Distribution of the organic matter in the channel-levees systems of the Congo mud-rich deep-sea fan (West Africa). Implication for deep offshore petroleum source rocks and global carbon cycle
|Author(s)||Baudin Francois1, Disnar Jean-Robert2, Martinez Philippe3, Dennielou Bernard4|
|Affiliation(s)||1 : Univ Paris 06, CNRS, UMR ISTeP 7193, Equipe Evolut & Modelisat Bassins Sedimentaires, F-75252 Paris 05, France.
2 : Univ Orleans, CNRS, Univ Tours, Inst Sci Terre Orleans,UMR 6113, F-45071 Orleans, France.
3 : Univ Bordeaux 1, CNRS, UMR 5805, EPOC, F-33405 Talence, France.
4 : IFREMER, Dept Geosci Marines, F-29280 Plouzane, France.
|Source||Marine And Petroleum Geology (0264-8172) (Elsevier Sci Ltd), 2010-05 , Vol. 27 , N. 5 , P. 995-1010|
|WOS© Times Cited||48|
|Keyword(s)||South-East Atlantic, Turbidites, Carbon isotopes, Nitrogen isotopes, Biomarkers, Source rocks|
|Abstract||The quantity and the source of organic matter preserved in the Recent turbiditic channel-levees systems around 4000 m-depth off the Congo River were determined using bulk geochemical approaches (Rock-Eval, elemental and isotopic analyses) as well as molecular and optical analyses on selected samples. These mud-rich sediments contain high amount of organic matter (3% Corg on average), the origin of which is a mixture of terrestrial higher-plant debris and deeply oxidized phytoplanktonic material. Although the relative contribution of continental source versus marine source of the organic matter cannot be precisely quantified, the continental fraction appears significant (at least 70-80%) especially for such depths and distances from the coast. The organic matter distribution appears very homogeneous at different scales, from the single turbiditic event to the entire levee, and changes in accumulation rates have a little impact on the quantity and quality of preserved organic matter. With a petroleum potential around 4.5 kg HC per t rock, the fine-grained turbiditic sediments in the Congo deep-sea system could be regarded as an analog of gas-prone source rocks for the deep offshore of the Atlantic margins. Finally, the Congo deep-sea turbiditic system is a major conveyor of organic carbon to the deep ocean. Further studies are needed to evaluate the efficiency of such systems for the storage of continental organic matter into the deep ocean in relation to sea-level and climatic changes. (C) 2010 Elsevier Ltd. All rights reserved.|