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 - Géosciences Marines
2 LETG - Littoral, Environnement, Télédétection, Géomatique UMR 6554
3 CSTJF - Centre scientifique et Technique Jean Feger
4 IFREMER - Institut Français de Recherche pour l'Exploitation de la Mer
5 TOTAL
6 IFPEN - IFP Energies nouvelles

Inactive and mostly elongated pockmarks of 100-200 m in dimension were recently discovered on the South Aquitaine Margin continental slope. They are distributed at water depths greater than 350 m in both interfluve and sediment wave areas, and are strongly controlled by the sedimentary morphology and architecture. Water column and seafloor backscatter and sub-bottom profiler data do not exhibit present-day or past gas evidence, e. g. massive and continuous gas releases at the seabed and fossil methane-derived authigenic carbonates. It is thus proposed that the pockmarks originated from a shallow source and result from relatively recent and short-duration gas or water expulsion events. Former near-bottom currents may have contributed to the elongation of these WNW-ESE oriented pockmarks whereas present-day weaker near-bottom currents may induce upwelling, contributing to the maintenance of the elongated shapes of the pockmarks.

Keywords: GIS; Aquitaine slope; seabed morphology; fluid; currents; Pockmark; 28 Pockmark; currents 29

Domains: Earth Sciences

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, 2017, 349 (8), pp.391 - 401. ⟨10.1016/j.crte.2017.10.003⟩. ⟨hal-01704712⟩