Heart of Africa
The Deep Earth and the Distant Past
Ludwig Combrinck (HartRAO, SA), Mioara Mandea (GFZ-Potsdam, Germany)
Under investigation:
- Earth and Ocean Monitoring Network across Southern Africa
- Comprehensive Magnetic Processes under the African Southern Subcontinent
- Quantifying Plateau Uplift, Climate Change and Eco-dynamics
- Plate Tectonics and Ecosystems on the Early Earth
- Tracking Continental Growth at the Southern End of Africa
Benefits:
- Earth’s magnetic field variations – communications and navigation systems
- Earth and Ocean Monitoring Network – natural hazard risk
- Uplift - aridity and erosion
- Deep structures - ore-forming processes
Project Descriptions
Earth and Ocean Monitoring Network across Southern Africa (SADC): a long-term regional project to support a multi-disciplinary Earth science approach, phase II
Participants (* indicates project coordinator)
| Hartebeesthoek Radio Astronomy Observatory (HartRAO) – Space Geodesy Programme (SA) | Ludwig Combrinck* |
| GeoForschungsZentrum (GFZ) Potsdam (Germany) | Mioara Mandea* |
| Tshwane University of Technology (TUT), SA | Stoffel Fourie |
| National Metrology Institute of South Africa (NMISA) | Louise Mostert |
| National Laser Centre (CSIR), SA |
Daniel Esser Hencharl Strauss |
| University of Pretoria (UP), SA |
Hannes Rautenbach Fritz van der Merwe |
| Observatoire de la Cote D’Azur (OCA), CNES, France | Francis Pierron |
| BKG (Wetzell Fundamental Station), Germany |
Wolfgang Schlueter Stefan Riepl |
| GeoForschungsZentrum (GFZ) Potsdam (Germany) |
Tilo Schoene Ludwig Grunwaldt |
| Alfred Wegener Institute (AWI), Germany | Hans Werner Schenke |
Summary
|
Within the framework of the Global Geodetic Observing System (GGOS) - http://ggos.org/, a project of the International Association of Geodesy (IAG) within the Global Earth Observation System of Systems (GEOSS) - www.earthobservations.org/geoss, phase II of this project will include the development and construction of a new observatory in the semi-arid Karoo region. It is envisaged that successful funding of the project will aid the establishment of the Space Geodesy and Earth Observation outstation of HartRAO, located at Matjiesfontein, South Africa. This new fundamental station will host all the main space geodetic techniques and will serve the needs of the SADC region in terms of research capacity development, student training and sustainability of the project SADC Earth and Ocean Monitoring Network. A big extra will be the Lunar Laser Ranging (LLR) device. It will also serve as a new Fundamental Space Geodetic Observatory for South Africa and will eventually replace the Space Geodesy Programme at Hartebeesthoek Radio Astronomy Observatory (HartRAO). |
COMPASS: COmprehensive Magnetic Processes under the African Southern Sub-continent
Participants (* indicates project coordinator)
| GeoForschungsZentrum Potsdam (GFZ), Germany |
Mioara Mandea* Anne Hemshorn Monika Korte* Vincent Lesur Eberhard Pulz Yoann Quesnel |
| Hermanus Magnetic Observatory (HMO), SA |
Pieter Kotze* Barry Pretorius Errol Julies Emmanual Nahayo |
| Hartebeesthoek Radio Astronomy Observatory (HartRAO) – Space Geodesy Programme (SA) | Ludwig Combrinck* |
Summary
|
The goal of this project is to achieve a better understanding of the Earth’s magnetic field over the southern African region (extending into the southern Atlantic Ocean). The focus will be on a better characterisation of the core field and its secular variation, as well as of the lithospheric field. Firstly, we note that the investigated area is an important one in the core field studies because of its intriguing behaviour at both the Earth’s surface and the coremantle boundary. To better characterize this behaviour we plan to install a new magnetic observatory in Botswana, and to continue, on yearly basis, measurements in the repeat stations network. Moreover, we will develop new mathematical tools to investigate the core field and its secular variation on a regional scale, in order to integrate ground-base and satellite-based data. Secondly, the source and the magnetic properties of the 1000 km east-west elongated Beattie Magnetic Anomaly (BMA) are unknown. By modelling of the magnetic signal and using a priori constraints from recent geophysical surveys, we will also investigate the geological source of the BMA. |
