ABSTRACT

Establishment of stone lines ƒ Above the lithomarges in the profiles, we see the frequent occurrence of gravelly layers (debris of cuirasses, quartz layers), often rather thin and parallel to the soil surface. Their origin is poorly understood. There are three possible explanations: • geochemical wasting involves the local collection, close to the

soil surface, of residues of quartz veins (Fig. 5.10a); • an old surface eroded and paved with stones [cf. the surface

accumulations in some deserts (Fig. 5.10b)] has been buried by colluviation or by termites that bring up the soil from just below (hypothesis of reversal);

• quartz veins have been disintegrated and distributed within the profile along the slope (Fig. 5.10c).