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Ferricrete seen in Gulf Coastal Plain deposits

Ferricrete is a hard, erosion-resistant layer of material at the land surface that consists of near surface sediments that have been cemented by iron oxide into a duricrust. Ferricretes contains sediments and other non-indigenous materials, which have been transported from outside the immediate area in which it occurs. The iron oxide cements are derived from the oxidation of percolating solutions of iron salts. The word is derived from the combination of ferruginous and concrete. Synonyms include ferruginous duricrust, hardpan and ironpan.

Ferricrete deposits along the Animas River watershed in Colorado have been classified as:[1]

alluvial iron oxyhydroxide-cemented conglomerates along old stream channels
colluvial iron oxyhydroxide cemented poorly sorted breccias with massive to minor layering subparallel to hillslopes
iron spring and bog deposits with few or no clasts, exhibiting fine, horizontal lamination
manganocrete deposits with gray to black matrix containing abundant manganese oxide minerals.

Ferricrete is used widely in South Africa to create roads in rural areas. It is better known in these regions by its Afrikaans name "Koffieklip" (coffee stone).

Ferricrete is also found in the United States in areas of the Gulf Coastal Plain and the Atlantic Coastal Plain. Ferricrete is also found in Western Australia and remote eastern areas of Australia.


  1. ^ Verplanck, Philip L.; et al.; Ferricrete Classification, Morphology, Distribution, and Carbon-14 Age Constraints in Environmental Effects of Historical Mining, Animas River Watershed, Colorado, US Geological Survey, Professional Paper 1651, 2007, p. 726 PDF