Two researchers from the LSCE (CEA-CNRS-UVSQ) have published an article in a special issue of Archeologia to mark the inauguration of the Cosquer cave facsimile in the Bouches-du-Rhône département.
This ornate prehistoric cave, now invaded by the Mediterranean and only accessible by diving, has been the subject of numerous studies. It features parietal representations drawn with charcoal, in very good condition. As soon as the cave was discovered in 1991, samples of the parietal representations were taken and dated using 14C (deduced from the 14C/12C isotope ratio of the sample and compared with the current 14C/12C ratio).
Samples were taken from various representations: 18 animals, 5 negative hands and 6 abstract graphics. 9 charcoal fragments found on the ground. All dating, except one carried out in Lyon on charcoal found on the ground, was carried out at the LSCE using mass spectrometry (Tandétron in Gif-sur-Yvette since 1991, Artémis in Saclay since 2007) due to the very low mass of carbon that can be sampled from parietal paintings.
In addition, two fragments of speleothems (limestone concretions that form in an underground cavity) that cover the floor of the cave were also dated by the uranium-thorium method, using multi-collector mass spectrometry coupled with inductively coupled plasma at the LSCE. This dating indicated that they were deposited during the Holocene (a geological epoch spanning the last 12,000 years, and still ongoing), proof that the cave still receives seepage water and bears witness to post-Paleolithic concretioning.
The ages of the various wall paintings range from 33,000 to 20,000 years, in good agreement with the fact that the cave was only accessible to humans during glacial periods, when the volume of water frozen in the glaciers caused a drop in sea level.
The various datings revealed two main periods of decoration in the cave, separated by several millennia:
- The first period, from 33,000 to 29,000 years ago, is characterized by negative hands, 4 animals and 2 abstract figures.
- A second period, from 25,000 to 20,000 years Before Present (1950), features the remaining animals and abstract figures. During this period, we also find traces of 2 hearths.
The dating also revealed some unexpected results. Representations of animals with similar stylistic traits, from the same area of the cave, were found to date from 2 very different periods. The most likely hypothesis is that stylistic conventions were maintained between the two periods of occupation, and that prehistoric man of the second period copied the first drawings. A second, less likely hypothesis is the late reuse of charcoal abandoned during the first period of occupation.
Today, the Cosquer cave is one of the most 14C-dated decorated caves in the world, but this number remains low compared with the abundance of its wall decorations, the creation of which still raises many questions that need to be answered before the sea destroys them.
