparing palaeoredox proxies with the inferred sequence stratigraphy for Sancerre suggests that episodes of short-term organic carbon enrichment were primarily driven by third-order sea level changes. These black shales exhibit remarkably well-expressed higher-frequency cyclicities in the concentration of redox-sensitive elements such as iron or vanadium whose nature has still to be determined through cyclostratigraphic analysis.

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Secular variation in Late Cretaceous carbon isotopes: a new δ13C carbonate reference curve for the Cenomanian–Campanian (99.6–70.6 Ma)

Geological Magazine ◽

10.1017/s0016756806002421 ◽

2006 ◽

Vol 143 (5) ◽

pp. 561-608 ◽

Cited By ~ 353

Author(s):

IAN JARVIS ◽

ANDREW S. GALE ◽

HUGH C. JENKYNS ◽

MARTIN A. PEARCE

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Sea Level Rise ◽

Sea Level ◽

Carbon Isotope ◽

Carbon Isotopes ◽

Reference Curve ◽

Organic Carbon Burial ◽

Isotope Stratigraphy ◽

Using Data

Carbon stable-isotope variation through the Cenomanian–Santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven Chalk successions in England. The sections show consistent stratigraphic trends and δ13C values that provide a basis for high-resolution correlation. Positive and negative δ13C excursions and inflection points on the isotope profiles are used to define 72 isotope events. Key markers are provided by positive δ13C excursions of up to +2‰: the Albian/Cenomanian Boundary Event; Mid-Cenomanian Event I; the Cenomanian/Turonian Boundary Event; the Bridgewick, Hitch Wood and Navigation events of Late Turonian age; and the Santonian/Campanian Boundary Event. Isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons. An age-calibrated composite δ13C reference curve and an isotope event stratigraphy are constructed using data from the English Chalk. The isotope stratigraphy is applied to successions in Germany, France, Spain and Italy. Correlation with pelagic sections at Gubbio, central Italy, demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the Cenomanian–Turonian stages, confirming established relationships between Tethyan planktonic foraminiferal and Boreal macrofossil biozonations. Correlation of the Coniacian–Santonian stages is less clear cut: magnetostratigraphic evidence for placing the base of Chron 33r near the base of the Upper Santonian is in good agreement with the carbon-iso-tope correlation, but generates significant anomalies regarding the placement of the Santonian and Campanian stage boundaries with respect to Tethyan planktonic foraminiferal and nannofossil zones. Isotope stratigraphy offers a more reliable criterion for detailed correlation of Cenomanian–Santonian strata than biostratigraphy. With the addition of Campanian δ13C data from one of the English sections, a composite Cenomanian–Campanian age-calibrated reference curve is presented that can be utilized in future chemostratigraphic studies.The Cenomanian–Campanian carbon-isotope curve is remarkably similar in shape to supposedly eustatic sea-level curves: increasing δ13C values accompanying sea-level rise associated with transgression, and falling δ13C values characterizing sea-level fall and regression. The correlation between carbon isotopes and sea-level is explained by variations in epicontinental sea area affecting organic-matter burial fluxes: increasing shallow sea-floor area and increased accommodation space accompanying sea-level rise allowed more efficient burial of marine organic matter, with the preferential removal of 12C from the marine carbon reservoir. During sea-level fall, reduced seafloor area, marine erosion of previously deposited sediments, and exposure of basin margins led to reduced organic-carbon burial fluxes and oxidation of previously deposited organic matter, causing falling δ13C values. Additionally, drowning of carbonate platforms during periods of rapid sea-level rise may have reduced the global inorganic relative to the organic carbon flux, further enhancing δ13C values, while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition. Variations in nutrient supply, changing rates of oceanic turnover, and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon-isotope ratios.

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Milankovitch Climate Cyclicity and its Effect on Relative Sea Level Changes and Organic Carbon Storage, Late Cretaceous Black Shales of Colombia and Venezuela

AAPG Bulletin ◽

10.1306/bdff6e90-1718-11d7-8645000102c1865d ◽

1993 ◽

Vol 77 ◽

Author(s):

VILLAMIL, TOMAS and ERLE G. KAUFFMA

Keyword(s):

Organic Carbon ◽

Sea Level ◽

Carbon Storage ◽

Late Cretaceous ◽

Black Shales ◽

Sea Level Changes ◽

Relative Sea Level ◽

Organic Carbon Storage

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Lower Wenlock black shales in the northern Holy Cross Mountains, Poland: sedimentary and geochemical controls on the Ireviken Event in a deep marine setting

