ZENG, JIANJUN, Bellaire Research Center, Shell Development Company, Houston, TX; and DONALD R. LOWE, Department of Geology, Stanford University, Stanford, CA

ABSTRACT: Numerical Simulation of Turbidity Current Flow and Sedimentation

A computer-based numerical model of turbidity-current flow and sedimentation includes three components: (1) a sedimentation/fluidization model for sediment-size fractionation in sedimenting multi-component suspensions, (2) a concentration-viscosity model for changes in resistance of such suspensions toward fluid and sediment motion, and (3) a layer-averaged flowmodel for tracing downslope flow evolution using continuity and momentum equations. Sedimentation history of turbidity flows is monitored in terms of evolution of flow velocity, thickness, sediment concentration and resulting rate of sedimentation and sediment size fractionation. Turbidites with downslope variations in their thickness and grain-size structuring are generated.

Calibration models using initial and boundary conditions approximating those of Bute Inlet, a modern turbidity flow system in British Columbia, yield turbidites closely resembling their natural counterparts. Additional flow experiments to quantify the effects of basin geometry, sediment sources and flow concentration on the formation and properties of turbidites were run. High-concentration flows show higher downslope velocities and lower sediment-settling velocities than more dilute flows, resulting in longer sediment-transport, fine-sediment bypassing, and poorer-sorting of turbidites. Model coarse-grained flows tend to deposit sediment more rapidly on the proximal slope than otherwise similar fine-grained flows, which tend to form turbidites with more tabular geometry, greater down lope extent, and lower surface relief.

The model partially fills the gap between observational and experimental analyses of deep-sea deposystems. Further improvements should enable it to become a predictive tool for facies architecture of deep-sea systems.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.