The National Research Vessel, the RV Celtic Explorer, arrived in Cork Harbour on Sunday June 3rd, just a day before the Cork City Marathon, at the end of another marathon leg of this years INFOMAR (INtegrated Mapping FOr the Sustainable Development of Ireland’s MARine Resource) survey.
New discoveries by Geological Survey of Ireland and Marine Institute scientists onboard include a major glacial moraine and a large trench just 300-400 metres off the Dingle coast.
The survey data build on existing coverage achieved over the last three years off the south west coast. The area surveyed covered a further 1,212 km2, achieved by sailing 3,967km in 17 days. Almost 200 sediment samples were collected from a series of ten defined seafloor regions for geochemistry, biology and particle size analysis.
The identification of ten seafloor sediment regions suggests the presence of a variety of different seafloor ecosystems. A series of previously unknown seafloor features have also been discovered, including an offshore ridge extending in a north westerly direction off the north shore of the Dingle peninsula. The ridge is five metres high and one kilometre wide with a traceable length of over ten kilometres. This is a notable discovery believed to be a glacial feature, possibly a terminal moraine, which marks the front of a glacier where rock debris which have been carried along by glacial melt water are deposited. The ridge has been dubbed the “Slava Ridge”, after the scientist on the survey who first noted it.
Another prominent feature of the area is a 500 to 600m wide trench-like feature, dubbed the “Brendan Trench”, orientated east / west and parallel with the shore stretched over 40km. The trench is between 15 and 25m deep and located only 300 to 400m off the coast. It has been interpreted by the geologists onboard as the seafloor traces of a major geological fault zone.
Meanwhile the magnetic data, which have now to be analysed in detail, indicate potential extension to the known volcanic centres at Clougher Head and the Blasket Island of Inishvickillane.
In sediment samples, collected from areas of coarse sand, low numbers of molluscs and tube dwelling worm species have been found, while muddy substrates show a much higher level of biodiversity and faunal numbers.
The INFOMAR programme is now beginning to produce the first complete coverage maps within this Biologically Sensitive Area since it was first mapped in the 1800s using leadlines (rope and attached lead weight) and sextants, from wooden-hulled sailing vessels. Additional datasets, using airborne Light Detection and Ranging (LiDAR) and smaller vessels, will extend the inshore coverage of this area over the next 12 months.
In the meantime, analysis of the hydrology, geology and biology of the amalgamated surveys off the southwest will continue and promise valuable discoveries. INFOMAR continues later in the year surveying the Kish Bank off Dublin, Galway Bay and Waterford Bay.
Shaded Relief Plot
Shaded relief of seafloor showing the coverage achieved on the second INFOMAR survey leg in 2007 (Arrows indicate the Brendan Trench).
Shaded relief plot (including scale and legend)
“Backscatter” across the survey area, indicating seafloor hardness and roughness (light areas indicate lower “reflectivity” from the seafloor) and sample locations (triangles indicate biological and geological samples, others symbols indicate geological samples only).
The probable Glacial terminal moraine feature (below) dubbed the “Slava Ridge” discovered during INFOMAR Survey CE07-02.