Geological Magazine ◽

10.1017/s0016756815001065 ◽

2016 ◽

Vol 154 (2) ◽

pp. 247-264 ◽

Cited By ~ 16

Author(s):

JUSTYNA SMOLAREK ◽

WIESŁAW TRELA ◽

DAVID P. G. BOND ◽

LESZEK MARYNOWSKI

Keyword(s):

Organic Carbon ◽

Total Organic Carbon ◽

Water Column ◽

Black Shale ◽

Bottom Water ◽

Black Shales ◽

Redox Conditions ◽

Pyrite Framboids ◽

Redox History ◽

Deposition Conditions

AbstractThe stratigraphic variability and geochemistry of Llandovery/Wenlock (L/W) Series boundary sediments in Poland reveals that hemipelagic sedimentation under an anoxic/euxinic water column was interrupted by low-density bottom currents or detached diluted turbid layers that resulted in intermittent seafloor oxygenation. Total organic carbon values and inorganic proxies throughout the Wilków 1 borehole section suggest variable redox conditions. U/Mo ratios > 1 throughout much of the Aeronian and Telychian stages, together with an absence of pyrite framboids, suggest oxygenated conditions prevailed. However, elevated total organic carbon near the Aeronian/Telychian boundary, together with increased U/Th and V/(V + Ni) ratios and populations of small pyrite framboids are consistent with the development of dysoxic/anoxic conditions at that time. U/Th, V/Cr and V/(V + Ni) ratios, as well as Uauthig and Mo concentrations, suggest that during the Ireviken black shale deposition, bottom-water conditions deteriorated from oxic during Telychian time to mostly suboxic/anoxic immediately prior to the L/W boundary, before a brief reoxygenation at the end of the Ireviken black shale sedimentation in the Sheinwoodian Stage. Rapid fluctuations in U/Mo during the Ireviken Event are characteristic of fluctuating redox conditions that culminated in an anoxic/euxinic seafloor in Sheinwoodian time. Following Ireviken black shale deposition, conditions once again became oxygen deficient with the development of a euxinic zone in the water column. The Aeronian to Sheinwoodian deep-water redox history was unstable, and rapid fluctuations of the chemocline across the L/W Series boundary probably contributed to the Ireviken Event extinctions, which affected mainly pelagic and hemipelagic fauna.

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Increase in ecosystem complexity aided organic carbon sequestration during the c. 2.22-2.06 Ga Lomagundi carbon isotope excursion

10.5194/egusphere-egu21-10828 ◽

2021 ◽

Author(s):

Frantz Ossa Ossa ◽

Stephan König ◽

Axel Hofmann ◽

Andrey Bekker ◽

Jorge E. Spangenberg ◽

...

Keyword(s):

