Regional Geology Reviews Series Editors Roland Oberha¨nsli Maarten J. de Wit Franc¸ois M. Roure More information about this series at http://www.springer.com/series/8643 . Maarten J. de Wit • Franc¸ois Guillocheau • Michiel C.J. de Wit Editors Geology and Resource Potential of the Congo Basin Editors Maarten J. de Wit Franc¸ois Guillocheau AEON- Africa Earth Observatory Geosciences Network, and ESSRI - Earth University of Rennes Stewardship Science Research Institute Rennes Cedex Nelson Mandela Metropolitan University France Port Elizabeth South Africa Michiel C.J. de Wit Geology University of Pretoria Pretoria South Africa ISBN 978-3-642-29481-5 ISBN 978-3-642-29482-2 (eBook) DOI 10.1007/978-3-642-29482-2 Springer Heidelberg New York Dordrecht London Library of Congress Control Number: 2014959861 # Springer-Verlag Berlin Heidelberg 2015 This work is subject to copyright. 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Cover illustration: Photo by Edmond Thorose Aerial view (helicopter flying at ca. 150 m above ground) looking northeast across the southwestern Congo Basin, 215 km southwest of Kinshasa, with outliers of poorly consolidated red sandstones of the Kwango Group (Jurassic-Cretaceous) capped by a subhorizontal hardpan of Cenozoic silcrete. These outliers represent the nothernmost remnants of the Kalahari Plateau, regional peneplanation surface (“the African Surface”) that is well preserved at ca. 1000 m across southern Africa. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) ThiS is a FM Blank Page Dedication Our Congo book is dedicated to three remarkable earth scientists whose work over a span of nearly 65 years, pre- and post-independent Sub-Saharan Africa, changed the course of knowledge about the geography, geology, and natural resources of the Congo Basin and surrounding regions of Central Africa: Lucien CAHEN (Belgium, 1912–1982), Norman Snelling (England, b. 1930), and Henri KAMPUNZU (DRC—Democratic Republic of Congo, 1952–2004) Lucien Cahen Norman Snelling Henri Kampunzu Cahen and Snelling were relatively shielded from the challenging sociopolitical and economic issues associated with colonial activities and the inevitable transition to African independence. They were able to focus mostly on what they loved: field geology and figuring out stratigraphy and tectonics using the early emergence of radiometric dating. By contrast, Kampunzu was a child of the African struggle for independence; he represented part of a new generation of African scientists freed from colonial suppression. He too loved geology and its history, and the field work needed to unravel its complexities, but he was also ‘caught up’ in the turbulent periods of transformation from the Belgian Congo to the Democratic Republic of Congo—DRC. Yet these three scientists formed a common bond through their scientific observations, curiosity, and writings, and the fact that they knew that they were building on the shoulders of a long line of fine, dedicated geoscientists with a love for Africa and its challenges. The work by these three outstanding geoscientists has left a solid foundation for a modern analysis of the geology of central Africa. We hope that this book will go some way towards expressing our appreciation and recognition for their dedicated work. Preface This book is a collection of scientific narratives about the origin and evolution of the Congo Basin and its surrounding regions. The Congo Basin is a vast near circular area of nearly 3.7 km2, some 300–400 m above sea level astride the Congo River; it is surrounded by elevated regions and flanked in the east by the African Rift System where, in places, elevations of Precambrian rocks and active volcanoes stand above 5,000 m; and in the west by the Atlantic Ocean into which the Congo River delivers vast volumes of detritus and dissolved loads (Fig. 1). The Congo River is the most powerful river in Africa: during the rainy seasons over 50,000 m3 (near 2 million ft3) of water per second flow into the Atlantic Ocean.1 ‘The force with which the Congo River empties into the Atlantic is so great that it changes the colour of the seawater for hundreds of kilometers