Is there continental crust underneath the northern Natal Valley and the Mozambique Coastal Plains?

Abstract

To draw conclusions about the crustal nature and history of the Natal Valley and the Mozambique Ridge, systematic potential field data were obtained during the AISTEK III cruise with R/V Pelagia in 2009. This paper presents and interprets the results of that expedition. The new magnetic data reveal a pattern of linear magnetic spreading anomalies, NW-SE trending in the southwestern part of the Mozambique Ridge and E-W trending on its central part. The Ariel Graben, which separates the Mozambique Ridge from the Northern Natal Valley, is represented by a pronounced negative anomaly in the magnetic-as well as the free-air gravity field. The Northern Natal Valley bears a complicated pattern of anomalies with mainly SW-NE trends. In the Northern Natal Valley, no indications for a continent-ocean-boundary between continental crust in the north and oceanic crust in the south exist, either in the free-air gravity or in the magnetic field. The magnetic wavelengths of the Mozambique Coastal Plains are similar to those of the Northern Natal Valley and the Mozambique Ridge. Particularly in the gravity data, the Mozambique coastal plains, the Northern Natal Valley and the Mozambique Ridge appear as one continuous geological province. We interpret the region from the Mateke-Sabi monocline in the north to the southwestern tip of the Mozambique Ridge as mainly being floored by thickened oceanic crust. Copyright 2011 by the American Geophysical Union.