Initial variations in thickness and quality of salt are introduced in the depositional environment. Sedimentary fabrics in halite (Hovorka, 1994) show that halite is typically deposited rapidly, producing large clear crystals. Impurities are introduced when environmental conditions shift, and halite deposition pauses. In shallow water, halite precipitates on the brine-pool floor as crusts of crystals that average a centimeter in height. When the brine pool is flooded by less highly evaporated marine water or by fresh rainwater, minor amounts of halite dissolve from the floor of the brine pool. Impurities within the halite accumulate as a lag on the brine-pool floor. If the floodwater is marine, a thin bed of gypsum commonly precipitates before halite precipitation resumes.

 

Halite on the brine-pool floor dissolved when the flat was flooded by marine water. (a) Truncated halite crystals contain chevron-growth structures defined by fluid inclusions, accumulation of impurities forming dark bands in Gulf PDB 03 core, 2,398 ft below datum. (b) Photomicrograph showing dissolution of halite (note truncated growth bands defined by fluid inclusion), followed by precipitation of gypsum (now replaced pseudomorphically by anhydrite and halite) before halite precipitation resumed. DOE-Stone and Webster G. Friemel core, 2,522 ft below datum.

Deposition of Salt — Continued