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36 Brown strongly sodic texture contrast soils on Quaternary basic volcanics

These soils occur extensively on the basic volcanic plains, generally in the less stony areas. The organic surface soils (10–15 cm) overlie a weakly pedal to massive subsurface (A2) horizon (to 20–50 cm) with some ferruginous (or ferromanganiferous) gravel, which abruptly overlies a brown coarse structured hardsetting mottled (red, orange) medium to heavy clay with some ferromanganiferous) gravel, which may overlie a highly calcareous clay horizon (90 cm or greater), which will overly parent material, usually with a clear boundary (>150 cm). Depth for the particular boundaries may vary due to the swelling nature of the soil, so that a subsurface horizon may not exist with clay close to the surface, but appear and be quite deep (and hence a greater depth to the heavy clay subsoil within metres). This is called gilgai or crabhole terrain; the components are called puffs and shelves. The lower subsoil may be more olive/yellow-brown at depth, indicating anaerobic conditions.

Notable features include: texture contrast, coarse structure (columnar), very hard when dry, strong sodicity in the subsoil and possibly the surface soil, variable vertical depth and horizontal distance characteristics of surface soil, free carbonate (calcareous) at depth, deep profiles, and some ferromanganiferous gravel.
CLRA Soil Unit 36

Soil Sites

Site Code
Soil-landform unit
1:100 000 mapsheet
Lower slopeEutrophic, Mesonatric, Brown SodosolDy3.43, Dg2.43T7621 - Colac
FlatEutrophic, Mottled-Mesonatric, Brown SodosolDb2.42T7622 - Ballarat
FlatVertic, Mottled-Mesonatric, Brown SodosolDy3.32T7522 - Skipton
Upper slopeFerric, Mottled-Mesonatric, Brown SodosolDy3.33T7522 - Skipton
Mid slopeHypercalcic, Mottled-Mesonatric, Brown SodosolDb2.13T7721 - Geelong
FlatEutrophic, Mottled-Hypernatric, Brown SodosolDy3.43T7721 - Geelong
FlatFerric, Mottled-Hypernatric, Brown SodosolDy3.43T7721 - Geelong
PlainManganic, Mottled-Mesonatric, Yellow SodosolDy3.42T7622 - Ballarat
Lower slopeVertic, Mottled-Mesonatric, Grey SodosolDy3.43T7522 - Skipton
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