From the Lebombo Monocline to the Mozambique Deep Basin, using combined wide-angle and reflection seismic data

The North Natal valley (NNV), South Mozambique margin, is a key area for the understanding of the SW Indian Ocean history since the Gondwana break-up as its crustal nature and geometry strongly impacted the reconstruction of the paleogeography before the rifting. It is also of considerable importance for the understanding of the evolution of a margin system as the NNV is situated at the transition between divergent and strike-slip segments and at the conjunction of Oxfordian-Kimmeridgian Indian Ocean and the Valanginian-Aptian Atlantic one. As one part of the PAMELA project (PAssive Margins Exploration Laboratories), the NNV and the East Limpopo margin have been investigated during the MOZ3/5 cruise (2016), through the acquisition of 7 intersecting wide-angle profiles and coincident marine multichannel (720 traces) seismic as well as potential field data. Simultaneously, land seismometers were deployed in the Mozambique coastal plain (MCP), extending six of those profiles on land for about 100 km in order to provide information on the onshore-offshore transition. Wide-angle seismic data are of major importance as they can highlight constraints on the crustal structure of the margin and the position of the continent-ocean boundary in an area where the crustal nature is poorly known and largely controversial. The MOZ3/5 data set therefore reveals new essential constraints for kinematic reconstructions. This work presents results on the crustal structure from P-waves velocity modeling along two E-W wide-angle profiles (MZ1 and MZ2) through the NNV, from the Lebombo Monocline to the Mozambique Basin (MB), and crossing the Mozambique Fracture Zone (MFZ). The new geophysical data reveals an upper sedimentary sequence characterized by low velocities generally not exceeding 3 km/s, and up to 3 km thick where a major contouritic structure was observed. This feature formes together with several other contouritic structures, a N-S alignment just west of the MFZ, which produces high positive gravity anomalies, previously ...