Studies of some Mesozoic-Cenozoic 'red beds' in France and in W African basins (Senegal and Ivory Coast) show that they are the result of in situ lateritic weathering of glauconitic sediments. The alterations took place without destruction of pre-existing sedimentary structures. Glauconitic grains are weathered to ferruginous öoids consisting of Al-goethite, or are weathered to a kaolinite+goethite matrix. Original clay fractions are transformed into kaolinite and ferruginous oxi-hydroxides. Apatite nodules or beds gave rise to crandallite, millisite and variscite

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