Numerical simulation of Rayleigh-Taylor instability for single and multiple salt diapirs

Abstract

The diapiric ascent of light rocks through a denser oberburden is simulated using a new numerical method based in part on finite differences. Rocks are modelled as viscous Newtonian liquids and the internal interfaces are located with the help of passive markers. These markers are relocated using a new algorithm equivalent to a cellular automaton rule. This allows the markers to be redistributed very rapidly. This new method appears to be well adapted to quickly resolving geological problems. Simulations of the growth of a single dome are performed under various viscosity ratios for the salt and the overburden. The effect of asymmetrical initial deformations of the salt layer is to produce diapiric structures that slowly return to symmetry as the diapir matures and rises in an isotropic medium. Simulations involving continuous sedimentation of the overburden are also performed. An initial geometry on a basin margin in which multiple diapirs eventually develop is studied. Diapirs grow relatively rapidly near the centre, while on the margins the salt layer flows upward following the basement. Simulations with salt that is more viscous than sediments show the development of previously unnoticed asymmetrical structures.