To understand the present day structure and the mechanisms of subsidence at passive margins we assess the first-order configuration of the sediments, crust and upper mantle combining data on the geometry and distribution of physical properties into basin-scale data-based, 3D structural models. The latter subsequently are used as a base for isostatic, 3D gravity and 3D thermal modelling, to evaluate the isostatic state, the density structure as well as the characteristics of the thermal field. Examples from the conjugate South Atlantic margins offshore western South Africa-Namibia and Argentina show that, in spite of sharing several structural similarities, the two South Atlantic margins differ with respect to their structural grain. 

Apart from this difference, both margins share a similar density and thermal structure. In the South Atlantic the lithospheric mantle is rather homogenous concerning both density and thickness beneath the margin and the adjacent ocean. Consequently, the lateral variations of heat input from the mantle are of minor importance in response to an old and cold oceanic lithosphere. Instead, the configuration of the radiogenic continental crystalline crust appears to control decisively the shallow thermal field. This finding is opposed to findings from younger passive margins such as those in the North Atlantic, where the configuration of the oceanic lithosphere exerts a first order influence on the shallow thermal field of the margin. These results demonstrate that differently aged passive margins may bear very different thermal signatures with respective lateral variations in present-day temperatures in the upper few km.

Furthermore, the lithospheric-scale 3D models are used as a starting point to reconstruct the subsidence history of the sedimentary basins of the passive continental margins. The derived paleotopographies for different time steps provide information on relative uplift and subsidence. We correlate these offshore vertical movements with recent onshore investigations to decipher tectonic effects on uplift/subsidence.

Poster

Lithosphere-scale 3D structural model of the West African continental margin

Subsidence analysis of the South Atlantic passive margins

Publications

Autin, J., Scheck-Wenderoth, M., Legering, M.J., Anka, Z., Vallejo, E., Rodriguez, J.F., Dominguez, F., Marchal, D., Reichert, C., di Primo, R., Götze, H.-J. (2013): Colorado Basin 3D structure and evolution, Argentine passive margin. Tectonophysics (in Press), doi:10.1016/j.tecto.2013.05.019

Hirsch, K.K., Scheck-Wenderoth, M. Paton, D.A., Bauer, K. (2007): Crustal structure beneath the Orange Basin, South Africa. South African Journal of Geology 110, 249-260, doi:10.2113/gssajg.110.2-3.249

Hirsch, K.K., Bauer, K., Scheck-Wenderoth, M. (2009): Deep structure of the western South African passive margin – Results of a combined approach of seismic, gravity and isostatic investigions. Tectonophysics 470, 57-70, doi:10.1016/j.tecto.2008.04.028

Hirsch, K.K., Scheck-Wenderoth, M., van Wees, J.-D., Kuhlmann, G., Paton, D.A. (2010): Tectonic subsidence history and thermal evolution of the Orange Basin. Marine and Petroleum Geology 27, 565-584, doi:10.1016/j.marpetgeo.2009.06.009

Maystrenko, Y.P., Scheck-Wenderoth, M., Hartwig, A., Anka, Z., Watts, A.B., Hirsch, K.K, Fishwick, S. (2013): Salt as a 3D element in structural modeling – Example from the Central European Basin System. Tectonophysics (in Press), doi:10.1016/j.tecto.2012.06.030

von Nicolai, C., Scheck-Wenderoth, M., Warsitzka, M., Schødt, N., Anderson, J. (2013): The deep structure of the South Atlantic Kwanza Basin – Insights from 3D structural and gravimetric modelling. Tectonophysics (in Press), doi:10.1016/j.tecto.2013.06.016

Project Partner

- Hans-Jürgen Götze, Christian Albrecht University Kiel, Germany
- Christian Reichert, Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany

- Yuriy Maystrenko, Geological Survey of Norway (NGU), Trondheim, Norway
- Julia Autin, EOST-IPGS, UMR7516 CNRS-University of Strasbourg, France

- Petrobras Argentina S.A.
- Inkaba ye'Africa

More information about the project SAMPLE