Seismic reflection data from the southern Mozambique Ridge, Southwestern Indian Ocean, show indications for a modification in the oceanic circulation system during the Neogene. Major reorganisations in the Indian Ocean circulation system accompanying the closure of the Indonesian Gateway led to the onset of current controlled sedimentation in the vicinity of the Mozambique Ridge at 14 Ma. The modifications in water mass properties and path are documented in changes in reflection characteristics in the Mozambique Ridge area. Correlating these with identified changes of the Nd isotope evolution in deep water masses the general present day large scale circulation in the southern Indian Ocean is suggested to have prevailed for the last 9 Ma. References should not be included in abstracts.SOUTH AFRICAN JOURNAL OF GEOLOGY, 2011, VOLUME 114. (Smith and Sandwell, 1997;Uenzelmann-Neben, 2005;Jokat, 2006 Lutjeharms, 1996).The Agulhas Current is the western boundary current of the Indian Ocean It extends to water depths greater than 2000 m and has a mean transport of 108 m 3 /s (Lutjeharms, 1996; De Ruijter et al., 1999). Southwest of Africa the Agulhas Current turns abruptly eastward in a tight retroflection loop and becomes known as the Agulhas Return Current. This current flows eastwards to the Agulhas Plateau where it forms a major northward loop around the plateau (Lutjeharms, 1996; De Ruijter et al., 1999).
Data Acquisition and AnalysisThis study is based on seismic reflection data gathered at the southern Mozambique Ridge (Figure 1a) (Uenzelmann-Neben, 2005). The seismic reflection data were collected using a three GI-gun cluster as source and a 2.4 km long digital streamer system with 180 channels to record the data. A sample rate of 1 ms guaranteed a theoretical vertical resolution of 4 m. (Lutjeharms, 2006). SF= secondary faults.