Quantifying submarine channel morphology and kinematics on structurally complex slopes: examples from the Niger Delta

Submarine channels form pronounced morphological features on the seafloor and play an important role in shaping the stratigraphic record. Over the last two decades, their morphology and architectural evolution have been studied in detail using a range of modern and ancient examples. While structural deformation is recognised as a major control, the temporal and spatial complexity associated with these systems means aspects of submarine channel dynamics and how their geomorphic expression translates into time-integrated sedimentary architecture, remain poorly understood. For example, structurally driven changes in slope morphology may locally enhance or diminish a channel’s ability to incise, aggrade and migrate laterally. In this thesis, I explore the sensitivity of submarine channel morphology to structural deformation and evaluate how channel-structure interactions are recorded in seismic stratigraphic architecture. I use novel seismic attribute analysis alongside concepts from landscape dynamics to provide quantitative insights into how the growth of structure on the southern Niger Delta slope has influenced submarine channel morphology and time-integrated stratigraphic architecture. From a 3D, time-migrated seismic reflection volume, I quantify a range of morphometric parameters including, channel gradient, width, depth, sinuosity, curvature, and stratigraphic mobility, on a number of modern and ancient submarine channel systems as they interact with structure. My results show that submarine channel morphology and longitudinal profile are unambiguously linked to the underlying structural template. The modern seafloor expression of submarine channels can be up to an order of magnitude higher aspect ratio and markedly more variable than their ancient, stratigraphic counterpart. Their depositional architectures are composite stratigraphic features that record the morphological response to spatial and temporal variations in structural growth rate. Based on this, three end-member styles of submarine channel architecture are recognised on structured slopes: pre-channel structural bathymetry, coeval positive relief, and coeval negative relief. This thesis quantifies how submarine channel systems integrate kinematic processes at the scale of the fundamental architectural unit, a channel element, and documents the systematic change in channel element kinematics on structured segments of the slope. My observations demonstrate the sensitivity of submarine channels to structural deformation and help us to constrain some of the most important sediment transport systems on planet Earth.Open Acces