Silcrete formation

Alexandre, A., Meunier, J.-D., Llorens, E., Hill, S.M. Savin, S.M. (2004) Methodological improvements for investigating silcrete formation petrography, FT-IR and oxygen isotope ratio of silcrete quartz cement, Lake Eyre Basin, Australia. Chemical Geology 211, 261-274. 

Ollier, C.D. (1991) Aspects of silcrete formation in Australia. Zeitschrift filr Geo-... 

Summerfield, M.A. (1984) Isovolumetric weathering and silcrete formation, Southern Cape Province, South Africa. Earth Surface Processes and Landforms 9, 135-141. 

Webb, J.A. Golding, S.D. (1998) Geochemical mass-balance and oxygen-isotope constraints on silcrete formation and its palaeoclimatic implications in southern Australia. Journal of Sedimentary Research 68, 981-993. 

Wopfner, H. (1983) Environment of silcrete formation a comparison of examples from Australia and the Cologne Embayment, West Germany. In Wilson, R.C.L. (Ed.) Residual Deposits Surface Related Weathering Processes and Materials. Special Publication 11, Geological Society of London, pp. 151-157. 

Stephens, C.G., 1971. Laterite and silcrete in Australia a study of the genetic relationships of laterite and silcrete and their companion materials, and their collective significance in the formation of the weathered mantle, soils, relief and drainage of the Australian continent. Geoderma, 5 5—52. 

Silcrete may form within, or by the replacement of, a range of host material types. Many Australian and South African silcretes have developed within deeply kaolinised or bleached regolith (Summerfield, 1978 1983b-d Wopfner, 1983 Milnes and Thiry, 1992 Thiry et al., 2006). Formation can, however, occur in (or on) unweathered bedrock or otherwise unaltered and unconsolidated sediments. Silcrete development is also frequently associated with the replacement of carbonate sediments or calcretes (Cros and Freytet, 1981 Twidale and Milnes, 1983 Ribet and Thiry, 1990 Armenteros et al., 1995 Nash and Shaw, 1998 Thiry and Ribet, 1999 Nash et al., 2004). 

Silicification is, in the majority of cases, demonstrably not contemporaneous with deposition or formation of the host material. Pedogenic silcretes... 

Despite the leaps in silcrete research over the past 20 years, work is still needed to fully understand the variations in silcrete micromorphology, mechanisms of formation (especially in non-pedogenic varieties), and... 

Leckie, D. A. Cheel, R.J. (1990) Nodular silcretes of the Cypress Hills Formation (Upper Eocene to Middle Miocene) of Southern Saskatchewan, Canada. Sedi-mentology 37, 445-454. 

McCarthy, T.S. Ellery, W.N. (1995) Sedimentation on the distal reaches of the Okavango Fan, Botswana, and its bearing on calcrete and silcrete (gannister) formation, Journal of Sedimentary Research A65, 77-90. 

Simon-Coinyon, R., Milnes, A.R., Thiry, M. Wright, M.J. (1996) Evolution of landscapes in northern South Australia in relation to the distribution and formation of silcretes. Journal of the Geological Society, London 153, 467-480. 

Thiry, M. Millot, G. (1987) Mineralogical forms of silica and their sequence of formation in silcretes. Journal of Sedimentary Petrology 57, 343-352. 

Youngson, J.H. (2005) Diagenetic silcrete and formation of silcrete ventifacts and aeolian gold placers in Central Otago, New Zealand. New Zealand Journal of... 

A characteristic of desert landscape in Australia and South Africa is a silica deposit termed silcrete, which may contain as much as 99% silica (Williamson [1957]). It has been suggested that this may be formed by the cementation of sand by upward movement of silica-rich waters, but this mode of formation certainly does not apply to all silcrete deposits (Jackson [1957]). Silica in the form of white powder has been noted on the surface of Hungarian solonetz soils. The KOH extracts from these soils contain silica and alumina in the ratio of 2 1, indicating degradation which can apparently be halted by organic maturing (Szabolcs and Darab [1958]). 

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