Analysis of submarine landslides along the NW African continental margin : failure processes of the Sahara Slide Complex and distribution of scarps

Various bathymetric data sets have been collected along the NW African continental margin using multibeam echosounders during designated surveys and transits. In this thesis, a workflow was developed to automatically process a large amount of bathymetric data collected by German research vessels over the last 30 years. Our processed bathymetric data have higher resolution (grid cell size: 50 m) than GEBCO 2022 GRID and EMODnet data. This allowed us to identify previously unknown scarps at the NW African continental margin, which are relatively small compared to major scarps of the known large submarine landslides. Most new minor scarps are close to areas with large landslides, which indicates the geomorphological complexity of submarine landslides along the NW African continental margin.

The integration of different types of data (multibeam echosounder, sediment echosounder, seismic reflection profiles, and sediment cores) allowed a detailed analysis of the headwall area of the Sahara Slide Complex including the reconstruction of the failure history and an investigation of preconditioning factors. Multiple slope failures have occurred in the past 60 kyr. The youngest event in the northeastern upper headwall area took place ~2 kyr ago. Six bedding-parallel glide planes appear as continuous high-amplitude reflection in sediment echosounder profiles. Seismic reflection data show that the glide planes are characterized by a reversed polarity reflection, that can be traced to the unfailed sections. The glide planes exhibit a cyclic pattern since the late Pleistocene. Time estimates suggest that the cyclicity is related to the 100 kyr glacial-interglacial cycle. A depositional pattern of glide planes with clay and diatom oozes might precondition the Sahara Slide Complex.