Seismic reflection data from the southern Mozambique Ridge, SW Indian Ocean, show indications for a modification in the oceanic circulation system. In the absence of an age-depth model based on a drill site we used information gathered from the study of radiogenic isotopes of ferromanganese nodules and crusts. Those were recovered via dredges from the Mozambique Ridge to gain knowledge on the origin of the modifications of the oceanic circulation system, which is documented in the distinct change in reflection characteristics. This is found to have occurred at 9 Ma.