Silcrete drainage-line

Figure 4.10 (A) Cores extracted from the bed of the Boteti River at Samedupe Drift, Botswana, showing a range of geochemical sediments developed beneath the channel floor, including massive and pisolithic drainage-line silcretes (after Shaw and Nash, 1998). (B) Section of silcretes in the Mirackina palaeochannel, South Australia (after Ollier and Pain, 1996), showing the planform distribution of silcrete outcrops along the palaeochannel course and the relationship of silcrete to underlying non-silicified units. (C) Schematic representation of geochemical sedimentation patterns in the vicinity of a pan or playa (after Summerfield, 1982).

Nash, D.J., Shaw, P.A. Ullyott, J.S. (1998) Drainage-line silcretes of the Middle Kalahari an analogue for Cenozoic sarsen trains Proceedings of the Geologists Association 109, 241-254. 

---