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Site Map / Index This page last modified: 7th January, 2008 ŠPaul Markwick 2000-2008 |
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Jacques, John M., Paul J. Markwick, Derek Fairhead, Kerri Wilson & David Wright (2005) Reducing risk and uncertainty in frontier exploration on and beyond the outer continental shelf of West Africa - the role of tectonics, palaeodrainage and Earth System modeling HGS/PESGB Africa Meeting, September 7-8, 2005, Houston, U.S.A. Abstract Based on inter-basinal characteristics that include spatial (pre-separation geographic association, e.g., rift geometry), temporal (e.g., source rock age) and mechanistic (e.g., trap style) similarities, several tectonostratigraphic provinces and sub-provinces are recognised along the South Atlantic passive margins in which their boundaries clearly correlate with several major transverse, intracontinental accommodation zones that extend across the African and South American continents. On a gross-scale, it is clear that basins along both conjugate margins (West Africa and South America) can be grouped into two megaprovinces according to their tectonostratigraphic history: (a) a Southern South Atlantic 'Volcanic' or 'Aptian' Anoxic Province; and (b) a Central South Atlantic 'Aptian' Salt Province. Collectively, they encompass 25 basins. Representing a possible subplate boundary, the NW-SE-trending intracontinental Paraná-Chacos Deformation Zone (coincident with the Rio Grande Rise-Walvis Ridge Volcanic Complex) appears to have strongly influenced the tectonostratigraphic evolution of the rift system, marking the boundary between these two megaprovinces. Using gravity and magnetic data, in combination with a variety of geological datasets, the position and continuity of the intraplate accommodation zones have been assessed, and the resultant structural /geological framework for the South Atlantic passive margins has been used to create a regional 'palaeotemplate' for plate tectonic modelling purposes. Alternative models have been tested by continental-scale plate tectonic modelling of the potential field data. With the focus, in this paper, being West Africa, we demonstrate how by integrating tectonics, geophysics, geochemistry and sedimentology with GIS technology, we can identify new and extend existing play fairways in these frontier areas. When combined with the application of GIS-based state-of-the-art techniques, such as palaeodrainage analysis and 'Earth System Modelling' (e.g., palaeoclimate and ocean modelling), a very powerful exploration tool is created for predicting the contemporary distribution of play elements (source, reservoir and seal). This paper will particularly focus on the influence of tectonics on the evolution of the West African continental margin, especially its influence on the dynamics of each basin (subsidence and uplift) and its associated landscape evolution (hinterland uplift, palaeodrainage, sediment supply and input). This, in turn, defines palaeogeography, which provides an essential constraint for understanding source rock, reservoir and seal distribution and quality. |
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