An open marine record of the Toarcian oceanic anoxic event

Abstract. Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic-rich sediments (black shales) and significant perturbations in the global carbon cycle. The expression of these perturbations is globally recorded in sediments as excursions in the carbon isotope record irrespective of lithology or depositional environment. During the Early Toarcian, black shales were deposited on the epi- and peri-continental shelves of Pangaea and these sedimentary rocks are associated with a pronounced (ca. 7‰) negative (organic) carbon isotope excursion (CIE) which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the Early Toarcian is thought to represent an oceanic anoxic event (the T-OAE). Associated with this event, there were pronounced perturbations in global weathering rates and seawater temperatures. Although it is commonly asserted that the T-OAE is a global event and that the distribution of black shales is likewise global, an isotopic and/or organic-rich expression of this event has as yet only been recognized on epi- and peri-continental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg) of Early Toarcian cherts from Japan that were deposited in the open Panthalassa Ocean was analysed. The results show the presence of a major (>6‰) negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the Early Toarcian negative CIE known from European epicontinental strata. Furthermore, a secondary ca. −2‰ excursion in δ13Corg is also recognized lower in the studied succession that, within the current biostratigraphical resolution, is likely to represent the excursion that occurs close to the Pliensbachian/Toarcian boundary and which is also recorded in European epicontinental successions. These results from the open ocean realm suggest that, in conjunction with other previously published datasets, these major Early Jurassic carbon cycle perturbations affected all active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric). An extremely negative δ13Corg value (−57‰) during the peak of the T-OAE is also reported, which suggests that the inferred open ocean mid-water oxygen minimum layer within which these sediments are thought to have been deposited was highly enriched in methanotrophic bacteria, since these organisms are the only plausible producers of such 12C-enriched organic matter.

Download Full-text

An open ocean record of the Toarcian oceanic anoxic event

Solid Earth ◽

10.5194/se-2-245-2011 ◽

2011 ◽

Vol 2 (2) ◽

pp. 245-257 ◽

Cited By ~ 63

Author(s):

D. R. Gröcke ◽

R. S. Hori ◽

J. Trabucho-Alexandre ◽

D. B. Kemp ◽

L. Schwark

Keyword(s):

Organic Matter ◽

Carbon Cycle ◽

Carbon Isotope ◽

Isotope Composition ◽

Global Carbon Cycle ◽

Open Ocean ◽

Black Shales ◽

Oceanic Anoxic Event ◽

Anoxic Event ◽

Global Carbon

Abstract. Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic matter-rich sediments (black shales) and significant perturbations in the global carbon cycle. These perturbations are globally recorded in sediments as carbon isotope excursions irrespective of lithology and depositional environment. During the early Toarcian, black shales were deposited on the epi- and pericontinental shelves of Pangaea, and these sedimentary rocks are associated with a pronounced (ca. 7 ‰) negative (organic) carbon isotope excursion (CIE) which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the lower Toarcian is thought to represent an oceanic anoxic event (the T-OAE). If the T-OAE was indeed a global event, an isotopic expression of this event should be found beyond the epi- and pericontinental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg of lower Toarcian organic matter-rich cherts from Japan, deposited in the open Panthalassa Ocean, was analysed. The results show the presence of a major (>6 ‰) negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the lower Toarcian negative CIE known from Pangaean epi- and pericontinental strata. A smaller negative excursion in δ13Corg (ca. 2 ‰) is recognized lower in the studied succession. This excursion may, within the current biostratigraphic resolution, represent the excursion recorded in European epicontinental successions close to the Pliensbachian/Toarcian boundary. These results from the open ocean realm suggest, in conjunction with other previously published datasets, that these Early Jurassic carbon cycle perturbations affected the active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric).

Download Full-text

Astronomical constraints on global carbon-cycle perturbation during Oceanic Anoxic Event 2 (OAE2)

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2017.01.007 ◽

2017 ◽

Vol 462 ◽

pp. 35-46 ◽

Cited By ~ 24

Author(s):

Yong-Xiang Li ◽

Isabel P. Montañez ◽

Zhonghui Liu ◽

Lifeng Ma

Keyword(s):

Carbon Cycle ◽

Global Carbon Cycle ◽

Oceanic Anoxic Event ◽

Oceanic Anoxic Event 2 ◽

Anoxic Event ◽

Global Carbon

Download Full-text

TESTING THE FIDELITY OF THE SILURIAN CARBON ISOTOPE RECORD AS A PROXY FOR THE GLOBAL CARBON CYCLE

10.1130/abs/2019am-340282 ◽

2019 ◽

Author(s):

Poul Emsbo ◽

◽

Patrick I. McLaughlin

Keyword(s):

