The influence of shortening and sedimentation on rejuvenation of salt diapirs: A new Discrete-Element Modelling approach

Abstract

This study employs a novel Discrete-Element Modelling approach to investigate the interplay of sedimentation with rejuvenation of diapirs by shortening. The inherent complexity of salt tectonics, the complications encountered when imaging structures beneath salt, and the lack of outcrop analogues, coupled with its importance to petroleum systems, make salt tectonics one of the most interesting and debated topics in basin studies. Model results successfully reproduce the geometric and dynamic behaviour of active diapirism and show the effects of sedimentation thickness, rate and timing on the generation of distinct diapir geometries, including i) salt tongues and ii) squeezed upright diapirs. Models with late sedimentation or a lower sedimentation rate relative to salt mobility show development of asymmetric diapirs with allochthonous salt tongues; whereas models with earlier sedimentation or a faster sedimentation rate generate upright squeezed diapirs. Early sedimentation at a moderate rate results in a symmetrical hour-glass shaped structure, resembling a tear-drop diapir. Results are fully reproducible and comparable with many natural examples, and include overburden deformation which is difficult to simulate using other numerical techniques. Extending this approach to different problems and basinal contexts could improve our understanding of deformation mechanisms and sediment distribution around salt structures.

The Impact of Pre‐Salt Rift Topography on Salt Tectonics: A Discrete‐Element Modeling Approach

“…While physical models provide invaluable insight into the 3D geometry, timing and planform sequential evolution of structures (Dooley et al, , ; Ferrer et al, , ; Vendeville and Jackson, ; ), they demand a significant amount of time, space and investment (Pichel et al, ). Numerical models based on continuum methods, such as finite‐element modeling (FEM), have proved very useful in understanding the dynamics of salt flow, allowing more numerical control and realistic stress–strain quantification (Albertz et al, ; Gemmer et al, ; Gradmann et al, ; Weijermars et al, ).…”

“…Nevertheless, the method allows a good first‐order approximation of viscous salt flow at a regional scale that can be used to analyze various aspects of salt tectonics and diapirism driven by regional stresses (Pichel et al, ). The advantages of DEM are: 1) scaling is not a restriction; 2) models are easily reproducible, not requiring constant and complex re‐meshing; 3) they provide higher resolution and analysis of small‐scale deformation within the overburden; and, 4) they promote a more realistic, natural development and evolution of faults and folds in the sedimentary cover than other numerical techniques (Finch et al, , ; Pichel et al, ). The DEM technique used in this study derives from the Lattice Solid Model (Mora & Place, , ; Place et al, ) and the Particle Dynamics Method (Finch et al, ).…”

“…The DEM technique used in this study derives from the Lattice Solid Model (Mora & Place, , ; Place et al, ) and the Particle Dynamics Method (Finch et al, ). The technique has been extensively applied to model the dynamic evolution of geological systems (Donzé et al, ; Place et al, ), including faulting and folding processes (Deng et al, ; Finch et al, , ; Finch & Gawthorpe, ; Schöpfer et al, ); and viscous flow associated with development of boudinage structures (Abe & Urai, ) and salt diapirism (Pichel et al, ).…”

“…The model salt viscosity is 1.1 x10 9 Pa.s, which is lower than its real viscosity (10 17 –10 20 Pa s – Gemmer et al, ; Jackson & Hudec, ). However, as models of salt flow involve solid‐state creep, negligible inertial forces and Reynolds number (Re < <1), geometric similarity ensures dynamic and kinematic similarity despite numerical parameters not being identical to the real world (Pichel et al, ; Schultz‐Ela et al, ; Weijermars et al, ; Weijermars & Schmeling, ). The Poisson's ratio (v) for 2D DEM models is 0.33 and the Young Modulus (E) of the elasto‐plastic overburden is of 6.75 GPa.…”

“…In this study, we employ a Discrete‐Element Modeling (DEM) approach (Abe & Urai, ; Finch et al, , ; Pichel et al, ; Schöpfer et al, ) to investigate translation across semi‐isolated salt sub‐basins. These sub‐basins are associated with horst and tilted fault‐blocks that are realistic base‐salt geometries along rifted passive margins.…”