Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model
A reaction-transport model was used to infer the long-term evolution of anaerobic organic matter degradation in Cretaceous black shales from the distribution of authigenic barite in sediments drilled at Demerara Rise (ODP Leg 207, Site 1258). In these sediments, sulfate-reduction and methanogenesis...
Published in: | Geochimica et Cosmochimica Acta |
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2009
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Online Access: | https://hdl.handle.net/1983/8bbc50be-a8fe-4e87-a828-be4a4562baef https://research-information.bris.ac.uk/en/publications/8bbc50be-a8fe-4e87-a828-be4a4562baef https://doi.org/10.1016/j.gca.2009.01.018 http://www.sciencedirect.com/science/article/pii/S0016703709000477 |
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ftubristolcris:oai:research-information.bris.ac.uk:publications/8bbc50be-a8fe-4e87-a828-be4a4562baef 2024-01-28T10:07:51+01:00 Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model Arndt, S. Hetzel, A Brumsack, H.-J. 2009-04 https://hdl.handle.net/1983/8bbc50be-a8fe-4e87-a828-be4a4562baef https://research-information.bris.ac.uk/en/publications/8bbc50be-a8fe-4e87-a828-be4a4562baef https://doi.org/10.1016/j.gca.2009.01.018 http://www.sciencedirect.com/science/article/pii/S0016703709000477 eng eng info:eu-repo/semantics/restrictedAccess Arndt , S , Hetzel , A & Brumsack , H-J 2009 , ' Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model ' , Geochimica et Cosmochimica Acta , vol. 73 , no. 7 , pp. 2000 - 2022 . https://doi.org/10.1016/j.gca.2009.01.018 article 2009 ftubristolcris https://doi.org/10.1016/j.gca.2009.01.018 2024-01-04T23:35:27Z A reaction-transport model was used to infer the long-term evolution of anaerobic organic matter degradation in Cretaceous black shales from the distribution of authigenic barite in sediments drilled at Demerara Rise (ODP Leg 207, Site 1258). In these sediments, sulfate-reduction and methanogenesis are the major pathways of organic matter decomposition and the depth-distribution of authigenic barite serves as an indicator for the temporal evolution of the sulfate–methane transition zone (SMTZ), the strength of the biogenic methane flux and, ultimately, the organic matter reactivity in the black shales over geological timescales. Organic matter degradation is described according to the reactive continuum model approach and parameters values are determined by inverse modeling, based on present-day porewater and authigenic barite profiles. Fully transient simulations were performed over a period of 100 Myrs and indicate that important features of the biogeochemical dynamics are associated to changes in the boundary forcing. Hiatuses in sediment accumulation rate result in quasi-steady-state conditions and lead to distinct accumulations of authigenic barites in the SMTZ. The inversely determined parameters reveal that the reactivity of the organic matter was already low (apparent first order rate constant ) at the time of its deposition in the Cretaceous. The geochemical characteristics of sediments drilled at Demerara Rise, as well as the presence of specific biomarkers, suggest that this low reactivity is most likely due to the euxinic palaeo-conditions which favored the sulfurization of the organic matter. Simulation results predict average initial organic carbon contents between 8.1 and 9.5 wt%, implying a high preservation efficiency of the organic matter (between 79% and 89%). Calculated mass accumulation rates (between 0.43 and 0.5 ) compare well with estimations for the western basin of the Cretaceous southern North Atlantic. Simulation results thus indicate that the enhanced preservation of organic matter ... Article in Journal/Newspaper North Atlantic University of Bristol: Bristol Research Western Basin Geochimica et Cosmochimica Acta 73 7 2000 2022 |
institution |
Open Polar |
collection |
University of Bristol: Bristol Research |
op_collection_id |
ftubristolcris |
language |
English |
description |
A reaction-transport model was used to infer the long-term evolution of anaerobic organic matter degradation in Cretaceous black shales from the distribution of authigenic barite in sediments drilled at Demerara Rise (ODP Leg 207, Site 1258). In these sediments, sulfate-reduction and methanogenesis are the major pathways of organic matter decomposition and the depth-distribution of authigenic barite serves as an indicator for the temporal evolution of the sulfate–methane transition zone (SMTZ), the strength of the biogenic methane flux and, ultimately, the organic matter reactivity in the black shales over geological timescales. Organic matter degradation is described according to the reactive continuum model approach and parameters values are determined by inverse modeling, based on present-day porewater and authigenic barite profiles. Fully transient simulations were performed over a period of 100 Myrs and indicate that important features of the biogeochemical dynamics are associated to changes in the boundary forcing. Hiatuses in sediment accumulation rate result in quasi-steady-state conditions and lead to distinct accumulations of authigenic barites in the SMTZ. The inversely determined parameters reveal that the reactivity of the organic matter was already low (apparent first order rate constant ) at the time of its deposition in the Cretaceous. The geochemical characteristics of sediments drilled at Demerara Rise, as well as the presence of specific biomarkers, suggest that this low reactivity is most likely due to the euxinic palaeo-conditions which favored the sulfurization of the organic matter. Simulation results predict average initial organic carbon contents between 8.1 and 9.5 wt%, implying a high preservation efficiency of the organic matter (between 79% and 89%). Calculated mass accumulation rates (between 0.43 and 0.5 ) compare well with estimations for the western basin of the Cretaceous southern North Atlantic. Simulation results thus indicate that the enhanced preservation of organic matter ... |
format |
Article in Journal/Newspaper |
author |
Arndt, S. Hetzel, A Brumsack, H.-J. |
spellingShingle |
Arndt, S. Hetzel, A Brumsack, H.-J. Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model |
author_facet |
Arndt, S. Hetzel, A Brumsack, H.-J. |
author_sort |
Arndt, S. |
title |
Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model |
title_short |
Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model |
title_full |
Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model |
title_fullStr |
Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model |
title_full_unstemmed |
Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model |
title_sort |
evolution of organic matter degradation in cretaceous black shales inferred from authigenic barite: a reaction-transport model |
publishDate |
2009 |
url |
https://hdl.handle.net/1983/8bbc50be-a8fe-4e87-a828-be4a4562baef https://research-information.bris.ac.uk/en/publications/8bbc50be-a8fe-4e87-a828-be4a4562baef https://doi.org/10.1016/j.gca.2009.01.018 http://www.sciencedirect.com/science/article/pii/S0016703709000477 |
geographic |
Western Basin |
geographic_facet |
Western Basin |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Arndt , S , Hetzel , A & Brumsack , H-J 2009 , ' Evolution of Organic Matter Degradation in Cretaceous Black Shales Inferred from Authigenic Barite: A Reaction-Transport Model ' , Geochimica et Cosmochimica Acta , vol. 73 , no. 7 , pp. 2000 - 2022 . https://doi.org/10.1016/j.gca.2009.01.018 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1016/j.gca.2009.01.018 |
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Geochimica et Cosmochimica Acta |
container_volume |
73 |
container_issue |
7 |
container_start_page |
2000 |
op_container_end_page |
2022 |
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1789336015705473024 |