|
Article |
1 British Institutions’ Reflection Profiling Syndicate, Bullard Laboratories, Madingley Road, Cambridge CB3 0EZ, UK
2 Institute Francais du Petrole, B.P. 311, 92506 Rueil-Malmaison, France
3 1nstitute of Oceanographic Sciences, Brook Road, Wormley, Godalming, Surrey GU8 5UB, UK
4 Department of Geology, Grant Institute, West Mains Road, Edinburgh EH9 3W, UK
5 IFREMER, Centre de Brest, B.P. 337, 29273 Brest, France
6 Centre Armoricain d’Etude Structurale des Socles, Campus de Beaulieu, 35042 Rennes, France
7 Elf-Aquitaine UK, Knightsbridge, London FW7 IRZ, UK
8 Etude de la Croûte Continentale et Océanique par Réflexion et Réfraction Sismique
Deep reflection data across the UK continental margin are used to test theories concerning the origin of a pervasive reflective fabric in the lower continental crust seen on many deep reflection profiles worldwide. The origin of the reflections is at present little understood, but clearly represents an important crustal process. The Western Approaches Margin (WAM) line was designed to determine the behaviour of the lower crustal reflections in crust which has undergone significant extension. The WAM profile across the continental shelf is characterized by bright, continuous lower crustal reflections, some of which reach 30 km in length and have minimum reflection coefficients of 0.1. Deep water multiples in the area of the continental slope partially obscure reflections from the lower crust, but detailed analyses show that reflectors are present in the lower crust on the continental slope. Adjacent to the continent-ocean boundary, the lower crust on the WAM profile is well-imaged and free of noise and multiples. This very thin crust exhibits the same reflectivity pattern as is observed on the continental shelf, i.e. the upper half of the crust is blank and the lower half contains sub-horizontal reflections. The lower crustal reflections adjacent to the continent-ocean boundary are less continuous than the reflections seen on the shelf, and are interpreted as being the remnants after extension of the lower crustal reflectors observed on the continental shelf. The lower crustal reflectors are thus interpreted to pre-date the extensional episode that led to the opening of the Atlantic. The preservation of thinned sections of both transparent upper crust and reflective lower crust adjacent to the continent-ocean boundary suggests that extension by pure shear was the mechanism by which the crust was thinned in the Goban Spur area.
This article has been cited by other articles:
 |
|
 |
|
  J. R. Cochran and G. D. Karner Constraints on the deformation and rupturing of continental lithosphere of the Red Sea: the transition from rifting to drifting Geological Society, London, Special Publications, 2007; 282: 265 - 289. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Smith Evolution of the Cockburn Basin: implications for the structural development of the Celtic Sea basins Geological Society, London, Special Publications, 1995; 93: 279 - 295. [Abstract] [PDF]
|
|
|
|
 |
|
 R. S. WHITE Crustal structure and magmatism of North Atlantic continental margins Journal of the Geological Society, 1992; 149: 841 - 854. [Abstract] [PDF]
|
|
|
|
|
|
R. S. White Magmatism during and after continental break-up Geological Society, London, Special Publications, 1992; 68: 1 - 16. [Abstract] [PDF]
|
|
|
|
|
|
M. P. Tate The Clare Lineament: a relic transform fault west of Ireland Geological Society, London, Special Publications, 1992; 62: 375 - 384. [Abstract] [PDF]
|
|
|
|
|
|
P. M. SHANNON The development of Irish offshore sedimentary basins Journal of the Geological Society, 1991; 148: 181 - 189. [Abstract] [PDF]
|
|
|
|
|
|
Discussion on crustal structure of the Goban Spur continental margin, Northeast Atlantic, from deep seismic reflection profiling Journal of the Geological Society, 1990; 147: 892 - 894. [Abstract] [PDF]
|
|
