Inflation and deflation of deeply buried salt stocks during lateral shortening

Abstract

We used scaled physical models to investigate how buried, dormant diapirs are rejuvenated by lateral squeezing. In Stage 1, regional shortening increased the pressure of the source layer, causing an inward plume of source-layer salt to intrude the dilating diapir and arch its roof. In Stage 2, the thrust front jumped forward to the salt stock, forming a major salient toward the foreland, and the stock roof was arched. Salt inflation still dominated, but a small outward plume of diapiric salt began to intrude the source layer on the foreland side of the diapir. With continued shortening in Stage 3, the converging diapir walls deflated the diapir, while a major overthrust prevented surface extrusion. Compressional uplift of the overburden created space for downward intrusion of diapiric salt into the source layer and diapiric pedestal. The models document a newly recognized type of active diapir that inflates under compression. The models also show how a salt diapir can weld shut where surface extrusion of salt is inhibited.