georefid:2012-043589SEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContact2013-07-08T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.2204/iodp.proc.308.215.2012<gco:CharacterString>Expedition 308 synthesis; overpressure, consolidation, and slope stability on the continental slope of the Gulf of Mexico</gco:CharacterString>2012-01-01publicationgeorefid:2012-043589doi:10.2204/iodp.proc.308.215.2012Flemings, Peter B.University of Texas at Austin, Department of Geological Sciences, Austin, TX, United StatesauthorJohn, Cedric M.Albert-Ludwigs-Universitaet Freiburg, GermanyauthorBehrmann, Jan H.University of California-Santa Cruz, United StatesauthorIODP Management International, Washington, DC, United StatespublisherdocumentDigitalIn: Flemings, Peter B., Behrmann, Jan H., John, Cedric M., Iturrino, Gerardo J., Aizawa, Yasutaka, Nguyen Thi Thanh Binh, De Silva, Neil, Dugan, Brandon, Edeskar, Tommy M., Franke, Christine, Gay, Aurelien, Gilhooly, William Patrick, III, Gutierrez-Pastor, Julia, Jiang Shaoyong, Li Qianyu, Long, Hui, Moore, J. Casey, Nunoura, Takuro, Pirmez, Carlos, Reichow, Marc, Sawyer, Derek E., Schneider, Julia, Shumnyk, Anatoliy V., Suzuki, Takahiro, Takano, Yoshinori, Urgeles, Roger, Yamamoto, Yuzuru, Zampetti, Valentina, Proceedings of the Integrated Ocean Drilling Program; Gulf of Mexico hydrogeology; Expedition 308 of the riserless drilling platform from Mobile, Alabama, to Balboa, Panama; Sites U1319-U1324, 30 May-8 July 2005308Integrated Ocean Drilling Program Expedition 308 quantified the coupling between sedimentation, consolidation, overpressure, fluid flow, and slope instability in continental margin settings. We summarize and synthesize peer-reviewed hydrogeologic studies published since the end of Expedition 308 that focus on Expedition 308 sites drilled in Ursa Basin: Sites U1322, U1323, and U1324. There is a rich stratigraphic complexity in the Ursa Basin, deepwater Gulf of Mexico. The sandstone-prone Blue Unit is a permeable aquifer overlain by mudstone-prone leveed-channel deposition. Multiple mass transport deposits, each densified relative to surrounding material, are present. Eight coeval surfaces mapped across the drilling transect span approximately 70 ka to present. Sedimentation rates were >10 mm/y at Site U1324. In situ penetrometer measurements document severe overpressures that begin at or near the seafloor and extend to the base of the drilled holes. Uniaxial consolidation experiments quantified the compression behavior of the sediments and provided an approach to predict pressure from porosity. Laboratory analysis of permeability and compressibility document that the coefficient of consolidation (hydraulic diffusivity) of Ursa Basin mudstones is 10 (super -8) m (super 2) /s over the effective stresses encountered during drilling at Ursa Basin (0.1 to 5 MPa). This low and constant value for the coefficient of consolidation is responsible for the presence of high overpressure very near the seafloor. Although permeability is very high, the sediments are also highly compressible. Forward modeling of Ursa Basin sediments shows that overpressure near the seafloor is reasonable given the rock properties and sedimentation rates that are observed. Modeling also illustrates that flow is driven laterally along an underlying aquifer, the Blue Unit. Soon after Blue Unit deposition, lateral flow induced submarine landslides. Later in the evolution of this system, overpressure may have preconditioned the slope to failure by earthquakes of magnitude 5.0.completedOceanographyAtlantic Oceanboreholescontinental margincoresExpedition 308experimental studiesGulf of MexicoIntegrated Ocean Drilling ProgramIODP Site U1322IODP Site U1323IODP Site U1324laboratory studieslithostratigraphyLouisianamarine sedimentsmass movementsmodelsNorth Atlanticnorthern Gulf of Mexicooverpressurepermeabilitypore pressureporositysedimentary rockssedimentsstratigraphic unitsUnited StatesUrsa Basinwell logsurn:org.iodp:exp:308urnlargerWorkCitationcampaignurn:org.iodp:exp:308:site:U1322urnlargerWorkCitationstudyurn:org.iodp:exp:308urnlargerWorkCitationcampaignurn:org.iodp:exp:308:site:U1323urnlargerWorkCitationstudyurn:org.iodp:exp:308urnlargerWorkCitationcampaignurn:org.iodp:exp:308:site:U1324urnlargerWorkCitationstudyurn:org.iodp:exp:308urnlargerWorkCitationcampaignEnglishgeoscientificInformation-89.0800-89.010028.050028.0600application/pdfunknownSEDIS Publication Catalogueana.macario@awi.dehttp://sedis.iodp.org/pub-catalogue/informationpointOfContacthttp://publications.iodp.org/proceedings/308/ERR/CHAPTERS/308_215.PDFdownload