ABSTRACT: Gilbert--A Three-Dimensional Sequence Stratigraphic Model for Lake Basins

CHASE, CLEMENT G., PIERRE VERHOYEN, ANDREW S. COHEN, and J. JURGENS, University of Arizona, Tucson, AZ

We have developed the user-interactive forward model Gilbert (named for G. K. Gilbert, a pioneer in both lake stratigraphy and landscape research), which simulates a variety of depositional processes and their stratigraphic products. Gilbert runs on the principle of the cellular automaton, in which automata depict randomly seeded sedimentary "events" of various types (i.e., storm-generated fluvial discharges, turbidity currents, and resuspension flows) occurring on a cellular grid. Automata called precipitons, turbiditons, or suspenditons (depending on the type of process they mimic) variously erode or deposit sediment as they move downslope within a lake basin. These seeding events serve as the clock by which other model process rates are established. Surficial suspended sediment dis ersal is modeled through a multipass diffusion process. Lake level fluctuation amplitudes and rates and subsidence/uplift rates can be varied by the user to simulate historical changes within a basin. Model outputs for 1 or 2 facies models include a wide variety of two- or three-dimensional cross sections, isopach, and bathymetric/topographic maps. Three-dimensional cross sections (effectively fence diagrams) can be viewed from any angle between side and plan view and from any coordinate perspective.

Our sensitivity testing of the model is currently in an early stage. However, stratal geometries generated on a modeled half-graben basin nicely mimic seismic cross sections obtained from several modern African rift lakes, giving us confidence that the model is capturing those depositional processes responsible for large-scale rift-lake facies architecture. The model clearly predicts increasing patterns of delta and fan delta avulsion and depositional granularity at increasingly fine time scales, both of which are also consistent with current understanding of rift-depositional processes.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)