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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 108,
3045,
11 PP., 2003
doi:10.1029/2000JC000327
Organic-rich sediments in ventilated deep-sea environments: Relationship to climate, sea level, and trophic changes
Departement de Géologie et Océanographie, UMR-CNRS, Université de Bordeaux I, Talence, France
Oceanography, Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, Canada
Fachbereicht Geowissenschaften, Universität Bremen, Bremen, Germany
Dunstaffnage Marine Laboratory, Oban, UK
Sédimentologie et Diagenèse de la Matière Organique, UMR, Université d'Orléans, Orléans, France
Sédimentologie et Diagenèse de la Matière Organique, UMR, Université d'Orléans, Orléans, France
Departement de Géologie et Océanographie, UMR-CNRS, Université de Bordeaux I, Talence, France
Departement de Géologie et Océanographie, UMR-CNRS, Université de Bordeaux I, Talence, France
Sédimentologie et Géodynamique, UMR-CNRS, Université de Lille 1, Villeneuve d'Ascq ce, France
Institut Français du Pétrole, Rueil Malmaison, France
Departement de Géologie et Océanographie, UMR-CNRS, Université de Bordeaux I, Talence, France
Laboratoire d'Océanographie Dynamique et de Climatologie, Université Pierre et Marie Curie, Paris, France
Muséum National d'Histoire Naturelle, Paris, France
Sediments on the Namibian Margin in the SE Atlantic between water depths of ∼1000 and ∼3600 m are highly enriched in hydrocarbon-prone organic matter. Such sedimentation has occurred for more than 2 million years and is geographically distributed over hundreds of kilometers along the margin, so that the sediments of this region contain a huge concentrated stock of organic carbon. It is shown here that most of the variability in organic content is due to relative dilution by buried carbonates. This reflects both export productivity and diagenetic dissolution, not differences in either water column or bottom water anoxia and related enhanced preservation of organic matter. These observations offer a new mechanism for the formation of potential source rocks in a well-ventilated open ocean, in this case the South Atlantic. The organic richness is discussed in terms of a suite of probable controls including local wind-driven productivity (upwelling), trophic conditions, transfer efficiency, diagenetic processes, and climate-related sea level and deep circulation. The probability of past occurrences of such organic-rich facies in equivalent oceanographic settings at the edge of large oceanic basins should be carefully considered in deep offshore exploration.
Published 21 February 2003.
Citation: (2003), Organic-rich sediments in ventilated deep-sea environments: Relationship to climate, sea level, and trophic changes, J. Geophys. Res., 108(C2), 3045, doi:10.1029/2000JC000327.
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