At La Roche-Cotard, the oldest engravings in France identified on the walls of a cave

Unearthed in 1846, the La Roche-Cotard cave remained inaccessible until 1912, when the owner of the land on which it is located excavated the blocked-up entrance, which he presented in a note in 1913, illustrated with photos and a map. In 1976, Jean-Claude Marquet, then at the University of Dijon, began excavations there.

It was only in 2008 that research work on the cave really got underway, thanks to a multidisciplinary project. It was this work that led to the discovery and contextualisation of the engravings, located on a wall of tuffeau (a soft stone used to build the decorations typical of Renaissance architecture in the regions around the Loire) some twelve metres long, covered at the top by a thin film of weathering.

Most of these marks were made with fingers, either by simply touching the surface of the weathered tuffeau, or by moving the finger. They represent non-figurative patterns, some rather simple such as finger impacts surrounding a large fossil embedded in the rock or forming long lines covering a vast area, some more elaborate.

An experimental study and precise measurements using the most effective methods (photogrammetry) have made it possible to characterise, record and experimentally reproduce such markings, confirming their human nature and eliminating any hypothesis of functional, natural, animal, geological or accidental production. These same studies, combined with an analysis of the traces of alteration and colorimetric differences, have ruled out the possibility that these tracings were made after the cave was opened in 1912. They therefore predate the 20^th century.

The question was therefore to find out when these engravings were made. A study of the soil showed that the cave had been partially flooded on several occasions by the Loire river, whose current course runs just two kilometres from the site. Over the millennia, flood silt invaded the cave and covered archaeological layers containing Neanderthal tools, discovered in 1912. This silt eventually blocked up the entrance to the cave, concealing it under several metres of sediment. Its closure was dated by determining the age of these deposits using optically stimulated luminescence.