Carbonate accumulation on islands in the Okavango delta, Botswana

• Published in: South African journal of science Vol. 82; no. 10; pp. 588 - 591
• Main Authors: MCCARTHY, T. S, MCIVER, J. R, CAIRNCROSS, B
• Format: Journal Article
• Language: English
• Published: Pretoria Foundation for Research Development 01.10.1986
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Freshwater; Geomorphology, landform evolution; Surficial geology; Trona; Southern Africa; Botswana; Calcium carbonate; Evapotranspiration; Vegetation; Sodium carbonate; Deltaic environment; Paludal environment; Thermonatrite
• ISSN: 0038-2353

Efflorescent crusts consisting predominantly of the sodium carbonate minerals trona and thermonatrite with minor sylvite are commonly developed on less vegetated portions of islands in the Okavango Delta where the land surface is less than about one metre above water level. This efflorescence represents the end product of evaporation of swamp water. At intermediate stages of evaporation, small calcite crystals are produced. These are brought to the surface by ants for the construction of termitaria, degradation of which produces concentrations of calcite on the surface. The low total dissolved solid content of swamp watersuggests that evaporation of swamp water occurs predominantly from islands. Carbonate build-up will have a major impact on the Okavango ecosystem in the future.