Seismic Geomorphology of an Early Eocene Canyon-Channel-Lobe System North of Shetlands

Abstract

Submarine canyon and channel systems are the primary paths for sediment transport from platforms to deep-sea terminal depositional fans and are present on all continental margins. The temporal morphological expression of such systems should be documented in order to fully understand the development of these important sediment pathways. We utilise a 3D seismic dataset from the northern Shetland Platform to the southern Møre Basin region and map two regionally continuous seismic horizons. The dataset includes an early Eocene northward-oriented canyon-channel system that allows high-resolution mapping of erosion and sedimentation. The morphology of the system allows a subdivision of platform, upper, middle, and lower slope, and basin floor. It is further subdivided from east to west according to the degree of erosive maturity. The platform contains channel shapes and their fill stretching from the south towards the platform edge and upper slope, where dendritic canyon heads developed. Scars in the canyon sidewalls indicate slope failure as an important widening mechanism. The slope canyons progressively shallow and widen basinward. At the canyon exits, deepwater submarine channels developed and continued onto the basin floor. We document progressive filling and overspilling of channels towards the terminal fan. The filling of the channels that resulted in overbank deposition is likely due to a decrease in slope gradient leading to an increased deposition rate that exceeds the channel capacity. Post-depositional differential compaction of the clastic channel fill and the surrounding muddy sediments causes the channel fills to form elongated ridges that lead towards the terminal fan. It is further shown that the morphological elements observed in the canyon-channel system adjust towards an equilibrium profile with a shallower gradient. These detailed observations provide an enhanced understanding of how canyon-channel systems develop on active margins and how sediment transport pathways are influenced by the submarine equilibrium profile and post-depositional processes.