It is often difficult to establish in the field the origin of the B horizon of buried truncated palaeosols. However, infrared spectral configurations of electrodialyzed humic acids can be used as a diagnostic tool. Decreased absorption on passing from 2500 to 1800 cm‐1indicates the presence of a chernozemic B horizon. The difference was explained on the basis of the conditions that existed at the time of the formation of these horizons. Burial did not change the structure of the humic substances responsible for the infrared spectral configuration