Isolating the Role of Downslope Turbidite Supply to the Buildup of a Continental Rise: Seafloor Morphology and Structure in the Northern Levant Basin, Eastern Mediterranean

The buildup of a continental rise depends on the supply of sediments from various sources, e.g., downslope slumps, turbidites, canyons, along-slope contourites and other deepwater currents. This combination results in a diverse assemblage of sedimentary patterns that dictates the morphology if its seafloor relief. We aim to isolate the contribution of one sedimentary source from the rest in order to examine its morphological effect. The current study focuses on the northern Levant continental rise (E. Mediterranean) at water depths 1200-1800 m, where the sedimentary supply during the Pleistocene arrived predominantly by downslope turbidity currents. These currents acted during high stand periods, distributing sediments across a 4000 km² in an upslope migrating cyclic steps pattern. The research is based on analysis of available multibeam bathymetry, backscatter, multichannel seismic reflection and seafloor sampling. Additionally, in a recent dedicated cruise conducted during 2018, we collected new multibeam and single-channel seismic data and retrieved four piston-cores (each 7-8 m long). Data shows that crests of the cyclic steps migrate upslope as a series of 12 m thick sequences. The sequences thin basinward to the WNW, together with an increase in distance between the crests of the steps and a decrease in their height above the immediate surroundings (averaging 4-6 m at 1400 m depth to 0-1 m at 1800 m). Piston-core data show evidence for several turbidite sequences. The new multibeam data, collected onboard the Israeli R/V Bat-Galim with a hull-mounted Kongsberg EM302 sonar, demonstrates superior data quality over the previously collected data. It also reveals two sets of sediment transport patterns - confined (channel-like) and unconfined (sheet-like) which affect the morphology of the sediment waves they form. We expect this ongoing study to better our understanding of the role of turbidites in building-up the continental rise.