Euhedral sparitic calcite in buried surface horizons in lake basins, southwestern Kalahari, Namibia

Rhombohedral sparitic calcite crystals are recognized in a subsurface interval in three pan basins of the southwestern Kalahari, eastern Namibia. They occur in the upper part of a correlatable unit, separated from the overlying deposits by a discontinuity that represents an important hiatus. The carbonates occur both in the groundmass and in pores. Crystals in the groundmass formed predominantly in the upper part of the buried interval, by partially incorporative intrasediment growth. Crystals in pores formed by evaporation of solutions in the macropore system, including pores created by animal activity and possible mouldic voids. The crystals are locally reworked in the basal part of the deposits that overlie the palaeosurface with which they are associated.

Research highlights► Associated sparitic calcite in groundmass and pores, formed by different processes. ► Identical occurrences in a buried surface horizon in separate lake basins. ► Study of recent example, contributing to interpretation of ancient occurrences.