The rather dull uniform rock formation of dark marlstone known as "black earth" or black badlands  is a very thick, deep rock formation (1,500 to 2,000m). In this group of layers, it is difficult to distinguish geological cuts and subdivisions. Only a few levels contain fossils that allow chronological references to be made.

Areas of "black earth" are widely found in almost all areas of the Haute-Provence UNESCO Global Geopark (for example, in Digne, La Robine, and Authon) and also in the neighbouring county, the Hautes-Alpes.

The sediments that constitute "black earth" were deposited in the Jurassic period between approximately 168 and 160 million years ago, at the bottom of the sea that occupied the region and covered the European continent. During the formation of the Alps, these sediments became rocks and were deformed and carried to higher altitudes. The syncline (sinking geological folds) in front of you is one of the oldest deformations: about 90 million years old.  It is associated with the vast Sigoyer anticline (uplifting geological folds).

Other geological deformations producing very complex structures took place during the Tertiary Era.

Then, more recently, in the Quaternary period, the Durance glacier filled the whole valley; it shaped the terrain and landscape and left moraines (glacial deposits) and alluvial (river) deposits when it retreated, such as the thick layer of pebbles that cuts through the "black earth" syncline (sinking geological fold).