Top Surface Geomorphology of Submarine Landslides and Its Impact on Turbidity Currents

Key words: 
• submarine landslide /
• landslide top surface geomorphology /
• submarine turbidity current

Abstract: [Objective] The catastrophic failure of large submarine landslides can result in the deformation and destruction of thousands of square kilometers of seafloor, transporting hundreds to thousands of cubic kilometers of submarine sediments. This process dramatically reconstructs the seafloor topography of the continental shelf-slope region and has a profound impact on subsequent submarine sedimentation processes. [Methods] The topographic features of different large submarine landslides were qualitatively described using multibeam bathymetric and seismic reflection data, and the key geometric parameters of the submarine landslide top surface, such as area and volume, were quantitatively characterized. Based on the scale, morphological features, and formation mechanisms of the associated reliefs on the submarine landslide top surface, these landslides were separated into three categories: head evacuation zone, locally negative accommodation associated with internal fault systems, and locally negative accommodation associated with internal deformation blocks. The mechanisms of the three types of negative accommodation on the subsequent turbidity current system are then discussed separately. [Results] Firstly, the head evacuation zone is typically associated with hundreds to thousands of square kilometers of negative accommodation, which acts as a "funnel" during sediment transport along the continental margin, effectively capturing and concentrating subsequent turbidity currents while enhancing the transport efficiency of gravel and coarse sand and playing a crucial role in the accumulation of marine organic matter. Secondly, the striped negative accommodation associated with internal fault systems and the irregular negative accommodation associated with internal deformation blocks can regulate the sedimentation dynamics of subsequent turbidity currents, such as constraining flow direction, enhancing erosion intensity, and forcing channels to avulse. Finally, the negative accommodations associated with the submarine landslide top surface may produce synergistic effects, influencing the sediment filling and evolution of sedimentary basins and the distribution of sedimentary centers over millions of years. [Conclusion] The investigation of the morphological characteristics of submarine landslide top surfaces and their controlling effects on the subsequent turbidity currents sedimentary dynamic process can provide key geological information for clarifying the transport process of marginal sediments, identifying the distribution of sand-rich reservoirs in deep-sea sedimentary basins, and predicting the development range of catastrophic turbidity currents.