How Do Relay Ramps Influence Sedimentation in Rift Settings? A Study Combining Sandbox and Numerical Experiments

In this experimental study the influence of relay ramps on submarine fan deposition is investigated by combining physical laboratory experiments with fluid flow computations. The laboratory experiments comprised a two-layer sandbox model with sand and silicone put under extensional stresses to produce a rift basin with relay ramps. Its laser-scanned topography served as digital elevation model for the FanBuilder program, in which turbidity currents were modelled under different inflow directions to the rift axis. The relay ramps were found to behave as pathway for the flow if the angle of incident was small compared to the ramp incline. Wide and antithetic relay ramps with small dips can thus function as depocentres. Narrow ramps are by-passed, and the turbidity currents flow down the main gradient of the rift edge to form basin floor deposits. In order to simulate syn-tectonic sedimentation the deposits obtained from the numerical calculation were physically added to the sandbox model before and during resumed extension. Serial cuts in the analogue model after the experiments exhibited the internal structure of the modelled rift basin.