Selected drillholes along a section through the Sable de Beauchamp formation at Charles de Gaulle airport in Roissy-en-France (Val-d’Oise). The thickness of the silicified layers (especially the thinner layers) has been exaggerated. See position on general geomorphological section in Figure 2. Drillhole numbers must have the prefix 01545 × 0 to match the national geological data bank (BSS-BRGM − InfoTerre, 2023).