Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK)

Xu, Weimu; Ruhl, Micha; Jenkyns, Hugh C.; Leng, Melanie J.; Huggett, Jennifer; Minisini, Daniel; Ullmann, Clemens V.; Riding, James B.; Weijers, Johan W. H.; Storm, Marisa; Percival, Lawrence; Tosca, Nicholas J.; Idiz, Erdem; Tegelaar, Erik; Hesselbo, Stephen P.

doi:10.1016/j.epsl.2017.12.037

Cited by 154 publications

(142 citation statements)

References 96 publications

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“…Thus, orbital changes and a decrease in pCO 2 levels toward the termination of T-OAE could have worked synergistically to favor a vigorous ocean circulation that, together with cooling, led to a reduced hydrological cycle and thus reduced continental weathering. This is in agreement with the return to nearly zero kaolinite/illite ratios (Xu et al, 2018) and lower osmium isotope values (Cohen et al, 2004;Percival et al, 2016;Them et al, 2017) observed at the termination of the T-OAE. Although further studies on the temporal evolution of the ocean dynamics during the Toarcian are needed, this study suggests that major changes through time and geographically observed in the redox proxy records of the northern EES are likely to be linked to variations in the ocean circulation and to have contributed to the termination of T-OAE.…”

Section: Temporal Variability In Oxygenation In the Northern Eessupporting

confidence: 89%

Ocean Circulation in the Toarcian (Early Jurassic): A Key Control on Deoxygenation and Carbon Burial on the European Shelf

Baroni

Pohl

Helmond

et al. 2018

Paleoceanog and Paleoclimatol

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The Toarcian Oceanic Anoxic Event (T‐OAE, ∼183 Myr) was a long‐lasting episode of ocean deoxygenation during the Early Jurassic. The event is related to a period of global warming and characterized by major perturbations to the hydrological and carbon cycles with high rates of organic matter burial in shelf seas. Ocean circulation during the Toarcian and its influence on marine biogeochemical cycles are still not fully understood. Here we assess the spatial extent of anoxia in the NW Tethys Ocean during the T‐OAE, the relationship with ocean circulation and the impact on organic carbon burial, using new and existing sedimentary records from the European Epicontinental Shelf in combination with general circulation model results. We demonstrate that bottom waters on the southwestern part of the shelf were mainly oxic during the T‐OAE, while those in the northeastern basins were mostly anoxic or even sulfidic. Results for two ocean‐atmosphere models (Fast Ocean‐Atmosphere Model and Massachusetts Institute of Technology general circulation model) suggest the presence of a strong clockwise gyre over the European Epicontinental Shelf, which brought oxygenated equatorial waters from the Tethys Ocean to the southern shelf. The northward limb of the gyre was significantly weakened due to the rough bathymetry of the northern shelf, making this relative small region highly sensitive to local ocean stratification. These sluggish ocean dynamics promoted bottom water anoxia and enhanced burial of organic carbon in the northeastern basins, which accounted for 3–5% of the total carbon extracted from the ocean‐atmosphere system as recorded by the positive carbon isotope shift.

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Section: Temporal Variability In Oxygenation In the Northern Eessupporting

confidence: 89%

Ocean Circulation in the Toarcian (Early Jurassic): A Key Control on Deoxygenation and Carbon Burial on the European Shelf

Baroni

Pohl

Helmond

et al. 2018

Paleoceanog and Paleoclimatol

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“…The margaritatus-spinatum zone boundary is marked by a sharp ∼4‰ drop in organic carbonisotope ratios, followed by a gradual positive shift throughout the spinatum zone. The Toarcian record comprises a lower Toarcian overarching positive CIE interrupted by the large negative CIE associated with the T-OAE, as described in previous studies (7,14,22,41). All larger-scale trends in the δ 13 C TOC data are reproduced in δ 13 C wood presented for the upper Sinemurian to Toarcian, although the latter dataset shows a larger degree of variability ( Fig.…”

Section: Resultssupporting

confidence: 72%

“…The strata primarily comprise calcareous mudstone, with varying silt and clay content, alternating with strongly bioturbated calcareous siltstone and silty limestone (36). Average Rock-Eval thermal maturation parameter (T max = ∼430°C) and vitrinite reflectance (R o = 0.38 to 0.63) from previous studies indicate the presence of immature to early mature sedimentary organic matter (7,22,40). δ 13 C data from total organic carbon (δ 13 C TOC ) and carbonates (δ 13 C carb ) generated in previous studies suggest that the Mochras sedimentary archive records the long-term pattern of global carbon-cycle change (7,14,22,41,42).…”

