Development of submarine depositional systems under dynamic interplays between sediment gravity flows and seafloor topography: A case study of the Potiguar Basin on the equatorial Atlantic Ocean

Seafloor topography plays a significant role in the modulation of gravity flow deposition and in the meantime, the associated depositional processes can modify the pre-existing topography. Given a lack of studies on the development of the submarine depositional systems as a consequence of the dynamic interplays between sediment gravity flows and seafloor topography, we analyze the local depositional records of the Potiguar Basin on the equatorial Atlantic Ocean. Using 3D seismic data along with spectral decomposition and spectral decomposition with red, green and blue (RGB) color blending techniques, we investigate the development of a submarine depositional system and then reveal the dynamic interactions between sediment gravity flows and seafloor topography. The results indicate that the main topographic low and the minor topographic low within initial topography of the study area played a major role in the deposition of early submarine channels and lobes. With the gentling of the slope along the main topographic low toward the distal provenance end, the velocities and competences of sediment gravity flows gradually decreased;correspondingly, their tendences of vertically downcutting and laterally broadening respectively weakened and strengthened, resulting in the cross-sectional geometries of submarine channels varying from V-shaped through deep Ushaped to dish-shaped downstream. Because submarine-channel confinement gradually decreased downstream, lobes occur at the unconfined terminal area, which grew headward, overlay on the early channel fills, and finally spilled out into the minor topographic low at the northwestern corner of the study area. The deposition of submarine channels and lobes significantly reduced the slope gradients in distal parts of the main topographic low. When subsequent mass flows were captured by the main topographic low, the capacity of mass flows to carry sediments was prone to get even weaker, thus resulting in more extensive accumulation of mass-transport complexes (MTCs) in distal parts of the main topographic low.