Turbidity current sediment waves on the submarine slopes of the western Canary Islands

Two sediment wave fields have been identified on the flanks of the western Canary Islands of La Palma and El Hierro, using a high-quality 2-D and 3-D dataset that includes GEOSEA and TOBI imagery, 3.5-kHz profiles, and short sediment cores. The La Palma sediment wave field covers some 20,000 km2 of the continental slope and rise, and consists of sediment waves with wave heights of up to 70 m and wavelengths of up to 2.4 km. The wave crestlines have a complex morphology, with common bifurcation and a clear sinuosity. Waves have migrated upslope through time. Cores recovered from the wave field contain volcaniclastic turbidites interbedded with pelagic/hemipelagic layers. The wave field is interpreted as having formed beneath unconfined turbidity currents. A simple, previously published, two-layer model is applied to the waves, revealing that they formed beneath turbidity currents flowing at 10\textendash100 cm/s-1, with a flow thickness of 60\textendash400 m and a sediment concentration of 26\textendash427 mg/l. The El Julan sediment wave field lies within a turbidity current channel on the southwest flank of El Hierro. The sediment waves display wave heights of about 6 m and wavelengths of up to 1.2 km. The waves are migrating upslope, and migration is most rapid in the centre of the channel where the flow velocity is highest. This wave field has been formed by channelised turbidity currents originating on the flanks of El Hierro.