Carbon in the Dark: The First Radiocarbon Dates for Cave Art in the Dordogne

The assumption was tidy, and it held for decades. The cave paintings of the Dordogne, including those at Lascaux, were made with mineral pigments: iron oxides for reds and yellows, manganese oxides for blacks. No carbon. That meant no radiocarbon dating. If you wanted to know how old these images were, you had to rely on the style of the figures, the geology of calcite layers that might have grown over them, or comparisons with dated sites elsewhere. Indirect methods. Educated guesses dressed up in calibration curves.

No study had ever actually confirmed the absence of carbon. The assumption was just that: an assumption.

Hyperspectral image obtained by reflectance imaging spectroscopy (RIS) of the Carrefour sign showing a visual contrast between the representations made with carbon black (in red, Cervid HB14 and Bison HB15) and those made with black manganese oxides (in green, Bison HB14). Credit: TU Delft, Matthias Alfeld

A team led by CNRS researcher Ina Reiche decided to check.¹ What they found at Font-de-Gaume, a cave in Les Eyzies that has been a UNESCO World Heritage Site since 1979, was charcoal, hidden in plain sight inside the black lines of paintings that had been studied for more than a century.