Three-dimensional numerical simulation of turbidity currents in a submarine channel on the seafloor of the Niger Delta slope

Abstract

[1] In the present work, we use a three‐dimensional numerical model to simulate turbidity currents in a large‐scale submarine environment. The model solves the Reynolds Averaged Navier–Stokes equations, along with a two‐equation turbulence closure model, the sediment conservation equations for multiple grain‐size classes and the Exner equation of bed sediment conservation. Four different grain‐size classes (30, 64, 125, and 250μm) are considered. The model is applied to a modern seafloor environment in the continental slope of the Niger Delta where bathymetric data and seven piston cores were collected in and around a sinuous channel. Detailed analyses show the grain‐size distribution for different beds within each core. Since the flow events responsible for the formation of this modern depository are unknown, we perform simulations with different inflow conditions in order to match the grain‐size data. The model realistically predicts the flow field and its evolution over the complex topography and shows the spatial distribution of different grain‐size classes. A strong lateral flow from the inner to the outer bank is observed at the bends of the low‐relief channel. From the computed deposition rate, we obtain the fraction of each grain‐size class at the core locations and compareD50 and D90 predicted from the model with the core data. The discrete values predicted from the model fall within the range of D50 and D90observed in different beds in the cores. The results demonstrates that a 3‐D numerical model can be a useful tool for understanding the distribution pattern, thickness, and grain size of the turbidity currents and their deposits at the field scale and can help constrain the variabilities of reservoir architecture.