The geology of Cabrières is particularly complex. The region forms part of the nappes of the Black Mountain ('la Montagne Noire') ; the rocks were heavily displaced by the folding of the Hercynian range and the sedimentary deposits are no longer in their original position.

For example, the oldest rocks to be found at the 'Pic de Vissou' (Ordovician and Devonian) are now above younger rocks (Carboniferous).
Geologists describe this phenomenon as the scales of Cabrières, 'les écailles de Cabrières' (presented in the permanent exhibition); something which was only really understood in the last few years.

The exhibition shows this formation in simplified form ; during the Carboniferous (Visean) period, the erosion of the mountains which began to rise up as a result of the folding process provoked an underwater sedimentation accompanied by major displacement of panels of rock, sometimes of huge proportions, as in the case of the scales of the 'Pic de Vissou'.

The marine basin, in the lee of the mountain range, was itself caught up in the folding process and its rocks were displaced tens of kilometres (displaced nappe).