Tectonic controls on Post-Oligocene Submarine Channel Evolution on the West African Margin Revealed using Isoproportional Slicing, Spectral Decomposition and Multi-Attribute RGB Blending

Oluboyo, Ayodeji P.^1,2 and Gawthorpe, Rob L.¹

¹Basin Studies and Petroleum Geoscience, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, Manchester, M13 9PL, United Kingdom.
²PGS Reservoir, 17 Marlow Road, Maidenhead, Berks SL6 7AA, United Kingdom.

Passive margins with mobile substratum are tectonically complex depositional settings with a wide range of controls on deepwater sedimentation. In particular, the 4D evolution of salt-cored fault and fold arrays generates complex dip- and strike-variability in the depositional surface, creating a continually evolving slope roughness that has a strong control on turbidite channel location and geometry. We present an integrated approach to the tectono-sedimentary evolution of deepwater turbidite channels and lobes within salt- induced mini-basins, utilizing a merged 3,000 km² 3D seismic dataset from the deepwater region offshore Angola.

Spectral decomposition, multi attribute blending and isoproportional slicing have been applied to seismic volumes from the margin, to investigate sedimentary response to the evolution of mobile substrates in the post Oligocene stratigraphic interval. The evolution of salt-related fault and fold arrays and associated salt massifs configures the morphology of intervening minibasins and also acts as a major trigger mechanism for mass transport complex initiation. By combining detailed analysis of the structural evolution of individual salt diapirs using conventional isochron analysis with attribute-based deepwater submarine channel geomorphology we show the structurally-related variations in channel morphometrics and geomorphology. Systematic variations in the geometry, location and stacking patterns of submarine channels are observed, as tortuous sediment fairways are adopted by turbidite channel systems 'flowing' around the growing fault and fold array. Complete bypass of certain mini-basins is observed in areas shadowed from the main sediment transport pathways.