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

Guillaume Michel; Stéphanie Dupré; Agnès Baltzer; Axel Ehrhold; Patrice Imbert; Mathilde Pitel; Benoît Loubrieu; Carla Scalabrin; Pascal Lazure; Louis Marié; Jean-Baptiste Geldof; Eric Deville

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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Journal articles

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Sciences of the Universe [physics] / Earth Sciences

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