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￿
Cambisol Rhodic . The soils on the Riss surfaces have an almost
metre-thick B middle horizon a bit more clayey than the other
horizons; it is quite red; we say it has undergone rubefaction
(from L. rubeus = reddish); the soil is of A/B/C type (Fig. 9.3a).
￿
Luvisol Rhodic . On the Mindel surfaces, a bleached depleted E
horizon appears and the profile is of A/E/B/C type; the red
clayey B horizon is 3-5 metres thick (Fig. 9.3b).
Fig. 9.3 a: Cambisol Rhodic; b: in a Luvisol Rhodic, the transition from the bleached E horizon
to the red B horizon at about 70-cm depth (France, the Rhône valley; photos : M. Bornand).
￿ Alisol Rhodic . See Chapter 5, Table 5.7. The B is still thicker on
the Günz surfaces; it is very red, but exhibits decolorized areas
demonstrating degradation; the pH falls, and so does the base
saturation; the profile is still of the A/E/B/C type, but with more
contrasted horizons.
￿ Gleyic Acrisol . See Chapter 5, § 5.4.3, Table 5.7. On the Villafranchian
surfaces, the B horizon no longer has overall red colour. Its upper
part is on the way to degradation and is variegated with red,
yellow and white patches. The lower part is yellowish. The sur-
face soil is greatly depleted; only quartzose pebbles and stones
with a reddish patina are found. The profile is of the A/E/B21/
B22/B23/C type. We shall discuss the B horizons in detail later,
their organization being complex.
From the uniform and thin material that it had been at the start of
pedogenesis, the profile has become differentiated, exhibiting horizons
with very specific textures, colours and mineralogical compositions.
The great depth of the Günz and Villafranchian soils is explained by
the duration of pedogenesis, the porosity of the parent material and the
general stability of the landscape (flat surface, absence of hydrographic
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