Discrete-Element Modelling of Diapirism and Sedimentation on Continental Margins: A New Modelling Approach of Salt Deformation

Abstract

This study uses a Discrete-Element Modelling technique to investigate the interplay of sedimentation with rejuvenation of diapirs by shortening and gliding along continental margins at local and regional scales. The inherent complexity of salt tectonics, the complications encountered when imaging structures beneath salt using seismic data, and the lack of outcrop analogues, coupled to its importance in petroleum systems, make salt tectonics one of the most interesting and debated topics in basin studies. This new modelling approach generates results that successfully reproduce the geometric and dynamic behaviour of salt under regional stresses and show the effects of variable initial diapir architecture, margin tilting, the thickness, rate and timing of sedimentation on the generation of distinct diapir and minibasin geometries, including salt tongues, sheets and squeezed up-right and tear-drop diapirs. Models with late or reduced sedimentation rate favour the development of asymmetric diapirs with allochthonous salt tongues, whereas models with earlier sedimentation and faster sedimentation rate generate upright squeezed and tear-drop diapirs. Initially rectangular salt stocks tend to ascend faster than more sinusoidal-shaped diapirs and favour complete roof dismembering. An increase in the basinward tilting of the salt detachment facilitates gliding and the development of more asymmetric structures. The roof thickness of diapirs also affects the overall evolution of the systems where thinner roofs allow the development of larger salt tongues and sheets by favouring lateral salt expansion on the top of diapirs. Results are fully reproducible and comparable with 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, which are important in the context of hydrocarbon exploration around salt diapirs and sheets.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018