An historic sign, possible Mesolithic menhir, DStretch, and problems in dating rock art to the Sauveterrian in the Massif de Fontainebleau

This paper uses typological analyses and image-enhancement software called DStretch to eliminate an engraved and pigmented monolith as a chronological marker for dating the largest concentration of supposed Mesolithic rock art in the world - the “classic” schematic engravings of the Massif de Fontainebleau. It shows that part of the block, which was thought to have lain undisturbed for over 7000 years and has been referred to as a “Rosetta Stone” for dating the area's art, actually bears historic letters. The orientation of these painted letters, whose tops all point towards the block's narrow end, and absence of both the letters and apparent medieval engravings around the other end indicate that the monolith's broader end was planted in the soil and more tapered one was exposed when the markings were made. This means that the monolith was upright. The only candidate we could find for keeping it vertical for long on a sandy floor was an oval cluster of small rounded boulders in the Mesolithic layer underneath. If these stones were used to brace the block, its exposed section could have been marked at any time between the monolith's erection and collapse up to 7 millennia later. But they also indicate that the monolith may be one of the oldest known menhirs in France.