Evaporites

Definition

An evaporite is a salt rock (in its broadest sense) originally precipitated from a saturated surface or near-surface brine in hydrological conditions driven by solar evaporation (Warren 2016). Most develop in hot arid coastal environments on evaporitic mudflats (sabkhas, e.g., in the United Arab Emirates) in shallow evaporitic seas or in inland salt lakes (salterns or salinas). Their ancient depositional environments were similar to the modern ones, but ancient deposits are considerably altered by complex diagenesis.

Seawater evaporation follows a depositional sequence becoming more saline with more exotic salts formed as the dissolved salt concentration increases. The first deposited minerals are alkaline Earth carbonates, followed by evaporites, gypsum/anhydrite, halite, sylvite, polyhalite, and finally complex evaporite minerals (Warren 2016). In enclosed continental evaporitic basins, gypsum and halite are common as are exotic salts; in very cold continental settings,...