Architectural style and quantification of a submarine channel-levee system located in a structurally complex area: Offshore nile delta

摘要

A Pleistocene channel-levee system located in a structurally complex area of the offshore Nile Delta is studied using a high-resolution three-dimensional (3D) seismic dataset. The seismic faciès and stacking patterns are characterized and quantitative analysis of its morphology (e.g., thalweg longitudinal profile, relief, width, and levee thickness) is utilized to understand the controls on channelized-flow processes and resultant architecture. Overall a change downslope from a degradational to aggradational style is observed, which can be related to the concave-up slope profile. In comparison to other channel-levee systems the Noor has a shorter length scale and displays a steepened thalweg slope. This is interpreted to be influenced by structural movements and an associated knickpoint, which controlled a change in flow processes (e.g., velocity, turbulence, and thickness) and the associated location of the canyon to channel-levee transition zone. An unusual feature of downslope levee thickening is observed. Instead of the normal reduction in overbank sedimentation downslope, it is suggested that structural modification causing relative steepening of seabed topography resulted in increased turbidity-current velocity, fluid volume discharge, and associated sediment load, which overcame the normal downslope loss of sediment due to overbank sedimentation. This study shows that architectural style is strongly linked to slope topography, and that structural movements can influence the slope profile and flow process, resulting in modification of the morphology and dimensions of channel-levee systems.