The geoseismic profile shown, panel 4a, illustrates the distribution, geometry, thickness and seismic facies of the Neogene sediments in the northern Faroe-Shetland Channel. The line comprises both high-resolution seismic data and conventional 2D data, and due to the inherent difficulties in combining these datasets, only one profile is shown in full. Two other dip lines,
Panel 4b and Panel 4c, are shown as line drawings, as is
Panel 4a, in order to illustrate the change in profile of the Faroese and UK margins, in addition to changes in sediment thickness and geometry, from north to south.
Panel 4a shows Miocene to lower Pliocene sediments of megasequence FSN-2 reaching a maximum thickness of approximately 650ms TWTT in the Faroe-Shetland Channel. On the Fugloy Ridge and on the West Shetland Shelf and upper Slope, FSN-2 deposits are absent or severely eroded, with discrete remnants of contouritic drifts on the middle to lower slope. On the Faroese margin, these sediments show upslope accretion beneath the overlying, erosional Intra-Neogene Unconformity. A second depocentre can be seen off the back of the Fugloy Ridge to the northwest, where the sediments largely comprise fan sands derived from the ridge itself. A parallel internal reflection pattern is characteristic of the FSN-2 megasequence, commonly onlapping the margin with mounded waveforms. To the far NE and SW, this is replaced by a seismically opaque, structureless signature.
The overlying FSN-1 megasequence attains a maximum thickness of approximately 400ms TWTT at the base of the West Shetland Slope, and is present across the entire profile. On the flanks and across the top of the Fugloy Ridge the unit is greatly reduced in thickness. A significant characteristic that is clearly seen on this profile is the presence of drift deposits at the base of the slope, on the Faroes margin, whereas similar facies occur both at base of slope and on the lower slope of the West Shetland margin. Shelf prograding sediment wedges and glaciogenic debris flows are characteristic of this megasequence, such as that seen at the change in slope on the West Shetland Shelf on profile
Panel 4a, with prograding clinoforms downlapping onto the intra-Neogene unconformity as well as interdigitating with the upslope accreting sediment-drift deposits. Internally, these debris-flow packages are chaotic and structureless.