Wednesday 16 May 2012

Dating the Chauvet Cave art.

Chauvet Cave is located in the Vallon Pont d’Arc commune of the Ardèche department of France. It is the site of some of the most spectacular and elaborate cave art in Europe, and possibly also some of the oldest. Estimates of the age of these cave paintings, based upon their style of art and level of sophistication have suggested they were made between 10 000 and 22 000 years ago, but radiocarbon (¹⁴C) dating has suggested the site may be as old as 30 000 to 32 000. This implies that early Europeans had reached a high level of artistic sophistication 10 000 years older than archaeologists had previously thought, something that has (unsurprisingly) been widely challenged.

Horses (top) and a Rhinoceros from Chauvet Cave. University of Massachusetts Boston.

In a paper published in the Proceedings of the National Academy of Sciences on 7 May 2012, a team of scientists led by Benjamin Sadier of the Laboratoire Environnements et Dynamiques des Territoires de Montagnes at the Université de Savoie and the Centre National pour la Recherche Scientifique, describe a study of the (sealed) entrance to the cave using ³⁶Cl ratios to establish the time of closure.

Plan (top) and cross-section (bottom) of Chauvet Cave. Sadier et at. (2012).

³⁶Cl, or Chlorine-36, is an unstable isotope of Chlorine formed cosmogenicly, when Gama Rays interact with certain minerals. It has a known half-life, 308 000 years, and decay products, ³⁶S and ³⁶Ar (Sulphur-36 and Argon-36), enabling scientists to calculate the last time a rock was exposed at the surface by determining the ratio of ³⁶Cl to ³⁶S/³⁶Ar present.

Using this method at Chauvet Cave revealed that the entrance was closed by a series of rockfalls occurring between 29 400 and 21 500 years ago, suggesting that the cave painting could not have been made after this time.

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