Geoscience Reference
In-Depth Information
Table 4.4 Contd...
Geric properties Very low cation exchange capacity
Gleyic colour pattern Colours corresponding to more than 90% reduced iron
Lithological discontinuity Horizon contrast unrelated to pedogenesis
Reducing conditions rH < 20, presence of reduced iron, sulphides, methane
Secondary carbonates Accumulation of carbonates in the horizon
Stagnic colour pattern Signs of reduction due to submergence under water
Vertic properties Slickensides, cracks, expanding clay minerals
Vitric properties Rich in vitreous materials
* Al
o
and Fe
o
: acid-oxalate extractable Al and Fe
** Cation exchange capacity in cmol (+) kg
-1
clay
The distinction of properties related to the materials is an interesting
feature of the WRB (Table 4.5).
Diagnostic materials
Table 4.5
Diagnostic materials retained by the WRB.
Diagnostic materials
Simplified definition
Artefacts
Material of anthropic origin (refuse): bricks, pottery…
Calcaric material
Calcareous material
Colluvic material
Colluvium of anthropic origin
Fluvic material
Material of alluvial origin
Gypsiric material
Contains gypsum
Limnic material
Produced by aquatic organisms
Mineral material
Inorganic components
Organic material
Contains much organic debris accumulated on the surface
Ornithogenic material
Bird excrement
Sulphidic material
Contains sulphides
Technic hard rock
Man-made consolidated material
Tephric material
Unconsolidated material related to volcanic eruptions
The reference soil groups are presented in Table 4.6 sorted in a simplified
way but in a manner that enables comprehension and complete
memorization of the list. The RSG in grey have not been studied in
detail because they are less important than the others for understanding
pedogenesis (top of the table) or because they are immature so that
there would be few things to say about them (bottom of the table).
The WRB provides a determinative key for classifying a given soil in
the appropriate RSG. But, with a little experience, one can mentally
select very quickly the two or three taxa from which the choice can be
made.
Reference soil groups of the WRB (RSG)
