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Geology of the Hebridean margin of the Rockall Trough

Published online by Cambridge University Press:  05 December 2011

E. J. W. Jones ,
R. G. Perry  and
J. L. Wild
E. J. W. Jones
Affiliation:
Department of Geological Sciences, University College London, Gower Street, London WC1E 6BT, England
R. G. Perry
Affiliation:
Department of Geological Sciences, University College London, Gower Street, London WC1E 6BT, England
J. L. Wild
Affiliation:
Department of Geological Sciences, University College London, Gower Street, London WC1E 6BT, England
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Synopsis

The geological structure and history of the Rockall Trough margin to the west of the Outer Hebrides (57°N-59°N) has been inferred from the analysis of bottom samples, seismic, sonar, magnetic, satellite altimeter and surface-ship gravity observations. Much of the continental shelf consists of a shallow platform of Precambrian Lewisian basement, covered by a thin (<300m) blanket of Cenozoic sediments. Apart from areas near the shelf break and immediately west of Lewis, the basement has not undergone the large-scale subsidence typical of many regions adjacent to the Rockall Trough. Beneath the outer shelf, the Lewisian dips steeply towards the deeper water and is covered by a westwardthickening succession (>3km) of Mesozoic and Cenozoic sediments.

The eastern margin of the Rockall Trough appears to have been well established as a site of deposition by the end of the Triassic. Further subsidence occurred during the late Jurassic and continued into the Cretaceous when the axial province of the Rockall Trough off the Hebrides was invaded by basic volcanic material. Subsequently, the region was profoundly affected by early Cenozoic igneous activity. The long-term buoyancy of the Lewisian basement under the Outer Hebridean platform and early-formed structural discontinuities within it have influenced the overall pattern of sediment accumulation and the distribution of volcanic activity along the margin. During the later stages of deposition, sedimentation was closely controlled by the presence of early Cenozoic volcanics, by bottom currents and by glacial processes.

Type
Research Article
Information
Proceedings of the Royal Society of Edinburgh, Section B: Biological Sciences , Volume 88: The Oceanography of the Rockall Channel , 1986 , pp. 27 - 51
Copyright
Copyright © Royal Society of Edinburgh 1986

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