Organic Carbon ◽

Sulfate Reduction ◽

Water Column ◽

Carbon Isotope ◽

Chemical Weathering ◽

Atmospheric Oxygen ◽

Black Shales ◽

Electron Acceptors ◽

Microbial Sulfate Reduction ◽

Carbon Isotope Excursion

The first dramatic rise in atmospheric oxygen to concentrations above 10-5 present atmospheric level (PAL), known as the Great Oxidation Event (GOE), was initiated during the early Proterozoic Eon c. 2.43-2.32 billion years (Gyrs) ago [1,2].&#160; Although atmospheric O2 concentrations are generally accepted to have remained below 1% PAL for at least 1.5 Gyrs following the GOE [3], high atmospheric O2 build up occurred during the Lomagundi carbon isotope excursion (LE) at the latest stage of the GOE [4]. The LE is the most pronounced and longest-lived carbon isotope excursion in Earth&#8217;s history that took place c. 2.22-2.06 Gyrs ago [4,5]. It reflects increased organic carbon (Corg) burial resulting from high primary productivity at the time of high phosphorous flux to the ocean associated with intense acidic chemical weathering of landmasses. However, mechanisms responsible for such high Corg sequestration are not yet fully resolved, nor has it been possible to precisely quantify the magnitude and expansion of oxygenation within the coeval atmosphere-ocean system.Here, we studied diagenetic concretions of pyrite and carbonate and their host black shales of the Francevillian Group, southeast Gabon, deposited during the LE. Light sulfur (&#948;34S &#8240;, VCDT) and carbon (&#948;13Ccarb &#8240;, VPDB) isotope ratios indicate that both pyrite and carbonate formed in sediments through microbial sulfate reduction and Corg remineralization, respectively. Selenium isotopic ratios (&#948;82/76Se &#8240;, NIST3149) of the pyrite concretions and their host shales are dominated by highly negative values as low as &#8211;3&#8240;, which is strong evidence for partial reduction of selenium oxyanions (SeOx2-) in the sediment below an oxygenated seawater column. Collectively, the data suggests an oxygenated water column in the Francevillian Basin with a large SeOx2- reservoir that continuously resupplied these electron acceptors to the sediment and prevented their quantitative reduction. The studied black shales host putative, fossilized large colonial multicellular organisms that had the ability to laterally and vertically migrate within the sediments [6]. We propose that bioturbation by these organisms allowed an increased flux of electron acceptors (e.g., O2, NO3&#8211;, SeOx2-, SO4-) into the sediments and pushed the microbial sulfate reduction and methanogenesis zones downward. As a consequence, CH4 and H2S generated in these zones were re-oxidized in more oxic upper levels of the sediments, which prevented them from escaping to the water column. An increase in ecosystem complexity thus likely aided Corg sequestration to the sediments and O2 accumulation in the atmosphere-ocean system during the LE.&#160;[1] Bekker et al. (2004), Nature, 427, 117&#8211;120. [2] Holland (2006), Philos. Trans. R. Soc. B 361, 903&#8211;91. [3] Colwyn et al. (2014), Geobiology, DOI: 10.1111/gbi.12360. [4] Karhu and Holland (1996), Geology, 24, 867&#8211;870. [5] Bekker (2014), Encyclopedia of Astrobiology, Springer-Verlag, 1&#8211;6. [6] El Albani et al. (2019), Proc. Natl. Acad. Sci. USA, 116, 3431&#8211;3436.

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Palaeoenvironmental evolution of the Southern Alps across the Faraoni Level equivalent: new data from the Trento Plateau (Upper Hauterivian, Dolomites, N. Italy)

Acta Geologica Polonica ◽

10.2478/agp-2013-0003 ◽

2013 ◽

Vol 63 (1) ◽

pp. 89-104 ◽

Cited By ~ 8

Author(s):

Alexander Lukeneder ◽

Patrick Grunert

Keyword(s):

Sea Level ◽

Oxygen Depletion ◽

Southern Alps ◽

Black Shales ◽

Positive Trend ◽

Southeastern Part ◽

Faunal Turnover ◽

Eastern Margin ◽

Upper Hauterivian ◽

C 30

Abstract Lukeneder, A. and Grunert, P. 2013. Palaeoenvironmental evolution of the Southern Alps across the Faraoni Level equivalent: new data from the Trento Plateau (Upper Hauterivian, Dolomites, N. Italy). Acta Geologica Polonica, 63 (1), 89-104. Warszawa. New stratigraphic and palaeoenvironmental data are presented for the northeastern part of the Trento Plateau (Puez area, Southern Alps, Italy). The studied section corresponds to the upper Hauterivian Balearites balearis and “Pseudothurmannia ohmi” ammonite zones and normal palaeomagnetic chron upper M5. A c. 30-cm-thick bed is identified as the equivalent of the Faraoni Level, based on its position within the Pseudothurmannia mortilleti Subzone, the composition of its ammonite fauna and the peak of a minor positive trend in the δ 13 C bulk record. Microfacies and geochemical proxies compare well with those of the southeastern part of the Trento Plateau and indicate palaeoceanographic continuity along the eastern margin of the plateau. The abundances of radiolarians and nannoconids suggest a turnover in the trophic structure from eutrophic conditions around the Faraoni Level equivalent to oligotrophic conditions. Low organic matter and sulphur content and frequent bioturbation indicate a well-oxygenated environment. Ammonite diversity and life-habitat groups document the influence of sea level on the plateau: while epi- and mesopelagic ammonites occur commonly during sea-level highstands, all life-habitat groups become reduced during a sea-level lowstand in the Spathicrioceras seitzi and P. ohmi subzones. The Faraoni event is heralded by a faunal turnover expressed as the diversification of epipelagic ammonites. Palaeoenvironmental conditions along the eastern margin of the Trento Plateau during the Faraoni event contrast with those of the organic-rich black shales in the west. A re-evaluation of the depositional model based on the new results suggests a general water depth of 300-500 m for the plateau. The severe reduction of mesopelagic ammonites during the sea-level lowstand indicates a shallowing towards the epi-/mesopelagic boundary. During the Faraoni event, the eastern areas of the Trento Plateau were located at the upper limit of the oxygen-minimum layer and were thus only occasionally affected by oxygen depletion, whereas the western areas were located well within the upper part of the oxygen-depleted layer.

