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Tetzlaff, D.M., 1987

A simulation model of clastic sedimentary processes

Bibliographic Reference

Tetzlaff, D.M., 1987, A simulation model of clastic sedimentary processes: Palo Alto, California, Stanford University, Ph.D. dissertation, 345 p.


This dissertation describes SEDSIM, a computer model that simulates erosion, transport, and deposition of clastic sediments by free-surface flow in natural environments. SEDSIM is deterministic and is applicable to sedimentary processes in rivers, deltas, continental shelves, submarine canyons, and turbidite fans. The model is used to perform experiments in clastic sedimentation. Computer experimentation is limited by computing power available, but is free from scaling problems associated with laboratory experiments. SEDSIM responds to information provided to it at the outset of a simulation experiment, including topography, subsurface configuration, physical parameters of fluid and sediment, and characteristics of sediment sources. SEDSIM was developed in three stages. The first stage involved a 'flow-only' model. The Navier-Stokes equations were integrated vertically and simplified to yield a depth-mean flow model. A 'marker-in-cell' numerical method was applied, resulting in a model capable of handling both steady and unsteady flow over an arbitrary topographic surface. In the second stage, criteria governing sediment erosion, transport, and deposition for a single sediment type were incorporated, and an algorithm was developed to simulate periods of time of geological significance. In the third stage, the model was expanded to deal with mixtures of sediment, accommodating up to four arbitrary particle sizes and densities, and their mixtures in any proportion. Extensive computer graphics are incorporated in SEDSIM. The user can display the three-dimensional geometry of simulated deposits in the form of successions of contour maps, perspective diagrams, vector plots of current velocities, and vertical sections of any azimuth orientation. The sections show both sediment age and composition. SEDSIM works realistically with processes involving channel shifting and topographic changes. Example applications include simulation of an ancient submarine canyon carved into a Cretaceous sequence in the National Petroleum Reserve in Alaska, known mainly from seismic sections, and a sequence of Tertiary age in the Golden Meadow oil field of Louisiana, known principally from well logs. The two examples illustrate the manner in which SEDSIM can be used in making geologic interpretations. I conclude that simulation models are useful tools in interpreting modern as well as ancient clastic deposits, and in predicting the shapes and orientation of specific sedimentary units in such deposits.

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