Vadose calcretisation commences with precipitation of micritic calcite from carbonate-rich meteoric water in the soil moisture zone. Through time, calcrete is subjected to repeated episodes of vadose cementation, dissolution, and brecciation of earlier-formed soil components, giving rise to stratigraphically complex soil profiles. The degree of complexity of individual profiles is largely influenced by the geomorphological setting and hydrological history of the local groundwater systems. Morphological similarities of calcrete duricrusts form the basis for establishing inventories of textural, compositional and physiographic features for Quaternary calcrete soil profiles and their evolutionary stages. Such inventories are useful tools for palaeo-environmental reconstruction, although calcrete duricrusts can be either an advantage or an obstacle for mineral exploration, depending on the level of understanding of calcrete and its relationship to the bedrock. Assessment of the timing of the main phases of carbonate precipitation indicates that calcrete soil profiles can attain maturity within a relatively short time. Problems with establishing a reliable time frame for differentiating Quaternary calcrete duricrusts from older counterparts represent a major challenge for further research.
