The Agadir Slide offshore NW Africa: Morphology, emplacement dynamics, and potential contribution to the Moroccan Turbidite System

• Published in: Earth and planetary science letters 2018-09, Vol.498, p.436-449
• Main Authors: Li, Wei, Krastel, Sebastian, Alves, Tiago M., Urlaub, Morelia, Mehringer, Lisa, Schürer, Anke, Feldens, Peter, Gross, Felix, Stevenson, Christopher J., Wynn, Russell B.
• Format: Article
• Language: English
• Subjects: Agadir submarine slide; Moroccan Turbidite System; multibeam bathymetry; Northwest Africa; turbidity current
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2018.07.005

•A giant submarine slide in the Agadir Canyon region was mapped and investigated.•The Agadir Slide was emplaced in two main events at 142±1 ka.•The Agadir Slide did not contribute to the Moroccan Turbidite System.•Seismicity related to fault activity and halokinesis likely triggered the slide. A newly identified large-scale submarine landslide on the NW African margin (Agadir Slide) is investigated in terms of its morphology, internal architecture, timing, and emplacement processes using high-resolution multibeam bathymetry data, 2D seismic profiles, and gravity cores. The Agadir Slide is located south of the Agadir Canyon at a water depth ranging from 500 m to 3,500 m, showing an estimated affected area of approximately 5,500 km2. The analysis of the Agadir Slide's complex morphology reveals the presence of two headwall areas and two slide fairways (the Western and Central slide fairways). Volume calculations indicate that ∼340 km3 of sediment were accumulated downslope along the slide fairways (∼270 km3) and inside the Agadir Canyon (∼70 km3). Stratigraphic correlations based on five gravity cores indicate an emplacement age of 142±1 ka for the Agadir Slide. However, its emplacement dynamics suggest that the slide was developed in two distinct, successive stages. The presence of two weak layers (glide planes) is a major preconditioning factor for the occurrence of slope instability in the study area, and local seismicity related to fault activity and halokinesis likely triggered the Agadir Slide. Importantly, the Agadir Slide neither disintegrated into sediment blocks nor was transformed into turbidity currents. The emplacement timing of the Agadir Slide does not correlate with any turbidites cored downslope across the Moroccan Turbidite System.