Salt diapir downbuilding: Fast analytical models based on rates of salt supply and sedimentation

Abstract

Salt diapir shapes are influenced by the rate of salt supply into the base of the diapir, the rate of sedimentation, regional slope, local deformation around the salt body, and regional deformation. Prior graphical solutions to this complex problem consider only the salt supply and sediment aggradation rate; but there are major problems with these existing plots. Precise computation of diapir shapes using a new, fast analytical approach reveals that the shapes shown in previous publications were incorrect. “Rise rate”, a proxy used for salt supply in previous models, was inconsistently defined. The fundamental controlling factors used in this study to predict salt diapir shapes are the volumetric rate of salt supply to the base of the diapir, and the rate of sediment aggradation. These are combined to create predictive charts of salt shapes for both radial and linear geometries. We discuss the strengths and limitations intrinsic to our fast analytical models, suggesting geological conditions where they may be appropriate. Simple downbuilding models may not be directly applicable to geological settings that involve subsequent deformation of the sediments or of the salt body. However, the modified salt downbuilding concept as elaborated in our study can explain many real-world situations where the salt body flares or tapers upwards.