Mechanical modeling and InSAR measurements of Mount Sedom uplift, Dead Sea basin: Implications for effective viscosity of rock salt



We present a mechanical model for the growth of an emerging salt diapir in a tectonically active basin. The analytical model is applied to and serves to constrain the effective viscosity of rock salt and strain rates during diapirism of the wall-shaped Mount Sedom rock salt diapir, Dead Sea basin. The model is based on one-dimensional flow of Newtonian viscous fluid (salt) in a vertical channel that has been driven by the load of the overburden and affected by shear along the channel walls. Because the Poiseuille (channel) flow profile is parabolic and the Couette (shear) flow profile is linear, a one-dimensional model provides three sets of predicted profiles: topography, uplift rate, and shear strain. The present topography of Mount Sedom represents the shape of the Sedom diapir, and hence the effective viscosity of rock salt can be constrained by a model that best fits the present topography of the mountain. The resulting Sedom rock salt viscosity is determined to be between 2 and 3 × 1018 Pa s, and the associated strain rate is between 5 and 6 × 10−13 s−1. Geological structures indicate strain rates of 9 × 10−13 s−1 and 3 × 10−14 s−1 during the Holocene emerging stage and at the Plio-Pleistocene pre-emergent stage of the Sedom diapir, respectively. The uplift history of Mount Sedom predicted by the model and the current topography are compared to Interferometric Synthetic Aperture Radar (InSAR) measurements of salt uplift. The maximum uplift rates of Mount Sedom are 8.3 and 5.5 mm/yr for its northern and southern parts, respectively. The InSAR uplift profiles resemble topographic profiles obtained along the same traverses, implying that the uplift history during the last 14,000 years is stable. Steep uplift gradients observed by InSAR along the western margin of the diapir are higher than predicted by modeling of Newtonian viscous flow. This could imply that flow of power law viscous fluid may be more suitable than that of Newtonian viscous fluid for the Sedom rock salt at high strain rates above 8 × 10−13 s−1.