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Filtered GRID 4 and 17, perspective view interpreted Interpretation

VSA Author: Taija Torvela
Date Created: 2010-11-15

The image shows the interpreted Moho (green), the upper limit of the Flannan reflector (purple; e.g. Brewer & Smythe, 1984) and of the Outer Isles Thrust (blue; e.g. Brewer & Smythe, 1984). In the area of the profiles, the OIT terminates before reaching the sea floor, being offset by and/or reactivated as normal faults during rifting. Note how the OIT becomes steeper toward the south and reaches closer to the seafloor; this geometry is probably also due to normal faulting combined with block rotation. The normal fault interpretations are not shown in this image. The convex-upward "antiform" geometry of the Flannan reflector (sometimes called Flannan Thrust of Flannan Fault) is clearly imaged. The FR is a wide shear zone reaching down into the mantle (e.g. Brewer & Smythe, 1984; Warner & McGeary 2007). It has been mostly interpreted a compressional feature, a Caledonian Thrust (e.g. Brewer & Smythe, 1984), although it has been suggested to be a mantle extensional feature (Reston, 1990). The Moine Thrust zone in the eastern part of the GRID 17 is not interpreted here. See the Survey docs & links for a location map.


  • Interpretation Administrator:
    • Taija Torvela
  • VSA Author:
    • Taija Torvela

Geological Interpretation

Deformation Structures
Linked Contraction-Extension, Thrusts, Negative

Moho, Continental Crust

Geological Context

Plate Settings and Margins
Orogenic belts

Orogenic Belt

Basin Setting
Passive Margin

Geographic Context

Physical Geography

Political Geography
United Kingdom of Great Britain & Northern Ireland


Survey Information
Marine, Multichannel 2D, >10s

Data Presentation
Vertical Scale - Time, Amplitude

Image Type
Vertical Profile