4. PEDOFEATURES

Definition

The term pedofeatures is defined in the Handbook for Soil Thin Section Description as discrete fabric units present in soils and recognisable from adjacent material by a difference in concentration in one or more of their components (for example, a grain size fraction, organic matter, crystals, chemical components) or by a difference in the internal fabric. Birefringent fabrics are not included in the concept of pedofeatures.

Actually, in the majority of the cases, they are reorganisations of the soil materials that cannot be attributed to an inheritance of the original material.

Soil material = Groundmass + Pedofeatures

Below are a few examples in order to clarify the concept of pedofeatures.



They are pedofeatures T hey are not pedofeatures Clay coatings Rock fragments Organic matter coatings Root fragments Iron nodules Mineral grains

Description of pedofeatures

The following characteristics of pedofeatures are described:

Nature

Size

External shape

Surface roughness

Internal fabric

Contrast with the adjacent material and type of limit

Abundance

Variability

Distribution and orientation



CLASSES OF PEDOFEATURES

Morphological classification

The following types can be distinguished, depending on their morphology, crystallinity and referred orientation patterns:



Pedofeatures related to voids, grains and aggregates

Coatings

Hypo-coatings

Cuasi-coatings

Infillings

Pedofeatures unrelated to voids, grains and aggregates

Crystals and crystals intergrowths

Nodules

Intercalations

Reworked pedofeatures

Fragmented and deformed pedofeatures

Keys to the morphological classification of pedofeatures

Classification by nature

Six main groups can be distinguished depending on the material's nature:



Texturals

Depletions

Crystallines

Amorphous and cryptocrystallines

Fabrics

Excrements

Compounds

Keys to the classification of pedofeatures by nature