As part of the characterization of a Tunisian red soil profile, six samples, taken at different depths, were investigated by MSssbauer spectroscopy at room temperature and at 80 K to obtain information about the various types of Fe oxides present. By considering magnetic hypertine field distributions, the spectra of goethite and hematite were well resolved. Chemical analyses of the samples revealed a partial substitution of Fe by A1 and Mn. The spectral behavior of the goethite was

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... influenced by crystaUinity and amount of A1 substitution which resulted in a reduction of the magnetic hyperfme field. The effect of Mn substitution was much more pronounced in the hematite spectrum as a consequence of a stronger suppression of the Morin transition by Mn than by AI.