Impact of methane seeps on the local carbon‐isotope record: a case study from a Late Jurassic hemipelagic section

Louis-Schmid, Beat; Rais, Pauline; Logvinovich, D.; Bernasconi, Stefano M.; Weissert, Helmut

doi:10.1111/j.1365-3121.2007.00744.x

Cited by 16 publications

(10 citation statements)

References 30 publications

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“…One of the best‐studied Jurassic methane seeps formed during Oxfordian time ( ca 160 Ma) at Beauvoisin, south‐east France (Peckmann et al ., ). Highly depleted δ 13 C carb values of down to −30‰ in calcite nodules within the Oxfordian section probably result from hydrocarbon‐sourced methane seepage (Louis‐Schmid et al ., ).…”

Section: Discussionmentioning

confidence: 97%

Orbital pacing of the Early Jurassic carbon cycle, black‐shale formation and seabed methane seepage

Ruhl

Hesselbo

et al. 2016

Sedimentology

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The Early Jurassic (ca 201 to 174 Ma) was marked by a series of rapid perturbations in climate, the environment and global geochemical cycles, which have been linked to volcanic outgassing and the release of biogenic or thermogenic methane into the ocean-atmosphere system. The state of the global carbon cycle and prevailing climatic and environmental conditions that existed at this time are, however, poorly constrained. Here, mudrocks of the Lower Sinemurian Arietites bucklandi ammonite Biozone at coastal exposures at Kilve, Somerset, UK, have been studied. This succession includes laminated organic-rich black shales, which are present throughout the Bristol Channel Basin, and coincides with a 2 to 3& negative carbon-isotope excursion, distinct changes in inferred land vegetation and abundant marine prasinophytes (green algae). The event itself does not represent a single perturbation of the regional environment, but follows in a sequence of eccentricity-modulated, precession-paced perturbations that occur throughout the preceding Hettangian stage, with the periodic formation of organic-rich laminated black shales in the Bristol Channel Basin. However, the Early Sinemurian event studied herein is more extreme in nature, with sedimentary total organic carbon values of 5 to 11% persisting over about 2 m, representing ca 100 kyr, possibly in phase with short (ca 100 kyr) and long (ca 405 kyr) eccentricity forcing. The formation of methane-seep carbonatecemented mounds took place relatively soon after the deposition of laminated black shales. Biogenic methane probably formed in response to microbial methanogenesis in the organic-rich black shale, which was subsequently channelled to the sediment-water interface approximately 5 m above the source bed, and ca 200 kyr after cessation of formation of the black shale.

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Section: Discussionmentioning

confidence: 97%

Orbital pacing of the Early Jurassic carbon cycle, black‐shale formation and seabed methane seepage

Ruhl

Hesselbo

et al. 2016

Sedimentology

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“…V and U both have in common that there is no detrital influence to their concentration in marine sediments. As already mentioned above, the turning point of the isotope excursion coincides with a major change in the Tethyan sedimentation pattern [1][2][3]. This was also the time of a profound rearrangement of the oceanic current system induced by the establishment of a new circum-global ocean passage in low latitudes.…”

Section: Discussionmentioning

confidence: 56%

“…the positive 13 C excursion senso stricto). Again, this correlation of the 13 C excursion with trends in Ti, Nb, and W as well as Mn and Fe contents seems to reflect changes in the Oxfordian palaeooceanography and climate [1][2][3][4]. The climate during the late Oxfordian was dominated by warm and arid conditions.…”

Section: +mentioning

confidence: 81%

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Trace Elements in Marine Sediments from the Oxfordian (Late Jurassic): Implications for Seawater Chemistry, Erosional Processes, Changes in Oceanic Circulation and More