Quantifying surface processes as a key to the Kalahari and Madagascar epeirogenies: The influence of plateau uplift on climate change and ecodynamics
Participants (* indicates project coordinator)
| GeoForschungsZentrum (GFZ) Potsdam (Germany) |
Samuel Niedermann* Joerg Erzinger |
| University of Cape Town, AEON (UCT), SA |
Maarten de Wit* John Decker Fenton Cotterill Frank Eckhart |
| University of Fort Hare (UFH), SA |
Judith Masters Stephanie de Villiers |
Summary
|
This project aims to quantify earth surface processes, particularly erosion, over geological timescales in the anomalously elevated regions of Southern Africa and Madagascar, in order to resolve causal links between mantle processes, epeirogeny, climate change and ecodynamics. |
Plate Tectonics and Ecosystems on the Early Earth: Geophysical analyses of the world’s oldest suture zones, Barberton Mountain Land, Mpumalanga
Participants (* indicates project coordinator)
| GeoForschungsZentrum Potsdam (GFZ) Germany |
Ute Weckman* Oliver Ritter Michael Weber Christian Haberland |
| AEON, University of Cape Town (UCT), SA |
Maarten de Wit* Eugene Grosch Christie Rowe |
| Council for Geoscience SA (CGS) | Martinus Cloete |
| University of Stellenbosch (US), SA | Gary Stevens |
| University of the Witwatersrand (UW), SA |
Summary
|
There is heated debate and controversy about how far back in time plate tectonics operated on Earth. On the one hand arguments are made that plate tectonics dates back to about 4.0 billion years (Ga). Others argue that plate tectonics only originated much later, between 2.5 and 1.0 Ga. We aim to use deep geophysical probing to test geo-biologic and geochemical models that imply plate tectonics is an integrate part of early Earth system processes, at least as far back as 3.5 Ga. This work will help unravel how the first stable continent of the world formed, and how life originated and survived on it. The Barberton Greenstone Belt in South Africa offers the best field laboratory in the world to carry out this research. The work will, for the first time in this area, dovetail field geology, petrology, geochemistry and thermochronology with high resolution Magnetotelluric (MT) and Near Vertical Reflection (NVR) Seismic imaging, and selected drilling. |
Tracking Continental Growth at the southern edge of Africa Deep crustal structure and lithospheric roots
Participants (* indicates project coordinator)
| GeoForschungsZentrum (GFZ) Potsdam (Germany) |
Oliver Ritter* Ute Weckmann Christian Haberland Michael Weber Trond Ryberg Robert Trumbull Jacek Stankiewicz |
| Alfred Wegener Institute (AWI) (Germany) |
Karsten Gohl Ansa Lindeque |
| University of Cape Town (UCT), AEON, SA |
Maarten de Wit David Bell |
| Council for Geoscience SA (CGS) |
Luc Chevalier* Coenie de Beer |
| University of the Western Cape (UWC), SA | Reginald Domoney/Paul Carey |
| University of Johannesburg (UJ), SA | Hassina Mouri |
| Nelson Mandela Metropolitan University (NMMU), PE, SA |
R Shone Peter Booth |
| University KwaZulu Natal (UKZN), SA | Michael Watkeys |
| Green’s Geophysics (SA) | Rod Green |
Summary
|
Southern Africa and its southern continental margin are unique regions to study continental accretion processes over a period of more than 3.5 billion years. Building on results from Inkaba ye Africa I we propose new geo-scientific investigations along the transect stretching from the Cape Fold Belt, the Namaqua-Natal Belt and into the Karoo Province and the southern Kaapvaal Craton, to develop a model of the evolution and crustal accretion as well as the continental break-up of this region. With the transect, we address multifold significant objectives such as the Mesoproterozoic accretion processes along the southern margin of the Kaapvaal Craton, the nature and formation of the Cape Fold Belt, the sources of the Beattie Magnetic Anomaly and the Southern Cape Conductivity Belt. High-resolution seismic reflection and magnetotelluric surveys along the proposed transects with additional three-dimensional coverage will provide structural details and physical constraints for the Earth’s crust and upper mantle. Integration of the geophysical data with geological, petrological and geochemical analyses on rock composition, age and alteration history will lead to a geodynamic model for the evolution of the entire region and its tectonic units. |
