Evaporitic deposition sequence (limestone, gypsum, halite) indicates deposition in which setting?

• A. A coal seam
• B. A basaltic lava flow
• C. A stratigraphic sequence including limestone, gypsum, and halite indicates evaporitic deposition
• D. A long sequence of sandstone

Answer: (C)

Evaporite deposition happens in a closed or restricted basin where water evaporates faster than it’s replenished, causing salts to precipitate from the concentrating brines. The sequence limestone, followed by gypsum, then halite shows the water’s salinity increasing over time. Limestone forms in more open carbonate conditions, but as evaporation rises, calcium sulfate precipitates as gypsum, and with even higher salinity, table salt (halite) precipitates. Seeing all three minerals in that order indicates an evaporitic setting such as a shallow, enclosed sea, a playa lake, or a sabkha in an arid climate where evaporation dominates and clastic input is limited. This wouldn’t fit a coal swamp, a basaltic lava flow, or a predominantly sandstone sequence, which reflect very different environments.