Hostname: page-component-586b7cd67f-rdxmf Total loading time: 0 Render date: 2024-11-29T07:53:59.987Z Has data issue: false hasContentIssue false
  • English
  • Français

Problems interpreting deep crustal reflectors beneath the Moine thrust between Shetland and the Scottish Highlands

Published online by Cambridge University Press:  01 May 2009

J. H. McBride  and
R. W. England
J. H. McBride
Affiliation:
British Institutions Reflection Profiling Syndicate, Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK
R. W. England
Affiliation:
British Institutions Reflection Profiling Syndicate, Bullard Laboratories, Department of Earth Sciences, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, UK
Get access Rights & Permissions [Opens in a new window]

Abstract

Offshore seismic reflection profiles crossing the Caledonian orogenic front (locally, ?Moine thrust) between Shetland and the Scottish Highlands show a singular coherent east-dipping reflection underlain by a highly reflective dipping zone in the middle crust extending down to the Moho discontinuity. This reflector pattern varies spatially with respect to the eastern edge of the Precambrian Lewisian foreland as well as to previously mapped locations of the Moine thrust. Southwest of Shetland, the reflector pattern coincides with the offshore projection of the Moine thrust, but further south, toward the Highlands, the reflector diverges to the west of the thrust and actually underlies autochthonous Lewisian foreland basement. Where this reflector pattern diverges from the Moine thrust, two interpretations are possible: the prominent reflector is part of a basement imbricate thrust duplex within the footwall (or ‘lower plate’) of the Moine thrust that merges with the thrust zone further north and/or it was originally a Proterozoic normal fault which, further north around Shetland, was reactivated or over-printed by the Moine thrust. The latter interpretation supports the importance of pre-existing crustal structure in controlling Caledonian compressional deformation.

Type
Articles
Information
Geological Magazine , Volume 132 , Issue 5 , September 1995 , pp. 465 - 472
Copyright
Copyright © Cambridge University Press 1995

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Andrews, I. J., 1985. The deep structure of the Moine Thrust, southwest of Shetland. Scottish Journal of Geology 21, 213–17.Google Scholar
Barr, D., Holdsworth, R. E., & Roberts, A. M., 1986. Caledonian ductile thrusting in a Precambrian metamorphic complex: The Moine of northwestern Scotland. Geological Society of America Bulletin 97, 754–64.Google Scholar
Brewer, J. A., & Smythe, D. K., 1984. MOIST and the continuity of crustal reflector geometry along the Caledonian-Appalachian orogen. Journal of the Geological Society, London 141, 105–20.CrossRefGoogle Scholar
British Geological Survey. 1985. Orkney Solid Geology Sheet 59° N-04° W 1:250,000 Series, HMSO.Google Scholar
British Geological Survey. 1986 a. Little Minch Solid Geology Sheet 57° N-08° W 1:250,000 Series, HMSO.Google Scholar
British Geological Survey. 1986 b. Rona Solid Geology Sheet 59° N-06° W 1:250,000 Series, HMSO.Google Scholar
British Geological Survey. 1989. Sutherland Solid Geology Sheet 58° N-06° W 1:250,000 Series, HMSO.Google Scholar
Butler, R. W. H., & Coward, M. P., 1984. Geological constraints, structural evolution and deep geology of the northwest Scottish Caledonides. Tectonics 3, 347–65.Google Scholar
Cheadle, M. J., McGeary, S., Warner, M. R., & Matthews, D. H., 1987. Extensional structures on the western UK continental shelf: a review of evidence from deep seismic profiling. In Continental Extensional Tectonics (eds Coward, M. P., Dewey, J. F., and Hancock, P. L.), pp. 445–65. Geological Society Special Publication no. 28.Google Scholar
Coward, M. P., 1983. The thrust and shear zones of the Moine thrust zone and the NW Scottish Caledonides. Journal of the Geological Society, London 140, 795–811.Google Scholar
Duindam, P., & van Hoorn, B., 1987. Structural evolution of the West Shetland continental margin. In Petroleum Geology of North West Europe (eds Brooks, J. and Glennie, K.), pp. 765–73. Graham and Trotman.Google Scholar
Dunning, F. W., 1985. Geological structure of Great Britain, Ireland and surrounding seas. Geological Society London Mapchart.Google Scholar
Enfield, M. A., & Coward, M. P., 1987. The structure of the West Orkney Basin, northern Scotland. Journal of the Geological Society, London 144, 871–84.CrossRefGoogle Scholar
Hitchen, K., & Ritchie, J. D., 1987. Geological review of the West Shetland area. In Petroleum Geology of North West Europe (eds Brooks, J. and Glennie, K.), pp. 737–49. Graham and Trotman.Google Scholar
Kelley, S. P., Reddy, S. M., & Maddock, R., 1994. Laser-probe 40Ar/39Ar investigation of a pseudotachylyte and its host rock from the Outer Isles thrust, Scotland. Geology 22, 443–46.Google Scholar
Lailey, M., Stein, A. M., & Reston, T. J., 1989. The Outer Hebrides fault: a major Proterozoic structure in NW Britain. Journal of the Geological Society, London 146, 253–59.CrossRefGoogle Scholar
McBride, J. H., & England, R. W., 1994. Deep seismic reflection structure of the Caledonian orogenic front west of Shetland. Journal of the Geological Society, London 151, 9–16.Google Scholar
O’Neill, P. S., & England, R. W., 1994. The structure of the Sea of the Hebrides Basin: an integrated gravity and seismic model. Scottish Journal of Geology 30, 1–9.Google Scholar
Rathbone, P. A., & Harris, A. L., 1979. Basement-cover relationships at Lewisian inliers in the Moine rocks. In Caledonides of the British Isles – reviewed (eds Harris, A. L., Holland, C. H. and Leake, B. E.), pp. 101–8. Geological Society, London, Special Publication no. 8.Google Scholar
Ritchie, J. D., Hitchen, K., & Mitchell, J. G., 1987. The offshore continuation of the Moine Thrust, north of Shetland, as deduced from basement isotopic ages. Scottish Journal of Geology 23, 163–73.Google Scholar
Sibson, R. H., 1975. Generation of pseudotachylite by ancient seismic faulting. Journal of the Royal Astronomical Society 43, 775–94.Google Scholar
Snyder, D. B., 1990. The Moine Thrust in the BIRPS data set. Journal of the Geological Society, London 147, 81–6.Google Scholar
Stoker, M. S., Hitchen, K. & Graham, C. C.. 1993. The geology of the Hebrides and West Shetland shelves, and adjacent deep-water areas. British Geological Survey United Kingdom Offshore Regional Report. London: Her Majesty’s Stationery Office, 149 pp.Google Scholar
Watson, J., & Dunning, F. W., 1979. Basement-cover relations in the British Caledonides. In Caledonides of the British Isles — reviewed (eds Harris, A. L., Holland, C. H. and Leake, B. E.), pp. 647–92. Geological Society, London, Special Publication no. 8.Google Scholar