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

Abstract : 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.
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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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