AEON Project Archive

This site is an archive of a project of AEON

Post-Gondwana tectonics from Namaqualand to the Kalahari

Under investigation:

  • Post-Gondwana history of stress in southwestern Africa  
  • Cretaceous tectonics and basaltic volcanism in the western Kaapvaal craton  
  • Tectonic-magmatic response of the Kaapvaal crust to the impact of the giant Morokweng meteorite (~144 Ma)
  • Intraplate crustal stability and the state of stress in the Cape offshore

Benefits:

  • Identification of mineral deposits and groundwater resources
  • Seismic risk assessment and hazard mitigation: human habitat, deep mines and key point facilities
  • Exploitation of offshore hydrocarbon deposits
Sub-Project Post-Gondwana tectonics in western South Africa: from the Namaqualand offshore to the Kalahari - Implications for hydrocarbon exploitation, mineral exploration and seismic risk mitigation

Core participants (* indicates project coordinator; ^ indicates postgraduate student, contract researcher)

GeoForschungsZentrum (GFZ) Potsdam (Germany) Oliver Heidbach
South African Nuclear Energy Corporation (Necsa), SA Marco Andreoli*  (UW)
Mbuthokazi Mandaba^
Universityof Cape Town(UCT), SA Anton LeRoex                                                                Andrew Logue^ (Necsa)
Namib Geovista (NG) – University of Pretoria (UP), SA Ingrid Stengel
Universityof Tel Aviv(UTV) -  (UCT) Zvi Ben-Avraham
Universityof Basel(UB), Switzerland Alex Kounov
Universityof Trondheim (UT)  - Geological Survey of Norway (GSN) Giulio Viola
University Stellenbosch (US), SA   Cathy Clarke-Dowding                                                   Olwethu Majodina^
Universityof KwaZulu-Natal(UKZN), SA Mike Watkeys                                                             Saumitra Misra
Hartebeesthoek Radio Astronomy Observatory (HartRAO) - Space Geodesy Programme (SA) Ludwig Combrinck
University of the Witwatersrand (UW), SA
 
Ray Durrheim                                                               Terence McCarthy                                                           Roger Gibson                                                                     Hlompo Malephane^                                                                           S Wela^

Summary
The end of the Jurassic, at ~144 Ma, is accompanied in southern Gondwana by the developing rift along the site of the future south Atlantic.  Another major event took place at that time in what became the South African sector of the Kalahari basin, namely the impact of the giant Morokweng meteorite.   This impact arguably produced the third largest crater in the terrestrial record, releasing the vertical tectonic stresses responsible for the rise of the ~240 km Morokweng/Ganyesa dome structure and the emplacement of basaltic dykes.  As Africa and America became increasingly separated by an expanding Atlantic ocean, the SE Atlantic escarpment experienced, with time, striking changes in both stress orientation and magnitude reflected in folding and faulting of thrusting, extensional and strike slip character.  These tectonic episodes are recorded not only by the Karoo and Cretaceous deposits in western Namibia and Namaqualand, but also in the offshore Orange and Bredasdorp basins and, onshore, in the northwestern Karoo basin and in the Ghaap Plateau (southwestern Kaapvaal craton).  As such, the study of these Cretaceous to post-Cretaceous tectonic events dovetails with other Inkaba ye Africa projects, and constitutes the background needed to assist in the interpretation of the present day strike slip stress field in western southern Africa.  This NW to NNW oriented, so-called Wegener field is of anomalous intensity, puzzling in orientation and may be responsible for the generally low to moderate seismic activity recorded in the western and northern Cape regions. Apart from the study of the Morokweng structure and its economic implications, much of the currently planned research focuses on the various facets of the Wegener stress anomaly, especially its variability in time and space, and its implications for seismic risk assessment and the optimal exploitation of offshore hydrocarbon resources. 

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