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Repeated fluid expulsions during events of rapid sea-level rise in the Gulf of Lion, western Mediterranean Sea
Auteur(s) : GAY, Aurelien Cavailhes, Thibault Grauls, Dominique Marsset, Bruno Marsset, Tania
Auteurs secondaires : Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC) ; Observatoire aquitain des sciences de l'univers (OASU) ; Université Sciences et Technologies - Bordeaux 1 - Institut national des sciences de l'Univers (INSU - CNRS) - Centre National de la Recherche Scientifique (CNRS) - Université Sciences et Technologies - Bordeaux 1 - Institut national des sciences de l'Univers (INSU - CNRS) - Centre National de la Recherche Scientifique (CNRS) - École pratique des hautes études (EPHE) - Centre National de la Recherche Scientifique (CNRS) Consulting, Pau Unité de recherche Géosciences Marines (Ifremer) (GM) ; Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)

Éditeur(s) : HAL CCSD Société Géologique de France
Résumé : Based on a High-Resolution 3D seismic block acquired in the Gulf of Lion in 2004–2005 we investigated fluid pipes and pockmarks on the top of the interfluve between the Hérault canyon and the Bourcart canyon both created by turbidity currents and gravity flows from the shelf to the deep basin in the north-western Mediterranean Sea. Combining the geometry of the potential fluid pipes with the induced deformation of surrounding sediments leads then to the ability to differentiate between potential fluid sources (root vs source) and to better estimate the triggering mechanisms (allochtonous vs. autochtonous cause). We linked together a set of derived attributes, such as Chaos and RMS amplitude, to a 3D description of pipes along which fluids may migrate. As previously shown in other basins, the induced deformation, creating cone in cone or V-shaped structures, may develop in response to the fluid pipe propagation in unconsolidated sediments in the near surface. The level at the top of a cone structure is diachronous. It means that stratigraphic levels over this surface are deformed at the end of the migration. They collapse forming a depression called a pockmark. These pipes are the result of repeated cycles of fluid expulsion that might be correlated with rapid sea-level rise instead of sediment loading. The most recent event (MIS 2.2 stage) has led to the formation of a pockmark on the modern seafloor. It has been used as a reference for calculating the effect of a rapid sea-level rise on fluid expulsion. As all physical and geometrical parameters are constrained, we were able to define that a + 34 m of sea level rise may account for triggering fluid expulsion from a very shallow silty-sandy layer at 9 m below seafloor since the last glacial stage. This value is consistent with a sea level rise of about 102 m during this period. This study shows that the episodic nature of fluid release resulted from hydromechanical processes during sea-level rise due to the interactivity between high pressure regimes and principal in situ stresses.
ISSN: 0037-9409

hal-01667241
https://hal.archives-ouvertes.fr/hal-01667241
DOI : 10.1051/bsgf/2017190

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