In 1979, before the establishment of the Géologique de Haute-Provence National Nature Reserve, earthworks began to uncover the slab and unearthed 600 ammonites over 160 square metres (1,700 sq ft).

[citation needed] The 160 square metres (1,700 sq ft) already unearthed in 1992 of the slab were molded in 1992 by the geological reserve for the city of Kamaishi in Japan (who desired to buy the original).

The Dalle à ammonites, as well as other sites in the area, are witnesses of the first step of this process, and of what was life in this ocean before the apparition of the mountains.

The good conservation of the shells give informations over the marine dynamism responsible for the deposit conditions : an hectic environment, like a beach or a coast, were the waves actions were strongly felt, with a tendency to break the shells, leading to fragmentary deposits, settled as faluns or lumachella.

The tapophenosis analysis, as well as the position of the shells, lead to the conclusion that the Dalle à ammonites was an accumulation facies : a large number of dead animals were carried by weak marine currents, towards their deposit site.