examination disclosed a spot where a small silex had been not only imprinted but ground to the level of the surrounding dirt (Figure 17). The soil has been fractured on either side of this silex, possibly under a combination of mechanical and thermal action. To the right of this area in Figure 17 it appears that the soil is darker and contains small vegetal shoots that have germinated after the gathering of the sample. The abrasion effect is less visible in that area.

Sample P1b comes from the same part of the ring as P1a. It exhibits similar compression effects as well as striations. It also shows a darker area that could correspond to foreign material or even to a transformation of the surface material (Figure 18). This is clearly observable in Figure 19 and also in Figure 20, where some plants are germinating and pushing back the black material.

3. Physico-Chemical Analysis (SNEAP)

The SNEAP laboratory in Boussens is often entrusted by GEPAN with preliminary analyses aimed at detecting and identifying organic or mineral

Fig. 17. Sample P1a, magnification = 6.4.