Pockmarks on the South Aquitaine Margin continental slope: the seabed expression of past fluid circulation and bottom currents

Guillaume Michel 1 Stéphanie Dupré 1 Agnès Baltzer 2 Axel Ehrhold 1 Patrice Imbert 3 Mathilde Pitel 1 Benoît Loubrieu 1 Carla Scalabrin 1 Pascal Lazure 4 Louis Marié 4 Jean-Baptiste Geldof 5 Eric Deville 6
1 GM - Unité de recherche Géosciences Marines (Ifremer)
2 LETG - Littoral, Environnement, Télédétection, Géomatique UMR 6554
3 CSTJF - TOTAL-Scientific and Technical Center Jean Féger
4 IFREMER - Institut Français de Recherche pour l'Exploitation de la Mer
5 TOTAL
6 IFPEN - IFP Energies nouvelles
Abstract : 18 Inactive pockmark.s of 100-200 m in diameter recently discovered on the South Aquitaine 19 Margin continental slope are present between 350 m and 1150 m water depth in both 20 interfluve and sediment wave areas. Water column and seafloor back.scatter and sub-bottom 21 profiler data do not exhibit present-day or past gas evidence, e.g. massive and continuous gas 22 relcases at the seabed a.J.d fossil · methane-derived atî 1.higenic carbonates. To discrirninate 23 hypothetical pockmark populations, e.g. due to the nature of the involved fluids (gas, water), a 24 detailed study of pockmark morphological characteristics based on a Geographical 25 Information System was performed. Pockmarks are divided in two groups from sub-circular l 26 to elongated shapes. It is proposed that pockmark elongation may mainly result from the 27 dynamics of near bottom currents, inducing upwelling, having thus reshaped the initially-28 formed subcircular pockmarks. 29
Keywords : GIS Aquitaine slope seabed morphology fluid currents Pockmark
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Guillaume Michel, Stéphanie Dupré, Agnès Baltzer, Axel Ehrhold, Patrice Imbert, et al.. Pockmarks on the South Aquitaine Margin continental slope: the seabed expression of past fluid circulation and bottom currents. Comptes Rendus Géoscience, Elsevier Masson, 2017, 349 (8), pp.391 - 401. ⟨10.1016/j.crte.2017.10.003⟩. ⟨hal-01704712⟩

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