Sirenians of the Col des Leques, 40 millions years ago

The Sirenians

The Sirenians of the Col des Lèques existed 40 million years ago. You have probably had the pleasure to read our previous article. So you certainly know the pass that leads to Castellane from Dignes; the Col des Lèques. Just after the camping des Sirènes on the right (coming from Castellane), you will find a parking lot. Leave your vehicle there, here begins the path. It will lead you to the site of the Sirenes, set up by the Geological Natural Reserve of Haute Provence. Count about thirty minutes of walking to discover the region 40 million years ago!

The Sirenians of the Col des Lèques are marine mammals also called sea cows but also manatees dugongs. Indeed, they are herbivores that feed on algae and aquatic plants. They live mainly near the coasts in warm regions. The fossils present on the site thus come from a very ancient relative of the current dugongs and manatees.


A deposit of sirenians unique in the world

This deposit is one of the oldest and most abundant in the world. Who would have thought that in addition to its many attractions, the Verdon region would also be the world capital of the Sirenians? Indeed, unlike other Sirenian deposits which generally present only a few dimensions, this one is much richer. He was able to bring to light skulls, lower jaws, forearms… Numerous bones which are very seldom present of accustomed. If the Sirenians were so well preserved, it is because they were buried very quickly. It is undoubtedly a storm or a hurricane which is the cause. A meteorological event that may have caused a collapse or a landslide covering this poor manatee population. The region has certainly known a tropical climate in the past, 40 million years ago.

Finally, the Sirenians are buried in marls and yellowish greasy limestones dating from more than 35 million years ago. The latter rest on Jurassic limestones dating from 145 million years ago! 110 million years separate them and are not represented by any rock?


Site formation

Indeed, after a first phase of erosion (from -145 million years to -35 million years), the sea returns and the primitive valleys are covered with water. The site was in fact at that time a kind of marine creek. The layers of mud and sand that were once deposited there became the yellowish rocks of today that contain the Sirenians.

A detail remains to be clarified; how is it that the site which shows fossilized marine mammals is today at an altitude of more than 1000 meters? Indeed, the uplift of the Alps began more than 30 million years ago. This enormous uplift gradually raised in altitude all that was in its periphery. It is this phenomenon that created the so-called “pre-Alpine” massifs such as the Vercors, the Chartreuse, the Diois-Baronnies, the Monts de Vaucluse-Luberon, the Préalpes de Digne and others. The Verdon massif is called “Préalpes de Castellane”.
In this respect, it is interesting to note that the Alps continue to rise by one millimeter per year in some places.

The Funny Helmets.