Lateral migration and channel bend morphology around growing folds (Niger Delta continental slope)

Understanding the interactions of submarine channels with seafloor deformations is challenging as these channels more often involve a wide variety of responses relying on both autogenic and allogenic factors. The effect of active growing structures on channel pathways is well documented, but the evolution of lateral migration and the internal architectures along the deflected channel bends around ongoing active structures remain poorly constrained. Here, we use 3D seismic interpretation and quantitative geomorphologic methods to examine the channel bend morphology and the kinematics of lateral migration near gravity-driven tectonic deformation. Using high-resolution seismic reflection data acquired from the offshore Niger Delta, two-channel levee systems (Amaku Major System and Amaku Channel Levee System) have been recognized in the seismic survey. Each system consists of three channel complexes, recording five types of deflected channel bends, defined here as: (i) avulsed bend, (ii) confined bend, (iii) chute cut-off bend, (iv) blocked bend and (v) kinked bend. Geomorphologic parameters including bend sinuosity, bend amplitude, along-bend length, straight-bend length, channel depth and width, were considered within the deflected channels. Lateral migration estimators; channel lateral shift (SH), and channel lateral spacing (CS), were assessed throughout the distances of cross-sectional channel patterns. The lateral migration estimators (SH and CS) were used to estimate the expression of internal architectures and the evolution of lateral migration around seabed deformation at the scale of the channel complex. The results show that the morphology and internal architecture of the deflected bends, although developing in the same structural context, display varied responses to structural deformation. Unlike previously published models of channel-fold interactions asserting tectonics as the solitary driver, here we demonstrate that the channel deflections around structures are sensitive to the lateral confinement produced by sediment relief of the outer levees, and the autogenic forcing of channel mechanisms. This study provides new insights into the evolution of submarine channels in active tectonic settings, shows detailed mechanisms of channel bends at a small scale and offers a better understanding of the distribution of sediments in the deep sea.