salt plug

A mass of salt which is injected as a diapir (a dome in which the overlying rocks have been ruptured by the squeezing-out of plastic core material) into overlying sedimentary rocks, thereby piercing and deforming them. The mechanism is similar to that of an intrusive magma, with the salt deforming and behaving plastically under pressure. It is of great economic importance because it assists in the formation of a "trap" structure for oil accumulation, in addition to its associated deposits of anhydrite, gypsum and sulphur. (Source: BJGEO / WHIT)