Soils having a mollic horizon (deep, dark coloured surface horizon with a significant accumulation of organic matter and high base saturation) and accumulation of secondary calcium carbonate within 100 cm from the soil surface. They have no diagnostic horizons other than an argic, calcic, cambic, gypsic, or vertic horizon.
Kastanozems occur mainly in the dry parts of the steppe regions of the world. Vast areas are found in central Asia and central USA. Smaller occurrences are reported from the Mediterranean region