La grotte du GRAND ROC - Les abris de LAUGERIE BASSE

To fully understand the various steps leading to the formation of limestone means going back millions of years.

The most ancient rocks appeared 3,7 billion years ago.

The Coniacian limestone that composes the cliffs of the VÈzËre valley formed 88 million years ago during the secondary era or "Superior Cretaceous" when the region was covered in a temperate and shallow sea.
Sediments accumulated on the ground to form limestone mainly composed of sand, marine and clay shells and possibly up to 60 metres thick.

At the end of the secondary era, 65 million years ago, the sea receded further west leaving Perigord high and dry.

During the Tertiary Era, all elements necessary for the formation of caves were united: limestone cracked under both the action of the tectonics and under the weight of the rock, sand and gravel coming all the way from the Massif Central covered it.
Erosion and infiltration could begin their work.

The formation of subrock shelters

1 - The formation of a rocky overhang: the cliff is slightly hollowed where there is a softer limestone layer, where the rock is less resistant to frost / defrost periods.

2 and 3 - Hollowing and filling of the shelter: frost / defrost periods make the rock break up, leading to the hollowing of the shelter, immediately followed by the accumulation of blocks and sediments on the ground.

4 - End of the evolution of the subrock shelter: the weight of the rock forming the roof of the shelter makes it collapse.