The panoramic landscape in front of us illustrates a major feature of the geology of the Haute-Provence UNESCO Global Geopark : the Digne geological-nappe (or geological thrust-sheet).
This is a thick block of rock (more than 4,000m) whose ages range from 220 million years ago to 30 or 35 million years ago. The thick block of rock, known as allochthonous, or non-indigenous, because it originated and moved over twenty kilometres from the NNE (North, North-East) to the SSW (South, South-West) to its current position. Subsequently, it has covered over other indigenous, original layers of rocks that were already formed and structured (folded, for example) and subject to erosion: this is the definition of autochthonous, i.e. indigenous, original layers.
This is how rocks can be observed resting on terrain that is more recent than them, which seems abnormal. This overlapping phenomenon is called a "thrust fault".
Here the bedrock-base of the thrust, on which the geological-nappe slide, or thrust-sheet took place, is located above the village of Courbons. It is marked by levels of clay and gypsum which facilitated the movement by their malleability and flexibility.
At Courbons, between the nappe, or thrust sheet, and the autochthonous base, or the indigenous layers, there are fragments torn off by the nappe from the latter. The variety of elements observed here illustrates the complexity of the history of Digne's geological-nappe, or thrust-sheet which took place between 7 and 2 million years ago.