Predicting Profile Geometry of Continental Slopes with a Multiprocess Sedimentation Model

Abstract

Physics-based numerical models can simulate sedimentation on continental margins. They provide for an ideal platform to examine the response of morphology to changing sedimentary and geological conditions. Numerical experiments were conducted with the multiprocess, basin-fill model SedFlux, to evaluate the evolution of the two-dimensional shape of siliciclastic continental slopes. The SedFlux experiments were able to isolate the effect of river plumes, shelf energy, sediment failure, gravity flows, subsidence, and sea-level fluctuations on the shape of the slope profile. Simulation results show that hemipelagic sedimentation along with shelf storms produce simple clinoforms of differing geometry. Oblique clinoforms are formed in association with low-energy conditions and sigmoid geometries associated with more energetic wave conditions. Simulated slope failure steepens the upper continental slope and creates a more textured profile. Topographic smoothing induced by bottom boundary-layer transport enhances the stability of the upper continental slope. Different styles of sediment gravity flows (turbidity currents, debris flows) affect the profile geometry differently. Debris flows accumulate along the base of the continental slope, leading to slope progradation. Turbidite deposition principally occurs on the basin floor and the continental slope remains a zone of erosion and sediment bypass. Sea level and flexural subsidence surprisingly show smaller impacts on profile shape. Initial basin steepness and water depth have a profound influence on the steepness of the equilibrium profile. When compared to the morphology of modern passive margins, most of the equilibrium profiles compare best with margins under the influence of relatively high sediment input.