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IAMG 2001--Cancún
Technical Program--Session H |
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Silliciclastic Sedimentary Processes and Profile Morphology of Continental Slopes
by James P.M. Syvitski*, INSTAAR, University of Colorado, USA, 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 multi-process, 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, on the shape of the slope profile, of river plumes, shelf energy, sediment failure, gravity flows, subsidence, and sea level fluctuations. Hemipelagic sedimentation along with shelf storms produces simple clinoforms of varying geometry. Oblique clinoforms are associated with low-energy conditions and sigmoid geometries associated with more energetic wave conditions. 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. |
