ABSTRACT
The cartographic exercise, resulting from a collective effort and patient compilation, albeit of a provisional character, is of both scientific and pedagogic interest. It permits comparison of the areas of duricrust phenomena with major climatic zones, vegetation types, geological structures, great soil groups and relief features. The international agencies recognise two facies common to the tropical world, with Australia having a unique facies. Three phases are therefore mapped: Petric phase, Petroferric phase, and Duripan phase. In view of the limited number of general synthesis maps, frequent reference will have to be made to the FAO-UNESCO map which is regarded as the basic document. The International Atlas of West Africa, which distinguishes lithosols on duricrusts from the indurations of ferruginous and ferrallitic soils, seems to exhibit a conservative view of the extent of duricrust. The World Soil Map, the only general synthesis available for tropical America, provides very generalised, succinct information on the extent of the petric facies alone.
