Overpressure within upper continental slope sediments from CPTU data,Gulf of Lion,NW Mediterranean Sea |
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| Authors: | S Lafuerza N Sultan M Canals J Frigola S Berné G Jouet M Galavazi F J Sierro |
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| Institution: | 1.GRC Geociències Marines, Departament d’Estratigrafia, Paleontologia i Geociències Marines,Universitat de Barcelona,Barcelona,Spain;2.Institut Fran?ais de Recherche pour l’Exploitation de la Mer (IFREMER),Plouzané,France;3.Université de Perpignan,Perpignan, Cedex,France;4.Fugro Engineers B.V,Leidschendam,The Netherlands;5.Departamento de Geología,Universidad de Salamanca,Salamanca,Spain |
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| Abstract: | Data from in situ piezocone tests (CPTU) and laboratory analyses are utilized for the interpretation of the stress history
of Quaternary sedimentary sequences in the upper continental slope of the Gulf of Lion, northwestern Mediterranean Sea. A
CPTU based preconsolidation pressure profile referenced to the current effective stress indicates that the deposit is underconsolidated
from 12 meters below the seafloor (mbsf) down to at least 150 mbsf. Excess pore pressure below 12 mbsf is further supported
by results from oedometer and dissipation tests. Subseafloor pockmarks and indications of free gas in seismic reflection profiles
reveal four main overpressure sources (SI–SIV) with overpressure ratios >0.3 at subseafloor depths coinciding with levels
where the dominantly silty-clayey sediment contains increased proportions of sand. We relate the excess pore pressure related
to free gas due to gas exsolution processes and sea level variations driven by Pleistocene sea level changes. |
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| Keywords: | Stress history Preconsolidation pressure Overpressure Continental slope Gulf of Lion |
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