Salt mineral distribution patterns in soils of the Otjomongwa pan, Namibia

The deposits of the Otjomongwa pan, southwestern Kalahari, Namibia, contain halite, thenardite and minor amounts of calcium-bearing sulfate minerals. The deposits show vertical variations in salt content, evaporite mineralogy and thenardite morphology, with similar patterns throughout the basin. The salt minerals were formed by evaporation of groundwater, within a groundmass of lacustrine deposits that did not contain synsedimentary evaporites. Lateral variations in total salt content are related to the direction of groundwater flow during a period with high groundwater levels following the end of lacustrine sedimentation in the pan basin. This was followed by a period without any groundwater influence that continues to the present. During this stage, leaching by rainwater occurred, resulting in changes in evaporite mineralogy, morphology and distribution.