The Congo basin

The Congo Basin in Central Africa is often cited as an example of an intracratonic basin due to its near-circular shape, pronounced negative free-air gravity anomaly, and long subsidence history. The basin probably initiated by late Precambrian rifting of thick cratonic lithosphere and a large part of its subsidence history could be explained by post-rift thermal relaxation. However, the upper 1 km of Mesozoic to Cenozoic sediments seems discontinuous in its evolution and several studies have proposed that these sediments were deposited in response to mantle processes.



We have examined gravity data and 18 seismic tomography models to evaluate the role of the sub-crustal mantle in the more recent evolution phase of the Congo Basin. Current seismic tomography and gravity data do not prove or disprove the various hypotheses put forward to explain the deposition of the Mesozoic-Cenozoic Congo Basin sedimentary rocks, but the large variability between the tomographic models indicates that it is unlikely that the mantle would play a major role in the subsidence of the Congo Basin. The Congo Basin probably initiated as a rift basin in the and likely developed as a sediment catchment basin in the latest stages of its evolution (Burke and Gunnell, 2008). The deposition of the Mesozoic-Cenozoic rocks might not be caused by subsidence. Instead, the sediments could have raised the surface elevation to the present ~400 m above sea-level, with subsidence merely being a consequence of the additional sediment load.

Buiter, S.J.H., B. Steinberger, S. Medvedev, J. Tetreault, Could the mantle have caused subsidence of the Congo Basin? Tectonophysics 514-517, 62-80, doi:10.1016/j.tecto.2011.09.024