Carbon Cycle ◽

Carbon Isotope ◽

Global Carbon Cycle ◽

Isotope Record ◽

Global Carbon

Download Full-text

Isorenieratane record in black shales from the Paris Basin, France: Constraints on recycling of respired CO2as a mechanism for negative carbon isotope shifts during the Toarcian oceanic anoxic event

Paleoceanography ◽

10.1029/2006pa001305 ◽

2006 ◽

Vol 21 (4) ◽

Cited By ~ 70

Author(s):

Yvonne van Breugel ◽

Marianne Baas ◽

Stefan Schouten ◽

Emanuela Mattioli ◽

Jaap S. Sinninghe Damsté

Keyword(s):

Carbon Isotope ◽

Black Shales ◽

Paris Basin ◽

Isotope Shifts ◽

Oceanic Anoxic Event ◽

Anoxic Event

Download Full-text

Molecular and petrographical evidence for lacustrine environmental and biotic change in the palaeo-Sichuan mega-lake (China) during the Toarcian Oceanic Anoxic Event

Geological Society London Special Publications ◽

10.1144/sp514-2021-2 ◽

2021 ◽

pp. SP514-2021-2

Author(s):

Weimu Xu ◽

Johan W. H. Weijers ◽

Micha Ruhl ◽

Erdem F. Idiz ◽

Hugh C. Jenkyns ◽

...

Keyword(s):

Organic Matter ◽

Sichuan Basin ◽

Large Scale ◽

Algal Growth ◽

Black Shales ◽

Content Type ◽

Oceanic Anoxic Event ◽

Anoxic Event ◽

Supplementary Material ◽

The Sichuan Basin

AbstractThe organic-rich upper Lower Jurassic Da'anzhai Member (Ziliujing Formation) of the Sichuan Basin, China is the first stratigraphically well-constrained lacustrine succession associated with the Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The formation and/or expansion of the Sichuan mega-lake, likely one of the most extensive fresh-water systems to have existed on the planet, is marked by large-scale lacustrine organic productivity and carbon burial during the T-OAE, possibly due to intensified hydrological cycling and nutrient supply. New molecular biomarker and organic petrographical analyses, combined with bulk organic and inorganic geochemical and palynological data, are presented here, providing insight into aquatic productivity, land-plant biodiversity, and terrestrial ecosystem evolution in continental interiors during the T-OAE. We show that lacustrine algal growth during the T-OAE accounted for a significant organic-matter flux to the lakebed in the palaeo-Sichuan mega-lake. Lacustrine water-column stratification during the T-OAE facilitated the formation of dysoxic-anoxic conditions at the lake bottom, favouring organic-matter preservation and carbon sequestration into organic-rich black shales in the Sichuan Basin. We attribute the palaeo-Sichuan mega-lake expansion to enhanced hydrological cycling in a more vigorous monsoonal climate in the hinterland during the T-OAE greenhouse.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5433544

Download Full-text

Onset of Oceanic Anoxic Event 2 in the Lower Saxony Basin – Insights fromhigh-resolution stable isotope stratigraphy and geochemical modelling

10.5194/egusphere-egu21-8748 ◽

2021 ◽

Author(s):

Pia Müller ◽

Ulrich Heimhofer ◽

Christian Ostertag-Henning

Keyword(s):

