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Silicic Soils

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Under arid conditions silica mobilized during weathering in the upper part of the soil precipitates as a massive or laminated dorbank (duripan) horizon, the depth of which appears to be related to the texture of the overlying soil. Other evaporite minerals such as gypsum, calcite, sepiolite and halite are sometimes also in evidence and many dorbank horizons are calcareous.


The distribution of silicic soils locally and globally suggests that, for enrichment with silica, peculiar circumstances of silica activation such as volcanic ash showers or regular atmospheric additions of sodium in rain, fog or dust are required in combination with hydrolysis and intense evaporation (Soil forms: Garies, Oudtshoorn, Trawal, Knersvlakte).




Source: Soils of South Africa - Systematic and Environmental Significance by Martin Fey (2005)