The Agulhas Magsat anomaly; implications for continental break-up of Gondwana

Antoine, L. A. G.; Moyes, A. B.

A new processing procedure is implemented on Magsat data over the Southern African region and surrounding oceans. The oceanic region of the ensuing map is interpreted in this study. The anomaly map is image processed and a composite image of Magsat with Seasat data is also presented. The Agulhas high-amplitude satellite-magnetic anomaly, situated off the southeastern coast of Africa in the southwestern Indian Ocean (31 degrees E, 35 degrees S), is clearly defined. In addition, a north-south oceanic anomaly bordering the west coast of Southern Africa, including in part the Walvis Ridge anomaly, is now recognised. The Walvis Ridge and Agulhas oceanic anomalies are interpreted to represent thickened, remanently magnetised (during Cretaceous quiet times) ocean crust. Similarities between the Walvis Ridge and the Agulhas Magsat anomalies suggest a common genesis. The Agulhas anomaly is interpreted to represent the remnant scar of the process that led to fragmentation of Gondwana. It is hypothesised that fragmentation of Gondwana was initiated by an upwelling of hotter than normal asthenosphere centred directly below the Agulhas anomaly.