Sedimentary Basin Models

Sedimentation Models

We use sedimentation models to dynamically simulate the generation, transport and deposition of sediment in space and time. These models use physical and conservation laws, combined with empirical generalizations, to move and deposit sediment dynamically under uniform or non-uniform flow conditions across dynamic depositional surfaces. Most sedimentation models are forward models, with time scales of 1,000 to 20,000 years and spatial scales on the order of tens to thousands of meters (Figure 1).

Most models simulate sedimentation in topographic basins, and are not coupled with geodynamic models; a few simulate sedimentation in stratigraphic basins, and are coupled with geodynamic models. Some models are coupled with atmospheric and/or ocean circulation models which provide the driving mechanism for transporting fluids.

Because they are based on fundamental laws and are concerned with simulating natural systems, sedimentation models appear to provide a more accurate representation of the real world. However, modeling even the transport of sedimentary grains requires an empirical generalization of the ways that turbulent or laminar flow move and deposit those particles. Sedimentation models are neither better nor more fundamental than other types of forward basin models. They are simply more appropriate for particular questions and scales of investigation. In general, we do not test sedimentation models against observed data, although there are some exceptions (e.g., Syvitski, 1989; Paola, 1989). The temporal and spatial scales of sedimentation models are generally too small for most exploration problems, given the limitations of the approximations used and the extensive computation time.

Stratigraphic models use theoretical and empirical approximations from the other two types of models, together with empirical generalizations, to explain or predict the distributions and volumes of lithologies within a basin. They are intermediate in scale, with temporal ranges on the order of one to 10 My and spatial scales on the order of a few to tens of kilometers.