Sources of iron oxides in reddish brown soil profiles from calcarenites in Southern Spain

Abstract We studied the distribution with depth of the different forms of iron in two reddish brown (rubified) soils developed on hematite-free calcarenites in the Province of Cordoba, southern Spain. Hematite appeared in significant amounts in the A and B horizons of the soils and seemed to have originated mainly from the weathering of the Fe-bearing clay minerals (smectites). Because of their low contents of Fe, both the non-clay fraction and the carbonate of the parent material contributed little to Fe-oxide formation. The distribution with depth of goethite in the clay fractions suggested that part of the initial goethite had been lost and might have been altered to hematite.