Müller¹

2012

TOGEOJ

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Abstract:The Oxfordian, first stage of the late Jurassic, is remarkably variable in terms of deposited sediments, geochemical tracers, and climate. The climate changed during the Middle Oxfordian from humid to arid with a temperature rise of more than five degrees. During this time, the 13 C reached maximum values. The positive excursion in 13 C of carbonates from the Oxfordian (with an amplitude of more than 1‰) was reproduced in hemipelagic sections from southeastern France. Analysis of major and trace elements of these carbonates were carried out by LA-ICP-MS in order to verify their application as palaeoproxies in conjunction with the changes mentioned in climate. As a novel approach 36 elements were measured with regard to establish a complete and comprehensive analysis of the geochemical situation. Concentration peaks of P, Sr, Mn, Fe, Ba point to a more oligotrophic setting within the lower part of the sediment profile from southeastern France. Conversely, the positive 13 C excursion with 13 C values rising from 2 to 3 ‰ within the uppermost part of the profile coincide with more elevated concentrations of V, Fe, Mn, U arguing for an ocean-wide anoxia (Oceanic Anoxic Events OAE). High detrital input during this arid period is recorded by enhanced concentrations of elements like Ti, Mn, Fe, Zr, Nb and W. This correlation of the 13 C excursion with trends in Ti, Nb, W as well as Mn and Fe contents reflects changes in the Oxfordian palaeooceanography and climate. During the late Oxfordian the environmental prerequisites were controlled by warm and arid conditions and an increased metal flux from the continent due to the intensified chemical and physical weathering, erosion of rocks, as well as aeolian and fluvial transport to the oceans.

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“…However, the finding of accumulated isotopically light archaeol, in combination with barite and dolomite enrichments, supports the concept that these signatures instead represent the imprint of a former SMT (Contreras et al, 2013) [59] and are thus a diagenetic feature. Similarly, Louis-Schmid et al (2007) [114] found that a 4% negative excursion in a Late Jurassic hemipelagic succession at Beauvoisin (SE France) is the result of local anaerobic methane oxidation and precipitation of authigenic carbonates, rather than a global signal.…”

Section: Diagenetic Vs Atmospheric Signatures?mentioning

confidence: 97%

The Carbon-Isotope Record of the Sub-Seafloor Biosphere

Meister

Reyes

2019

Geosciences

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Sub-seafloor microbial environments exhibit large carbon-isotope fractionation effects as a result of microbial enzymatic reactions. Isotopically light, dissolved inorganic carbon (DIC) derived from organic carbon is commonly released into the interstitial water due to microbial dissimilatory processes prevailing in the sub-surface biosphere. Much stronger carbon-isotope fractionation occurs, however, during methanogenesis, whereby methane is depleted in 13C and, by mass balance, DIC is enriched in 13C, such that isotopic distributions are predominantly influenced by microbial metabolisms involving methane. Methane metabolisms are essentially mediated through a single enzymatic pathway in both Archaea and Bacteria, the Wood–Ljungdahl (WL) pathway, but it remains unclear where in the pathway carbon-isotope fractionation occurs. While it is generally assumed that fractionation arises from kinetic effects of enzymatic reactions, it has recently been suggested that partial carbon-isotope equilibration occurs within the pathway of anaerobic methane oxidation. Equilibrium fractionation might also occur during methanogenesis, as the isotopic difference between DIC and methane is commonly on the order of 75‰, which is near the thermodynamic equilibrium. The isotopic signature in DIC and methane highly varies in marine porewaters, reflecting the distribution of different microbial metabolisms contributing to DIC. If carbon isotopes are preserved in diagenetic carbonates, they may provide a powerful biosignature for the conditions in the deep biosphere, specifically in proximity to the sulphate–methane transition zone. Large variations in isotopic signatures in diagenetic archives have been found that document dramatic changes in sub-seafloor biosphere activity over geological time scales. We present a brief overview on carbon isotopes, including microbial fractionation mechanisms, transport effects, preservation in diagenetic carbonate archives, and their implications for the past sub-seafloor biosphere and its role in the global carbon cycle. We discuss open questions and future potentials of carbon isotopes as archives to trace the deep biosphere through time.

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Impact of methane seeps on the local carbon‐isotope record: a case study from a Late Jurassic hemipelagic section

Cited by 16 publications

References 30 publications

Orbital pacing of the Early Jurassic carbon cycle, black‐shale formation and seabed methane seepage

Orbital pacing of the Early Jurassic carbon cycle, black‐shale formation and seabed methane seepage

Trace Elements in Marine Sediments from the Oxfordian (Late Jurassic): Implications for Seawater Chemistry, Erosional Processes, Changes in Oceanic Circulation and More

The Carbon-Isotope Record of the Sub-Seafloor Biosphere

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