Geophysical investigations in the Faeroes to Scotland region, Northeast Atlantic

Abstract

Gravity, magnetic and seismic reflection profiles from the sea area between the Faeroe Islands and Scotland were obtained on the 1967 and 1968 cruises of RRS John Murray, The submarine shelf adjacent to the Faeroe Islands is separated from the continental shelf and slope north of Scotland by the Faeroe-Shetland Channel, The purpose of the cruises was to provide geophysical evidence of the geological structure of the region. Gravity and seismic reflection profiles across the Faeroes shelf, SE of the Faeroe Islands, indicate a substantial thickness of post- Mesozoic sediments. The gentle submarine slopes bordering the Faeroe-Shetland Channel are made up of seaward dipping sediments. Gravity profiles show that the Channel is associated with a Bouguer anomaly "high". This is interpreted as caused by a thinning of the crust beneath the Channel in close agreement with the predictions of the Airy-Heiskanen hypothesis of isostasy. Geophysical surveys around the Hebrides, Orkneys and Shetlands represent a large area of previously uninvestigated British continental shelf and slope. The Bouguer anomaly map shows a large gravity "high" reaching 94 mgal which is continuous for 250 km and trends NNE-SSW across the shelf. This is interpreted as caused by a seaward extension of dense Precambrian basement rocks outcropping in NW Scotland, Large amplitude gravity "lows" have been outlined on the shelf and slope north of Scotland, A large amplitude "low" 70 km west of the Shetlands has been interpreted as caused by a deep sedimentary basin infilled by Mesozoic/Tertiary sediments and bounded on its SE margin by a large normal fault. A buried basement ridge has been located west of the gravity "low", near the shelf break in slope. Recent sediments form the continental slope which gently truncates the older Caledonian structures on the shelf.