Direct access to the 2018 marine cruises, by clicking below:
Marine expedition GAZCOGNE3
GAZCOGNE project’s leader: Stéphanie Dupré (REM/GM/LAD)
Onboard team: 10 people (REM/GM)
Place: Aquitaine Basin
Period: 27th August-3rd September
Research vessel: Thalassa
Equipment: Multichannel seismic streamer (48 traces @ 3.125 m, Ifremer/REM/GM) combined with an airgun source (mini-GI 13 inches3, Genavir) and a Sparker source (SIG 2000)
The primary objective of the marine expedition GAZCOGNE3 is to constrain the in-depth geometry of the microbial fluid system of the Aquitaine Shelf (Dupré et al. 2014; Pierre et al. 2017; Ruffine et al. 2017). To achieve this, multichannel seismic equipment designed for submarine shelf studies were deployed. Indeed, available data from previous marine expeditions (ITSAS I, BOBGEO2, GAZCOGNE1) in the area are not able to properly image the uppermost sediments as well as the fluid system in its in entirety. This is partly due to the presence of indurated rocks (methane-derived authigenic carbonates) at the seafloor and in sub-surface within the sedimentary pile. These carbonates are causing strong amplitude anomalies in seismics and strongly prevent the signal from penetrating underneath.
The new multichannel seismic streamer from the Marine Geosciences Unit (Ifremer) dedicated to shelf studies (48 traces with an inter trace of 3.125 m) is particularly well suited to explore the Aquitaine Shelf fluid system. During the marine expedition GAZCOGNE3 (2018) onboard the R/V Thalassa, this multichannel streamer was coupled with an air gun (mini-GI 13 inches3, Genavir). This type of source is used for the stability of its signature and its energy (required because of the presence of hard substrates). A second seismic source (Sparker) was however deployed for its high-resolution quality, and this, along a few selected profiles.
In total 320 nm long seismic lines were acquired during GAZCOGNE3 thanks to very good weather conditions for the end of August. Newly acquired seismic data once processed onland are going to provide much better images the roof of the fluid system, and possibly of the entire fluid system depending on its vertical extent. Gas and carbonate distributions could be therefore better defined thanks to high-resolution seismic imaging and sediment characterisation by velocity analyses.
In addition to the seismic dataset, complementary data were acquired with the hull-mounted echosounders of the R/V Thalassa : ADCP (38 kHz) and wide-band single beam echosounder EK80 (18, 38, 70, 120, 200 and 333 kHz) for water column imagery, and a sub-bottom profiler echosounder (1.5-6.5 kHz) for imagery of the surface sedimentary layers.
SYPOCO – The sedimentary SYstem and POckmarks of the bay of COncarneau
Collaboration: SHOM, Université de Nantes, Intechmer, Phares et Balises
Position: Bay of Concarneau
Dates: 28th April-9th May ; 4th-29th June
Research vessel: R/V Thalia
The Bay of Concarneau is a natural laboratory for studying the migration of fluids in the sediment up through the water column: In the middle of the Bay, several thousands of pockmarks were identified at the surface around fifteen years ago.
The SYPOCO expedition on the Thalia aims to spatially and temporally understand the dynamics of the formation of pockmarks by addressing the origin and nature of the fluids (methane cycle) seeping from the sediment; the migratory paths they use up to the surface of the seabed; the trigger mechanisms causing destabilization of the seabed and formation of pockmarks; the dynamics of this field of pockmarks over time; and lastly, the nature and structure of the sediment accumulated in the bay over the last several to tens of thousands of years, and the network of faults fracturing the subsurface of the Armoricaine region.
Expedition leader: Marie-Anne Cambon-Bonavita (REM-EEP-LMEE)
Collaborations: UPMC AMEX ; MIO ; Universities of Lille and Hamburg ; MNHN
Position: Mid-Atlantic Ridge, permit area on sites of TAG and Snake Pit
Dates: from 27th January to 11th March 2018
Research Vessel: R/V Pourquoi pas?
Pluridisciplinary integrated programme on the active hydrothermal sites of TAG and Snake Pit on the Mid-Atlantic Ridge with a focus on the inactive and peripheral zones. Our studies aimed at comparing geological, geochemical, microbiological and biological data, integrating global approaches and more targeted approaches on selected animals (Rimicaris exoculata, Rimicaris chaceiet Bathymodiolus puteoserpentis).
Our main objectives :
- Specifically characterize the geochemical context of the habitats of the two sites and their peripheral zones, the plume and their geomicrobiological interactions ;
- Complete the biodiversity study of the sites and pursue the inventory and addition to the collection of species of the deep ocean and describe the assemblies in connection with their habitat and their succession in time and space ;
- Complete the study of the life cycle of founder species, mainly Rimicaris sp., via in situ research on the larvae stages, test the seasonality of reproduction and distribution of individuals and use in vivo experimentation to assess their capacity to adapt and disperse and to infer patterns of connectivity ;
- Improve the identification of the limits of the functioning of symbioses and their sustainability.