Crustal formation and evolution processes in the Natal Valley and Mozambique Ridge, off South Africa

The evolution of seafloor spreading of Africa, South America, and Antarctica is key to understanding the initial break-up of Gondwana. Vector geomagnetic surveys were conducted in the Natal Valley and Mozambique Ridge, off South Africa. We summarize the nature of the crust using the results of dense vector geomagnetic anomaly data, as well as satellite gravity data. Based on both inversion and forward analytical results, we identified areas of stretched continental crust, with basaltic magma intrusion in parts, as the northern Natal Valley, north part of the Mozambique Ridge, and north part of the southern Natal Valley. Oceanic crust was identified in the south part of the southern Natal Valley and south part of the Mozambique Ridge. Magnetic isochrons M0–M10 were identified in the south part of the southern Natal Valley. Clear magnetic lineations were observed in the south part of the Mozambique Ridge, where some areas were distorted by hotspot volcanism. The location of the continental ocean boundary in the Natal Valley, along with a four-stage model of tectonic evolution of the study area since about 183 Ma, are newly proposed.