The drilling of a cold water coral carbonate mound in Irish Waters
Thinking about Coral Reefs one always tends to visualize them in a warm, bright and shallow area, such as in Australian waters or the Bahamas. However, they have also been found in gloomy, cold and deep waters, off the coasts of 41 countries including Ireland. They occur at depths of hundreds of metres to just a few tens of metres, in several settings across almost all of the world’s oceans.

Locating these coral banks has been possible because of the latest acoustic and optic marine technologies. These enable high-resolution mapping of even the deepest oceans, and provide detailed video footage of the seafloor using remotely operated vehicles.

Deep-water corals are widespread along the European continental margin where they are often associated with carbonate mounds. Carbonate mud mounds are found in Irish Atlantic waters along the edges of the Rockall Trough and the Porcupine Bank and extending into the Porcupine Seabight. They are massive features some reaching heights of hundreds of metres, and stretching several kilometres across their bases and are composed of carbonate mud, the skeletal remains of corals and material from associated fauna together with sediment.

The idea of drilling into these giant mounds to unveil the secrets trapped in these cemeteries of coral and sediments originated a few years back. But it was only in May of 2005 that the idea finally materialized when an international research expedition took place entirely in Irish waters. The expedition concentrated on drilling the Challenger mound (170m high) in
the Porcupine Seabight. From an environmental perspective this mound was chosen very carefully as it is mostly covered by dead coral.

The expedition was part of the Integrated Ocean Drilling Program (IODP), an international marine research programme that explores the Earth's history and structure as recorded in seafloor sediments and rocks. IODP is managed by an American management agency, IODPMI, and funded by USA, Japan, ECORD (European interests) and China.

The platform to carry out this ambitious drilling programme was the American rig vessel, the Joides Resolution (124m). Leaving Dublin Port on April 28th she successfully drilled 11 holes, of average 200m length, in three target sites, recovering 1,400m of sediment core.

Scientists from the expedition are now working up answers to some very important questions. They have already demonstrated that the mound developed around 1.8 million years ago and consists of a 155m thick sequence of coral fragments and sediments from top to base. They are now studying the coral fragments for information about the past climate in the region in order to perhaps predict future trends. Such research and results originating from an innovative and prestigious expedition in Irish waters will heighten awareness of the development of cold-water coral banks in the Atlantic, and will significantly enhance Irish marine science’s reputation across the globe.

For further information on this cruise please contact Xavier Monteys at 01 678 2807 or by e-mail.