A QUANTITATIVE MODEL OF DYNAMICAL SEDIMENT DEPOSITION AND EROSION IN 3 DIMENSIONS

Modeling of sediment deposition in three dimensions is accomplished by taking quanta of sediments. released at different locations on a basi nal slope, and allowing the sediments to flow constrained by the exist ing topography of basin slope and previously deposited sediment flows. Sediments released in each quanta are transported downslope and depos ited when their flow energy drops below a critical value. The sediment flow also can cause erosion of the existing basin slope, and the tota l mass of sediments then follows the transport rules. Each quantum of sediment can be composed of variable fractions of up to ten lithologic types, ranging from very fine-grained material to coarse-grained sedi ments. Deposition takes place dependent upon the parameter values assi gned to each lithologic type; default values are arranged so that coar se-grained material is deposited first and fine-grained material last. The computer program, named MOSED3D (MOdel of SEdiment Deposition in 3-Dimensions), is written in C with an X Window System Toolkit, which provides a user-friendly interface for MOSED3D. Model results can be d isplayed in contour map form, as isopachs, and also as 2-D cross secti ons drawn in arbitrary, user-defined, directions across the system. Th e code is fast, requiring about 2 min CPU time on a SUN SPARC 3 for a typical run, so that many different geological scenarios with multiple parameter assignments can be investigated quickly for accordance with either required behaviors or with observed patterns of deposition. Th is paper describes the mathematical formulation, program structure, an d some test cases designed to illuminate individual factors the code i s capable of handling.