Factors leading to sub-surface pan silcrete formation in north-central Botswana

Sue Ringrose*, Sorcha Diskin, Lin Cassidy, Stefan Coetzee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

New evidence was sought for sub-pan silcrete formation along the southern margin of Ntwetwe Pan in the Botswana Makgadikgadi basin. This was achieved by integrating drillhole and surface sample descriptions with element and isocon analysis. The silcrete deposit which lies ~1.0 m below the pan surface, comprises Ntane sandstone fragments and detrital infill, cemented by amorphous silica. The deposit probably evolved during sequential periods of palaeolake infilling and drying since at least the Mid-Pleistocene. Changes in basin water pH brought about during fresher water infill interspersed with brine evapo-concentration and later evaporative pumping, induced the mobilisation and precipitation of the silica cement immediately below the pan floor.
Original languageEnglish
Pages (from-to)93-112
JournalSouth African Journal of Geology
Volume126
Issue number1
Early online date10 Feb 2023
DOIs
Publication statusE-pub ahead of print - 10 Feb 2023

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