During the Miocene period, the sea that surrounded the Alps covered Haute-Provence. As it's known today, the area of Les Duyes would have been close to the shoreline in the ancient tidal zone. A large quantity of sand that would become the current sandstone was deposited in this gulf.
The particularity of this site is that the deposited sediment both recorded and preserved the rhythm of the tides during a period of four months. The layers of sandstone, fine or coarse, are distributed according to a regular rhythm controlled by the phases of the moon.