a) This high-resolution profile was collected as part of the STRATAGEM project in the NW Rockall Trough. It shows gentle anticlinal doming of Eocene and younger strata that continues to influence the present-day sea-bed topography. The onlap of the post-Eocene sediments suggests that this dome was a developing structure prior to the Neogene interval. The upturned ends of the reflections within the RPb megasequence imply a degree of syn-depositional doming. It remains uncertain, however, whether or not the sediments of the RPa megasequence are draping the dome or are being presently uplifted
b) This multichannel profile, extending from the Ymir Ridge (western part of the Wyville-Thomson Ridge) into the Rockall Trough, shows that the anticlinal doming also affects the Palaeogene laves, and thus has a deep structural root. In a regional context, it suggests that the Wyville-Thomson–Ymir ridge complex is probably a more extreme expression of such deformation. Sediment-drift deposits of the RPb megasequence, which onlap both the anticline and the Ymir Ridge, presently have a restricted occurrence due to partial removal by early Pliocene erosion (C10 Unconformity). The overlying RPa deposits have a more-parallel, sheeted, reflection configuration that suggests a relatively stable bottom-current regime since the C10 event.
c) This high-resolution profile extends from the Wyville-Thomson Ridge into the NE Rockall Trough, and shows the variable nature of the sediment drift complex that characterises megasequence RPa in the NE corner of the basin. A distinctive elongate drift and associated erosional moat occur adjacent to the Ridge, whereas a gently domed, broad, sheeted drift and associated sediment waves occupy much of the basin floor. The inset shows the detail of the sediment waves buried beneath debris flows at the distal edge of the Sula Sgeir Fan. Note the upward change from asymmetric to sinusoidal waves. The contrasting styles of drift and wave development reflect formation under a variable bottom-current regime (Stoker
et al. 1998).
Reference
Stoker, M.S., Akhurst, M.C., Howe, J.A. & Stow, D.A.V. 1998. Sediment drifts and contourites on the continental margin off northwest Britain.
Sedimentary Geology¸ 115, 33-51.
