A survey of Galway Bay’s seabed onboard the RV Celtic Voyager this summer has revealed, for the first time, the detailed seafloor and geology of the bay. It also confirmed the location of the Galway Bay Fault, a fault line in the North Sound running northwest to southeast, between Lettermullan/Gorumna Islands in west Connemara and the Aran Islands. The fault line demarks the limits of Galway’s granite landscape.
According to Koen Verbruggen, Geological Survey of Ireland (GSI) “Initial analyses, as well as defining the Galway Bay Fault and revealing it to be a more complex feature than thought, show a parallel ridge off Rossaveel and clear definition of the extent of the granite and limestone areas.” Features on the GSI geological maps and reports of Galway Bay and adjoining onshore areas can now be confirmed and revised based on the latest data.
The INFOMAR (Integrated Mapping for the Sustainable Development of Ireland’s Marine Resource) team mapped seabed features including the “Red Strand Bank” a seabed feature off Arkeen Point in a water depth of 24m; a series of three areas which become gradually shallower between the mainland and Inis Oirr, the Killa (17m), Craigmore (28m) and Gurnet Patches (26m); and a number of “holes” 50m in depth.
Other features of Galway seabed mapped during the three week survey include distinct fissures in exposed bedrock on the Brocklinmore and Brocklinbeg Banks, which become shallow just north of Inis Mór causing standing waves at changes in the tide, shown on navigation charts as “breaks with swell”. A series of sand wave fields of different scales are evident between Inis Mór and Inis Meáin. Clare’s limestone landscape was shown to continue underwater just off Doolin where underground caves open onto the seafloor.
The survey by Geological Survey of Ireland (GSI) and the Marine Institute covered approximately 60% of the bay, from the Aran Islands in. When combined with the coverage achieved in 2006 by light aircraft mounted LiDAR (Light Detection and Ranging) only about 20% now remains to be covered. The remaining area consists of two strips close to the shore, one along the north of the bay and the second along the west Clare coast, and a portion of the inner bay between Spiddal and Oranmore. This will be completed by a further contract survey later this year and LIDAR of the North East coast in 2008.
Data are now being processed and will be merged with inshore survey and ground-truthing data collected under contract in the next few months and further airborne LiDAR in 2008 to produce hydrographic, geologic and habitat maps of the area. All data are freely available and provided to the UK Hydrographic Office to update Marine Navigation Charts, and to the recently approved research programme of the new Biogeoscience Facility being developed at NUI-Galway and supported by the Griffiths Geoscience Awards further investigating Galway Bay.
Focus for INFOMAR has now moved further south, as surveying will take place in Bantry and Dunmanus Bays and the approaches to Cork and Waterford Harbours over the next six weeks.
For further information and details of access to and INFOMAR and Irish National Seabed Survey data visit the GSI website and Marine Institute website.
Notes to editors
INFOMAR is an ambitious joint venture between the Geological Survey of Ireland and the Marine Institute to map Ireland’s most productive and commercially valuable inshore waters. Covering some 125,000 square kilometres of underwater territory, INFOMAR will produce integrated mapping products covering the physical, chemical and biological features of the seabed. The INFOMAR programme began last summer with surveys of valuable fishing and fish farming areas in Bantry Bay, Dunmanus Bays and fish spawning areas off the South West Coast.
INFOMAR is exploring and mapping the seafloor using high resolution multibeam sonar, measuring gravity and magnetic variation, and recovering grab samples for biological, chemical and geological analysis.