3D-SEDFLUX: COUPLING FLUVIAL AND STRATIGRAPHIC SIMULATION MODELS

The depositional architecture of fluvio-deltaic systems is controlled by complex interactions between many factors including basin drainage area,climate, sea-level fluctuations, offshore slope, tectonics, waves and tides. Two dimensional fluvio-deltaic models capture the essence of longitudinal deposition patterns, but since these controlling factors vary in space, it is necessary to model in three dimensions. Sedflux3D, a process-response numerical marine stratigraphic model, is used to explore how sediment is delivered to a basin by hypopycnal river plumes and the subsequent reworking of the sediments by storms, tides and longshore currents.

We have added a subaerial delta model to Sedflux3D to examine the coupled delta/basin deposition record. In the fluvial domain, the model employs a nested approach, in which the dynamics of a main channel belt are calculated and sediment is distributed laterally by overbanking. The lateral extent of the sedimentation zone is determined by process proxies which are environment specific, e.g. asymmetric distribution of the sediment depends upon channel sinuosity. The model is capable of simulating size-selective sediment transport; presently we use four different grainsize classes.

Although still in development, the model has been used to explore the relative importance of changes in sea level versus channel switching in determining the progradational pattern of the delta front. The differences between simulating river avulsions as a statistical process versus modeling levee breaks and steepest descent flow patterns are also presented.