Organic Matter ◽

High Resolution ◽

Stable Isotope ◽

Carbon Cycle ◽

Geochemical Modelling ◽

Positive Anomaly ◽

Lower Saxony ◽

Data Set ◽

Oceanic Anoxic Event ◽

Anoxic Event

The Oceanic Anoxic Event (OAE) 2 spanning the Cenomanian-Turonian boundary (93.5 Ma) represents a major perturbation of the global carbon cycle and is marked by organic-rich sediments deposited under oxygen-depleted conditions. In many studies the eruption of the Caribbean LIP is considered to be the cause for rapidly increasing CO2 concentrations and resulting global warming accompanied by widespread oceanic anoxia. In the Lower Saxony Basin of northern Germany, the deposits of the OAE 2 are exposed in several industry drill cores. In this study, the lower part of the OAE 2 has been studied in the HOLCIM 2011-3 drill core. Sedimentary rocks are composed of limestones, marly limestones, marls and black shales and have been analysed with a high-resolution stable isotope approach (approximately one sample every 2 cm) combined with geochemical modelling. Using stable carbon isotopes, bulk rock parameters and petrographic analysis, the onset of OAE 2 has been investigated in detail. The high-resolution &#948;13C curve exhibits overall stable values around 3 &#8240; before the onset of the Plenus event. This background level is interrupted by three short-lived and small but significant negative carbon isotope excursions (CIEs) down to &#948;13C values of 2.5 &#8240;, 2.7 &#8240; and 1.9 &#8240;. Immediately before the main rise in the Plenus bed, a longer-lasting negative CIE down to 2.8 &#8240; is observed, preceding the large positive CIE of the OAE 2 to values of 5.2 &#8240; over 33 ka. Thereafter, the &#948;13C values decrease to 3.5 &#8240; over a period of approximately 130 ka. The results can be correlated with the lower-resolution data set of Voigt et al. (2008) but enable a more accurate characterization of the subtle features of the CIE and hence events before and during this time interval. Carbon cycle modelling with the modelling software SIMILE using a model based on Kump & Arthur (1999) reveals that the negative excursion before the Plenus bed can be explained by a massive volcanic pulse releasing of 0.95*1018 mol CO2 within 14 ka. This amount corresponds to only 81 % of the calculated volume of CO2 release during emplacement of the Caribbean LIP by Joo et al. (2020). In the model the volcanic exhalation increases atmospheric CO2 concentrations. This will increase global temperatures, intensify the hydrological cycle and thus increase nutrient input into the ocean, resulting in an expansion of the oxygen minimum zone, the development of anoxic conditions and an increase in the preservation potential for organic material. In the model enhanced primary productivity and organic matter preservation can be controlled by the implemented riverine phosphate input and the preservation factor for organic matter. For the positive anomaly, the riverine phosphate input must be nearly doubled (from 0.01 &#956;mol/kg PO4 to 0.019 &#956;mol/kg) for the period of the increasing &#948;13C values (app. 33 ka), with a concomitant rise of the preservation factor from 1 % to 2 %. This model scenario accurately reproduces the major features of the new high-resolution &#948;13C record over the onset of the OAE 2 CIE.

Download Full-text

Recurrent global carbon cycle disturbances during the Aalenian: Evidence from France and Chile

10.5194/egusphere-egu21-8206 ◽

2021 ◽

Author(s):

Alicia Fantasia ◽

Thierry Adatte ◽

Jorge E. Spangenberg ◽

Emanuela Mattioli ◽

Enrique Bernárdez ◽

...

Keyword(s):

High Resolution ◽

Carbon Cycle ◽

Middle Jurassic ◽

Environmental Changes ◽

Global Carbon Cycle ◽

Oceanic Anoxic Event ◽

Carbon Substrates ◽

Rock Eval ◽

Resolution Dataset ◽

Global Carbon

The Jurassic was punctuated by several episodes of abrupt environmental changes associated with climatic instabilities, severe biotic crisis, and perturbations of the global carbon cycle. Over the last decades, the Toarcian Oceanic Anoxic Event (Early Jurassic, ~183 Ma) and the early Bajocian Event (Middle Jurassic, ~170&#8211;168 Ma) have attracted much attention because they represent such episodes of global and severe environmental change. Bracketed in between the Toarcian and the Bajocian, the Aalenian stage (Middle Jurassic, ~174-170 Ma) has received less attention, although there is some evidence from Tethyan and Boreal records that it was a time of environmental changes marked by marine biotic turnovers. The lack of knowledge about the Aalenian palaeoenvironments leaves a gap in our understanding of the wider context of the Toarcian and Bajocian events and hence of environmental feedback mechanisms surrounding Mesozoic carbon cycle perturbations. In this study, we provide a high-resolution, biostratigraphically well-defined carbon isotope records (&#948;13Corg&#160;and &#948;13Ccarb) combined to Rock-Eval data for the upper Toarcian&#8211;lower Bajocian interval from two expanded marl/limestone alternation successions from France (French Subalpine Basin) and Chile (Andean Basin). The comparison with available records from the Tethyan and Boreal domains highlights that medium-term &#948;13C fluctuations are reproducible across different palaeoceanographic settings from both hemispheres and between different carbon substrates. The new high-resolution dataset highlights the complexity of the Aalenian &#948;13C record, including previously identified &#948;13C shifts and hitherto undescribed fluctuations. This study provides one of the most expanded high-resolution chemostratigraphic reference records for the entire Aalenian stage, and shows compelling evidence from both hemispheres that it was a time marked by recurrent perturbations to the global carbon cycle and environmental changes.&#160;

Download Full-text

Coastal carbon transfer in the past - a box model study

10.5194/egusphere-egu21-8700 ◽

2021 ◽

Author(s):

Anne Kruijt ◽

Jack Middelburg ◽

Appy Sluijs

Keyword(s):