Evolution of the Continental Margin of southern Africa: structural and geomorphic mapping programme in the Cape Mountains and its coastal fringes to complement geophysics transects and phylogeography
Participants (* indicates project coordinator)
| GeoForschungsZentrum (GFZ) Potsdam (Germany) |
Hermann Kaufmann* A Douglas Christian Mielke |
|
University of Cape Town (UCT), SA
University Stellenbosch (US), SA |
Maarten de Wit* Eugene Grosch Frank Eckardt Fenton Cotterill Christie Rowe Paul Skelton |
| Nelson Mandela Metropolitan University (NMMU), SA | Peter Booth |
| Council for Geoscience SA (CGS) |
Luc Chevallier Coenie de Beer |
| University of the Western Cape (UWC) | Reginald Domoney/Paul Carey |
Summary
|
The Cape Mountains, often mistakenly referred to as the Cape Fold Belt, form a formidable range of ridges and valleys flanking the east and south coast of southern-most Africa. These mountains have influenced historical migrations of indigenous people and colonists, and helped shape distinctly different biodiversity hotspots to the north and south of these ranges. The mountains are known to host significant stores of groundwater reservoirs, and are the site of micro-seismicity and occasional intra-plate earthquakes, both of unknown origin. The Cape Mountains are thus a cultural, biological and geological heritage of South Africa. The origin of the Cape Mountains dates back to end-Palaeozoic tangential deformations resulting in the formation of the Cape ranges as a fold and thrust belt (the Cape Fold Belt s.s.) followed by long lived early Mesozoic extension facilitated along deep listric normal faults that root in the mid-crust. The origin of this inversion tectonics is not understood. This is in part because modern structural mapping in the Cape Mountains is lacking and because geochronology and thermo-chronology are almost absent. In addition there is no high-resolution deep geophysical image to help extend compressional surface features to depth, even if only down to upper crustal depths, from which the formation of the Mountain ranges might be deciphered. Along the Cape Fold Belt (s.s.), the style and structure of the compressional deformation features vary considerably, within and between regional domains. There is heated controversy about tectonic duplication, and whether or not there was thick- or thin-skinned tectonics (or both) during the formation of the fold and thrust belt. It has recently also become apparent from fission track analyses that the Cape Mountains were in part also shaped during several exhumation episodes in the mid-end Cretaceous. In this respect they simulate on local scale the formation of the Great African escarpment, in response to regional uplift and erosion during the Kalahari epeirogeny. This overprint of up to 6 km exhumation hampers clear differentiation the Cape Mountains structures formed during horizontal lithosphere strains (orogeny) within the Cape Fold Belt (s.s.), from those formed during subsequent vertical motions of southern Africa (epeirogeny). For the first time ever, there is now a prospect of resolving this using the newly planned deep high-resolution near vertical seismic reflection profile across the belt to complement the MT profile and two long refraction lines produced during Phase 1 of Inkaba yeAfrica. This development, however, requires that more robust structural analyses of the surface exposures must be undertaken to complement these geophysical profiles. This project will concentrate on geomorphic and structural mapping, and metamorphic analyses complemented by thermo-chronology, of key areas within the Cape Mountains, and will closely link these with the geophysical analyses to provide a model for the structure of the crust and lithosphere beneath the Cape Mountains. Without this information, the geo-bio evolution of this part of the African continental margin is likely to remain unresolved. |