Section: Geological Settingmentioning

confidence: 80%

“…Throughout the Toarcian, TOC values fluctuate between 0.5 and 1.5 wt %, with HI values of ∼100 mg HC/g TOC (7). Slightly higher TOC and HI values are recorded in the bifrons and variabilis zones, and elevated TOC and HI values (up to 2.5 wt % up to 339 mg HC/g TOC, respectively) are associated with the negative CIE interval in the serpentinum zone (7).…”

Section: Resultsmentioning

confidence: 98%

“…A calcite-veined interval in the mid-Sinemurian oxynotum zone may be marked by a fault which, if present at all, cuts out less than one ammonite subzone (36). A small hiatus may also be present at the level of intraformational conglomerate at 627.38 mbs (36) within the upper Toarcian pseudoradiosa zone, and a further unconformity is present at the top of the Lower Jurassic (at 601.85 mbs), where sediments of the uppermost Toarcian aalensis zone are overlain by Paleogene strata (7,36). In all other respects, the Lower Jurassic succession appears to be stratigraphically complete.…”

Section: Geological Settingmentioning

confidence: 99%

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Orbital pacing and secular evolution of the Early Jurassic carbon cycle

Storm

Hesselbo

Jenkyns

et al. 2020

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

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118

111

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Global perturbations to the Early Jurassic environment (∼201 to ∼174 Ma), notably during the Triassic–Jurassic transition and Toarcian Oceanic Anoxic Event, are well studied and largely associated with volcanogenic greenhouse gas emissions released by large igneous provinces. The long-term secular evolution, timing, and pacing of changes in the Early Jurassic carbon cycle that provide context for these events are thus far poorly understood due to a lack of continuous high-resolution δ13C data. Here we present a δ13CTOC record for the uppermost Rhaetian (Triassic) to Pliensbachian (Lower Jurassic), derived from a calcareous mudstone succession of the exceptionally expanded Llanbedr (Mochras Farm) borehole, Cardigan Bay Basin, Wales, United Kingdom. Combined with existing δ13CTOC data from the Toarcian, the compilation covers the entire Lower Jurassic. The dataset reproduces large-amplitude δ13CTOC excursions (>3‰) recognized elsewhere, at the Sinemurian–Pliensbachian transition and in the lower Toarcian serpentinum zone, as well as several previously identified medium-amplitude (∼0.5 to 2‰) shifts in the Hettangian to Pliensbachian interval. In addition, multiple hitherto undiscovered isotope shifts of comparable amplitude and stratigraphic extent are recorded, demonstrating that those similar features described earlier from stratigraphically more limited sections are nonunique in a long-term context. These shifts are identified as long-eccentricity (∼405-ky) orbital cycles. Orbital tuning of the δ13CTOC record provides the basis for an astrochronological duration estimate for the Pliensbachian and Sinemurian, giving implications for the duration of the Hettangian Stage. Overall the chemostratigraphy illustrates particular sensitivity of the marine carbon cycle to long-eccentricity orbital forcing.

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The Osmium Isotope Signature of Phanerozoic Large Igneous Provinces

Dickson

Cohen

Davies

2021

Large Igneous Provinces

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The emplacement of Large Igneous Provinces (LIPs) throughout the Phanerozoic Eon introduced vast quantities of mafic rocks to the Earth's surface, which were subsequently weathered into the oceans. Osmium isotope data can be used to track these LIP-related weathering fluxes, providing a global fingerprint of the timing and magnitude of LIP emplacement, and guiding assessments of the impact of these events on ocean biogeochemistry and the regulation of the global climate system. Sedimentary Os isotope records spanning late Phanerozoic LIP events are reviewed herein and new observations from Eocene hyperthermal event ETM-2 are presented. While Os isotope stratigraphy can pro vide major constraints on LIP activity in the geological record, it cannot always distinguish whether the extrusive activity was subaerial or submarine. The utility of osmium isotopes as a global tracer of past volcanism may be enhanced when used alongside proxies such as mercury concentrations, which may be more diagnostic of the style of individual episodes of LIP emplacement. Hitherto, only a few high-resolution Os-isotope records across Phanerozoic LIPs have effectively exploited the short oceanic residence time of Os. Future high-resolution studies across suitable, well-preserved stratigraphic records will significantly improve our understanding of the nature, progression, and consequences of LIP emplacement.

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Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK)

Cited by 154 publications

References 96 publications

Ocean Circulation in the Toarcian (Early Jurassic): A Key Control on Deoxygenation and Carbon Burial on the European Shelf

Ocean Circulation in the Toarcian (Early Jurassic): A Key Control on Deoxygenation and Carbon Burial on the European Shelf

Orbital pacing and secular evolution of the Early Jurassic carbon cycle

The Osmium Isotope Signature of Phanerozoic Large Igneous Provinces

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