--> New Ways of Looking at the Evolution of Entrenched Sinuous Channels off Angola, by Martin James Roland Gee, Samuel Julio Friedmann, and Robert L. Gawthorpe; #90037 (2005)

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New Ways of Looking at the Evolution of Entrenched Sinuous Channels off Angola

Martin James Roland Gee1, Samuel Julio Friedmann2, and Robert  L. Gawthorpe1
1 University of Manchester, Manchester, United Kingdom
2 Energy & Environmental Directorate, Livermore, CA

Deep water turbidite channels are an important element of the Angolan continental margin as hydrocarbon reservoirs, sedimentary distributary and slope building systems. Despite this, adequate predictive models for the processes that erode and deposit these systems are still lacking. The early phases of channel incision and evolution are particularly poorly known due to erosion and enlargement. This paper investigates the early evolution of turbidite channels within a large Miocene fan complex where a wide range of channel scales and geometries are preserved in different stages of evolution. Results indicate that channels evolve rapidly from straight, low sinuosity systems into highly sinuous, incised systems with gentle channel axis gradients. We examine four channel systems of increasing sinuosity, incision and decreasing gradient which appear to have been preserved in different stages of evolution. Sinuosity, gradient and incision for four different channel systems were quantified and used as a proxy for channel maturity. Results indicate thresholds for channel geometry and characterise the evolution of incised, highly sinuous channels. Two end members are recognised; low sinuosity systems characterised by 'gull winged' levees and narrow channels and highly sinuous systems with enlarged, complex channels and weakly developed levees. The rarerest form of channel identified has moderate incision, low to medium sinuosity and a moderate channel axis gradient. The results improve our ability to predict subsurface channel geometries and recognise key trends and thresholds in channel evolution.