Some 150 million years ago, western France was covered by the sea. It later receded, exposing an accumulation of marine deposits. These deposits were then eroded by the widening of valleys, with streams wearing away the softer formations. The karsts constitute the fossil record.
The physical weathering of the cliffs, mainly through gelifraction, gave rise to rock shelters. Alternating periods of freezing and thawing hollowed out the softer and more porous rock banks. Over time, this created an overhang, freeing up a shelter and a terrace or rocky base. The space thus formed, known as a rock shelter, was conducive to the arrival of Palaeolithic peoples, providing them with shelter from the elements and a place to live in the light of day.
Sediments and rock fragments built up on the shelter floor, quickly covering over remains left by humans.