an evaluation of regional active along-slope and down-slope processes of the nw european continental...
Post on 19-Dec-2015
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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 MarineFlag TelecomGeminiGlobal Crossing / Global MarineTyco
• To develop a semi-quantitative summary of active slope
processes
• Risk assessment for submarine cables
• To reduce time and costs to UK telecommunications industry
Aims
• Compilation of all available datasets relating to slope processes and stability
• Evaluation of datasets
• Model ‘Risk Assessment’ in Geographical Information Systems (GIS)
Objectives
Datasets
• Swathe bathymetry
• Swathe Backscatter
• Side-Scan Sonar
• 3.5kHz Pinger Profiles
• Gravity / Box Cores
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)
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
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 (?)
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