Madagascar is the result of the breaking up of the Gondwana land. It is constituted by two main geological entities:

• polystructured crystalline unity, which would be older than 500 millions years, called “Madagascar Precambrian crystalline basement”, it forms the crystalline core of the island and crops out on the 2/3 of its surface;


• the sedimentary series, none metamorphosed and little bit deformed, lay on the crystalline basement. It is more developed in the West than in the East.