Geoscience Reference
In-Depth Information
Fig. 9.1
Organization of terraces on the left bank of the Rhône river (from Bornand 1978).
W = Würm, R = Riss, M = Mindel, G = Günz. The Bonnevaux plateau corresponds to the old-
est surface, namely, the Villafranchian.
Many hundreds of profiles described and analysed by the author
enables us bring out a typical sequence. From the youngest terrace
to the oldest, we see progressively older, deeper, more evolved soils
(Fig. 9.2).
Gleyic
Acrisol
Alisol
Rhodic
(red B)
0
Luvisol
Rhodic
(red B)
A
E
Cambisol
Rhodic
(red B)
Rubic
Cambisol
(brown)
A
E
5
E
B
B
21
A
B
C
B
(B)
C
Arenosol
C
A
C
10
B
22
C
15
B
23
C
Günz
Villafranchian
20
Mindel
Recent alluvia
Würm
Riss
Fig. 9.2
Chronosequence of the soils in the Rhône valley (Bornand 1978). The drawings of
the different profi les have been simplifi ed.
Arenosol
. In the recent alluvia, the profile is of the A/C type, with
little differentiation; the horizons are calcareous.
Rubic Cambisol
. On the Würm surfaces, the soils are brown or red-
dish-brown, not highly differentiated, of the A/(B)/C type; the B
is nearly 40-cm thick; carbonates have already disappeared from
the A and B horizons, but the soil clays are calcium-saturated.
