32. Sodic, yellow and grey texture contrast soils/Siliceous dunefields: Parabolic and linear dunes

These soils have developed on Quaternary unconsolidated material, generally of aeolian origin in the North West Dunefields and Plains, in swales, flats or plains amongst the dunefields. Soils are generally whole coloured, but some may have yellow subsoils with red mottling or red/brown deep subsoil. The soils have acidic surfaces with alkaline subsoils.

The surface soil is usually a dark greyish brown loamy sand to sandy loam, which are apedal (sandy) and have loose consistence. This soil occasionally overlies a loamy sand to sandy clay subsurface horizon, which is bleached and apedal either sandy or massive. There is a clear change to a light yellowish brown (occasionally brownish yellow, yellow or light grey) medium to heavy sodic clay upper subsoil. This is strongly structured (with coarse parting to medium sized peds), often with a reddish yellow mottle. This grades into similar material with few carbonate and manganese segregations and is less well structured. This soil then grades into a paler medium to heavy clay, strongly mottled, with slickensides and occasionally with weathered sandstone. The profile depth is about 120 cm or more with variable depths of the surface horizons, generally 10 cm for the surface and 5-15 cm for the subsurface, occasionally deeper.

Notable features include:

• Texture contrast soil, variable surface friability (generally sandy and soft but can be hardsetting).
• Occasional bleached subsurface soil (may be loose or cemented).
• Mottled subsoil strong consistence (strength) when dry, has restricted soil drainage as strongly sodic at depth.
• Subsoils are calcareous but few carbonate segregations.