AEON Project Archive

This site is an archive of a project of AEON

Heart of Africa

The Deep Earth and the Distant Past


Theme Co-ordinators:
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


Projects:

1.1 Earth and Ocean Monitoring Network across Southern Africa (SADC): a long-term regional project to support a multi-disciplinary Earth science approach, phase II
1.2 COMPASS: COmprehensive Magnetic Processes under the African Southern Sub-continent
1.3 Quantifying surface processes as a key to the Kalahari and Madagascar epeirogenies: The influence of plateau uplift on climate change and ecodynamics
1.4 Plate Tectonics and Ecosystems on the Early Earth: Geophysical analyses of the world’s oldest suture zones, Barberton Mountain Land, Mpumalanga
1.5a Tracking Continental Growth at the southern edge of Africa Deep crustal structure and lithospheric roots
1.5b 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

 


Project Descriptions



Project 1.1:

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).

Global Navigation Satellite Systems (GNSS) type instrumentation will be placed throughout the SADC region to achieve multiple goals: the densification of Space Geodetic equipment, to facilitate research and to develop capacity for research throughout the region. The geodetic infrastructure of most countries in Africa is based on a variety of outdated co-ordinate reference frames and systems. In order to achieve most of the objectives set out by the Southern African Development Community (SADC) development programmes, it is essential that a reliable and sound geospatial information framework or Geographic Information System (GIS) be in place in a country, region or continent. The establishment of a geodetic network will facilitate the establishment of modern and accurate reference systems, geographical information systems, and will provide the required infrastructure for numerous scientific applications. This project will aid the establishment of the African Reference Frame (AFREF), and will both facilitate and stimulate numerous applications and local research groups. This in turn will have subsequent infrastructure and social advantages to poorly developed countries of this region.

Manpower, training, maintenance and sustainability of the projects will primarily be supported by the National Research Foundation (NRF) of South Africa, in collaboration with other stakeholders, to ensure a sustainable, long-term programme in the SADC region. Capital funding for the construction of the new Space Geodesy and Earth Observation observatory is sought from Department of Science and Technology (DST), about R120-million in total. The Space Geodesy and Earth Observation outstation of HartRAO, could be a new National Facility participating in Earth observations, satellite orbit determination and maintenance, fundamental physics as well as Moon and Interplanetary Missions. It will be a hub for training of post-graduate students in the fields of Space and Earth science, placing South Africa in a stronger global position through the development of its Earth and Space Science capacity. A separate, more detailed White Paper for  the Space Geodesy and Earth Observation outstation of HartRAO is available on the http://geodesy.hartrao.ac.za/ website (under Matjiesfontein Outstation > Research Perspectives).

 

 

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Project 1.2:

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.

 

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Project 1.3:

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.

Key to this project will be the use of cosmogenic nuclides, particularly of He and Ne, in order to measure current (10^3 to 10^6 yr) surface exposure ages and erosion rates at choice geomorphic localities under a range of surface conditions.

By comparing our findings with other, long-term proxies for weathering and erosion, notably exhumation thermochronology, laterite geochronology and offshore sediment studies, we intend to assess current tectonic and geochemical (climate) models for the response of erosion and weathering to Mesozoic flood basalt volcanism and epeirogeny in the independent continental fragments of Southern Africa and Madagascar.

Furthermore, we intend to dovetail our study with ongoing molecular biology and drainage studies in these regions, in order to better appreciate the influence of epeirogeny on the evolution of habitats and endemic biodiversity. Our results will also provide a baseline for understanding human-induced surface erosion in order to formulate sustainable land management policies.


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Project 1.4:

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.


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Project 1.5a:

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.


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Project 1.5b:

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                                                                                      
PESA Institute Aquatic Biodiversity
Rhodes University (RU, Grahamstown), 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.

 

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