Controls and Timing of Structural Inversion in the NE Atlantic Margin

Tuitt, Adrian Kern¹, John Underhill², Derek Ritchie³, Roger Scrutton⁴, Howard Johnson³, Ken Hitchen³ (1) University of Edinburgh, Ediburgh, EH9 3LA, United Kingdom (2) University of Edinburgh, Edinburgh, United Kingdom (3) British Geological Survey, Edinburgh EH9 3LA, (4) University of Edinburgh, Edinburgh EH9 3JW,

Continental margins were once thought to be ‘passive' in nature. However, the interpretation of newly acquired and existing 2-D seismic data from the Faroe Shelf to the Rockall Plateau has revealed the presence of prospective anticlinal traps affecting Cenozoic sediments along the NE Atlantic Margin (eg. Hatton Bank, Ymir and Wyville Thomson Ridges).

Three unconformities of Late Eocene, Early-Mid Miocene and Early Pliocene ages have previously been defined and dated within the South Rockall Trough (Stoker et al., 2001). Whilst these unconformities were originally attributed to bottom-water current activity at these times, new evidence available to this study suggests that at least two of these unconformities were instead formed by previously undocumented compression. Comparison with other unconformities that have been mapped and dated elsewhere along the NE Atlantic Margin shows that the growth of the compressional features primarily occurred during seven main phases - the late Ypresian, late Lutetian, Late Eocene, Mid Oligocene, Late Oligocene, Miocene and Early Pliocene.

It remains unclear what the main driver of the deformation was. However, horizontal compression within the NE Atlantic Margin resulting from ridge push, Alpine stresses, depth-dependent stretching and/or plate reorganisation may all have played a role at one time or another. If they are not dependent upon the disposition of pre-existing structures, sediment loading or lithospheric structure, the temporal and spatial variation in the orientation, location, nature and timing of compressional features may be indicative of the inversion mechanisms involved.