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Organic Facies Variations, Source Rock Potential, and Sea Level Changes in Cretaceous Black Shales of the Quebrada Ocal, Upper Magdalena Valley, Colombia

AAPG Bulletin ◽

10.1306/522b43cf-1727-11d7-8645000102c1865d ◽

1997 ◽

Vol 81 (1997) ◽

Author(s):

Ute Mann and Ruediger Stein

Keyword(s):

Sea Level ◽

Source Rock ◽

Black Shales ◽

Sea Level Changes ◽

Organic Facies

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Links between iron supply from Asian dust and marine productivity in the Japan Sea since four million years ago

Geological Magazine ◽

10.1017/s0016756819000554 ◽

2019 ◽

Vol 157 (5) ◽

pp. 818-828

Author(s):

Lina Zhai ◽

Shiming Wan ◽

Ryuji Tada ◽

Debo Zhao ◽

Xuefa Shi ◽

...

Keyword(s):

Organic Carbon ◽

Primary Productivity ◽

Japan Sea ◽

Major And Trace Elements ◽

Asian Dust ◽

Sea Level Changes ◽

Aeolian Dust ◽

Iron Supply ◽

Organic Carbon Burial ◽

The Japan Sea

AbstractAeolian dust input exerts significant influence on oceanic biogeochemical cycles and further potentially controls atmospheric CO2 concentrations. However, the possible link between long-term aeolian dust supply and primary productivity in the western North Pacific remains poorly understood. Here, we present a comprehensive study of major and trace elements and total organic carbon (TOC) concentrations of sediments from Integrated Ocean Drilling Program (IODP) Site U1430 in the southern Japan Sea, in order to reconstruct oceanic palaeoproductivity evolution and test its possible link to Asian dust input since 4 Ma. Palaeoproductivity proxies indicate remarkable increases in productivity at ∼3–2 Ma followed by high-frequency oscillations in productivity since 1.2 Ma. We suggest that higher dust-derived iron supply from Central Asia at 3–2 Ma, which was likely driven by the growth of the Northern Hemisphere ice sheets, could account for enhanced primary productivity and export production in the Japan Sea. Such increased oceanic palaeoproductivity could enhance organic carbon burial, which might contribute to the decrease in atmospheric CO2 concentrations, and provide a positive feedback to the global cooling. However, the Tsushima Warm Current (TSWC) intrusion via the southern Tsushima Strait, which was controlled by glacioeustatic sea level changes, has been the principal cause of the rapid changes in primary productivity and benthic redox condition since 1.2 Ma, regardless of continuously increased Asian dust input.

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A record of seafloor methane seepage across the last 150 million years

10.5194/egusphere-egu2020-8396 ◽

2020 ◽

Author(s):

Davide Oppo ◽

Luca De Siena ◽

David Kemp

Keyword(s):

Organic Carbon ◽

Sea Level ◽

Methane Emission ◽

Temporal Correlation ◽

Biogenic Methane ◽

Methane Seepage ◽

Carbon Burial ◽

Organic Carbon Burial ◽

Rapid Generation ◽

Extinction Events

Methane seepage at the seafloor is a source of carbon in the marine environment and has long been recognized as an important window into the deep geo-, hydro-, and bio-spheres. However, the processes and temporal patterns of natural methane emission over multi-million-year time scales are still poorly understood. The microbially-mediated methane oxidation leads to the precipitation of authigenic carbonate minerals within subseafloor sediments, thus providing a potentially extensive record of past methane emission. In this study, we used data on methane-derived authigenic carbonates to build a proxy time series of seafloor methane emission over the last 150 My. We quantitatively demonstrate that variations in sea level and organic carbon burial are the dominant controls on methane leakage since the Early Cretaceous. Sea level controls variations of methane seepage by imposing smooth trends with cyclicities in the order of tens of My. Organic carbon burial shows the same cyclicities and instantaneously controls the volumes of methane released thanks to the rapid generation of biogenic methane. The identified fundamental (26-27 My) cyclicity matches those observed in the carbon cycle associated with plate tectonic processes, the atmospheric CO2, the oceanic anoxic events, and mass extinction events. A higher (12 My) cyclicity relates to modulations of Milankovitch eccentricity cycles and to variations in global tectonics. These analogies demonstrate that the seafloor methane seepage across the last 150 My relates to a large spectrum of global phenomena and thus has key implications for a better understanding of methane cycling at the present day. Temporal correlation analysis supports the evidence that the modern expansion of hypoxic areas and its effect on organic carbon burial may lead to higher seawater methane concentrations over the coming centuries.

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