Multi-Valued Logic Modeling to Visualize Conceptual Uncertainty in a Mixed Carbonate-Siliciclastic System

A computer model developed on the principles of multi-valued logic simulates the depositional processes of a mixed carbonate and siliciclastic system. This modeling approach is advantageous for simulating complex mixed sedimentary processes. Through the use of "degrees of truth," the model denotes the extent to which various propositions are justified based on predefined first principles, thereby allowing examination of conceptual uncertainty in the geologic model. The model simulates the deposition of terrestrial to subtidal environments by integrating local, regional and global variables including sea-level change, climate, latitude, seafloor topography, water energy, water depth, and erosional patterns.

Previous studies of the Middle Jurassic Ellis Group of Wyoming and Montana have ascribed its stratal geometries and depositional facies to the influence of tectonic movement, sea-level change, and incipient topography. Modeling indicates that the Ellis Group was deposited during two transgressive-regressive segments. Transgressive episodes were dominated by carbonate and evaporite deposition related to changing ocean chemistry and increasing accommodation space. Regressive periods are distinguished by progradational supratidal redbeds. Modeling confirms that the depositional cycles in the lower Ellis Group developed due the interplay between sea-level change and tectonic subsidence related to the evolution of a retro-arc foreland basin. Modeling strongly supports the interpretation that localized syndepositional tectonic movements complicated depositional and erosional patterns.