Calcisols and other Soils on Carbonate-Bearing and Sulphate-Bearing Materials - Major Soil Groups of the World - page 229

7.5 TYPOLOGY AND CLASSIFICATION
7.5.1 Classification of Carbonate-Bearing Soils
The WRB

For the WRB, Calcisols are soils in which pedogenesis has accumulated
carbonates in visible traces ( petrocalcic horizon or calcic horizon
+ carbonate-containing groundmass) in part of the profile. Separated
from Calcisols are the soils that have a calcic horizon but come under
specific taxa because of other features; they are given the prefix 'Calcic',
for example 'Calcic Vertisol' or 'Calcic Solonchak'. A 'Calcic Cambisol'
does not exist because there is contradiction between the presence of a
calcic horizon and the feeble development corresponding to the idea of
a Cambisol. And there will be redundancy in coining Calcic Calcisols!
If the soil is immature but is simply calcareous in the bulk, it is given
an explicit suffix: Leptosol Calcaric , Fluvisol Calcaric , etc.
A horizon hardened by gypsum is petrogypsic (Chernozems,
Gypsisols).

The US Soil Taxonomy also distinguishes the diagnostic calcic , petrocalcic
and petrogypsic horizons. Horizons enriched with lime are particularly
found in the Aridisols (Calc-ids).
In the Mollisols, the first division, at the Suborder level, is traditionally
based on hydric and thermic regimes. But the feature 'Calcic' may
be introduced at the Great Group level: Calci-aqu-olls, Calci-cry-olls,
Calci-ud-olls, Calci-ust-olls, Calci-xer-olls. But the same feature appears
at the Subgroup level too, for example, Calcic Hapl-ud-olls, Calcic
Haplo-cry-olls, etc.
Soils that are calcareous in bulk are grouped under a special
Suborder: the Rendolls. The comparison with Rendzina, a common
taxon in many classifications, is not proper, for these soils form only
the Subgroup of Lithic Hap-rend-olls in the Rendolls.
In Inceptisols, one may find base-saturated soils: Eutro-cry-epts and
Eutr-ud-epts.

Soil Taxonomy

7.5.2 Examples of Carbonate-Bearing and Sulphate-

Bearing Soils
Calcisol (WRB) on calcareous clay (Fig. 7.17)

The following photograph illustrates a very classic example.