Geoscience Reference
In-Depth Information
8.2.3
The Evolutionary Sequence
An evolutionary sequence has been observed in the field. It forms an
indisputable reality that has been characterized all over northern France
(Jamagne 1973) and is now the great classic reference. It corresponds
to increasingly clayey B horizons, more and more depleted E horizons,
profiles with more and more horizon contrasts and signs of segregation
of iron in the most evolved stages (Fig. 8.8). Acidity and desaturation
increase at the same time.
Planosol
Luvic
Cambisol
Dystric
Cambisol
Haplic
Luvisol
Albeluvisol
A
A
(E)
B
A
Eg
A
Eg
A
E
watertable
(B)
B
Bg
Bg
C
C
C
C
C
towards Podzols
(see Chap. 11)
Fig. 8.8
Sequence of increasing evolution from Cambisol to Planosol. The terms have been
translated and simplifi ed from the French of Jamagne (1973). Ferruginous concretions are
shown in black.
As always in pedology, the final stages of evolution are not
necessarily reached, because time was lacking or because the profile
had found its equilibrium with the environment at a less advanced
stage of transformation. Also, these final stages are quite varied. Glossic
soils are abundant in clayey silts that crack quite easily in the vertical
direction. Podzols and related soils (Chap. 11) essentially pertain to
sandy parent materials (Jamagne and Begon 1984). Figure 8.9 shows two
soils characteristic of this evolutionary sequence.
Very complete analyses of the Diou profile can be found in various
publications (Legros and Boyer 1969—profile 39; de Coninck
et al
. 1976;
Legros 1982—profile 39).
