At present the Duric and Mellic great groups are only known to occur in Red or Brown Kandosols, particularly the former. The Duric soils are confined to the arid zone. Soils with a red-brown hardpan either within or directly underlying the B horizon . Soils with a thin ironpan which occurs within or directly underlying the B horizon . B horizons that are very porous with a weak consistence strength when moist.
Bulk density appears to be relatively low.
Soils in which the major part of the B2 horizon is dystrophic . Soils in which the major part of the B2 horizon is eutrophic but the B and BC horizons are not calcareous . Other soils with a calcareous horizon . Any peds present do not possess smooth faces. It is thought that the following subgroups will cater for most situations, although obviously some will not be relevant for particular great groups of particular suborders.