Photo : Wikimedia Commons
La Dalle à Ammonites
The ammonite slab is one of the best-known palaeontological sites in France. Located a few kilometres north of Digne-les-Bains, on the road to Barles, it is part of the Haute-Provence Geological Nature Reserve. This slab of grey limestone, inclined at about 60 degrees, carries more than 1,500 ammonites, some reaching 70 cm in diameter. They date from the Sinemurian, at the beginning of the Jurassic, and the species Coroniceras multicostatum alone accounts for about 90% of the fossils.
The shells accumulated on an ancient seabed, then were covered with thick sediments before fossilising with the rock. The uplift of the Alpine chain later raised the slab to about 630 metres' altitude and laid it bare. The slab was partly discovered during roadworks, probably in 1941, then gradually cleared, which explains why its visible surface has increased over the decades to several hundred square metres.
