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Michael Cunningham, Sophie Hodgson, Lindsay Parson and Doug Masson

An evaluation of regional active along-slope and down-slope processes of the NW European continental margin. Michael Cunningham, Sophie Hodgson, Lindsay Parson and Doug Masson. In conjunction with: BT Marine Flag Telecom Gemini Global Crossing / Global Marine Tyco. Aims.

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Michael Cunningham, Sophie Hodgson, Lindsay Parson and Doug Masson

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  1. An evaluation of regional active along-slope and down-slope processes of the NW European continental margin Michael Cunningham, Sophie Hodgson, Lindsay Parson and Doug Masson In conjunction with: BT Marine Flag Telecom Gemini Global Crossing / Global Marine Tyco

  2. Aims To develop a semi-quantitative summary of active slope processes Risk assessment for submarine cables To reduce time and costs to UK telecommunications industry

  3. Objectives Compilation of all available datasets relating to slope processes and stability Evaluation of datasets Model ‘Risk Assessment’ in Geographical Information Systems (GIS)

  4. Datasets Swathe bathymetry Swathe Backscatter Side-Scan Sonar 3.5kHz Pinger Profiles Gravity / Box Cores

  5. Data Modelling and Interpretation GIS Layers: 3.5kHz Echo-facies (grid/image/line/point/polygon) Aspect (grid) Backscatter (grid/polygon) Bathymetric Shaded Relief (grid) Cables (line) Contours (line) Morphology (grid/polygon) Relief (grid) Sediment samples (point) Side-scan sonar (geoTiff) Slope (grid) Metadata (line/point/polygon/xml)

  6. Conclusions (Goban Spur) Asymmetrical sediment waves infer NW sediment transport Continental shelf break transition dominated by glacial erosive features Along-, down-slope gullies/channels, and sediment slides S margin indented by large U-shaped canyons, with evidence of sediment slides Canyon floors – incised channels following topographic fault bounded escarpments

  7. Conclusions (Celtic Margin (1)) Sand waves on shelf break, mainly orthogonal to the canyon axes, and asymmetry infers sediment transport into the canyon heads Symmetrical sand waves appear to be inactive, now being overprinted Active down-slope sediment transport in the form of turbidity currents dominates upper reaches of canyons Drainage basins on canyon heads, interpreted as retrogressive mass wasting and shelf indention Recent or Active NNW-SSE faulting (?)

  8. Conclusions (Celtic Margin (2)) Sediment deposition mid-slope Canyon over-bank spill – unconfined turbidite deposits Active down-slope sediment transport (turbidity currents) dominate upper reaches of canyons Major asymmetrical levees at foot of continental slope / rise Turbidity currents incised a major channel into the low gradient of the continental rise and the flat abyssal plain. Over-spill deposits form sediment waves and the build up of wide levees

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