Pockmarks on the South Aquitaine Margin continental slope: The seabed expression of past fluid circulation and former bottom currents
2017
Michel, Guillaume | Dupre, Stephanie | Baltzer, Agnes | Ehrhold, Axel | Imbert, Patrice | Pitel, Mathilde | Loubrieu, Benoit | Scalabrin, Carla | Lazure, Pascal | Marie, Louis | Geldof, Jean-baptiste | Deville, Eric
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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