Geo-Marine Letters

, Volume 25, Issue 5, pp 281-292

First online:

ROV study of a giant pockmark on the Gabon continental margin

  • H. OndréasAffiliated withDépartement Géosciences, IFREMER Email author 
  • , K. OluAffiliated withDépartement Environnement Profond, IFREMER
  • , Y. FouquetAffiliated withDépartement Géosciences, IFREMER
  • , J. L. CharlouAffiliated withDépartement Géosciences, IFREMER
  • , A. GayAffiliated withLaboratoire GTS, place Bataillon, Université Montpellier II
  • , B. DennielouAffiliated withDépartement Géosciences, IFREMER
  • , J. P. DonvalAffiliated withDépartement Géosciences, IFREMER
  • , A. FifisAffiliated withDépartement Environnement Profond, IFREMER
  • , T. NadaligAffiliated withLaboratoire de Microbiologie et de Génétique, Université Louis Pasteur, CNRS-FRE 2326, Institut de Botanique
    • , P. CochonatAffiliated withDépartement Géosciences, IFREMER
    • , E. CauquilAffiliated withTOTAL
    • , J. F. BourilletAffiliated withDépartement Géosciences, IFREMER
    • , M. Le MoigneAffiliated withDirection Environnement Littoral, IFREMER
    • , M. SibuetAffiliated withDépartement Environnement Profond, IFREMER

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


A giant, 800-m wide pockmark, called Regab, was discovered along the Equatorial African margin at 3160-m water depth and was explored by remote operated vehicle (ROV) as part of the Zaiango (1998–2000) and Biozaire (2001–2003) projects carried out conjointly by TOTAL and a number of French research institutes. A microbathymetric map obtained using the ROV sensors shows that the pockmark actually consists of a cluster of smaller pockmarks aligned N70 along a 15-m deep depression. Methane was recorded all over the pockmark, the highest values along the axis of the depression where massive carbonate crusts and dense seep communities were also found. Several faunal species belong to the Vesicomyidae and Mytilidae bivalve families, as well as to Siboglinidae (Vestimentifera) tubeworms. Preliminary analyses confirm their association with symbiotic bacteria, thus documenting their dependence on fluid seeps. The pockmark appears to be related to an infilled channel, visible on the seismic data 300 m below the seafloor, which may act as a reservoir for biogenic fluids supplied to the trap from the surrounding sediments.