HCA numerical modelling of interacting salt and extensional tectonics from growth strata patterns

The complex interplay between extensional tectonics and gravity-driven salt migration and doming, is now widely recognised as a major factor controlling the architecture and evolution in many passive margin environments. Unravelling specific contributions of the two factors is a very difficult task, given their intimate feedback. Analysis of growth strata patterns may provide a useful tool to address deformation history in such complex tectono-sedimentary environments. We carefully simulated the evolution of sedimentation trough time in response to both extension and salt tectonics by using the Hybrid Cellular Automata (HCA) forward modelling algorithm, which is a numerical, hybrid methodology between the cellular automata (CA) and the finite element method (FEM) philosophies. Layered rock units were simulated by a mesh of a very large number of semi-independent cells. Syntectonic sedimentation was achieved by properly adding new cell strata on top of the structure with the proper link to the existing mesh.The careful simulation of the evolution of sedimentation through time allowed to recognise the individual contribution of salt doming and fault activity in the present day distribution of the sediment thickness along a sector of the southern Atlantic passive margin. Forward modelling the internal architecture of offshore geosesmic sections allowed to recognise that in areas where the salt overburden was not sufficient to induce diapirism, the latter was triggered in later time by the activity of listric extensional faults.