Carbon Cycle ◽

Coastal Zone ◽

Light Attenuation ◽

Global Carbon Cycle ◽

Open Ocean ◽

Box Model ◽

Zone Model ◽

Large Variability ◽

Carbon Transfer ◽

Global Carbon

The shelf represents a relatively small fraction of global oceanic area but plays an important role in the global carbon cycle because of high production and burial of organic matter and calcium carbonate. Biological processes on the shelf can greatly alter the partial pressure of dissolved CO2, causing disequilibrium with the atmosphere and fluxes significantly larger than those in the open ocean. Also the transport of major ions from land to open ocean is mediated by shelf processes. Available models resolving the governing processes are typically designed to simulate specific regions. Global carbon cycle models typically implement all shelf processes in one simple box. Global earth system models typically impose a flux of riverine export products from land directly into the open ocean without accounting for processes in the coastal zone. However, the global role of the coastal zone in the carbon cycle on various time scales remains poorly quantified, partly due to the large variability in continental margin environments, hampering proper understanding of past, present and future global carbon cycle dynamics. We develop a new coastal zone model that links river biogeochemistry with open ocean models, focusing on the transfer of carbon. Our first approach represents a box model in which number, size and depth of boxes can be varied. We apply global fluxes of carbon into the system and include functions describing first order organic and inorganic carbon processes in each of the boxes. With this conceptual model of the coastal zone we aim to test the effect of changes in bathymetry, temperature and light attenuation on the way carbon is transferred through the coastal interface, suitable for paleo and future applications.

Download Full-text

The carbon isotopic response of algae, (cyano)bacteria, archaea and higher plants to the late Cenomanian perturbation of the global carbon cycle: Insights from biomarkers in black shales from the Cape Verde Basin (DSDP Site 367)

Organic Geochemistry ◽

10.1016/j.orggeochem.2008.01.012 ◽

2008 ◽

Vol 39 (12) ◽

pp. 1703-1718 ◽

Cited By ~ 61

Author(s):

Jaap S. Sinninghe Damsté ◽

Marcel M.M. Kuypers ◽

Richard D. Pancost ◽

Stefan Schouten

Keyword(s):

Carbon Cycle ◽

Higher Plants ◽

Global Carbon Cycle ◽

Black Shales ◽

Cape Verde ◽

Carbon Isotopic ◽

Global Carbon ◽

Dsdp Site

Download Full-text

Major palaeoenvironmental upheavals in both marine and terrestrial realms during the Toarcian oceanic anoxic event: a multi-proxy approach

10.5194/egusphere-egu2020-21187 ◽

2020 ◽

Author(s):

Francesca Galasso ◽

Susanne FeistBurkhardt ◽

Annette Schmid- Röhl ◽

Stefano Benasconi ◽

Elke Schneebeli-Hermann

Keyword(s):

Carbon Isotope ◽

Seawater Temperature ◽

Black Shales ◽

Land Plants ◽

Open Pit ◽

Large Igneous Province ◽

Isotopic Study ◽

Data Set ◽

Oceanic Anoxic Event ◽

Anoxic Event

The Toarcian oceanic anoxic event (TOAE) ~183 Ma is not only associated with oceanic anoxia and rapid seawater temperature increase but also with a marine mass extinction event. These biotic and environmental upheavals are linked to the emplacement of the Karoo-Ferrar large igneous province. Negative carbon excursions and widespread deposition of black shales are typical for Toarcian sedimentary successions.The occurrence and growth of dinoflagellates is influenced by environmental factors like oxygen content, salinity, temperature and nutrient availability. For land plants, changes in dominance structure of ecosystems reflected in spore pollen assemblages can be indicative of ecological disturbance. Thus species composition (and morphology) of dinoflagellates and land plants can be used to understand major environmental perturbations.An extensively studied TOAE section is the former Rohrbach Zement quarry at Dotternhausen (today Larfarge-Holcim) with comprehensive data of carbon isotope analyses, total organic and inorganic carbon content and rock eval analysis. The Dotternhausen quarry is not accessible anymore but a new open pit in Dormettingen ~2 km NW of Dotternhausen offers excellent outcrop conditions. Litho- and biostratigraphy of the new section is well documented and calibrated to the old Dotternhausen section on subzone levels. Comparison of the two sites showed that sedimentology, geochemistry and faunal data are laterally constant. Palynological analysis of 59 outcrop samples from the Dormettingen section yielded an excellent quantitative data set of the Early Toarcian Posidonienschiefer sediments. Here we provide a high-resolution, multi-proxy study of this section including chemostratigraphy, particulate organic matter and palynology in order to understand the environmental conditions during the TOAE.Carbon isotopic study reveals a negative excursion during the TOAE, varying between -33.49&#8240; and -26.5&#8240;, with a negative shift in the Falciferum Zone (Elengatum, Exeratum and Elegans Subzone) concurrent with the dinoflagellate "blackout". &#160;The vegetation shows significant changes from a mixed assemblage of pollen and spores in the lower part of the section, to exclusively spore-bearing during the negative carbon isotope excursion. The isotopic signal, the marine dinoflagellate &#8220;blackout&#8221; and the changes in terrestrial vegetation indicate/document major palaeoenvironmental upheavals in both the marine and terrestrial realms.

Download Full-text