Thick and widespread evaporites are known from the Neo-Proterozoic to throughout the Phanerozoic. The contribution of the different salts to evaporite sequences varies greatly. This results from different modes of salt precipitation in shallow and deep basins, with and without brine reflux, often modified by sea-water seepage and loss of highly concentrated brine by leakage. Shallow groundwater/brine circulation and deeper, more closed flow systems largely transform the primary evaporites into secondary evaporites. Further modifications (tertiary evaporites) are caused by uplift and erosion of buried salt rocks.
