Research paperReconstruction of the southwestern African continental margin by backward modeling

- We restore paleobathymetries of the southwestern African margin.
- We use as much present-day information as possible to calculate individual subsidence components.
- From restored paleobathymetries we have evidence for uplift events at the southwestern African margin.
- The minimum estimate of uplift during the post-rift phase is in the range of ∼1000 m.

As the evolution of the southwestern African passive continental margin and in particular, the vertical movements in this area are still a matter of debate, this study aims to quantify the past vertical movements by reconstructing the paleobathymetric evolution of the southwestern African margin during the post-rift phase. To quantify the vertical movements, inferred from paleobathymetries, different subsidence components that have affected the passive continental margin are calculated and interpreted with respect to the generating processes.Our investigation takes advantage of information on the present-day sedimentary thicknesses and the crustal configuration along the SW African margin. By using this detailed information and modeling backward in time we attempt to separate different subsidence components such as the load induced subsidence and the thermal subsidence for different time intervals during the post-rift phase. Calculating the amounts of each subsidence component and subtracting them from the present-day configuration yields paleobathymetries which are interpreted with respect to the evolution of the southwestern African passive margin.These restored paleobathymetries for different time steps during the post-rift phase indicate spatial and temporal variations of vertical movements including phases of seafloor uplift. As a result, our investigation allows to give minimum estimates of the vertical movements that have occurred during the post-rift phase. In addition to predominant subsidence, about 1000 m of seafloor uplift are deduced for the northern and southern parts of the SW African margin. Quantifying the amounts of vertical movements cannot finally clarify the generating processes behind these movements but the timing and magnitude of seafloor uplift indicate a deep mantle mechanism.