around’ (Van Reybrouck 2010, 2014). Below sea level, gravity-driven currents and suspended sand clouds have carved an immense submarine canyon across the Fig. 1 Image of the Congo Basin and surrounding regions covered in this book. Thin black outline marks the edge of the Congo drainage system. Note that the perspective for the horizontal scale bar due to the ‘depth’ and orientation of the image (the image is more diamond shape than square) is correct only near the centre of the image (i.e. the km distance between the Congo River arc is within 10 % [100 km] accuracy). However, for the areas around the East African Lake District and near the Atlantic coast the accuracy is closer to within 20 %. Note also the vertical exaggeration (figure courtesy of Tyrel Flugel). See Chaps. 14 and 15 in this book for location names and greater information about the landscapes and river systems 1 The Congo’s discharge at its mouth ranges from 23,000 cubic metres per second (810,000 cu ft/s) to 75,000 m3/s (2,600,000 cu ft/s). For a more detailed account of the Congo Basin drainage system, see Chap. 15 in this Book. ix x Preface TUNISIA MOROCCO ALGERIA LIBYA EGYPT WESTERN SAHARA / SAHRAWI ADR MAURITANIA MALI NIGER NORTH SUDAN CHAD ERITREA SENEGAL GUINEA- BURKINA FASO DJIBOUTI BISSAU GUINEA BENIN NIGERIA SOMALIA SIERRA LEONE TOGO IVORY GHANA ETHIOPIA SOUTH SUDAN LIBERIA COAST CAR CAMEROON EQUATORIAL GUINEA UGANDA SAO TOME REP OF KENYA AND PRINCIPE GABON CONGO RWANDA DEMOCRATIC BURUNDI REPUBLIC OF CONGO TANZANIA COMOROS ANGOLA MALAWI ZAMBIA MOZAMBIQUE ZIMBABWE MADAGASCAR NAMIBIA BOTSWANA SWAZILAND 0375 750 1,500 km LESOTHO Congo Basin: 3.67 million km2 SOUTH AFRICA Fig. 2 (a) Map of Africa with country names. Red box shows the approximate sub-Saharan region of Central Africa that is the focus of the geophysics, geology, and geochronology of the crustal foundations of the Congo Basin (see Chaps. 1 and 2). (b) Relative size of Africa and the Congo Basin and, for direct comparisons to other selected nations, as plotted on an equal area projection continental shelf through which these turbidites are transported into the oceanic abyss. The Congo River is the second longest river in Africa, close to 5,000 km long. It emerges in the highland of the great Lake District of East Africa in the southern Hemisphere. From there, the journey to the sea snakes northward across the flatlands of the Congo Basin passing first through the savannas and swamps of Katanga, and then across the equator and through the endless equatorial forest in the northern hemisphere before it carves its way through the canyons and waterfalls of the rugged mountains of Bas-Congo to finally end up in the mangroves and the Congo Fan at the coast. It is constantly fed by alternating rainy seasons north and south of the equator. Van Reybrouck writes: ‘If the map of Congo looks like a balloon, Bas-Congo is the neck through which everything passes’. Because it is sometimes hard to comprehend the immenseness of the Congo Basin, which occupies just under 12 % of the surface area of Africa (about 40 % of the USA; and about half of Australia or the EU), it is worthwhile to compare the size of these regions on an equal area projection (Fig. 2b). It is also true that many casual observers of Africa are challenged to name all its 50 nations, or even the 18 odd countries of central Sub-Sahara, whose livelihood is directly affected by the present drainage system of the Congo Basin, and by the underlying geology and mineral wealth all of which are explored in this book (Fig. 2a). Port Elizabeth, South Africa Maarten J. de Wit Rennes, France Franc¸ois Guillocheau Pretoria, South Africa Michiel C.J. de Wit August, 2014 Background to a Punctuated History of Geoscience in the Congo Quantum leaps in knowledge about geography, geology, and mineral resources of Central Africa, and in particular within the bounds of the Congo Basin, occurred across major transitions between six periods: pre-1885 (the ‘Kongo’2); 1985–1908 (the Congo Free State); 1908–1960 (the Belgian Congo); 1960–1965 (the Republic of Congo); 1965–1997 (the Republic of Zaı¨re); and post-1997 (the Democratic Republic of Congo—DRC).