JC015

Introduction (from JC015 cruise Report)

In 2007 the British Geological Survey (BGS) was awarded survey time on the NERC vessel the RRS James Cook under the command of Captain Robin Plumley. Originally the cruise aimed to carry out sea-bed sampling in the northern Atlantic Ocean, with the bulk of operations to be carried out on Hatton Bank. However, due to very poor weather conditions, most operations were carried out within the sheltered waters of the Inner Hebrides .

The modified aims of the cruise were:

• To test the 15m rock-drill in the Moray Firth at a location east of Wick where i) thin Holocene sediments overlie rockhead comprising Lower Cretaceous sediments, ii) thin Holocene sediments overlie glacial till deposits, and iii) Holocene sediments several metres in thickness overlie glacial till.

• To investigate the area immediately surrounding and to the north of Nun Rock located 28km north of Cape Wrath. Recently collected Maritime and Coastguard Agency multibeam echosounder data in the area of interest reveals extensive rock outcrop at sea bed. A linear feature observed on these data may be a northward extension of the Moine Thrust. A transect of 15m rock-drill sites across this feature, from footwall to hanging wall was proposed to test this hypothesis.

• To investigate a positive magnetic anomaly located immediately west of the Isle of Lewis (Outer Hebrides) on the Flannan High.

• To ground-truth a series of glacial moraines and intervening sediments using the 15m rock-drill, 6m vibrocorer and the BGS gravity-corer in the Summer Isles area. This work builds on the multibeam echosounder data and shallow seismic data collected during BGS cruise 2005/04 and shallow sea-bed samples collected during BGS cruise 2006/04.

• To deploy the 15m rock-drill and the 6m vibrocorer to sample the encrusting cold-water coral mounds located in The Minch near the island of Mingulay. These sample sites aim to determine the age of accumulation of these features, historic temperature variation during their evolution and to confirm the lithology of the bedrock to which the cold-water corals are anchored. The role of the representative from the Scottish Association for Marine Science (SAMS) was to ensure that no live cold-water coral was damaged during operations in this area. Using real-time video footage during deployment of the equipment allowed an accurate assessment of sea-bed conditions to be made.

• To determine the offshore extent of the Younger Dryas in the Loch Hourn, Loch Linnhe, Loch Nevis and the island of Muck area.

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