Research paperExperimental studies of the controls of the geometry and evolution of salt diapirs

Experimental models were conducted to study the controls of the evolution and geometry of salt diapirs, and the transition from passive to active diapirism. Both constant and variable sedimentation rate experiments were conducted. Constant sedimentation rate experiments show that the evolution of diapirs is strongly dependent on the rates of sand deposition and the thickness of the source layer. Low rates of sedimentation result in high ratios of salt flow to aggradation, leading to cylindrical diapirs which subsequently develop flared shapes with overhangs, whereas high sediment rates result in low ratios of salt flow to aggradation, resulting in tapered shapes and eventual eclipse and occlusion of the diapirs. Thick source layers result in higher salt flow rates than thin layers. Variable sedimentation rates result in changing shapes of diapirs over time. A small increase in sedimentation rates for flared or cylindrical diapirs result in an initial eclipse followed by tapering and a transition to active diapirism, enabling the diapir to pierce the overlying sediments. The narrower diapir continues to grow by passive diapirism. A large increase in rates results in a permanent eclipse, because the tapered diapir is unable to penetrate the greater thickness of the overburden. Finally, thicker source layers generally result in wider diapirs during both phases of deformation. Tapering and flaring are mechanisms of maintaining equilibrium between the rate of sedimentation and net salt flow rate. The resulting models are directly applicable to the analysis of poorly or partially imaged salt diapirs in natural subsurface examples.