29th April - 9th May ; 4th - 29th June
In the bay of Concarneau, over nearly 40 km², the muddy bottom presents a multi-metric to decametric crater facies of pockmarks a few metres deep. Pockmarks are linked to fluids present in the sediment, seeping to the surface. Several oceanographic expeditions have enabled to map this system and study the nature of seeping fluids (gas in the water column and sometimes up to the atmosphere).
This field of pockmarks has probably been active for a very long time and covers a corridor 2 km wide between the Pointe de la Jument at a depth of 20 m and the north-west of the plateau of La Basse Jaune at a depth of 40 m.
The SYPOCO project, supported by the Marine Geoscience Research Unit at Ifremer, in collaboration with the Deep Sea Environment Research Unit, aims at understanding the functioning of these structures and the fluid system sustaining them:
- What are the origins and nature of the fluids seeping from the sediments in the bay?
- What are the migration paths to the surface from the bed and up to the water column?
- What are the trigger mechanisms causing the destabilization of the seabed and formation of pockmarks?
- What are the dynamics/evolution of this pockmark field?
- What are the nature and structure of the sediment accumulated in the bay over the last several to tens of thousands of years?
To address these issues, SYPOCO has been structured in several legs:
- LEG 1 : Cartography of the seabed and explusion of gas bubbles into the water column - 28/04 - 09/05/2018
- LEG 2 : Insight into the sub surface and chemistry of the waters around the pockmarks - 05-09/06/2018
- LEG 3 : Structure of the sedimentary fill, nature of deposits and geochemistry of sediments - 11-16/06/2018
- LEG 4 : Seabed instrumentation for long-term recording of variations in the sediment - 17-22/06/2018
- LEG 5 : In situ measurements of degassing on contact with the seabed
We have decided to communicate this oceanographic expedition through “comic strip” photographs which will be available progressively for each leg. The whole SYPOCO mission is now available !