Recent sedimentary processes of the seabed in the Gulf of Guinea, SW Niger Delta: evidence from multibeam bathymetry and facies prediction

Abstract

High-resolution seafloor imageries, bathymetry and shallow profile data reveal a range of geomorphic expressions in the Gulf of Guinea, SW Niger Delta, which can be tied to processes of sediment transport and deposition. A complete suite of acoustic data was acquired during the survey from the 10th and 20th April, 2014.The data provided a detailed image of the present seafloor and subsurface. Sand, silt and clay facies were identified using onboard instrumentation of side scan sonar, sub bottom profiler, multi/single beam echo sounder, differential global positioning system and gyro compass in the study area. The integration of the seafloor and shallow subsurface data assisted in defining the processes responsible for each of the acoustic facies. Morphologically, the northern and southern parts are very different and the average water dept is 25m. The northern part has amphitheater-shaped slump scars by recent sediment accumulation, and it shows relatively low backscatter (clay). Outcrops and positive relief features were relatively captured in sub bottom profiles. The southern wall was characterized mostly by depository processes and relatively high backscatter. Interpretation shows the presence of a wide range of processes (sediments weathering, erosion, transportation, deposition, etc) shaping the present-day seafloor. The depositional processes are mostly located in the shallow area with a sandier seabed on the south and silty sediment near the north, indicating a field of wavy seafloor. Hyperbolic echoes cover the seafloor indicating also how widespread the erosive processes are in the study location. Factors like erosion, transport medium and environment of deposition of the area affected the sediment types, topography and water depth