26. Calcareous gradatio nal soils/Calcareous dunefields: Linear dunes subdominant

These soils have developed on Quaternary unconsolidated material in the North West Dunefields, particularly with linear dunefields. The soil is alkaline and calcareous throughout.

The surface soil is usually a very dark greyish brown clay loam (sandy), which is weakly structured (coarse sized peds).

This abruptly and clearly overlies a reddish yellow light clay. This is moderately structured (medium sized peds) with calcium carbonate soft segregations (weaker structure with greater calcium carbonate). This soil grades into a heavier redder lower subsoil, with moderate structure and with calcium carbonate soft segregations and manganese flecks. The profile depth is about 150 cm or more with variable depths of the surface horizons, generally 10-15 cm for the surface, occasionally deeper.

Notable features include:

• Gradational profile with a heavier textured subsoil at depth.
• Highly calcareous upper soil with some free carbonate but high exchangeable sodium and soluble salts at depth.
• Limited surface friability (generally hardsetting), strong consistence (strength) when dry.
• Sodic, often strongly at depth, restricting drainage but reddish colours would indicate slight restriction to water movement.
• Occasional brown subsoil variants.