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Recent sedimentation of organic matter along the SE Atlantic Margin : A key for understanding deep offshore petroleum source rocks.
François Baudin 1, Raphaël Blanke 1, 2, Laetitia Pichevin 3, J. Tranier 3, 4, Philippe Bertrand 3, Jean-Robert Disnar 2, Elisabeth Lallier-Vergès 2, F. Van Buchem 4, Mohammed Boussafir 2, François Frohlich 5, Luis Martinez 6, J. Giraudeau 3, Fatima Laggoun-Défarge 2, Didier Kéravis 2

Classical views for the deposition of organic-rich sediments in deep-sea environments invoke two principal types of oceanographic and sedimentologic settings. The first is confined basins in which stratified oxygen depleted waters lead to anoxic preservation of organic matter in the water column and in underlying sediments (Demaison and Moore, 1980). The second is an open ocean setting where the episodic mass transfers due to slope sediment instability lead to the rapid burial of outer-shelf and upper slope-derived organic matter and its consequent preservation due to limited oxic or anoxic degradation (Stow, 1987). Other studies have shown, however, that organic matter in modern deep-sea sediments may occur in high amounts where oxygen is not significantly depleted (Pedersen and Calvert, 1990). Recent studies have demonstrated that highly biological productive areas, such as the upwelling zones associated to the Benguela Current in S-E Atlantic, may deliver sufficient quantity of organic material to (1) outbalance the degradative capacity of the water column and (2) sustain the formation of organic-rich sediments even in deep and oxygenated conditions (Bertrand et al., 2003). It appears that the S-E Atlantic margins provide a good example for revisiting the sedimentology of organic matter in deep water environments in the frame of the GDR Marges Continentales. This may have important implications for a better understanding of the distribution of ancient source rocks in deep offshore petroleum systems (Huc et al., 2001; Bertrand et al., 2003).
1:  Paléobiodiversité et paléoenvironnements
CNRS : UMR5143 – Université Pierre et Marie Curie (UPMC) - Paris VI
2:  Institut des Sciences de la Terre d'Orléans (ISTO)
CNRS : UMR6113 – INSU – Université d'Orléans
3:  Environnements et Paléoenvironnements OCéaniques (EPOC)
CNRS : UMR5805 – INSU – Université Sciences et Technologies - Bordeaux I – École Pratique des Hautes Études [EPHE] – Observatoire Aquitain des Sciences de l'Univers
4:  IFP Energies Nouvelles (IFPEN)
IFP Energies Nouvelles
5:  Laboratoire de minéralogie du Muséum National d'Histoire Naturelle (LMMNHN)
CNRS : FRE2456
6:  Géologie et gestion des ressources minérales et énergétiques (G2R)
CNRS : UMR7566 – INSU – Université Henri Poincaré - Nancy I – Institut National Polytechnique de Lorraine (INPL)
Sciences of the Universe/Earth Sciences/Geochemistry
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