A study of the Precambrian massifs of the central Sahara confirms movements of great magnitude in the basement rocks which affected the overlying strata. There were successive readjustments along the faults and reactivation of the folds. The major period of dislocation and deformation of the sediments was the Mesozoic and not the Hercynian. Because of its wide extent this period is called the 'Ramadian movements.' It ended after the lower Eocene and at the time of the Tertiary movements (Timetrinian phase or episode).