georefid:2004-078148SEDIS Publication Catalogue

ana.macario@awi.de

http://sedis.iodp.org/pub-catalogue/informationpointOfContact2011-06-23T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=2004-0781482003-01-01publicationgeorefid:2004-078148Gay, A.Universite de Lille I, Laboratoire Sedimentologie et Geodynamique, Villeneuve d'Ascq, FranceauthorLopez, M.University of Adelaide, AustraliaauthorCochonat, P.Aberswyth University of Wales, United KingdomauthorSultan, N.University of Brunei Darussalam, BruneiauthorCauquil, E.Institut Francais de Recherche et d'Exploitation de la Mer, FranceauthorBrigaud, F.Total-Fina-Elf, FranceauthorGeological Society of London, London, United KingdompublisherdocumentHardcopyIn: van Rensbergen, Pieter (editor), Hillis, Richard R. (editor), Maltman, Alex J. (editor), Morley, Christopher K. (editor), Subsurface sediment mobilization216173-189Pockmarks on the slope of the Lower Congo Basin are distributed along a meandering band on seafloor coincident with a shallow buried palaeochannel imaged from the 3D-seismic database. Each pockmark originates systematically at the channel-levee interface and the seafloor expression of the palaeochannel's sinuosity is mimicked by the sinuous trend of pockmarks. 3D-seismic on the slope, calibrated by biostratigraphic data from cores of the Leg ODP 175, indicate a seaward decrease of the sedimentation rate. We suggest that this condition induces a differential loading of the hemipelagic cover over the palaeochannel and propose a model for episodic dewatering of fluids trapped in the buried turbiditic channel. The consequence is a fluid flow caused by a longitudinal pressure gradient along the buried channel. A hydromechanical model proposed for the formation of shallow pockmarks indicates that the sedimentation rate cannot generate the overpressure required for pockmark formation on the seafloor. Therefore, it is suggested that hydrocarbon migration from deeper overpressured reservoirs is added to the pore fluid pressure in the shallow subsurface sediments. Horizontal drainage by the turbiditic palaeochannel and vertical migration along many vertical conduits (seismic chimneys) probably initiated at shallow subbottom depth. It is concluded that these shallow processes have important implications for fluid migration from deeply buried hydrocarbon reservoirs.completedSedimentary petrologyApplied geophysicsAtlantic Oceanbottom-simulating reflectorsburialburied channelsconsolidationdepositional environmentdiapirsfluvial featuresgas hydratesgeophysical methodsgeophysical profilesgeophysical surveyshigh-resolution methodsintrusionsLeg 175Lower Congo Basinmarine environmentOcean Drilling ProgramODP Site 1076overpressurepipespockmarkspore pressurereflection methodsreservoir rockssedimentary structuressedimentationsedimentation ratesseepageseismic methodsseismic profilesseismic stratigraphyslope environmentsoft sediment deformationSouth Atlanticsubmarine environmentsurveysturbiditeurn:org.iodp:exp:175urnlargerWorkCitationcampaignurn:org.iodp:exp:175:site:1076urnlargerWorkCitationstudyurn:org.iodp:exp:175urnlargerWorkCitationcampaignEnglishgeoscientificInformation9.300011.3000-6.3000-4.3000Includes appendix