Abstract: In advanced geosciences contexts, the Mentawai forearc basin, trench-parallel elongated trends NW-SE, is relatively unexplored. However, acquired sub-bottom profile, bathymetric map, and deep sea sediment core data sets from R/V Sonne SO-184 cruise have afforded a more detailed investigation on the basin. Their integration and correlation give practical applications for submarine sediment transport and depositional processes interpretations. Six sub-facies types are identified and grouped into two main classes. They related to finely-layered drapes of hemipelagic areas in upper slope; chaotic of debrite areas in foot of slope; and high-reflective sediment sheets of basinal turbidites areas in basin floor.

Meanwhile, mid-slope depicts the occurrences of wavy layers of slumping and creeping areas; rough surface of slopes; and hyperbolae of gully areas. The distribution patterns of sediment transport suggest slope failures and leads to creeps, slumps or debris flows. Turbidity currents continuously erode the steep slopes in the basin and inhibit sediment deposition through incised gullies to the southeastern end of the basin. The potential cause of slope failures is triggered by seismo-tectonic activities in Sunda Arc. It appears that seismo-tectonics in Sunda Arc also play a significant role in the basin expressing active faults near Mentawai Islands known as Mentawai Fault Zone; and compressing the basin. Yet, seismo-tectonics is not the only factor influencing the slope failure and sediment deposition. In particular, the sediment input discharged from Sumatra, geomorphology of the basin, and cyclic sediment load related to sea level oscillations are also becoming the important factors.