The basement of the region is made of sandstone and limestone.
These two types of rock were formed during the Paleozoic era (-540 to -250 million years).
At that time, the morphology of the Earth was totally different from now.
Our region was below the surface of the water in the tropics.
For millennia, deposits have formed there on the sea floor.
As time passed, the pressure eventually transformed these different layers into stone:
✔ the sand became sandstone
✔ corals, shells and skeletons of marine animals have turned into limestone
These sedimentary rocks are the foundation of the karst basements.