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The Formation and Evolution of Africa from the Archaean to Present: Introduction

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The Formation and Evolution of Africa from the Archaean to Present: Introduction Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 The formation and evolution of Africa from the Archaean to Present: introduction DOUWE J. J. VAN HINSBERGEN1,2*, SUSANNE J. H. BUITER1,2,3, TROND H. TORSVIK1,2,3,4, CARMEN GAINA1,2,3 & SUSAN J. WEBB4 1Physics of Geological Processes, University of Oslo, Sem Sælands vei 24, NO-0316 Oslo, Norway 2Center for Advanced Study, Norwegian Academy of Science and Letters, Drammensveien 78, 0271 Oslo, Norway 3Centre for Geodynamics, Geological Survey of Norway (NGU), Leiv Eirikssons vei 39, 7491 Trondheim, Norway 4School of Geosciences, University of the Witwatersrand, WITS 2050 Johannesburg, South Africa *Corresponding author (e-mail: [email protected]) The African continent preserves a long geological This special volume contains 18 original contri- record that covers almost 75% of Earth’s history. butions about the geology of Africa. It celebrates The Pan-African orogeny (c. 600–500 Ma) brought African geology in two ways. First, it celebrates together old continental kernels (or cratons such as multidisciplinary Earth Science research, highlight- West African, Congo, Kalahari and Tanzania) ing the formation and evolution of Africa from 18 forming Gondwana and subsequently the superconti- different angles. Second, this volume celebrates nent Pangea by the late Palaeozoic (Fig. 1). the work of Kevin Burke and Lewis Ashwal. We The break-up of Pangea since the Jurassic and hope that this ‘Burke and Ashwal’ volume portrays Cretaceous, primarily through the opening of the the wide range of interests and research angles that Central Atlantic (e.g. Torsvik et al. 2008; Labails have characterized these two scientists throughout et al. 2010), Indian (e.g. Gaina et al. 2007; Mu¨ller their careers working in Africa and studying et al. 2008; Cande et al. 2010) and South Atlantic African geology (Ashwal & Burke 1989; Burke (e.g. Torsvik et al. 2009) oceans and the compli- 1996; Burke et al. 2003). cated subduction history to the north gradually shaped the African continent and its surrounding oceanic basins. Many first-order questions of Content of the volume African geology are still unanswered. How many accretion phases do the Proterozoic belts represent? This volume focuses on the formation of Africa as a What triggers extension and formation of the East coherent continent, from the formation of some of African Rift on a continent that is largely sur- the oldest continental crust known today in the rounded by spreading centres and, therefore, Kaapvaal Craton (de Wit et al. 1992) to billions of expected to be mainly in compression? What is years of collisions and arc-accretions, amalgamat- the role of shallow mantle and edge-driven convec- ing these old continental fragments (Hoffman tion (King & Ritsema 2000)? What are the sources 1991; Stern 1994; Zhao et al. 2002; Torsvik 2003) of the volcanic centres of Northern Africa (e.g. into Gondwana and the supercontinent Pangea. Tibesti, Dafur and Afar) and can they be traced to The contributions in this volume cover most of the the lower mantle? Is the elevation of Eastern and African continent (Fig. 2), span .2 Ga of its Southern Africa caused by mantle processes? history and approach its complex history from a What is the formation mechanism of intracratonic geophysical, geological, geochemical and physical sedimentary basins, such as the Taoudeni Basin on geographical point of view. the West African Craton and the Congo Basin In recent years, the importance of deep mantle (e.g. Hartley & Allen 1994; Giresse 2005)? How processes as a trigger for surface volcanism includ- do sedimentation and tectonics interact (Burke & ing world-changing (?) Large Igneous Province Gunnell 2008)? Can we reconstruct this elevation emplacement (Burke & Torsvik 2004; Burke and its impact on climate evolution (e.g. Wichura et al. 2008), diamond-bearing kimberlite formation et al. 2011)? (Torsvik et al. 2010) and dynamic topography From:Van Hinsbergen, D. J. J., Buiter, S. J. H., Torsvik, T. H., Gaina,C.&Webb, S. J. (eds) The Formation and Evolution of Africa: A Synopsis of 3.8 Ga of Earth History. Geological Society, London, Special Publications, 357, 1–8. DOI: 10.1144/SP357.1 0305-8719/11/$15.00 # The Geological Society of London 2011. Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 2 D. J. J. VAN HINSBERGEN ET AL. Fig. 1. Age of African crustal basement (after Gubanov & Mooney 2009). The ages are the time of crustal formation or the time of thermal or tectonic crustal reworking. (e.g. Lithgow-Bertollini & Silver 1998) has become Letts et al. (2011) provide new, high-quality evident. Several contributions in this volume shed palaeomagnetic poles for c. 2 Ga old rocks from new light on these processes and their geological the Kaapvaal Craton. By comparing their new and environmental effects. results with published information, they demon- strate that the Kaapvaal Craton was not associated with high rates of apparent polar wander during Part 1: The making of the African crust: The the c. 2.1–1.9 Ga interval. Van Schijndel et al. Archaean–Palaeozoic phases (2011) provide new detrital zircon data from sand- stones in the Rehoboth province of Namibia that The first part of this volume covers the formation identify three dominant periods of continental of Africa from old cratons through assembly crust formation: between 1.3–1.1, 2.0–1.8 and in the Pan-African orogeny to the formation of 3–2.7 Ga, the latter of which was previously Gondwana. unknown. Key et al. (2011) report an extensive Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 INTRODUCTION 3 Fishwick & Bastow El Hachimi et al. Deenen et al. et al. Capitanio Endress et al. Ruiz-Martinez et al. et al. De Wall De Wall Ayelew Braitenberg et al. Wichura et al. Mahaney et al. et al. Wendorff Ganerød Ganerød Longridge et al. et al. van Schijndel et al. Key Letts et al. Torsvik & C ocks Fig. 2. Study areas covered in this volume. geological survey of the basement rocks of Mada- of Gondwana between 510 and 250 Ma. They gascar, providing an overview of the five Archaean detail the locations of passive and active margins to Proterozoic basement blocks that are recognized around Gondwana throughout the Palaeozoic, on the island. They review the Neoproterozoic col- continental shelves, evaporite deposits, volcanism lision and amalgamation history of the Madagascar and glaciations, including those affecting Africa segment of the East Africa–Antarctica Orogen, and Arabia. which was finalized during the Terminal Pan-African Event 560–490 Ma ago. Wendorff (2011) provides new insights into the history of Part 2: Africa since the break-up of Pangea: the Lufilian Arc, which formed as a result of the The Mesozoic–Cenozoic phases Pan-African collision between the Kalahari and Congo cratons. The structural and stratigraphic The papers in the second part discuss events from evolution of this belt shows evidence for two pre- the break-up of Pangea to the late Cenozoic. viously unidentified rift and foreland basins. De During this time Africa moved relatively slowly Wall et al. (2011) study the metamorphic and tec- (Burke 1996). El Hachimi et al. (2011) focus their tonic history of the Terminal Pan-African Event in attention on the Central Atlantic Magmatic Province Ethiopia. They provide new metamorphic and mag- (CAMP) that was emplaced around 200 Ma. The netic fabric data from the Central Steep Zone, a mantle plume that led to its emplacement probably transpressional belt that can be traced into Eritrea. triggered Pangea dispersal (Burke & Dewey They argue that the deformation and metamorphism 1973). El Hachimi et al. (2011) study the mor- in their study area results from closure of the phology, internal architecture and emplacement Mozambique Ocean and the final assembly of mechanisms of CAMP lavas in the Argana Basin Gondwana. Longridge et al. (2011) provide a of Morocco. They demonstrate that the emplace- detailed structural geological and geochronological ment mechanisms are in line with continental study of the Central Zone of the Pan-African flood basalt facies models. Deenen et al. (2011) Damara orogen in Namibia. They unravel a take a stratigraphic approach to the CAMP, and history of crustal thickening, heating of the mid- use magnetostratigraphic and cyclostratigraphic crust, exhumation and orogen-parallel extension techniques to correlate the Moroccan segment of between c. 540 and 500 Ma. Torsvik & Cocks the CAMP to their counterparts on the NW side of (2011) provide nine new palaeogeographic maps the Atlantic Ocean in Canada and the United Downloaded from http://sp.lyellcollection.org/ by guest on September 24, 2021 4 D. J. J. VAN HINSBERGEN ET AL. States. They provide new age constraints and corre- and Quaternary. Capitanio et al. (2011) study the lations on the largest Large Igneous Province that Sirte Basin in northern Lybia, a peculiar extensional led to the break-up of Pangea and the formation of domain that has historically been seismically active Africa as a continent. Ruiz-Martinez et al. (2011) and has experienced Pliocene extension. They provide a new palaeomagnetic pole for a c. 93 Ma correlate this extensional deformation with the sedimentary section in SW Morocco, which forms contemporaneous Sicily Channel rift, and argue the first Turonian palaeopole for Africa. Given that the strong slab-pull gradients of the subducted their large dataset, they can correct their results for African plate in the central Mediterranean region compaction-induced shallowing of the inclination have tectonic effects up to 1400 km south of the and provide a reliable pole. They discuss their subduction zone. results within the context of Africa’s apparent polar wander path for the Cretaceous. Ganerød Part 3: Current state of the African crust et al.
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